By August 19, 2005 Street Lighting Best Practices Prepared by: Kevin J. Mara, P.E. Braxton Underwood, P.E. John Pasierb Hi-Line Engineering, LLC 1850 Parkway Place, Suite 800 Marietta, GA 30067 With contributions from: Michele McColgan, Ph.D. Peter Morante Lighting Research Center Rensselaer Polytechnic Institute 21 Union St. Troy, NY 12180 For American Municipal Power- Ohio 2600 Airport Drive Columbus, OH 43219 TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................................................ I TABLE OF FIGURES ............................................................................................................................................. III I. INTRODUCTION..............................................................................................................................................1 II. EXECUTIVE SUMMARY................................................................................................................................2 ILLUMINATION LEVELS .............................................................................................................................................2 Priorities ..............................................................................................................................................................2 Pedestrian Conflict Areas ....................................................................................................................................2 Safety....................................................................................................................................................................2 Security ................................................................................................................................................................2 Design of Roadway Lighting................................................................................................................................3 Consequences of Roadway Lighting ....................................................................................................................3 PROPER CODE SELECTION AND IMPLEMENTATION ....................................................................................................3 NEC & NESC.......................................................................................................................................................3 OSHA Requirements ............................................................................................................................................4 Department of Transportation .............................................................................................................................4 WIRING AND CONSTRUCTION STANDARDS ................................................................................................................5 FIXTURE TYPES .........................................................................................................................................................5 Flood Lights.........................................................................................................................................................5 Cobra Head..........................................................................................................................................................5 Other Fixtures......................................................................................................................................................5 NESC GROUNDING REQUIREMENTS .........................................................................................................................6 Use of System Neutral to Effectively Ground Street Light Poles and Mast Arms ................................................6 Street Lighting Utilization Voltages.....................................................................................................................7 METHODS OF CONTROL OF STREET LIGHTING CIRCUITS ...........................................................................................7 OPERATION AND MAINTENANCE PLAN......................................................................................................................8 Group Relamping.................................................................................................................................................8 Street Light Inventory ..........................................................................................................................................8 Annual Maintenance Cost....................................................................................................................................8 Street Light Poles.................................................................................................................................................8 Dedicated Street Light Wiring .............................................................................................................................8 Street Light Fixture Maintenance and Repair......................................................................................................9 Low Capital Cost Street Light Fixtures (cobra heads) ........................................................................................9 High Capital Cost Street Light Fixtures (decorative post tops, etc.) ...................................................................9 SPOT RELAMPING VERSUS GROUP RELAMPING .........................................................................................................9 SAFETY INSPECTION CHECKLIST ...............................................................................................................................9 OPERATIONS AND MAINTENANCE CHECKLIST ........................................................................................................10 SUMMARY ...............................................................................................................................................................11 III. ILLUMINATION LEVELS .......................................................................................................................12 PRIORITIES FOR STREET LIGHTING ..........................................................................................................................12 PEDESTRIAN CONFLICT AREAS................................................................................................................................12 SAFETY ....................................................................................................................................................................12 SECURITY ................................................................................................................................................................13 DESIGN OF ROADWAY LIGHTING .............................................................................................................................13 EFFICIENT TECHNOLOGIES ......................................................................................................................................13 APPROPRIATE POLE HEIGHTS ..................................................................................................................................13 APPROPRIATE POLE SPACING ..................................................................................................................................14 CONSEQUENCES OF ROADWAY LIGHTING ...............................................................................................................14 RECOMMENDATIONS ...............................................................................................................................................15 Pedestrian Conflict Areas ..................................................................................................................................15 Illumination Levels and Roadway Classifications .............................................................................................15 Design of Roadway Lighting..............................................................................................................................16 I Consequences of Roadway Lighting ..................................................................................................................16 AASHTO’S CLASSIFICATION OF ROADWAYS, WALKWAYS, AND AREAS ...............................................................20 Roadway and Walkway Classifications .............................................................................................................20 Area Classifications ...........................................................................................................................................20 ANSI/IESNA’S ROADWAY, PEDESTRIAN WALKWAY, AND BIKEWAY CLASSIFICATIONS ......................................21 PEDESTRIAN CONFLICT AREA CLASSIFICATIONS.....................................................................................................22 IV. PROPER CODE SELECTION AND IMPLEMENTATION .................................................................24 WHICH CODE APPLIES TO MUNICIPAL STREET LIGHTS? .........................................................................................25 CASE STUDIES FOR PROPER APPLICATION OF ELECTRICAL CODES .........................................................................26 OSHA REQUIREMENTS ...........................................................................................................................................27 DEPARTMENT OF TRANSPORTATION........................................................................................................................28 V. WIRING AND CONSTRUCTION STANDARDS .......................................................................................30 NESC GROUNDING REQUIREMENTS .......................................................................................................................31 USE OF SYSTEM NEUTRAL TO EFFECTIVELY GROUND STREET LIGHT POLES AND MAST ARMS .............................33 STREET LIGHTING UTILIZATION VOLTAGES ............................................................................................................35 VI. METHODS OF CONTROL OF STREET LIGHTING CIRCUITS......................................................37 PHOTOCELLS ...........................................................................................................................................................37 MONITORING AND CONTROL SYSTEMS ...................................................................................................................38 VII. OPERATION AND MAINTENANCE PLAN – PRACTICES DETERMINED FROM SURVEY CONDUCTED BY LRC ...........................................................................................................................................40 STREETLIGHT POLES ...............................................................................................................................................40 DEDICATED STREETLIGHT WIRING..........................................................................................................................40 STREETLIGHT FIXTURE MAINTENANCE AND REPAIR ...............................................................................................41 LOW CAPITAL COST STREETLIGHT FIXTURES (COBRA HEADS)................................................................................41 HIGH CAPITAL COST STREETLIGHT FIXTURES (DECORATIVE POST TOPS, ETC.) .......................................................41 RECOMMENDATIONS ...............................................................................................................................................41 SPOT RELAMPING VERSUS GROUP RELAMPING .......................................................................................................42 SAFETY INSPECTION CHECKLIST .............................................................................................................................45 OPERATION AND MAINTENANCE CHECKLIST ..........................................................................................................46 APPENDIX A ............................................................................................................................................................49 APPENDIX B.............................................................................................................................................................85 APPENDIX C ............................................................................................................................................................91 UNDERSTANDING GROUNDING ................................................................................................................................96 APPENDIX D ..........................................................................................................................................................101 TRAINING PREREQUISITE .......................................................................................................................................103 SEMINAR GOALS ...................................................................................................................................................103 TRAINING OBJECTIVE ............................................................................................................................................103 TERMINAL OBJECTIVES .........................................................................................................................................104 TRAINING STRATEGIES ..........................................................................................................................................104 TRAINING CURRICULUM ........................................................................................................................................106 BIBLIOGRAPHY ...................................................................................................................................................109 II TABLE OF FIGURES Figure 1 Angles referenced by the IESNA Cutoff Classifications ............................................... 15 Figure 2 Touch Potential Concerns................................................................................................. 1 Figure 3 Touch Potential Concerns Hand to Hand Contact.......................................................... 34 Figure 4 Bonding of Street Light Pole to a Fence ........................................................................ 35 Figure 5 Effects of Electricity on Humans ................................................................................... 95 Figure 6 Example Circuit, Equipment Case Remotely Grounded................................................ 97 Figure 7 Example Circuit, Equipment Case Bonded to System Neutral ...................................... 98 Figure 8 Example Circuit, Equipment Case Remotely Grounded and Bonded to System Neutral ............................................................................................................................................... 99 III I. INTRODUCTION Lighting of our roadways and pedestrian areas is employed everywhere to conserve human life and reduce the risk of injury while also protecting property. The proper implementation of lighting designs is essential in obtaining these goals to preventing unnecessary exposure of the public to hazardous conditions. The American Public Power Association, at the request of American Municipal Power – Ohio and City of Columbus, Ohio Division of Electricity, chartered the completion of this report to help define the best practices in street lighting. Hi-Line was engaged as the prime contractor in development of this report with assistance from Lighting Research Center at Rensselaer Polytechnic Institute. With a combined experience level greater than forty years, the report authors from Hi-Line consisted of: Kevin J. Mara, P.E., Braxton J. Underwood, P.E., and John Pasierb. Key personnel for the Lighting Research Center were Michele McColgan, Ph.D. and Peter Morante. The purpose of Street Lighting Best Practices is to: interpret and specify the proper implementation of electrical code requirements (National Electric Code or National Electrical Safety Code) for differing street lighting systems, identify various roadway categories, and provide a curriculum for training individuals responsible for inspecting and approving new street lighting construction. Included in the identification of various roadway categories is a survey of the best practices used in street lighting. The survey provides: proper illumination levels, correct pole wiring design, and construction standards for the rehabilitation of existing and new construction of underground street lighting systems. Also included are recommendations for streetlight operation and maintenance guidelines. Emphasis of this report is placed on heightening awareness of advantages and disadvantages provided by different lighting designs and how different designs impact system operations. In addition to impacts on system operations, the report names possible hazards exposed to the public. A discussion of grounding and bonding is included, allowing utilities a chance to examine advantages and disadvantages offered by distinct methods or combinations of methods. This report attempts to guide utilities, and other parties owning street-light systems, to develop safe and effective street lighting designs and practices. 1 II. EXECUTIVE SUMMARY Street Lighting Best Practices is an effective tool designed to identify main areas of concern for utilities and entities involved in street-light design, maintenance, and operation. From these areas of concern, suggested practices are recommended based upon survey responses and industry practices. This summary will provide a quick reference to significant recommendations in each area of concern. Illumination Levels Priorities There are numerous priorities existing for making street lighting decisions. It is important to recognize that not all priorities are based on safety and security. When making street lighting decisions, societal goals, economic development, and illumination of set area are each valid arguments for street light placement. Pedestrian Conflict Areas Vehicle-pedestrian interaction is responsible for a disproportionate amount of nighttime fatalities. The magnitude of pedestrian flow is almost always related to the abutting land use. Low, medium and high are three classifications of pedestrian night activity levels and types of land use are. Areas with very low volumes of night pedestrian usage are assigned the ‘low’ classification. Areas where lesser numbers of pedestrians utilize the streets at night are classified ‘medium’. Areas expecting significant numbers of pedestrians to use sidewalks or crosswalks during dark are classified ‘high’. The survey and research showed that the American Association of State Highway and Transportation Officials (AASHTO) definition and terminology was used for the determination of classifications. Further, the areas were lit in accordance with AASHTO recommendations based upon the classification. Safety Street lighting provides more than just illumination of roadways. Adjacent areas such as walkways and yards benefit from street lighting as well. This illumination provides the extra benefit of safety for pedestrians, cyclists, and children. With pedestrian areas lit, drivers see these groups sooner, possibly avoiding a fatal collision. Security In addition to safety, street lighting can produce a sense of security. People feel safer more secure walking in a well lit area. The incident of crime in a well lit area is likely to be less than that of a poorly or unlit area, as delinquents prefer cover of dark. In order for security lighting to be effective, minimum light levels providing objectives of brightness and uniformity must be achieved. These light levels are recommended by AASHTO. 2 Design of Roadway Lighting Proper illumination levels on roadways are paramount when considering driver safety. Proper positioning of lights on roadways will help provide consistent and even lighting, providing drivers with increased visibility. Appropriate pole height and spacing allow for consistent and even lighting. Proper mating of fixtures to pole height also contributes to consistent lighting patterns. AASHTO “Information Guide for Roadway Lighting” and ANSI/IESNA RP-8-00 are two sources of information for proper lighting of roadways. The survey found most terminology follows that of AASHTO and the terminology used by IESNA is synonymous. Consequences of Roadway Lighting When designing roadway lighting, negative impacts should be minimized. Light trespass is an important negative impact that should be avoided. Light trespass can be minimized by: using the minimum light levels to meet the lighting objective, choosing light fixtures which are cutoff and full cutoff minimizing uplight and glare, and considering the impact on adjacent properties when placing lights. Proper Code Selection and Implementation Street lighting must be designed to meet lighting levels while complying with the applicable safety codes. Selection of the appropriate code should be determined based on the type of personnel who are operating the system. NEC & NESC Two primary codes are used in the United States; the National Electrical Code (NEC) and the National Electrical Safety Code (NESC). California, however, uses its own code for utilities; California Public Utilities Commission General Order 95 and General Order 128. These General Orders apply to those utilities under the jurisdiction of the Public Utilities Commission, State of California. The major distinction between NEC and NESC is the style in which the codes are written. The NESC is a performance-based code while the NEC is a prescriptive-based code. A performance base code provides rules for how a system should perform, but does not provide details on how to achieve this performance. This difference in the style of the codes leads to confusion when comparing design options for street lighting systems. The NESC method leaves design decisions to the engineer, who is responsible for complying with the performance standards. The NEC provides explicit rules for the design, which if followed, achieve the NEC’s safety objectives. 3 The NESC applies to utilities, public and private, provided the street lighting is in exclusive control of the utility. In a case where convenience outlets are installed for special lighting (Christmas lights) and the outlets can be reached by a non qualified person, the outlets must conform to the NEC. If a municipality without an electric utility installs streetlights, it must comply with the NEC. Review of the case studies better illustrates safety code requirements. OSHA Requirements In addition to the safety codes for the design of the street lighting system, Occupational Safety and Health Administration (OSHA) requirements are applicable. OSHA requirements are geared towards personnel operating and maintenance of the street lighting system. OSHA defines who can work on these systems and what requirements are necessary for their protection. OSHA’s protection of workers from electrical hazards is broken into two parts. OSHA standards subpart S of the General Industry Standards address electrical utilization systems, i.e., installations of electric conductors and equipment which use electric energy for mechanical, chemical, heating, lighting, or similar purposes. Subpart S protects most employees from the hazards associated with electric utilization equipment and with premises wiring. Subpart S would apply to electricians working on premises wiring which include area lightning. Further, subpart S relates more to the electrical systems covered by the NEC since the hazards are associated with utilization equipment. It should be noted, not all municipalities fall under OSHA control. OSHA developed 29 CFR 1910.269 that focuses on the operation and maintenance of electric power transmission and distribution systems. OSHA also states only qualified persons may work on or with exposed energized lines or parts of equipment operating at 50 volts or more. OSHA defines a qualified person as one knowledgeable in the construction and operation of the electric power generation, transmission, and distribution equipment involved, along with the associated hazards. Department of Transportation Each state adopts its own requirements with regards to safety within the rights-of-way of their state and county roads. These requirements are typically based on the recommendation contained in the following documents; “An Information Guide for Roadway Lighting, American Association of State Highway and Transportation Officials (AASHTO) “Report 152 – Warrants for Highway Lighting, National Cooperative Highway Research Program (NCHRP) “American National Standard Practice for Roadway Lighting (ANSI/IESNA RP8-00), Illuminating Engineering Society of North America in ANSI Practice for Roadway Lighting ANSI RP-8) In general, all ground mounted luminaire supports exposed to traffic and located within the clear zone should be provided with breakaway or yielding bases, unless they are located with the protection of a barrier (An Informational Guide for Roadway Lighting AASHTO 1984). AASHTO Roadside Design Guide, 3-6 (2002) defines the clear zone based on vehicle speed, 4 average daily traffic, and shoulder slopes. AASTHO recommends that efforts should be made in all breakaway poles that house electrical components to effectively reduce fire and electrical hazards posed after structure impact. The AASHTO publication Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals, 2001 provide standards for breakaway poles. This document states that breakaway supports shall be designed to yield, fracture or separate when struck by an errant vehicle. Other sources of information on breakaway poles are Recommended Procedures for Safety Performance Evaluation of Highway Features and AASHTO’s Roadside Design Guide. Wiring and Construction Standards The purpose of construction standards is to provide drawings and specifications that apply to repetitive installations. This enables safety, reliability, operability, uniformity, appearance, and economy to be coordinated in the system’s construction practices. Fixture Types Fixtures utilized depend on the task lighting requirements and aesthetics. Some utilities define the types of system by assigning particular fixture wattage to categories of street lighting. One utility defines a 70 watt fixture as an alley light, a 100 watt fixture as a local light, a 150 watt fixture as a collector light, and a 250 watt fixture as a major light. However, this is not typically the norm. Most utilities consider anything 100 watts or below as a security light and anything above as a street or area light. Flood Lights Flood lights used by utilities are typically 400 watt or 1000 watt high pressure sodium fixtures. They are utilized when high intensity illumination of a specific non-roadway area is needed. The most common utilization voltages seen are 120 or 240 volts. Cobra Head The most common fixture used for a roadway luminaire is a cobra head fixture. Typical sizes are 150, 250, and 400 watt. The mounting heights and types vary; typically one can expect to see the cobra head fixture mounted between 30 to 37 feet above the roadway. Most utilities purchase and maintain a stock of high pressure sodium vapor fixtures. Other utilities currently using mercury vapor fixtures are planning to convert to the more efficient and cost effective high pressure sodium vapor fixture. These fixtures are typically available as drop prismatic refractor glass, flat glass, short semi- cutoff, medium semi- cutoff, medium cutoff, and full cutoff. Other Fixtures Other fixtures utilized, but not as prevalent, are high mast and teardrop fixtures. These have a more specialized application in roadway lighting. The high mast luminaire is ideal for use on interstate highways or large areas requiring maximum pole spacing. The teardrop fixture is used for a more 1930’s nostalgic look, providing a style of yesteryear while also being energy 5 efficient. Decorative fixtures are utilized for street lighting as well, however they are typically confined to downtown areas or housing subdivisions. A typical style of decorative light employed by utilities is the Acorn fixture. NESC Grounding Requirements The NESC provides rules on grounding of components as a means to safeguard any person from injury that could be caused by electrical potential. The rules on grounding can be found in Section 9, Grounding Methods for Electric Supply and Communication Facilities, of the NESC 2002 edition. There are two purposes for protective grounding; 1. Enhanced operation of system overcurrent protective devices 2. Minimize exposure of personnel to electrical potential In Rules 215C1 and 314B, the NESC requires that certain metal supporting structures, including lamp posts, be effectively grounded. It should be noted that these rules do not apply as long as the voltage is less than 300 volts. However, when the voltage does exceed 300 volts, to comply with this performance requirement, it is necessary to understand the definition of “effectively grounded.” In Section 2 of the NESC, the definition of effectively grounded is given as “intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to limit the buildup of voltages to levels below that which may result in undue hazard to persons or to connected equipment.” Use of System Neutral to Effectively Ground Street Light Poles and Mast Arms During normal operation, the current flow in the neutral will cause a voltage drop and therefore a potential difference may appear at the metal pole. This voltage rise will be less than 4 volts and not perceptible to humans. The grounded circuit conductor (neutral) is used to ground a metal street light pole or mast arm. If a short occurs between the hot leg and the metal pole there are two paths for the fault current back to its source. One path is through the system neutral conductor. The other path is through the individual’s hand, out his feet, and through the earth. The current division is based on the ratio of resistances of the two paths. The path to ground may not always involve contact through an individuals hand and out his foot. If the system neutral impedance, from the pole back to the source, is much less than the resistance of the body and the ground resistance at the person’s feet or other contact point, then the pole would be effectively grounded. NESC Rule 350F alludes to bonding all above ground metallic equipment that is separated by less than 6 feet. Bonding these objects reduces the potential difference for metal-to-metal touch potential. Refer to this section and Appendix C for a more detailed discussion of touch potential. 6 Street Lighting Utilization Voltages Electrical energy losses are reduced at higher voltages, however, past 300 volts, rules from the National Electrical Safety Code (NESC) begin to apply. In order to operate efficiently, one must strike the proper balance of voltage levels, acceptable electrical losses, and the amount of regulation you must contend with. The Lighting Research Center of Rensselaer Polytechnic Institute (LRC) survey performed for this report shows a majority of utilities use a 120 volt street lighting system (62%) followed by a 240 volt street lighting system (28%). Street lighting system voltages of 480 volts (7%) and 277 volts (3%) are less frequently used. Most utilities distribution practices include stringing 120/240 volt service wire along the roadways to service customers. Rather than running a second set of wires, and using a different voltage, utilities will generally tap the existing 120/240 volt service wire for the street lighting instead. Another factor is the cost differential between the common 120/240 volt and 480 volt transformers. Another reason that 120/240 volt service is selected over 480 volt service is the increased likelihood of electrocution if a person comes in direct contact with the wire. Typical skin resistance permits a current flow of approximately 0.024 to 0.080 amperes if a person touches a 120 volt conductor. This may be enough to cause fibrillation given sufficient time. However, the current flow would be 0.096 to 0.320 amps if a person touches a 480 volt conductor, resulting in a much higher likelihood of fibrillation. One final consideration is the additional code compliance requirements. Those utilities governed by the NESC will need to comply with performance based rules 215C1 and 314B. These require that certain metal supporting structures, including lamp posts, must be effectively grounded. These rules apply only to street lighting systems greater than 300 volts. Utilities operating at 480 volts would thus be required to comply with these extra performance based rules. Based upon the survey results, common utility practices indicate the use of either a 120 or 240 volt service for street lighting as a best practice. Methods of Control of Street Lighting Circuits Photocells have and continue to be the most common method of street and floodlight control in the electric utility industry. Based on a survey conducted for this document by the LRC, photocells are utilized in 82% of lighting installations. Photocells can be used in conjunction with external relays to energize multiple lights at the same time, often called a master control. This is accomplished utilizing a circuit dedicated to street lighting. The line is energized only when the photocell actuates the relay. According to the survey, only 17% of respondents utilize this means of control. Utilities tend to use photocells more frequently (83% for Municipal Utilities and 87% for Investor Owned Utilities) than municipally owned street lighting (68%). The use of master controllers for street lighting is 7 mainly used by municipalities that own street lighting systems and accounts for a much smaller portion of the overall control of street lighting (17%). Operation and Maintenance Plan Nearly half of the survey respondents (48%) report that maintenance of streetlights is performed by dedicated streetlight crews. Contractors perform this function 26% of the time and 26% of the time it is performed by regular line crews. The use of high voltage linemen to perform streetlight maintenance was reported by 50% of respondents. However, municipalities that own streetlights are more likely to use low voltage line personnel. Group Relamping Group relamping is only used by 38% of the respondents. All survey respondents indicated that streetlight fixtures, poles and wiring are only replaced upon failure. Street Light Inventory Inventories of streetlights in use are conducted by 71% of the survey respondents either as part of any group relamping or conducted as separate inventories. Streetlight outage reporting is predominately provided by customers (55%) and by police and a dedicated person within the streetlight owning entity (21% each). Annual Maintenance Cost The annual maintenance cost per streetlight as reported in the survey varies greatly from a low of $10 to a high of $400. The most likely costs for entities not conducting group relamping is approximately $40. Street Light Poles As stated above, all survey respondents indicated they only replace streetlight poles upon failure. This practice is recommended. Inspection of any wood streetlight only poles should occur at the same inspection interval as wood overhead line poles. Dedicated Street Light Wiring The vast majority of survey respondents (79%) indicated they do not perform any streetlight wiring inspections. Streetlight wiring is only replaced upon failure according to all survey respondents. Replacement of only failed streetlight wiring is the recommendation set forth here, with a noted exception. Certain types of underground/direct buried electrical wires are known to deteriorate more rapidly than their original specifications. 8 Street Light Fixture Maintenance and Repair All survey respondents indicated they only replace streetlight fixtures upon failure of the fixture. It is believed this is a sound economic and safety policy. Therefore, it is recommended that streetlight fixtures only be replaced upon their failure. Low Capital Cost Street Light Fixtures (cobra heads) The recommended definition of failure for these fixtures is anything that fails beyond lamps, photocells and the glass globe. Replacing/repairing ballasts and other electrical components may cost (parts and labor) more than replacing a low cost fixture. High Capital Cost Street Light Fixtures (decorative post tops, etc.) All efforts should be made to repair the higher cost streetlight fixtures. Replacement of ballasts, lenses, glass, photocells, etc. will be less costly than replacing the entire fixture. Spot Relamping versus Group Relamping Spot Relamping is defined as fixing lighting lamps only when they are broken. This program is usually dependent on drive by inspections at night or consumer/police outage reports. Group Relamping is defined as replacing lamps on a periodic replacement schedule or “best time schedule”. A group relamping program is usually defined by area within a system and is largely influenced by the luminaire life curves provided by lamp manufacturers. A “best time schedule” is based on when the total cost of energy use, cost of installation, and relamping is at its minimum. Effectiveness less than 50% is a good indicator while 33% to 25% of lamp life remaining offers a good mix as well. The survey not withstanding, it is recommended that group relamping be pursued. All economic studies on this subject show potential savings by using group relamping. The Illuminating Engineering Society of North America (IESNA) design guide DG-4-03, Design Guide for Roadway Lighting Maintenance, illustrates an analysis of spot versus group relamping. A review of their assumed costs shows them to be reasonable. The use of the non-cycling, environmentally friendly HPS lamp will further improve the economics of group relamping because of the extended life of these lamps. The group relamping schedule can be stretched from four years to five years. Safety Inspection Checklist Developing a proper safety inspection checklist for street lighting maintenance is very important to maintain adequate safety levels and reliability. An excellent guideline for safety inspection is the California Public Utility Commission’s General Order #95, which outlines requirements for street and decorative lighting. 9 The following timetable for inspection is based upon the American Association of State Highways and Transportation Officials, An Information Guide for Roadway Lighting. The survey respondents averaged 6.67 years for inspections; Municipalities averaged every 5 years and Investor Owned Utilities averaged 7.5 years. The timetable is: • Electrical Connections • Fuses • Grounding • Security The following is a timetable for inspection: • Electrical Connections – Inspect when lamp is replaced • Fuses - Inspect when lamp is replaced • Grounding- Inspect when lamp is replaced • Security- Inspect when lamp is replaced Operations and Maintenance Checklist Developing a proper operations and maintenance inspection checklist for street lighting maintenance is very important to maintain adequate levels of reliability. The survey results and industry research found the most common items checked in an operation and maintenance plan. The following is a summary of checklist items: • Lighting Controls • Check/Replace Lamps • Clean Refractors • Check Luminaire Parts • Check Pole • Wiring • Voltage • Night Patrolling • Troubleshooting The following timetable for inspection is based upon the American Association of State Highways and Transportation Officials, An Information Guide for Roadway Lighting. The survey respondents averaged 6.67 years for inspections; Municipalities averaged every 5 years and Investor Owned Utilities averaged 7.5 years. The timetable is: • Lighting Controls – Inspect when lamp is replaced • Check/ Replace Lamps – Replace based on replacement schedule • Cleaning Refractors- Inspect when lamp is replaced • Check/ Replace Luminaire Parts- Inspect when lamp is replaced • Check/ Replace Pole- Inspect when lamp is replaced. Replace only when broken. 10 • • • • Wiring- Inspect when lamp is replaced. Replace only when broken. Voltage- Inspect when lamp is replaced Troubleshooting- On an as needed basis to determine problems Night Patrolling- On an as needed basis to determine problems Summary The Street Lighting Best Practices report compiles the most common utility applications of street lighting techniques in an effort to enlighten and inform. Every effort is made to explain the purpose of each section, helping others avoid common mistakes and pitfalls. Special attention is focused on touch potential, explaining the hazards associated with it and measures that can be taken to help avoid it. Electric shock and how it affects a person is addressed as part of the touch potential explanation. Another integral part of the report focuses on the need to protect life and property. The use of breakaway poles, to protect occupants of the vehicle from impact injury, and dead break wiring to prevent the ignition of a fire or the inadvertent electrocution of vehicle occupants is crucial with poles located in the clear zone. The proper pairing of light fixture to pole height is paramount in developing uniformity in lighting conditions. The more uniform the light, the more able the driver is to see obstructions or people on the roadside, possibly preventing a tragedy. When a well designed and maintained system is in place, an increase in safety, security and aesthetics is the result. 11 III. ILLUMINATION LEVELS A complete summary of the illumination guidelines for roadway lighting is provided at the end of this section. For major, collector, and local roadways, the recommended illumination levels in both the AASHTO “An Information Guide for Roadway Lighting” guide and in IESNA/ANSI RP-8-00 “American National Standard Practice for Roadway Lighting” are equivalent. However, this assumes that the three classifications that define the level of pedestrian conflict are equivalent. While the alley is defined in IESNA RP-8-00, illumination levels are not given for that roadway type, whereas they are given in the AASHTO guide. The AASHTO classifications are the same as those used by utilities and include residential, intermediate, and commercial. A study performed by the Kentucky Transportation Center includes the results of a survey of states and the guidelines that they use to light their roadways. This study found that the AASHTO and ANSI/IESNA RP-8-00 guides were used most often as guidelines to set illumination levels. It should be noted that both AASHTO and ANSI/IESNA documents include design recommendations to limit the veiling luminance (glare) from roadway lighting applications. In the tables included at the end of this section, recommendations for the veiling luminance ratio for each roadway type are given. Priorities for Street Lighting Safety is not the only consideration when city or municipality representatives are making street lighting decisions. Societal goals may include increasing safety and security, enhancing economic development, highlighting historic areas or landmarks, and sending messages. Pedestrian Conflict Areas For the determination of appropriate illumination levels, each type of roadway has associated pedestrian conflict classifications. Pedestrian conflict is related to the number of pedestrians that walk along the roadway of interest. The AASHTO guide and IESNA RP-8-00 both define these pedestrian conflict areas. AASHTO defines the level of pedestrian conflict using the terms residential, intermediate, and commercial. IESNA/ANSI RP-8-00 uses the terms Low, Medium, and High. These pedestrian conflict classifications are loosely synonymous. However, in IESNA/ANSI RP-8-00, guidelines are provided to relate the number of pedestrians walking on the street within a given time frame to a pedestrian conflict classification. For example, they suggest that for a roadway with over 100 pedestrians walking on a street within the hours of 18:00 to 19:00, the pedestrian conflict is high. Safety While headlights on cars provide forward lighting for the driver, street lighting illuminates the roadway showing the driver changes in direction up ahead, obstacles in the way, and the roadway surface conditions. Street lighting lights more than just the road; walkways and adjacent areas to the road also benefit. Pedestrians, cyclists, children playing in the front yard, and other non-motorists are more readily seen with street lighting. In their recommended practices, the IESNA (1999 and 2000) has recommendations for lighting that illuminates 12 intersections allowing oncoming drivers to see other vehicles, as well as pedestrians and cyclists. Street lighting helps to mitigate headlight glare as well. Security While there is controversy about whether electric lighting improves security (Painter, 2001, Boyce 1990, Tien 1979), there is no question that one feels safer walking or driving on well-lit streets and in well-lit parking lots. Boyce (1990) found that an illuminance of 1-3 footcandles provides the appearance of good security. Security may be thought of as freedom from worry in regard to the security of people and property. The purpose of security lighting is to deter the intruder, aid law-abiding citizens in recognizing danger, and to help law enforcement in the identification process after a crime has occurred. An intruder may be deterred if the criminal is easily seen at a distance allowing the victim time to prepare. Brightness of the neighborhood, uniformity of the brightness of the area, and whether there is lighting outside of the area lit by security lighting are three factors that influence deterrence. In order for security lighting to be effective, minimum light levels that achieve the objectives of brightness and uniformity must be met (Boyce 2000, Rombauts 1989, Boyce 1990). Design of Roadway Lighting Once the decision to light has been made, selecting an appropriate lighting fixture is in order. A number of factors must be considered in the design of a lighting installation. These factors include fixture style, height, placement, lamp type, brightness, color, life, and cost. Many of these factors and a list of manufacturers that offer roadway luminaires is available in Specifier Reports: Parking Lot and Area Luminaires (McColgan et al. 2004). Efficient Technologies There is no single best technology for street lighting, but there are relative benefits and drawbacks of different types of lamps and luminaires. Mercury vapor lamps are found in many older street lighting installations but these lamps are relatively inefficient and should not be used in any new or retrofit installations. Almost all lamps used in street lighting require a ballast to provide the proper voltage and current to the lamp; these will also use some energy and impact the overall energy use. Finally, even the most efficient lamp and ballast can be made very inefficient by using luminaires that trap light inside. A luminaire that emits less than half of the light generated by the lamp and ballast should be avoided. Appropriate Pole Heights In different locations, different pole heights can be appropriate for the desired appearance and required lighting. The "cobra head" type of luminaire seen on many streets and roadways is often found on approximately 30 foot poles. Architectural or decorative types of luminaires might have a scale that requires shorter pole heights. At the same time, the use of high-wattage, very efficient light sources on lower poles could possibly lead to unwanted glare. These factors must be balanced. When existing utility poles are used, careful attention to luminaire selection is important so that it is suitable for the pole heights. 13 Appropriate Pole Spacing The height of street lighting poles will impact how uniform the light levels are in the street and surrounding area. At times, visibility can be reduced if lighter and darker areas have large differences in light level. A well designed lighting installation will have sufficient uniformity. This issue can be especially important in a retrofit installation where existing pole mounting locations are going to be used with no additional pole mountings, or, as described above, when existing utility poles are to be used. Changes in luminaire type and pole height can also impact the uniformity. Consequences of Roadway Lighting The purpose of roadway lighting is to provide visibility to drivers at night. Increasing safety and reducing the number of automobile crashes are typical goals when roadway lighting is being considered. While the driving public demands roadway lighting, there are also negative aspects to roadway lighting. Light pollution is an unwanted consequence of roadway lighting and includes such effects as sky glow, light trespass, and glare. Sky glow is the brightening of the sky due to outdoor lighting and is usually objected to because it inhibits one’s ability to see and appreciate the stars. Light trespass is light falling where it is not wanted or needed. Light from a streetlight or a neighbor’s floodlight that illuminates your bedroom at night is an example. Glare is excessive brightness causing discomfort or visual disability. Two examples that may result in discomfort or disability glare include an unshielded luminaire where the lamp can be directly seen or a misaimed vehicle headlight. Concerns about light pollution and light trespass are growing. Many states and localities are adopting lighting ordinances to limit the quantity of light used, the type of lighting fixtures used, and the amount of light allowed onto adjacent properties. The IESNA (2000) has developed a classification system for the distribution of light from outdoor lighting luminaires. The cutoff classification system limits the amount of light emitted directly above the horizontal and, in addition, limits the amount of light emitted between 80º and 90º from nadir. Angles referenced by the IESNA cutoff classifications are illustrated in Figure 1. 14 Figure 1 Angles referenced by the IESNA Cutoff Classifications The two most stringent classifications are cutoff and full cutoff luminaires. Full cutoff luminaires emit no light upward and tend to emit very little at angles near horizontal. Cutoff luminaires may emit some light upward and also tend to emit little light near horizontal. The semi cutoff classification is the least stringent and usually permits more light upward and at angles near the horizontal. However, it is possible for a semi cutoff luminaire to generate no upward light, if it exceeds certain limits for light near horizontal angles. This could lead to increased glare but might be suitable for environments when vertical illumination is desired for recognition of people or other vertically oriented objects. Light trespass may be minimized by adding shields to luminaires to block light into unwanted locations. A limit on light trespass is sometimes specified as a maximum vertical illuminance on a window (ILE, 2000) or as the illuminance at the eye in a plane perpendicular to the line of site (IESNA 1999). Environmental zones are also used to limit light trespass and uplight (IESNA 1999, CIE 1997). Environmental zones allow for different lighting requirements for different levels of population and desire for darkness. Recommendations Pedestrian Conflict Areas The pedestrian conflict areas of residential, intermediate, and commercial are consistent with the definitions provided by AASHTO. These pedestrian conflict area definitions are used by many states to define their roadways. This terminology is loosely synonymous with the terminology used by IESNA. Consider the IES recommendation of monitoring the pedestrian traffic on roadways that obviously fit into these pedestrian classifications. Associate the pedestrian traffic value to each pedestrian conflict area to simplify the determination of future roads. Illumination Levels and Roadway Classifications The roadway classifications alley, local, collector, and major are consistent with the definitions provided by AASHTO. These roadway classifications are used by many states to define their roadways. This terminology is synonymous with the terminology used by IESNA. 15 Select illumination levels provided by AASHTO “Information Guide for Roadway Lighting”. These illumination levels are the same as those in ANSI/IESNA RP-8-00. A majority of states around the country also use these two documents as guidelines for illumination levels. The current terminology used by some utilities matches the terminology used in the AASHTO document. Design of Roadway Lighting Develop a street lighting design process that includes selecting appropriate luminaires, using efficient lamp and ballast technologies, and selecting appropriate pole heights and spacing to meet the desired lighting objectives. Consequences of Roadway Lighting When designing roadway lighting, minimize light pollution by: • Using the minimum light levels to meet the lighting objectives. • Using cutoff and full cutoff fixtures to minimize glare and uplight. • Considering the negative impact of the lighting on adjacent properties. AASHTO’S GUIDELINES FOR “AVERAGE MAINTAINED ILLUMINANCE” Average Maintained Horizontal Illuminance * for Roadways Other Than Freeways, Walkways and Bicycle Lanes R1 Roadway and Walkway Classification Footcandles Average Illuminance Pavement Classification R2&R3 R4 FootFootUniformity Lux candles Lux candles Lux avg/min Expressway**¹ Commercial Intermediate Residential 0.9 0.7 0.6 10 8 6 1.3 1.1 0.8 14 12 9 1.2 0.9 0.7 13 10 8 3:1 Major¹ Commercial Intermediate Residential 1.1 0.8 0.6 12 9 6 1.6 1.2 0.8 17 13 9 1.4 1 0.7 15 11 8 3:1 Collector¹ Commercial Intermediate Residential 0.7 0.6 0.4 8 6 4 1.1 0.8 0.6 12 9 6 0.9 0.7 0.5 10 8 5 4:1 Local¹ Commercial Intermediate Residential 0.6 0.5 0.3 6 5 3 0.8 0.7 0.4 9 7 4 0.7 0.6 0.4 8 6 4 6:1 Commercial 0.4 4 0.6 6 0.5 5 16 R1 Roadway and Walkway Classification Alleys Sidewalks Footcandles Average Illuminance Pavement Classification R2&R3 R4 FootFootUniformity Lux candles Lux candles Lux avg/min Intermediate Residential 0.3 0.2 3 2 0.4 0.3 4 3 0.4 0.3 4 3 6:1 Commercial Intermediate Residential 0.9 0.6 0.3 10 6 3 1.3 0.8 0.4 14 9 4 1.2 0.7 0.4 13 8 4 3:1 4:1 6:1 1.4 15 2 22 1.8 19 3:1 Pedestrian Ways and Bicycle Lanes² *Average illuminance on the traveled way or on the pavement area between curb lines of curbed roadways. **Both mainline and ramps. Expressways with full control of access are covered in the section on Freeways. ¹This assumes a separate facility. Facilities adjacent to a vehicular road should use the illuminance or luminance levels for the roadway. ² Adapted from “American National Standard Practice for Roadway Lighting,” ANSI/IESNA RP-8, 1983: Illuminating Engineering Society of North America. Used by Permission. AASHTO’S GUIDELINES FOR “AVERAGE MAINTAINED LUMINANCE” Average Maintained Luminance Design Values for Roadways Other than Freeways Luminance Veiling Luminance Uniformity Ratio foot(cd/m²) lamberts Lavg/Lmin Lmax/Lmin Lv (max)/Lavg 1.0 0.29 3:1 5:1 0.8 0.23 3:1 5:1 0.3:1 0.6 0.17 3.5:1 6:1 Lavg Roadway Classification Expressway* Commercial Intermediate Residential Major* Commercial Intermediate Residential 1.2 0.9 0.6 0.35 0.26 0.17 3:1 3:1 3.5:1 5:1 5:1 6:1 Commercial 0.8 0.23 3:1 5:1 17 0.3:1 Veiling Luminance Luminance Uniformity Ratio footL (cd/m²) lamberts Lavg/Lmin Lmax/Lmin v (max)/Lavg 0.6 0.17 3.5:1 6:1 0.4:1 0.4 0.12 4:1 8:1 Lavg Roadway Classification Collector* Intermediate Residential Local* Commercial Intermediate Residential 0.6 0.5 0.3 0.17 0.15 0.09 6:1 6:1 6:1 10:1 10:1 10:1 0.4:1 Alleys Commercial Intermediate Residential 0.4 0.3 0.2 0.12 0.09 0.06 6:1 6:1 6:1 10:1 10:1 10:1 0.4:1 *Adapted form “American National Standard Practice for Roadway Lighting,” ANSI/IES RP-8, 1983: Illuminating Engineering Society of North America. Used by permission. ANSI/IESNA’S GUIDELINES FOR “AVERAGE MAINTAINED ILLUMINANCE” Illuminance Method – Recommended Values (RP-8) Road and Pedestrian Conflict Area Pavement Classification Road Pedestrian R1 R2&R3 R4 Conflict Area lux/fc lux/fc lux/fc Freeway Class A 6.0/0.6 9.0/0.9 8.0/0.8 Freeway Class B 4.0/0.4 6.0/0.6 5.0/0.5 High 10.0/1.0 14.0/1.4 13.0/1.3 Expressway Medium 8.0/0.8 12.0/1.2 10.0/1.0 Low 6.0/0.6 9.0/0.9 8.0/0.8 High 12.0/1.2 17.0/1.7 15.0/1.5 Major Medium 9.0/0.9 13.0/1.3 11.0/1.1 Low 6.0/0.6 9.0/0.9 8.0/0.8 High 8.0/0.8 12.0/1.2 10.0/1.0 Collector Medium 6.0/0.6 9.0/0.9 8.0/0.8 Low 4.0/0.4 6.0/0.6 5.0/0.5 High 6.0/0.6 9.0/0.9 8.0/0.8 Local Medium 5.0/0.5 7.0/0.7 6.0/0.6 Low 3.0/0.3 4.0/0.4 4.0/0.4 18 Uniformity Ratio Eavg/Emin 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 4.0 4.0 4.0 6.0 6.0 6.0 Road and Pedestrian Conflict Area Road Pedestrian Conflict Area Freeway Class A N/A Freeway Class B N/A High Expressway Medium Low High Major Medium Low High Collector Medium Low High Local Medium Low Average Luminance Uniformity Ratio Uniformity Ratio Lavg (cd/m²) 0.6 0.4 1.0 0.8 0.6 1.2 0.9 0.6 0.8 0.6 0.4 0.6 0.5 0.3 Lavg/Lmin (maximum Allowed) Lmax/Lmin (maximum Allowed) (maximum Allowed) 3.5 3.5 3.0 3.0 3.5 3.0 3.0 3.5 3.0 3.5 4.0 6.0 6.0 6.0 6.0 6.0 5.0 5.0 6.0 5.0 5.0 6.0 5.0 6.0 8.0 10.0 10.0 10.0 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.4 0.4 0.4 0.4 0.4 0.4 Veiling Luminance Ratio Lvmax/Lavg NCHRP’S GUIDELINES FOR “AVERAGE MAINTAINED ILLUMINANCE” NCHRP Report 152 “Warrants for Highway Lighting” Recommendations for Average Maintained Horizontal Illumination Roadway Class Foot-candles Lux Freeways, including major 0.6 6.0 interchanges Primary arterials, 1.0 11.0 expressways, major highways 0.6 6.0 Secondary arterials, major collectors, secondary highways Minor collectors, minor 0.4 4.0 commercial roads Local roads, streets, alleys 0.2 2.0 19 AASHTO’S Classification of Roadways, Walkways, and Areas Roadway and Walkway Classifications (a) Freeway. A divided major highway with full control of access and with on crossing s at grade. (b) Expressway. A divided major arterial highway for through traffic with full or partial control of access and generally with interchanges at major crossroads. Expressways for non-commercial traffic within parks and park like areas are generally known s parkways. (c) Major. The part of the roadway system that serves as the principal network for through traffic flow. The routes connect areas of principal traffic generation important rural highways entering the city. (d) Collector. The distributor and collector roadways serving traffic between major and local roadways. These are roadways used mainly for traffic movements within residential, commercial and industrial areas. (e) Local. Roadways used primarily for direct access to residential, commercial, industrial, or other abutting property. They do not include roadways carrying through traffic. Ling local roadways will generally be divided into short sections by collector roadway systems. (f) Alleys. A narrow public way within a block, generally used for vehicular access to the rear of abutting property. (g) Sidewalks. Paved or otherwise improved areas for pedestrian use, located within public street rights of way which also contain roadways for vehicular traffic. (h) Pedestrian ways. Public sidewalks for pedestrian traffic generally not within rights of way for vehicular traffic roadways. Included are skywalks (pedestrian overpasses), subwalks (pedestrian tunnels), walkways giving access to park or block interiors and crossing near centers of long blocks. (i) Bicycle Lanes. Any facility that explicitly provides for bicycle travel. Area Classifications (a) Commercial. That portion of a municipality in a business development where ordinarily there are large numbers of pedestrians and a heavy demand for parking space during periods of peak traffic or a sustained high pedestrian volume and a continuously heavy demand for off-street parking space during business hours. This definition applies to densely developed business areas outside of, as well as those that are within, the central part of a municipality. (b) Intermediate. That portion of a municipality which is outside of a downtown area but generally within the zone of influence of a business or industrial development, often characterized by a moderately heavy nighttime pedestrian traffic and a somewhat lower parking turnover than is found in a commercial area. This definition includes densely developed apartment areas, hospitals, public libraries, and neighborhood recreational centers. (c) Residential. A residential development or a mixture of residential and commercial establishments, characterized by few pedestrians and a low parking demand or turnover at night. This definition includes areas with single family homes, townhouses, and/or small apartments. Regional parks, cemeteries, and vacant lands are also included. 20 ANSI/IESNA’S Roadway, Pedestrian Walkway, and Bikeway Classifications a) Freeway. A divided major roadway with full control of access (no crossings at grade). This definition applies to toll as well as non-toll roads. i. Freeway A. Roadways with greater visual complexity and high traffic volumes. Usually this type of freeway will be found in major metropolitan areas in or near the central core and will operate through some of the early evening hours of darkness at or near design capacity. ii. Freeway B. All other divided roadways with full control of access. b) Expressway. A divided major roadway for through traffic, with partial control of access and generally with interchanges at major crossroads. Expressways for noncommercial traffic within parks and park-like areas are generally known as parkways. c) Major. That part of the roadways system that serves as the principal network for throughtraffic flow. The routes connect areas of principal traffic generation and important rural roadways leaving the city. These routes are often known as “arterials,” “thoroughfares,” of “preferentials.” They are sometimes subdivided into primary and secondary; however, such distinctions are not necessary in roadway lighting. d) Collector: Roadways servicing traffic between major and local streets. These are streets used mainly for traffic movements within residential, commercial and industrial areas. They do not handle long, through trips. Collector streets may be used for truck or bus movements and give direct service to abutting properties. e) Local: Local streets are used primarily for direct access to residential, commercial, industrial, or other abutting property. They make up a large percentage of the total street system, but carry a small proportion of vehicular traffic. f) Alley: narrow public ways within a block, generally used for vehicular access to the rear of abutting properties. g) Sidewalk: Paved or otherwise improved areas for pedestrian use, located within public street rights-of-way, which also contain roadways for vehicular traffic. h) Pedestrian Walkway: A public walk for pedestrian traffic, not necessarily within the right-of-way for a vehicular traffic roadway. Included are skywalks (pedestrian overpasses), subways (pedestrian tunnels), walkways giving access through parks or block interiors, and mid-block street crossings. i) Isolated Intersection: The general area where two or more non-continuously lighted roadways join or cross at the same level. This are includes the roadway and roadside facilities for traffic movement in that area. A special type is the channelized intersection, in which traffic is directed into definite paths by islands with raised curbing, 21 j) Isolated Traffic Conflict Area: A traffic conflict area is an area on a road system where an increased potential exists for collisions between vehicles, vehicles and pedestrians, and vehicles and fixed objects. Examples include intersections, crosswalks and merge areas. When this area occurs on a roadway without a fixed lighting system (or separated from one by 20 seconds or more of driving time), it is considered an isolated traffic conflict area. k) Bikeway: Any road, street, path, or way that is specifically designated as being open to bicycle travel, regardless of whether such facilities are designated for the exclusive use of bicycle or are to be shared with other transportation modes. Five basic types of facilities are used to accommodate bicyclists: l) Shared lane: shared motor vehicle/bicycle use if a “standard”-width travel lane. m) Wide outside lane: an outside travel lane with a width of at least 4.2 m (13.8ft.). n) Bike lane: a portion of the roadway designated by stripping, signing, and/or pavement markings for preferential or exclusive use of bicycles. o) Shoulder: a paved portion of the roadway to the right of the edge stripe designed to serve bicyclists. p) Separate bike path: a facility physically separated from the roadway and intended for bicycle use. (See IESNA DG-5-94, Lighting for Walkways and Class 1 Bikeways for requirements in these areas.) q) Median: The portion of a divided roadway physically separating the traveled ways for traffic in opposite directions. Pedestrian Conflict Area Classifications The major, collector and local street classifications appropriately describe general conditions of vehicular traffic conflict, which is responsible for a disproportionate number of nighttime fatalities, is the vehicle/pedestrian interaction. The magnitude of pedestrian flow is nearly always related to the abutting land use. Three classifications of pedestrian night activity levels and the types of land use with which they are typically associated are given below: High – Areas with significant numbers of pedestrians expected to be on the sidewalks or crossing the streets during darkness. Examples are downtown retail areas, near theaters, concert halls, stadiums, and transit terminals. Medium – Areas where lesser numbers of pedestrians utilize the streets at night. Typical are downtown office areas, blocks with libraries, apartments, neighborhood shopping, industrial, older city areas, and streets with transit lines. 22 Low – Areas with very low volumes of night pedestrian usage. These can occur in any of the cited roadway classifications but may be typified by suburban single family streets, very low density residential developments, and rural or semi-rural areas. The choice of the appropriate lighting level for a street is engineering decision. If needed, one hour pedestrian counts can be taken during the average annual first hour of darkness (typically 18:00 to 19:00hours). A section of typical land use can be sampled by counting one or two representative blocks, or a single block of unusual characteristics can be counted, perhaps at a different hour, such as discharge from a major event. The volume of pedestrian activity during the hour of count that warrants increased lighting levels is not fixed and represents a local option. Guidelines for possible local consideration are: Low – 10 or fewer Medium – 11 to 100 High – over 100 These volumes represent the total number of pedestrians walking on both sides of the street plus those crossing the street at non-intersection locations in a typical block or 200 meter (656 ft.) section. 23 IV. PROPER CODE SELECTION AND IMPLEMENTATION Outdoor lights used to illuminate streets must be designed in compliance with the applicable safety codes. The initial task is determining which code is appropriate for the individual street lighting system. The selection of the appropriate code should be determined based on the type of personnel who are operating the system. There are two primary codes used in the United States; the National Electrical Code (NEC) and the National Electrical Safety Code (NESC). However, California uses its own code for utilities, California Public Utilities Commission General Order 95 and General Order 128. These General Orders apply to those utilities under the jurisdiction of the Public Utilities Commission, State of California. The NEC is developed and maintained by the National Fire Protection Association with updates every two years. This code can generically be described as applying to public and private premises and the associated common areas (refer to Article 90.2(A)(2)). The NESC is maintained by a committee of the Institute of Electrical and Electronics Engineers, Inc. (IEEE) and is approved by the American National Standards Institute (ANSI). This code is updated every 4 to 5 years with the next revision scheduled for 2007. This code generally applies to electric and communication utilities (refer to Section 1 Rule 011.A). The transition point from the NESC to NEC is referred to as the “service point” (refer to Section 1 Rule 011.B). The major distinction between the two codes is the style of the codes. The NESC is a performance-based code while the NEC is a prescriptive-based code. A performance base code provides rules for how a system should perform, but does not provide details on how to achieve this performance. An example is the NESC requires 12 kV conductors be 18.5 feet above ground, but it does not say how this is to be achieved. The designer can use short poles with short spans or tall poles and long spans but when the design is complete, it must provide 18.5 feet of clearance above ground. The NEC, however, is a prescriptive-based code. This code does not list performance criteria; rather the code says exactly how a system is to be designed. This achieves the safety objectives contained in Article 90.1(A). An example is the very specific rules in sizing of protective devices to achieve the safety objective of preventing overloaded system components. One reason for a prescriptive-based code is that many jurisdictions have no inspections and others have inspectors with no specialized electrical training. Another reason for a prescriptive-based code is it does not require an advanced engineering degree to design a system. Rather, the designer need only adhere to all of the NEC requirements. This difference in the style of the codes leads to confusion when comparing design options for street lighting systems. The NESC method leaves the design decisions to the engineer who is responsible for complying with the performance standards. Whereas the NEC provides explicit rules for the design, which if followed, achieve the NEC’s safety objectives. 24 This difference will be more apparent as the issue of grounding options is explored in more depth. Which Code Applies to Municipal Street Lights? The NEC and NESC have been developed by separate organizations which have lead to conflicting codes. In the last few updates of both codes, an effort has been made to coordinate the requirements of the codes. Included in this coordination is the definition of the scope of the codes. Article 90.2(B)(5) states the NEC does not cover “installations under the exclusive control of an electric utility where such installations are located in legally established easements, rights-ofway, or by agreement.” A complimentary set of rules is found in the NESC: These rules are used to determine which code would apply to municipal street lights. It may be necessary to expand on certain definitions to help identify the proper code. First, the NESC defines a qualified person as an individual “having been trained in and having demonstrated adequate knowledge of the installation, construction, or operation of lines and equipment and the hazards involved, including identification of and exposure to electric supply lines and equipment in or near the workplace” (refer to Part 1 Section 2, definitions, of the NESC). Typically, this individual is thought of as a high voltage lineman or a first class lineman but when applied exclusively to street lighting systems, which operate below 600 volts, it is appropriate to use individuals trained only in these lower voltages. The next definition to be considered is service point. This point is defined in both the NEC and NESC as “the point of connection between the facilities of the serving utility and the premises wiring”. (NEC Article 100, Definitions and NESC Section 2, Definitions). The point of demarcation is generally defined by the serving utility who indicates where utility’s responsibility ends. This point is not necessarily determined by who installed the conduit or conductors but rather by which party has responsibility for operations, maintenance, and replacement. 25 Another important definition to be considered is “utility” as used within the context of the NESC. The NESC defines utility to mean “an organization responsible for the installation, operation, or maintenance of electric supply or communications systems” (Part1 Section 2, Definitions). Within this definition, a municipal water utility is not considered a utility by the NESC. The following case studies will help us apply the proper code, as defined above, to a given situation. These cases are meant as a guide to help determine which codes govern the installation. Case Studies for Proper Application of Electrical Codes Municipal Electric Utility Provides Street Lighting When a municipality operates an electric utility and installs street lighting, the appropriate code is the NESC. It must be recognized that the street lighting systems be in the exclusive control of the electric utility. This means access to street light control boxes must be limited, in addition to convenience outlets, which are often times included on street light poles. If the public can access and use these outlets, the outlets are not in the exclusive control of the utility. In this instance, the outlets must conform to the requirements of the NEC which would require ground-fault circuit-interrupters on these outdoor outlets (refer to NEC article 210.8) and a separate grounding conductor. If, however, the convenience outlets are located high enough on the pole to limit public access, the NESC would be the appropriate code (refer to NESC Rule 232B for appropriate height requirements). The NESC provides no direction or rules regarding outlets, but, the NEC is an excellent resource to determine appropriate measures to meet the general performance requirements of the NESC as defined in Rule 011. Electric Utility Provides Street Lighting When an electric utility provides street lighting as a service to the municipality, the lights will be governed by the NESC if the streetlights are in exclusive control of the utility. The use of convenience outlets on these poles are commonly used for decorative displays for Christmas and other holidays. The use of these outlets should be limited to the electric utility or to individuals deemed qualified by the electric Qualified Person: Having been trained in and utility. The NESC allows qualified having demonstrated adequate knowledge of the installation, construction, or operation of contractors to work on the electric lines and equipment and the hazards involved, utility’s system (NESC Section 1 including identification of and exposure to Rule 011.C). Thus the electric electric supply lines and equipment in or near utility should be aware that the workplace providing permission to the (NESC Part 1 Section 2, Definitions) municipality’s personnel to access these convenience outlets implies that the utility believes the municipality is utilizing 26 “qualified” persons. Alternately, the convenience outlets must be designed to meet the requirements of the NEC if the utility does not recognize the municipal worker as a qualified person. Municipal Without an Electric Utility Installs Street Lights In this scenario, a municipality receives power from an electric utility at utilization voltage, then installs and maintains lights along its streets. For the NESC to be the applicable code, the municipal must fit the definition of a utility. It may be difficult to define that portion of the municipality that operates and maintains the street lights as a utility. Often they are personnel who work for other municipal departments such as water or parks and recreation. In most cases, if the municipality is not providing retail electric service, the municipality should comply with the NEC. Under this scenario, convenience outlets on the poles would also need to comply with the NEC. These individuals must be trained as required by OSHA Subpart S of the General Industry Standards to work on the electrical components of a street light system. It should be noted that many municipal utilities are not required to comply with OSHA requirements. Municipal Electric Utility Provides Street Lighting Outside of Their Service Territory Some states have very distinct service territory lines between municipal electric systems and other electric utilities. In these cases, as city limits expand, the service territory does not expand. However, the city may want to provide street lighting on city streets outside of their franchised service territory. In this case, the Municipal Electric Utility is receiving power at utilization voltage from another electric utility and installing a street lighting system. Because the Municipal Electric Utility fits the NESC’s definition of a utility and assuming the Municipal Electric Utility is using qualified personnel, the appropriate code for the street lighting system would be the NESC. This would even be true if there is a meter at the point of service (which is not always the case). Just because the Municipal Electric Utility receives energy at utilization voltage does not require the street lighting system to comply with the NEC. Article 90.2(B)(5)(a) defines those systems exempt from the NEC in the exclusive control of electric utilities that are located in legally established easements, or rights-of-way. Any convenience plugs will be governed by the NESC if the plugs are under the exclusive control of the utility (i.e. not accessible to the general public). OSHA Requirements OSHA requires that person be trained in and familiar with the safety related work practices, safety procedures, and other safety requirements that pertain to their respective job assignments. OSHA standards in Subpart S of the General Industry Standards address electrical utilization systems, i.e., installations of electric conductors and equipment which use electric energy for mechanical, chemical, heating, lighting, or similar purposes. Subpart S protects most employees from the hazards associated with electric utilization equipment and with premises wiring. However, subpart S does not contain requirements protecting employees from the hazards arising 27 out of the operation or maintenance of electric power transmission or distribution systems. Thus subpart S would apply to electricians working on premises wiring which would include area lightning. Further, subpart S relates more to the electrical systems covered by the NEC since the hazards are associated with utilization equipment. OSHA along with the electric power industry and the International Brotherhood of Electrical Workers (IBEW) developed 29 CFR 1910.269 which focuses on the operation and maintenance of electric power transmission and distribution systems. 29 CFR 1926 Subpart V provides rules for the construction of these systems. A qualified person shall be trained and competent in all aspects of 29 CFR 1910.269(a)(2)(ii) through (vii). OSHA also states only qualified persons may work on or with exposed energized lines or parts of equipment operating at 50 volts or more (OSHA 1910.269(l)(1)). OSHA defines a qualified person as one knowledgeable in the construction and operation of the electric power generation, transmission, and distribution equipment involved, along with the associated hazards. These work rules provide requirements for training when working with electrical systems but do not directly address street lighting issues such as grounding practices. OSHA 1910.269(l)(9) requires workers to treat non-current carrying metal parts as energized at the highest voltage to which they are exposed unless the employer determines that these parts are grounded before work begins. This rule can be important in the grounding methods used for metal poles and fixtures. Some utilities provide a separate grounding conductor at the base of a street light mast arm. This visible ground would provide confirmation of grounding. Other utilities rely simply on the bonding of the neutral conductor inside the fixture for grounding of the mast arm. This method would require the arm be treated as if it were energized with the voltage inside the light fixture. Grounding of the base a metal pole or standard can be accomplished is many difference ways. The method used can affect the work rules on how the pole will be inspected. Department of Transportation Each state adopts its own requirements with regards to safety within the rights-of-way of their state and county roads. These requirements are typically based on the recommendation contained in the following documents; “An Information Guide for Roadway Lighting, American Association of State Highway and Transportation Officials (AASHTO) “Report 152 – Warrants for Highway Lighting, National Cooperative Highway Research Program (NCHRP) “American National Standard Practice for Roadway Lighting (ANSI/IESNA RP8-00), Illuminating Engineering Society of North America in ANSI Practice for Roadway Lighting ANSI RP-8) The AASHTO standards, with regards to street lighting, focus mostly on the need to clear space adjacent to the traveled edge of the roadway. There is a greater probability of a vehicle contacting a pole when the pole is close to the traveled edge of a roadway. The AASHTO 28 standards recognize that the speed of traffic is a component in determining this distance. The problem faced by transportation engineers is that the poles must be close to economically light the roadway. Without the lights the roadway is not as safe, but, with a pole near the edge of the roadway, the roadway is not as safe. Thus a balance must be found between these conflicting requirements. In general, all ground mounted luminaire supports exposed to traffic and located within the clear zone should be provided with breakaway or yielding bases, unless they are located with the protection of a barrier (An Informational Guide for Roadway Lighting AASHTO 1984). AASHTO Roadside Design Guide, 3-6 (2002) defines the clear zone based on vehicle speed, average daily traffic, and shoulder slopes. The AASHTO publication Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals, 2001 provide standards for breakaway poles. This document states that breakaway supports shall be designed to yield, fracture or separate when struck by an errant vehicle. Other sources of information on breakaway poles are Recommended Procedures for Safety Performance Evaluation of Highway Features and AASHTO’s Roadside Design Guide. AASTHO recommends that efforts should be made in all breakaway poles that house electrical components to effectively reduce fire and electrical hazards posed after structure impact. Upon knockdown, the support should electrically disconnect as close to the pole base as possible. Industry groups, such as the Illuminating Engineers Society of North America and AASHTO, provide recommendations for lighting levels on roadways, provide sample lighting design calculations, and set standards for fixtures and lens. However, they do not address the electrical service or grounding requirements of the poles or light fixtures. 29 V. WIRING AND CONSTRUCTION STANDARDS The purpose of construction standards is to provide drawings and specifications that apply to repetitive installations. This enables safety, reliability, operability, uniformity, appearance, and economy to be coordinated in the system’s construction practices. This holds true for every aspect of the transmission and distribution system, including street lighting. The task of developing a street lighting best practices document required the review of many electric system standards. The review of these standards ran the gamut from large investor owned utilities, greater than 1 million customers, to Municipal systems with 100,000 customers. The following will show the typical industry standard for each class of light found during our research. The use of flood lights by utilities was typically 400 watt or 1000 watt high pressure sodium fixtures. They were utilized when high intensity illumination of a specific non-roadway area was needed. They are most commonly used for leased security lighting installations, such as parking lots, business locations, apartment complexes, or transportation terminals. The most common utilization voltages seen are 120 or 240 volts. Care must be observed in aiming and spacing the floodlights. In order to maximize the useful light output, the floodlight should be aimed 2/3 of the distance across the area to be lighted. Another rule of thumb to maximize the useful output is to aim the light at a distance of 2 times the mounting height. Using the lower value of these two methods is recommended. Other factors to avoid are directing the light into the face of oncoming traffic as well as directing light trespass onto adjacent property. If tighter control of lighting is required, consideration should be given to a visor. The spacing of floodlights is important as well. Typical flood lights will give adequate lighting up to 45 degrees on either side of the aiming line. If greater coverage is required, the use of two flood lights should be considered. If two flood lights are utilized, overlapping is preferred to enhance light uniformity. Wiring is typically run from a terminal block inside the fixture, out through a mast or arm, and connected to an existing 120/240 volt line running along the pole line. The floodlight case is bonded to the arm by means of attachment, and the arm is typically grounded to the system neutral or ground wire lead. Street lighting is of extreme importance in protecting the public from crime, pedestrians from being struck, and motor vehicle accidents. These factors contribute to the need of uniform lighting of roadways, bicycle travel lanes, and intersections. Utilities have a wide choice of fixtures to accomplish these tasks. The fixtures utilized depend upon the task lighting requirements and aesthetics. Some utilities define the types of street lighting by assigning particular fixture wattage to categories of street lighting. One utility defines a 70 watt fixture as an alley light, a 100 watt fixture as a local light, a 150 watt fixture as a collector light, and a 250 watt fixture as a major light. However, this is not typically the norm. Most utilities consider anything 100 watts or below as a security light, and anything above as a street or area light. Within these categories, several fixture types exist. The most common fixture used for a roadway luminaire is a cobra head fixture. Typical sizes are 150 watt, 250 watt, and 400 watt. The mounting heights and types vary; typically one can expect to see the cobra head fixture mounted between 30 to 37 feet above the roadway. They may be mounted on wooden distribution, aluminum, or fiberglass poles. Most utilities purchase and maintain a stock of high pressure sodium vapor fixtures. Other utilities currently using mercury vapor fixtures are 30 planning to convert to the more efficient and cost effective high pressure sodium vapor fixture. These fixtures are typically available as drop prismatic refractor glass, flat glass, short semicutoff, medium semi- cutoff, medium cutoff, and full cutoff. A recent push by an organization to reduce light trespass into the night skies, Dark Skies, has seen the increased usage of medium and full cutoff units. As indicated in the survey, most are currently utilizing a fixture of this nature and the remaining utilities are heading in this direction. Other fixtures which are utilized, but not as prevalent, are high mast and teardrop fixtures. These have a more specialized application in roadway lighting. The high mast luminaire is ideal for use on interstate highways or large areas requiring maximum pole spacing. The teardrop fixture is used for a more 1930’s nostalgic look, providing a style of yesteryear while also being energy efficient. Decorative fixtures are utilized for street lighting as well, however they are typically confined to downtown areas or housing subdivisions. A typical style decorative light employed by utilities is the Acorn fixture. It compliments parks, downtown, and residential roadways as well as having excellent photometric capabilities and the lowest cost of most decorative fixtures. These are all reasons why it is popular with utilities. The security light, or alley and local light as referred to by some utilities, comes complete and ready for mounting in areas such as barnyards, service drives, storage facilities, and roadways with light traffic. These are normally rented to homeowners by the utility for lighting their yards and drives for safety and security considerations. These are often referred to as bug lights. Almost all of the utilities operate these fixtures at 120 or 240 volts. The standards for these typically address the height of the fixture on the pole, the grounding of brackets or metallic poles, clearances from primary lines, and protection details. In areas of high probability of vehicle to pole contact, some utilities opt for breakaway pole options. There are many wiring options available for street and security lighting. Street lighting can be accomplished utilizing existing wood distribution poles or aluminum poles dedicated to lighting. The distribution pole wiring is typically run from a terminal strip inside the cobra head fixture, through a mast or arm, and connected to a 120/240 volt line running along the pole line. The head is bonded to the arm which in turn is grounded to the system neutral or ground wire lead. In a case where an aluminum pole is utilized for support of the fixture, most utilities attach a ground conductor from the pole and bond to the neutral run with the feed wire or to a separate ground rod. The review process compared a variety of standards from many utilities to that of the City of Columbus, Ohio standards. It was found that the City of Columbus, Ohio standards were equal to or exceeded the standards of the other utilities reviewed. The major difference was the inclusion of specifications by the City of Columbus, Ohio for 480 volt lighting, which were not found in the other utilities standards which were reviewed. NESC Grounding Requirements Grounding is a means used to provide safety to electrical workers and any people that may come into contact with structures such as street light mast arms, metal poles and guy wires. The NESC provides rules on grounding of components as a means to safeguard any person from injury that could be caused by electrical potential. The rules on grounding can be found in Section 9, Grounding Methods for Electric Supply and Communication Facilities, of the NESC 2002 edition. There two purposes for protective grounding; 31 1. Enhanced operation of system overcurrent protective devices 2. Minimize exposure of personnel to electrical potential Clearing a fault quickly reduce the exposure of the person to the hazard. A low impedance path to the source is required for overcurrent protective devices, to distinguish between load current and fault current. In Rules 215C1 and 314B, the NESC requires that certain metal supporting structures, including lamp posts, be effectively grounded. It should be noted that these rules do not apply as long as the voltage is less than 300 volts. However, when the voltage does exceed 300 volts, to comply with this performance requirement it is necessary to understand the definition of “effectively grounded.” In Section 2 of the NESC, the definition of effectively grounded is given as “intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to limit the buildup of voltages to levels below that which may result in undue hazard to persons or to connected equipment”1. There are two parts to this requirement. 1) Adequate current-carrying capacity 2) Sufficiently low impedance to prevent the buildup of hazardous voltages Adequate current-carrying capacity refers to the conductor or conducting path used for grounding the structure. If a grounding conductor is to be used, it must meet the requirements of Rule 093. Simply stated the grounding conductor must have the ampacity of the phase conductor that would supply the ground fault current or the maximum current that can flow though the grounding conductor2. The grounding conductors are typically #8 AWG as a minimum. A #6 or #4 AWG are also commonly used. Table 250.66 of the NEC provides some guidance on the selection of grounding conductors for secondary circuits. Another method allowed by the NESC for selecting the ampacity of a single grounding conductor connected to an electrode (driven ground rod) is to divide the supply voltage by the resistance of the electrode. The metal structure of the street light pole is allowed to be a part of the grounding path3. Thus the grounding conductor can be attached at the base of the metal pole and does not need to run all the way up to the street light fixture. The other requirement is sufficiently low impedance to limit the buildup of voltages below levels which may be hazardous. There are three possible methods to achieve the low impedance requirement. One is to use the secondary circuit grounded conductor (the system neutral) to bond to the metal structure or case. The other is to bond to a made electrode. The third is a combination of the neutral and the made electrode. 1 Institute of Electrical and Electronic Engineers, Inc., Seventh Interim Collection of the National Electrical Safety Code Interpretations, 1996-1997. New York, 1997, page 7. 2 Institute of Electrical and Electronic Engineers, Inc., National Electrical Safety Code, 2002 Edition, 093C8. New York, 2002, page 20. 3 Institute of Electrical and Electronic Engineers, Inc., National Electrical Safety Code, 2002 Edition, 093A. New York, 2002, page 18. 32 Use of System Neutral to Effectively Ground Street Light Poles and Mast Arms The grounded circuit conductor (neutral) is used to ground a metal street light pole or mast arm. This would be very similar to the situation described in Electric Shock and The Human Being, Appendix C, Figure 7. During normal operation, the current flow in the neutral will cause a voltage drop and therefore a potential difference may appear at the metal pole. This voltage rise will be less than 4 volts and not perceptible to humans. Figure 2 shows touch potential concerns when the neutral conductor is used for ground.If there is a short between the hot leg and the metal pole, there are two paths for the fault current back to its source. One path is through the system neutral conductor. The other path is through the individual’s hand, out his feet and through the earth. The current division is based on the ratio of resistances of the two paths. Figure 2 Touch Potential Concerns The path to ground may not always involve contact through an individuals hand and out his foot. An incident occurred, resulting in a fatality, where a young boy contacted a street light pole and fabric fence with his back and chest. This was a result of the boy trying to squeeze by the pole and fence. The resistance with this type contact may be less than a hand entry and foot exit, especially if wearing rubber sole footgear. Another possible entry exit point is an individual’s back to his leg. This may occur if a person leans against a street light pole while sitting on a guardrail, a likely scenario for a person resting while changing a tire on a motor vehicle. Many contact and exit points exist having different resistance values. These need to be considered when determining if a pole is effectively grounded. Figure 3 shows touch potential concerns with a fabric fence within six feet of the utility pole. If the system neutral impedance, from the pole back to the source, is much less than the resistance of the body and the ground resistance at the person’s feet or other contact point, then the pole would be effectively grounded. During a system fault, the return current will travel in 33 the system neutral and will have a voltage drop resulting in a potential at the pole when referenced to remote earth or even to earth three feet away from the pole. Figure 3 Touch Potential Concerns Hand to Hand Contact In addition, unlike household wiring, there is normally no other grounded object within reach of a utility pole which is one of the reasons why NESC does not utilize a safety ground and the NEC does. However, NESC Rule 350F alludes to bonding all above ground metallic equipment that is separated by less than 6 feet. While bonding does reduce the potential difference for metal-to-metal touch potential, other issues may arise from this practice. Using Figure 4, Bonding of Streetlight Pole to a Fence, as an example, the illustration shows the bond creates an equipotential ground plane along the fence until the discontinuity of the fence at the gate. The gate on one side will be on the same ground plane as the street light; however, the other side may not be at the same potential, thus possibly creating a touch potential issue. Upon closer inspection, each fence post will act as a ground rod and provide an alternate path back to the source. Is the ground path sufficient enough to avert a touch potential incident? All variables cannot be accounted for to definitively say yes. If the ground resistance of the post, acting as a ground rod, is less than the resistance of the person coming into contact with the differing ground planes, then the person may have averted a possible touch potential incident. Now consider the following scenarios. A speed limit sign is six feet from a street light pole. The proximity of the sign to the pole lends itself to being able to be reached by the average adult person. In an effort to protect people, the speed limit sign is bonded to the pole to create an equipotential ground plane. Now, within six feet of the speed limit sign is a school zone sign, should the school zone sign be bonded to the speed limit sign? A difference in potential may exist because the ground plane was extended from the street light pole to the speed limit sign possibly increasing the occurrence of a touch potential situation. Consider further a bus stop sign six feet from the school zone sign? Should bonding of the object occur for the same reason as before? Where does this lead? Should bonding be performed at all? Should the gate have a jumper connection to provide continuity and be afforded the protection of bonding? How far should the daisy chain 34 continue? These are all valid questions, but one must look at what is trying to be accomplished by the bonding of the objects, which is, to effectively ground the equipment and reduce the occurrence of a touch potential incident. Each of these objects is another ground point, acting like a ground rod. When you parallel ground rods, you have an effect of lowering the resistance at each point. If the resistance, at the point of the ground, is less than the resistance of the person, the probable flow of objectionable current will be through the ground back to the source. As a possible means to improve site safety, bonding of objects within six feet of a streetlight pole, the average reach of an adult, will typically afford more protection for a touch potential incident than just a ground rod located locally would. One may consider the use of bonding as a prudent step in an attempt to protect the public. Figure 4 Bonding of Street Light Pole to a Fence The low impedance of the neutral will assure that the overcurrent protection will clear any faults. Also, the voltage rise relative to the earth will be a function of the fault current and the resistance of the neutral conductor or neutral network. If the item to be grounded is a metallic mast arm, the height of the mast arm provides space separation from the public. In this case, workers are required by Rule 441 to de-energize equipment operating above 300 volts, or use appropriate protective equipment such as gloves. For lower voltages, there is no requirement for protective equipment. In order to be hazardous to that employee, a short inside the lamp would have to occur while the worker was in contact with the arm and another grounded component. Using the system neutral as a grounding conductor on a metal street light pole is similar to Appendix C, Figure 7. This implies that all of the metal street light poles must have a sufficient grounding system to limit touch potential voltages to below a lethal level. However, as a performance based code, the NESC Rule 215C1 states that on overhead supplied “metal or metal-reinforced supporting structures, including lamps posts, metal conduits, hangers of equipment...and operating handles shall be effectively grounded.” There is an exception to this rule that exempts this grounding requirement for metal conduits, frames, and hangers if these components are not exposed to voltages over 300 volts. This exception does not apply to the metal supporting structure. Rule 314B requires that all underground cables supplying conductive lighting poles shall be effectively ground. Street Lighting Utilization Voltages One of the more important decisions to make in the street lighting design process is determining the voltage level at which you will operate your system. A lower operating voltage will result in a greater current and fewer lights operating on your circuit. The opposite is also true, a higher voltage will allow for a lower current and more lights on the circuit. Electrical energy losses are reduced at higher voltages, however, past 300 volts, rules from the National Electrical Safety Code (NESC) begin to apply. In order to operate efficiently, one must strike the proper balance 35 of voltage levels, acceptable electrical losses, and the amount of regulation you must contend with. The Lighting Research Center of Rensselaer Polytechnic Institute (LRC) survey, performed for this report, shows a majority of utilities utilize a 120 volt street lighting system (62%) followed by a 240 volt street lighting system (28%). Street lighting system voltages of 480 volts (7%) and 277 volts (3%) are less frequently used. Cooperative utilities are more likely to utilize the 120 volt street lighting system (70%) closely followed by investor owned utilities (65%). Municipalities owning and operating street lighting systems use 120 volt street lighting systems 59% of the time and municipal electric utilities 56%. The survey found municipal electric utilities utilize the 240 volt street lighting system more than other utilities, with 42% of the systems reporting this utilization voltage. Municipally owned systems account for 36% of the utilization of the 240 volt street lighting system and investor owned utilities account for 22%, Cooperative utilities rarely utilize this voltage level. A 277 volt street lighting system appears to be extremely rare, with the only respondents utilizing this voltage being cooperative utilities. The 480 volt street lighting system is also not often used by the survey respondents (7%). Investor owned utilities are the most frequent users of the 480 volt street lighting system, followed by municipally owned street lighting systems. A need for additional wires may explain why only a small number of survey respondents are utilizing the 480 volt street lighting system. This becomes an issue when pole space is at a premium. Utilities governed by the NESC must maintain a vertical spacing of at least 6” between conductors of differing voltages on any structure. This requirement can be found in NESC Table 235-6. Most utilities distribution practices include stringing 120/240 volt service wire along the roadways to service customers. Rather than running a second set of wires, and using a different voltage, utilities will generally tap the existing 120/240 volt service wire for the street lighting instead. Another factor is the cost differential between the common 120/240 volt and 480 volt transformers. Another reason that 120/240 volt service is selected over 480 volt service is the increased likelihood of electrocution if a person comes in direct contact with the wire. Typical skin resistance permits a current flow of approximately 0.024 to 0.080 amperes if a person touches a 120 volt conductor. This may be enough to cause fibrillation given sufficient time. However, the current flow would be 0.096 to 0.320 amps if a person touches a 480 volt conductor, resulting in a much higher likelihood of fibrillation (see Appendix C for more information on electrical shock and the body). One final consideration is the additional code compliance requirements. Those utilities governed by the NESC will need to comply with performance based rules 215C1 and 314B. These require that certain metal supporting structures, including lamp posts, must be effectively grounded. These rules apply only to street lighting systems greater than 300 volts. Utilities operating at 480 volts would thus be required to comply with these extra performance based rules. Based upon the survey results, common utility practices indicate the use of either a 120 or 240 volt service for street lighting as a best practice. 36 VI. METHODS OF CONTROL OF STREET LIGHTING CIRCUITS Utilities have many control methods for street lighting. These methods range from the average electric photocell to advanced functions such as SCADA controlled dimming. The following is a brief overview and introduction of technologies available in street lighting control. Photocells Photocells have and continue to be the most common method of street and floodlight control in the electric utility industry. Based on a survey conducted for this document by the LRC, photocells are utilized in 82% of lighting installations. The survey results are contained within Appendix A of this document. Their low cost and high reliability make photocells a formidable opponent. Photocells have changed throughout the years with increasing efficiency and better on –off control. The principle of operation, for a conventional control, is not very complex. It consists of a cell that is in series with a resistor which is mated to a strip of metal with certain characteristics. During the day, light shines on the cell and it conducts. This lets the line voltage through to the resistor. The resistor heats causing the metal mated to it to deflect. This deflection opens a set of contacts which turns the light off. In the evening, limited light shines and the cell does not conduct. The resistor does not heat and the metal does not deflect. At this point the contact closes and the light is energized. The principle of operation for an electronic control is more complex. The incoming line voltage is converted to direct current and sent to an electronic circuit. The signal is taken from an analog state to a digital state, which is either an on or off signal. The signal then initiates a coil with either full voltage or no voltage. This conversion process removes the contact chatter associated with a slow break. Photocells can be used in conjunction with external relays to energize multiple lights at the same time, often called a master control. This is accomplished utilizing a circuit dedicated to street lighting. The line is energized only when the photocell actuates the relay. According to the survey, only 17% of respondents utilize this means of control. Utilities tend to use photocells more frequently (83% for Municipal Utilities and 87% for Investor Owned Utilities) than municipally owned street lighting (68%). The use of master controllers for street lighting is mainly used by municipalities that own street lighting systems and accounts for a much smaller portion of the overall control of street lighting (17%). The following is a quick review of advantages and disadvantages of conventional and electronic controls: Thermal Controls4 • Initial cost is low. • Calibration tolerances are too wide causing large on/off ratios. • Delayed turn off wastes energy in mornings. • Poor quality (very short life leading to frequent replacements) • Infrequently utilized by utilities. AC Relay Controls5 4 American Electric Lighting Photo Control Guide 5 American Electric Lighting Photo Control Guide 37 • • • • • • Instant turn on-off. Contact chatter prior to breaking load. Initial cost is low. Previously the most common type used by Utilities. Delayed turn off wastes energy in mornings. A lightning flash can cause the lamp to go off. Cool down and re-strike may take several minutes. Electronic Control with Thermal Switch4 • Effectively filters out short on or off cycles. • The 30 to 60 second time delay for on/off is considered excessive. • The on/off ratio can be 1:1. Electronic Control with DC Relays4 • Instantaneous switching with no chatter or buzz. • Small ratio will not cause excessive morning burning time. • Large enough ratio to give positive switching with fast moving clouds. • The control can be adapted to be blind to lightning or poorly aimed car headlights. • Most common use control with utilities. Monitoring and Control Systems Monitoring and control systems available to electric utilities offer a great amount of flexibility in the control and maintenance of the light, as well as the reduction of power consumption and costs. These systems operate on many different software platforms and communications options. They can be integrated into a Utilities SCADA or GIS system allowing a spatial representation of street lights on system maps. These systems offer the ability to control street lights on an individual or group basis, as well as an entire urban area. The energy consumed when dimming or shutting off lights is then reduced. This can be accomplished through automated measures or light intensity measurements. Control can be accomplished manually, by internet, or cell phone, or a fixed time program. The monitoring aspect allows the utility to obtain maintenance efficiencies resulting in a decrease in operating expenses, reduction of calls related to lamp faults or failures, and data collection with reporting capabilities. The system can also be utilized to reduce light trespass. Organizations, such as the International Dark-Sky Association (IDA) and other grass roots organizations have pushed government entities to pass legislation for a reduction in light trespass. These systems can help supplement other programs working to reduce light emissions and come closer to meeting the objectives of IDA. A majority of respondents to the survey (54%) indicated that they utilize a full cutoff fixture to meet the demands of groups like IDA while the remainder is looking at requiring full cutoff lighting in the future. 38 A concern of Utilities and Public Safety officials is the failure of the central unit or communications media. A system communications or processor failure does not mean illumination will not occur. Most systems have a fail safe built in so that each light will fall back to an internal program and continue to illuminate the street. As technology advances and economies of scale are achieved, these systems will become prevalent in the industry. Control, maintenance, and data acquisition from these systems will fuel higher demand. 39 VII. OPERATION AND MAINTENANCE PLAN – Practices Determined From Survey Conducted by LRC A survey of street lighting practices was prepared by the LRC and handed out to participants in the 2004 Street and Area Lighting Conference. Based on the responses of the survey respondents, best practices for operation and maintenance were developed. Nearly half of the survey respondents (48%) report that maintenance of streetlights is performed by dedicated streetlight crews. Contractors perform this function 26% of the time and 26% of the time it is performed by regular line crews. The use of high voltage linemen to perform streetlight maintenance was reported by 50% of respondents. However, municipalities that own streetlights are more likely to use low voltage line personnel. Group relamping is only used by 38% of the respondents. All survey respondents indicated that streetlight fixtures, poles and wiring are only replaced upon failure. Inventories of streetlights in use are conducted by 71% of the survey respondents either as part of any group relamping or conducted as separate inventories. Streetlight outage reporting is predominately provided by customers (55%) and by police and a dedicated person within the streetlight owning entity (21% each). The annual maintenance cost per streetlight as reported in the survey varies greatly from a low of $10 to a high of $400. The most likely costs for entities not conducting group relamping is approximately $40. Dedicated streetlight maintenance crews may be warranted if sufficient streetlights are owned by a single entity. Streetlight Poles All survey respondents indicated they only replace streetlight poles upon failure. This practice is recommended. Inspection of any wood streetlight only poles should occur at the same inspection interval as wood overhead line poles. In fact, the inspection of wood streetlight poles should occur at the same time as the line poles in the area are being inspected. This will eliminate separate inspection trips for just the streetlight poles. Dedicated Streetlight Wiring The vast majority of survey respondents (79%) indicated they do not perform any streetlight wiring inspections. Streetlight wiring is only replaced upon failure according to all survey respondents. Replacement of only failed streetlight wiring is the recommendation set forth here. However, there is an exception to this recommendation. Certain types of underground/direct buried electrical wires are known to deteriorate more rapidly than their original specifications. If these types of wires begin to have multiple failures throughout the streetlight system, it might be less costly to replace all of this type of streetlight wire under a designed replacement plan rather 40 than wait for failures to occur. In order to determine these types of failures, a database must be maintained. The use of databases will be addressed in further detail later in this document. Inspection of streetlight wiring for safety purposes is discussed elsewhere. However, there is one inspection that is recommended at the time of group relamping of underground fed streetlights. If the streetlight wires are terminated at the base of the streetlight pole within a wiring hand hole in the pole, inspections to ensure the cover for these hand holes is present and properly installed should be conducted. Streetlight Fixture Maintenance and Repair All survey respondents indicated they only replace streetlight fixtures upon failure of the fixture. It is believed this is a sound economic and safety policy. Therefore, it is recommended that streetlight fixtures only be replaced upon their failure. Low Capital Cost Streetlight Fixtures (cobra heads) What is deemed a fixture failure for low cost streetlight fixtures? The recommended definition of failure for these fixtures is anything that fails beyond lamps, photocells and the glass globe. Replacing/repairing ballasts and other electrical components may cost (parts and labor) more than replacing a low cost fixture. High Capital Cost Streetlight Fixtures (decorative post tops, etc.) All efforts should be made to repair the higher cost streetlight fixtures. Replacement of ballasts, lenses, glass, photocells, etc. will be less costly than replacing the entire fixture. The higher cost fixtures should be chosen with maintenance in mind. Easy to maintain fixtures that have snap in connections for ballasts, photocells and other electrical components will reduce maintenance costs. Recommendations Based on the results of the survey, it is not perfectly clear that group relamping is a best practice for street lighting maintenance; however; it appears that larger utilities with a greater quantity of lights would benefit more from a group relamping methodology. Smaller utilities with fewer lights to maintain and patrol would probably realize that group relamping is too costly and therefore spot relamping combined with night patrolling for burned out lamps would be more economical. It is recommended that larger utilities establish a more pro-active street light maintenance and repair program. This program would include a replacement rotation schedule based on the following replacement criteria: type of light, area installed, age of lamp, and useful life of lamp (utilizing life cycle curves provided by manufacturers). The results of the survey showed that 71% of the respondents took inventory of their street lighting systems either through relamping or a separate inventory. This step is essential in order to determine which types of lights are present on the system, their classifications, and most importantly their physical location. A GIS based mapping system would be ideal for developing a street lighting maintenance plan. 41 A representative sample of one utilities’ methodology for categorizing the types of street lighting are broken down below. They are separated into 4 categories based on wattages of the fixtures and their locations: Alley – 70 watts Local – 100 watts Collector – 150 watts Major – 250 watts Within these major lighting categories there are many types of fixtures including flood lighting, street lighting, security lighting, and decorative lighting. It will be important to note the specific fixture types at each location will need to be incorporated into the GIS mapping system in order to prepare the operations and maintenance crews and allow for proper stocking of the repair trucks. A GIS system is also a very valuable tool that can be used to track the in service dates of street lighting equipment. By using these in service dates and comparing the hours in service for lamps in the field to manufacturers life cycle curves, a more pro-active approach for lamp replacement can be formulated. In addition, early failures of lamps could be noted and new life cycle curves for lamps could be prepared. Spot Relamping versus Group Relamping Spot Relamping is defined as fixing lighting lamps only when they are broken. This program is usually dependent on drive by inspections at night or consumer/police outage reports. Group Relamping is defined as replacing lamps on a periodic replacement schedule or “best time schedule”. A group relamping program is usually defined by area within a system and is largely influenced by the luminaire life curves provided by lamp manufacturers. A “best time schedule” is based on when the total cost of energy use, cost of installation, and relamping is at its minimum. Effectiveness less than 50% is a good indicator while 33% to 25% of lamp life remaining offers a good mix as well.6 The most debated issue surrounding lamp replacement is whether to do group relamping or to replace lamps only upon notification of failure, i.e. spot relamping. Survey respondents indicated a strong preference for spot relamping. Municipally owned utilities had even a stronger preference for spot relamping. The survey not withstanding, it is recommended that group relamping be pursued. All economic studies on this subject show potential savings by using group relamping. The Illuminating Engineering Society of North America (IESNA) design guide DG-4-03, Design Guide for Roadway Lighting Maintenance, illustrates an analysis of spot versus group relamping. A review of their assumed costs shows them to be reasonable. The use of the non-cycling, environmentally friendly HPS lamp will further improve the economics of group relamping because of the extended life of these lamps. The group relamping schedule can be stretched from four years to five years. 6 Design Guide for Roadway Lighting Maintenance (DG-4-03) by IESNA Roadway Lighting Committee 42 Group relamping offers the appeal of more evenly aged lamps, while spot relamping can limit light depreciation which is important for overall safety and security. While a spot relamping program requires little planning to implement, a group relamping program requires considerable planning to develop the schedules and personnel requirements for a cleaning or group relamping program. Spot relamping is generally more expensive due to the increased labor costs involved with the increased travel times that are incurred by replacing lamps across a wide service territory. In addition, by relying on consumer or police outage reports, a utility employing a spot relamping program may incur some liability with burned out lamps. An example of the costliness of liability surrounding the maintenance of street lights happened to a Florida utility. A civil case in Florida pitted the family of a man killed by a delivery truck against a Florida utility. In this particular case, a young man was walking along a road during the early morning hours and was struck and killed by a passing delivery truck. The family of the deceased claimed that the street light near the accident, of which the utility owned and was responsible for maintenance, was burned out. Since the light was burned out, the truck driver could not see the man, and therefore the blame rested on the utility. The case went through several courts and was ultimately decided for the Plaintiff. The utility had to write a check to the family and agree to better maintenance procedures. By adopting a group relamping program, a utility is better shielded from this type of litigation due to better service records and by being able to prove that maintenance of street lights is performed in a timely manner. Many states define an allowable percentage street lights out at a given time or have recommendations for making repairs after outage calls. Connecticut and Massachusetts utilities are required to re-lamp fixtures within 72 hours of notice of a problem. California requires a specific maintenance schedule. The Institute Of Lighting Engineers (United Kingdom) recommends that no more than 2% of public lighting should be out on any one night. The City of Philadelphia has three different parties involved with their street lighting maintenance, including the city street lighting shop, PECO Energy7, and a contractor. The contractor works at night and is responsible for lamps and photocontrols. The contractor is also required to perform weekly streetlight inspections. They report on problems and fix minor problems such as a lamp replacement or a photocell. Otherwise, they submit a work order for the city or PECO Energy to handle. The city shop is responsible for poles and luminaires. PECO Energy is responsible for electrical distribution and taps. The contractor is allowed no backlog. The city shop is allowed a backlog of 10 days on average for major repairs. PECO Energy is allowed a backlog of 20 days on average for underground circuit repairs Some of the benefits of a group relamping and maintenance plan for street lighting are as follows: • Maintaining high standards of light output 7 Based on a presentation by Joseph Dyle, chief street lighting engineer for the city of Philadelphia , at the 2003 IESNA Street and Area Lighting Conference. 43 • Minimizing the higher costs associated with random lamp failure replacement • • Confining maintenance work to pre-planned areas Preventing the expensive replacement of lighting control failure caused by burning the lamp to destruction • Keeping energy usage to a minimum Several studies have been performed by utilities to determine whether they should pursue a group relamping program or continue their current program of spot relamping. The results of these studies show that the total cost of maintaining a group relamping program can be more cost affective than a spot relamping program. Some of the utilities who have had success with group relamping include Madison Electric and Gas (MGE) and Upper Peninsula Power Company (UPPCO). Each utility is different in terms of consumers, equipment used, cost of labor, and capabilities. Utilities are urged to do a cost analysis to determine whether or not a group relamping program is right for them. The IESNA Design Guide for Roadway Lighting Maintenance (DG-4-03) is an excellent source for an example of maintenance practices and for guidance in performing a cost benefit analysis. An economic analysis of group relamping for a large municipal utility using the methodology depicted in Table 1 of IESNA DG-4-03 follows. It assumes the utility has 90,000 streetlights in place. It also assumes the use of the non-cycling HPS lamps. Cost of these lamps are approximately $11.50, the group relamping cycle is five years, group relamping costs are $12 per streetlight and spot relamping costs are $100 per streetlight. These costs include travel time, time to setup, replace the lamp and clean the fixture. Item Description 1. Total Number of Streetlights in System Group Relamp 90,000 Spot Relamp 90,000 2. Average Lamp Cost $11.50 $11.50 3. Number of Lights Cleaned & Group Re-lamped per Yr . $18,000 $0.00 4. Cost of Labor, Truck & Components – Spot Relamp $100.00 $100.00 5. Cost of Labor, Truck & Components – Group Relamp $12.00 $0.00 6. Annual Spot Relamping/Cleaning Rate – Weighted average failure rate. Data taken from lamp manufacturers 0.048 0.116 7. Estimated number of Spot Replacements per Year (#1x#6) $4,320 $10,440.00 8. Annual Cost – Spot Relamping (#2+#4)x#7 $481,680 $1,164,060.00 mortality curves and modified for non-cycling lamp. 44 9. Annual Cost – Group Relamping (#2+#5)x#3 $423,000 $0.00 Total Cost $904,680.00 $1,164,060.00 After a utility has adopted a group relamping program, it is important to remember that in addition to changing out lamps on a pre-determined cycle, proper maintenance should be performed on the luminaire and supporting pole as well. The easiest way to ensure that this maintenance is performed correctly will be to establish an inspection checklist. The inspection checklist needs to be developed with several important criteria in mind. First and foremost the safety of the public and that of the maintenance workers needs to be ensured. In addition, ensuring proper operation of the lamps so they can operate at maximum efficiency needs to be a top priority as well since it also affects safety and security. Theoretically, 2 inspection checklists will be prepared: a safety inspection checklist and a maintenance inspection checklist. The two different checklists will be discussed below. Safety Inspection Checklist Developing a proper safety inspection checklist for street lighting maintenance is very important to maintain adequate safety levels and reliability. An excellent guideline for safety inspection is the California Public Utility Commission’s General Order #95, which outlines requirements for street and decorative lighting. In addition, safety inspections should be performed whenever a light standard is worked on. The following is a summary of checklist items with a brief description of the task. a) Electrical Connections - The first item to inspect should be the secondary electrical connections that supply the luminaire, whether it is an overhead or an underground connection. Inspect the connection to ensure proper connection with involved conductors (i.e. squeeze on connectors, bolt on connections, crimp on connection, etc…). Also, the maintenance personnel should look for any signs of arcing or frayed conductors. A simple test for power lead reversal should also be performed using a multimeter rated for the proper voltage level. Any conductors or connections in need of repair or replacement should be addressed immediately. b) Fuses – Fuses on the hot leg of the lighting conductor and the neutral conductor (if fused) should be visually inspected. Caution should be exercised in the use of neutral fusing, as the fuse may open up under a fault, while the hot leg remains energized. This may result in the fault current path being through the metal pole to the ground rod and back to its source.. The fuses on lighting conductors are critical in the case of a fault and are designed to prevent damage to the luminaire and a hazard to the public. Failed fuses should be changed out immediately. c) Grounding – Special attention needs to be paid to ensuring that proper grounding techniques are in use and operational at each installation. The proper bonding of metallic street light components to the neutral and/or safety ground for each installation should be checked for proper installation. If a separate ground rod is present for each installation, 45 maintenance personnel should check for corrosion and proper connection to the ground wire. Any problems should be remedied immediately. d) Security – The security of the inspection plates should be checked to make sure they still perform their job of keeping the public out of the standard were contact with energized conductors can occur. If the plate is faulty or inadequate, the problem should be remedied immediately. The following timetable for inspection is based upon the American Association of State Highways and Transportation Officials, An Information Guide for Roadway Lighting. The survey respondents averaged 6.67 years for inspections; Municipalities averaged every 5 years and Investor Owned Utilities averaged 7.5 years. The timetable is: Electrical Connections – Inspect when lamp is replaced Fuses - Inspect when lamp is replaced Grounding- Inspect when lamp is replaced Security- Inspect when lamp is replaced Operation and Maintenance Checklist a) Lighting Controls – Photocontrols should be checked for dirt build-up, proper orientation, and proper operation. Master controls and timers should be checked to ensure that lights are turned on properly when operated. Faulty control devices should be repaired or replaced immediately to ensure timely operation. b) Check/Replace Lamps – Manufacturers can provide Lamp Lumen Depreciation curves for the lamps that utilities use. These curves show the approximate useful life of the lamp and its decreased light output over time. Most lamps last approximately 20,000 hours which yields about 5 years when used approximately 11 hours per day. c) Clean Refractors – Refractors should be checked for breakage or discoloration and cleaned during inspection. The dirt build up affects the amount of light that can pass through the refractor, so it is important to keep these clean to ensure proper light output. d) Check Luminaire Parts - Seals should be checked to prevent water and contaminants from entering which could cause overheating and damage. Gaskets, wildlife shields, filters, and hardware should be inspected for breakages, dirt build-up, or corrosion. e) Check Pole – Lighting poles should be inspected to make sure that they are sturdy enough to support the load of the luminaire and any wind loading on the pole. Maintenance personnel should check for any breakage, dents, weak spots, or stresses that may have been caused by a pedestrian or vehicle collision, mowing or trimming vehicle, or by acts of God. Faulty poles should be replaced as soon as possible to ensure safety. f) Wiring - Streetlight wiring is only replaced upon failure according to all survey respondents. Replacement of only failed streetlight wiring is the recommendation set 46 forth here. However, there is an exception to this recommendation. Certain types of underground/direct buried electrical wires are known to deteriorate more rapidly that their original specifications. If these types of wires begin to have multiple failures throughout the streetlight system, it might be less costly to replace all of this type of streetlight wire under a designed replacement plan rather than wait for failures to occur. g) Voltage – Voltage fluctuations affect light life by causing lamps to re-strike (low voltage) or to become damaged (excessive voltage). The voltage levels on the service conductors should be checked with a multi-meter to ensure that proper voltage levels are being maintained. Light ballasts in most lamps are used to control the current flow in the arc tube. Voltage fluctuations can cause permanent damage to the ballast or arc tube. The ballasts should be checked to ensure that they are operating properly and that they are sized correctly to the lamp wattage. Voltage problems should be remedied using prudent engineering solutions. h) Night Patrolling – Night patrolling is an extremely important practice if a utility wants to be pro-active with street light maintenance and repair. Relying solely on customers and policemen to report outages is a practice that is barely adequate and spotty at best. Utilities should use their mapping system to plan routes for night patrolling in order to identify burned out lamps or underperforming lamps. By being more pro-active in identifying and repairing faulty lamps, a utility can better provide safety to its consumers and protect themselves from liability concerns. i) Troubleshooting – There are many different causes of failure in lamps used on utility street lighting system. The location of the outage including address, pole number, or relative location should be included in any paperwork so it can be added to the GIS system for future reference. This information will also help to develop new life cycle curves for the different types of lamps on the system. The malfunction type, such as, Dayburner, Light Out, Light Cycles, Other Damage, should be noted for future reference. Common causes of failure for the most common types of lamps in use are listed below8: • • 8 Mercury Vapor and Metal Halide Lamp Failure – The ballast is a current limiting device that is used to control current flow. Deterioration of the electrodes in the arc tube and on the ballast are a common cause of light impairment and failure. A mismatch in the ballast and lamp will also cause failure. Gases or metals lost from the arc tube through migration to the outer bulb or air leaking into the outer bulb will cause failure. End of life arc tube rupture can cause damage to the outer envelope. High Pressure Sodium Lamp Failure – This lamp type is also controlled by ballast. When a mismatch between the ballast and arc tube occurs, gases can leak into the outer envelope, causing a failure. As these fixtures age, the voltage required to keep the lamp operating increases beyond the capacity of the ballast Design Guide for Roadway Lighting Maintenance (DG-4-03) by IESNA Roadway Lighting Committee 47 • and the lamp will extinguish. Once the lamp cools, it will re-ignite, causing a continuous cycling on and off until the lamp fails permanently. Low Pressure Sodium Lamp Failure – Deterioration of electrodes in the arc tube is the most common cause of failure. Timetable for Inspection: The following inspection timetable is based on a pro-active group relamping and maintenance program. It is assumed that during the visit to re-lamp the fixture these inspections will be performed. When group re-lamping is not employed, the schedule is still valid and is a prudent program to implement for protection of the public and personnel. Several Public Utility Commissions have intervened regarding inspection cycles, the most recent being New York. The more stringent testing and inspection program required by the New York Public Utilities Commission revolves around a fatal electrocution of a woman and her pet in New York City in January 2004. The New York Public Service Commission Case 04-M-0159- Proceeding on motion of the Commission to Examine the Safety of Electric Transmission and Distribution Systems, is the catalyst for the inspection program. This Case set forth a requirement that all utilities under control of the New York Public Service Commission inspect their electric facilities on a minimum of a five year cycle. This Case is available at the New York Public Service Commission website for complete details of the inspection requirements. The following timetable for inspection is based upon the American Association of State Highways and Transportation Officials, An Information Guide for Roadway Lighting. The survey respondents averaged 6.67 years for inspections; Municipalities averaged every 5 years and Investor Owned Utilities averaged 7.5 years. The timetable is: Lighting Controls – Inspect when lamp is replaced Check/ Replace Lamps – Replace based on replacement schedule Cleaning Refractors- Inspect when lamp is replaced Check/ Replace Luminaire Parts- Inspect when lamp is replaced Check/ Replace Pole- Inspect when lamp is replaced. Replace only when broken. Wiring- Inspect when lamp is replaced. Replace only when broken. Voltage- Inspect when lamp is replaced Troubleshooting- On an as needed basis to determine problems Night Patrolling- On an as needed basis to determine problems 48 APPENDIX A STREET LIGHTING SURVEY RESULTS Submitted to: Hi-Line Engineering, LLC Submitted by: Lighting Research Center Date: January 3, 2005 Lighting Research Center Rensselaer Polytechnic Institute 21 Union Street Troy, NY 12180 518-687-7100 518-687-7120 (fax) 51 SUMMARY Background The street lighting survey was undertaken as a means of understanding current practices of utilities and municipalities to provide street lighting services within their designated service areas and to determine best practices. The Lighting Research Center (LRC) was retained as a subcontractor to Hi-Line Engineering, LLC to conduct a street lighting best practices survey. The survey was conducted of willing participants who attended the 2004 Street and Area Lighting Conference. Attendees included municipality and utility representatives, as well as outdoor lighting designers and manufacturers. This document presents the findings of the survey and analyzes the data. Research Objectives The research objectives for the survey were to explore: • Safest operating voltage level and proper wiring methods. • Illumination levels to alleviate public safety concerns. • Types of streetlight fixtures and structures used for long service life and low maintenance. • Selection practices of overhead versus underground service. • Comparison of operating voltages (120, 240 or 480 volts). • Standardization of inventory. • Lighting efficiency with regards to energy use. • Types of equipment used in maintenance and installation of streetlights. • Procedures and methods used in installation and maintenance. • Costs, on a per streetlight basis, for maintenance and installation. Methodology The LRC developed a surveying instrument to collect data regarding the specifications, standards, installation and maintenance practices, personnel training and record keeping of street lighting programs of selected utilities and municipalities. The survey was reviewed, amended and approved by Hi-Line Engineering, AMP-Ohio and the City of Columbus, Ohio prior to its distribution. All participants of the 2004 Street and Area Lighting Conference received a survey and instructions for its completion with the promise that the results would be made available to all who completed the survey. 50 surveys were completed. However, some of the surveys were duplicates from the same utility or municipality. There were also some surveys from street lighting manufacturers and consultants. The duplicates and non-street lighting entity surveys were not included in the data analysis. 40 surveys were available for analysis. Of the 40 surveys used not all respondents provided answers to all the questions. Conversely, some of the questions required multiple responses from the same entity. 52 Survey responses were placed in sub-categories based on the type of entity owning the streetlights. These sub-categories are: • Municipalities that own streetlights – These are towns or cities that own the streetlights within their boundaries. They do not, however, own or maintain the electrical distribution system. They may own the wiring to the streetlights from some distribution point of the electrical system. On the following tables, these entities are referred to as “Municipality”. • Cooperative Utility – These are utility companies that are organized under the rural electric cooperative style. These entities own the streetlights and the electrical distribution system. On the following tables, these are referred to as “Utility – Coop”. There were insufficient responses to conduct any meaningful analysis on this class. • Investor owned utilities – These are utility companies that own the streetlights and transmission and distribution facilities within their designated service areas. On the following tables, these are referred to as “Utility – IOU”. • Municipal utilities – These are utility companies owned by a municipality. They provide both the electric distribution system and the streetlights to the town or city they serve. On the following tables, these are referred to as “Utility – Municipal”. • Other – One entity reported itself as other. This entry refers to a municipality where some of the streetlights are owned by the municipality and others are owned by the local utility. On the following tables, this is referred to as “Nonutility, Other”. Survey Demographics Survey respondents represented most areas of the United States. The exceptions were the northern plains and Rocky Mountain states. Most of the respondents (72%) own more than 50,000 streetlights each. The large majority (82%) of these streetlights are high pressure sodium. However, there still remains in use a substantial amount (11%) of inefficient mercury vapor streetlights. Streetlights Owned by Survey Respondents 50% 40% 30% 20% 10% 0% Less than 10,000 10,000 to 50,000 53 50,000 to 100,000 greater than 100,000 KEY FINDINGS Specifications and Standards To determine how many streetlights to place along a roadway, someone has to define the type of road. Survey respondents indicated they either used the Illuminating Engineering Society of North America (IESNA) definitions (48%) or the type of road is defined by the municipality (29%). After defining the roadway, choosing and/or approving the location of streetlights falls to the municipality in 72% of survey respondents’ cases. In 32% of these cases, the utility recommends the location of the streetlight. How are Roadways Defined 60% 50% 40% 30% 20% 10% 0% IESNA National Municipality Not Highw ay Classified System Other Who Selects Streetlight Locations O ther Munic ipality Utility Rec ommends , Munic ipality Approv es Utility 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Statistically accurate information regarding illumination levels by street type was not attainable through the survey. Too few respondents indicated any design criteria for illumination levels. This may be an indication there is no set level of illuminance based on roadway type for most entities responding to the survey. Continuous street lighting along roadways is not practiced except under certain specific conditions. Only one-third of survey respondents indicated using continuous roadway 54 street lighting on collector or major types of roadways. Continuous roadway lighting on other types of roads was used infrequently. The most common streetlight operating voltage was 120 volts (62%) followed by 240 volts (28%). Most entities that own streetlights (82%) use individual photocells to control the on/off function of the streetlight. The use of low mercury content lamps in streetlights is used mostly by investor owned utilities (IOUs) and municipal utilities. This is not true for municipalities that own streetlights. Streetlight Voltages 70% 60% 50% 40% 30% 20% 10% 0% 120 volts 240 volts 277 volts 480 volts Streetlight Controllers 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Photocells Time Clocks Master Control Full cutoff streetlight fixtures are now mandated in the majority of jurisdictions with the remainder of survey respondents expecting they will be mandated shortly. The most common streetlight fixture is the cobra head (69%). When respondents were asked to rank the criteria for selecting streetlight fixtures, quality was ranked ahead of cost. 55 Type s of Stre e tlights 80% 70% 60% 50% 40% 30% 20% 10% 0% Cobra Head Post Top Decorat ive Shoe B ox Ot her Wood is still the most popular material used for dedicated streetlight poles. Mounting heights of streetlights vary based on the location and type of street. Types of Streetlight Poles Other Cast Iron Aluminium for High Mounting Aluminium for Decorative Wood for High Mounting Wood for Low Mounting Fiberglass for Low Mounting 35% 30% 25% 20% 15% 10% 5% 0% All survey respondents indicated they keep some type of streetlight records. Computerized records account for 62% of the records. The most popular information included within the records are streetlight location, fixture type, lamp type, lamp size, date of installation, pole type and who pays for the use of the streetlight. Safety codes are followed in the installation of streetlights. IOUs and municipal utilities tend to follow the National Electric Safety Code while municipalities that own streetlights follow either the National Electrical Code or state mandated codes. The code that is followed sets the grounding standards that are practiced. 56 Safety Codes Used 60% 50% 40% 30% 20% 10% 0% NEC NESC State Other Installation Practices – Overhead Distribution Surprisingly, the survey results indicate the use of qualified high voltage linemen (58% of respondents) to install streetlights on overhead distribution facilities. High voltage linemen are more expensive to use than other qualified individuals. In terms of payment, if someone is charged for the installation of streetlights on overhead distribution facilities, it is normally the developer of the new development. This is especially true (83%) where the municipality owns the streetlights. However, in 40% of the cases, there are no charges for streetlight installations in overhead distribution areas. Where the municipality owns the streetlights or for a municipal utility, dedicated streetlight wiring is more likely to be used. Grounding of streetlights is a function of which electrical safety code is used. Municipalities, following the NEC, will tend to use a driven ground rod. Utilities, following the NESC, will normally tie the ground to the neutral conductor which is attached to a ground. Type of Grounding 60% 50% 40% 30% 20% 10% 0% Secondary Driven Rod Equipment Neutral 57 Neutral & Ground Together None Other Installation Practices – Underground Distribution Unlike overhead installation practices, the use of high voltage linemen, low voltage linemen and a mixture of both to install streetlights in underground distribution areas is fairly evenly split among survey respondents. Municipalities that own streetlights are more likely to use conduit for streetlight wiring under all circumstances. Those utilities not using conduit in all circumstances tend to use it under paved areas and in downtown areas. The excavation for the conduit and its installation is most like done by the developer (56%) or by the utility (36%). The majority of streetlight owning entities (70%) charge for the installation of streetlights on underground distribution systems in new developments. The cost is either the full price of the installation or the differential between the overhead cost and the underground cost. On existing streets, the municipality picks up the installation cost 40% of the time followed by a developer 29% of the time. Who Pays for Underground Fed Streetlights 60% 50% 40% 30% 20% 10% 0% Utility Developer Municipality No Charge Developer Pay Differential Grounding practices, similar to overhead, follow the safety code practices being followed. Those entities using ground rods are split as to the requirement for impedance to ground. Forty-two percent have no impedance requirement, 29% require impedance less than 25 ohms and 29% require impedance less than 50 ohms. Maintenance Practices Nearly half of the survey respondents (48%) report that maintenance of streetlights is performed by dedicated streetlight crews. Contractors perform this function 26% of the time and 26% of the time it is performed by regular line crews. The use of high voltage linemen to perform streetlight maintenance was reported by 50% of respondents. However, municipalities that own streetlights are more likely to use low voltage line personnel. 58 Who Maintains Streetlights 60% 50% 40% 30% 20% 10% 0% Dedicated Streetlight Crews Regular Line Crews Contractors Group relamping is only used by 38% of the respondents. All survey respondents indicated that streetlight fixtures, poles and wiring are only replaced upon failure. Inventories of streetlights in use are conducted by 71% of the survey respondents either as part of any group relamping or conducted as separate inventories. Streetlight outage reporting is predominately provided by customers (55%) and by police and a dedicated person within the streetlight owning entity (21% each). The annual maintenance cost per streetlight as reported in the survey varies greatly from a low of $10 to a high of $400. The most likely costs for entities not conducting group relamping is approximately $40. Training The majority of entities owning streetlights provide some type of training to their streetlight designers, installers and inspectors. This training mostly is in the form of onthe-job training. Low voltage training is provided to some of the installers. RECOMMENDED BEST PRACTICES The recommendations made as part of this report reflect the results of the survey. It does not include recommendations that are not supported by the survey outcome or were not part of the survey. Specifications and Standards • Lighting design practices need to start somewhere. The best place to start is by defining the types of roadways within a municipality and the type of lighting that each roadway will receive. It is recommended that municipalities define their roadways by using the IESNA definitions or developing their own. 59 • • • • Since the municipality will pay either for the rental of streetlights from a utility or be the owner of streetlights, it is recommended that the municipality set up a procedure for approving the installation and location of any new streetlight requested. The practice of continuous street lighting, as defined by IESNA, should only be practiced along select sections of roadways where required for safety or aesthetics. The use of full cutoff streetlight fixtures is recommended. They are already mandated by most jurisdictions and all indications are they will be mandated in the remainder of jurisdictions. The keeping of streetlight records is essential. Periodic updating of these records through physical inventory is recommended. Installation Practices • • • Installations should be made in accordance with whichever electrical safety code the streetlight owning entity is required to follow. This includes grounding practices. Use of the least costly installers and maintenance personnel is recommended. This usually means the use of low voltage qualified line personnel. The use of dedicated streetlight crews with the proper equipment may also reduce costs provided there are sufficient numbers of streetlights to install and/or maintain to keep a full time crew busy. Charges are recommended for the added cost to install streetlights in new developments where underground electrical distribution systems exist. The added cost should be borne by the developer. Maintenance • • • • Any benefits of group relamping cannot be supported by the outcome of the survey. Dedicated streetlight maintenance crews may be warranted if sufficient streetlights are owned by a single entity. The annual cost to maintain street lighting in proper order should be around $40 per streetlight owned. This is based on spot relamping only. It is recommended to replace streetlight fixtures, poles or wiring only upon failure. Training • Training of streetlight system designers, installers and inspectors is recommended to ensure proper street lighting systems are installed and maintained. At a minimum, installers should receive low voltage training. 60 STUDY FINDINGS Demographic Information of Survey Respondents Fifty surveys were completed from 40 unique streetlight serving entities. Table 1 describes the type and size of entities responding to the survey. The majority of the respondents (24) were from investor owned utilities and the majority of those owned greater than 100,000 streetlights each. There is a sufficient sampling of municipalities that own streetlights and from municipally owned utilities to segment the findings by these two subsets as well as investor owned utilities. The sample size from cooperative utilities is insufficient to develop data for this group. However, their responses are included in the findings from the total survey population. Table 1: How many streetlights do you own? Utility Types and Lights Owned % of Count % of % of % of group of Less group 10,000 group 50,000 group More reporting to Type Utilities than reporting to reporting reporting than more 10,000 less than 50,000 10,000 to 100,000 50,000 to 100,000 in than Group 10,000 50,000 100,000 100,000 Municipality 7 1 14.3% 2 28.6% 2 28.6% 2 28.6% Non-utility 1 1 100% 0 0% 0 0% 0 0% Other Utility - Co2 0 0% 1 50% 1 50% 0 0% Op Utility - IOU 24 1 4.2% 1 4.2% 9 37.5% 13 54.2% Utility 6 1 16.7% 3 50% 1 16.7% 1 16.7% Municipal Total 40 4 10% 7 17.5% 13 32.5% 16 40% Survey respondents represented most sections of the United States. Only the northern plains and the Rocky Mountain States were not represented. 61 Table 2 illustrates the type of light source used by each of the types of street lighting entities. Over 80% of streetlights use high pressure sodium regardless of the entity type. The largest difference between investor owned utilities (IOU) and municipal provided street lighting appears to be in the amount of metal halide streetlights provided by the IOUs. It is also necessary to point out there still exists large quantities of energy inefficient mercury vapor streetlights in all entity categories but more so with municipal providers (14%). Table 2: Percent of streetlights by type of lamp. Utility Types and Streetlight Types Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility Municipal Total % % Metal HPS Halide 82% 0% 100% 0% % Mercury Vapor 14% 0% % % Low Pressure % Incandescent Sodium Other 1% 0% 2% 0% 0% 0% 80% 81% 87% 15% 11% 12% 0% 0% 0% 0% 1% 0% 0% 0% 0% 11.5% 0.1% 0.4% 0.3% 5% 7% 2% 82.8% 4.9% Specifications and Standards of Survey Respondents Respondents were asked to describe how or who defines different types of streets for determining to what degree each type of street will be lighted. Table 3 depicts the findings from this inquiry. Streets are defined using either the IESNA definition guidelines (48%) or directly by some entity within the municipality (39%). This is true regardless of the type of entity providing the streetlights. Table 3: How do you define different types of roads to determine what type & how many streetlights will be installed? Utility Types and Highway Definitions Used Type Municipality % of % of % of % of Count of National Group % of Group Group Group Not Group Responses IESNA Hwy reporting Municipality reporting reporting Other Classified reporting reporting in Group Sys National Municipality Not IESNA "Other" Hwy Sys Classified 5 1 2 40% 0 0% 0 0% 0 0% 3 60% 0 0% 0 0% 0 0% 0 0% 1 100% Utility - CoOp 2 1 50% 0 0% 1 50% 0 0% 0 0% Utility - IOU 29 7 14 48% 4 57% 2 7% 0 0% 11 38% 2 29% 1 3% 0 0% 1 3% 1 14% 44 21 48% 2 5% 17 39% 1 2% 3 7% Non-utility Other Utility Municipal Total 62 As table 4 illustrates, streetlight locations, in the majority of cases (72%), are determined by some entity within the municipality. In 32% of the cases, the utility recommends streetlight locations to the municipality who then approves the locations. Table 4: Who determines the number and location of streetlights on a street? Utility Types and Streetlight Location Determiner Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Count of Responses Utility in Group % of Group Utility % of Group % of Group % of Group where Recommends, where where Utility Municipality Other responding Utility Municipality Municipality Recommends "Other" Determines Approves Determines 7 1 0 0% 0 0% 2 29% 0 0% 4 57% 0 0% 1 14% 1 100% 2 0 0% 1 50% 1 50% 0 0% 45 8 8 18% 4 50% 15 33% 2 25% 18 40% 2 25% 4 9% 0 0% 63 12 19% 20 32% 25 40% 6 10% Data regarding illuminance levels for different types of roads was inconclusive to determine current practices of utilities or municipalities. Most survey respondents (20 no response and 12 illuminance levels not determined by road type) did not provide data to this question. One respondent’s data was deemed inaccurate. The remaining data is insufficient to reach any statistically accurate conclusions. This may be an indication the survey respondents do not have set illuminance levels by street type. Average values from the remaining data by type of roadway are: Alley – 0.3 foot-candles Local – 0.96 foot-candles Collector – 1.0 foot-candles Major – 1.64 foot-candles Continuous lighting of roadways, as defined by IESNA, indicates that there is an average illuminance or luminance level and an acceptable uniformity ratio along a portion of a roadway based on the roadway type. Many streets do not require continuous lighting. The survey requested respondents to identify the types of streets where continuous lighting is used. Table 5 presents the findings on the issue of continuous lighting of roadways. Approximately one-third of all respondents indicated continuous lighting was practiced on collector and major road categories. Municipal owners of streetlights and municipal utilities also had a higher response of continuous lighting on local type roadways, 25% and 31% respectively, than IOUs at 22%. 63 Table 5: What types of streets are designed for continuous/uniform level of street lighting? Utility Types and Continuous Lighting Streets Type % of % of % of % of % of Count of responses responses responses responses responses Responses Alley Local Collector Major Other indicating indicating indicating indicating indicating in Group Alley Local Collector Major "Other" Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total 12 3 1 8% 0 0% 3 25% 1 33% 4 33% 1 33% 4 33% 1 33% 0 0% 0 0% 3 0 0% 1 33% 1 33% 1 33% 0 0% 46 16 3 7% 0 0% 10 22% 5 31% 15 33% 5 31% 17 37% 5 31% 1 2% 1 6% 80 4 5% 20 25% 26 33% 28 35% 2 2% The dominant voltage used for street lighting purposes is 120 volts (62%) followed by 240 volts (28%) as can be seen in Table 6. Very few municipalities or utilities use 480 volts for street lighting purposes. This is attributed to the distribution practices found along most streets. Secondary 120/240 wiring is common along roadways. Utilities, rather than running another set of wires at a different voltage, will tap the streetlights off the secondaries that are found on the pole already. Table 6: At what voltage do you operate your streetlights? Utility Types and Operating Voltage Percentages Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility - Municipal Total 120 volts 59% 0% 70% 65% 56% 62% 240 volts 36% 100% 5% 22% 42% 28% 277 volts 0% 0% 25% 3% 0% 3% 480 volts 5% 0% 0% 10% 1% 7% There were only seven responses to the typical streetlight lamp wattages found by type of street. Similar to the illuminance levels by street type, insufficient data is present to reach any statistically accurate conclusions. Given that most respondents did not provide illuminance levels by street type, not responding to the similar question on wattage by street type could be expected. For the data that was provided the mean wattage lamp by street types are: Alley – 70 watts Local – 100 watts Collector – 150 watts Major – 250 watts 64 Lamps used in street lighting applications are now available with a minimum amount of mercury. These lamps have a cost premium over the standard lamps used for street lighting. As Table 7 indicates, most utilities (greater than 80%) have switched to the more ecologically acceptable low mercury lamps and the remaining utilities are considering the switch. The opposite is true for municipal owned streetlights. Most municipalities (80%), while considering a switch to the low mercury lamps, still employ the older technology. Table 7: Do you use ecologically (low mercury) enhanced streetlight lamps? If no, would you consider using ecologically enhanced streetlight lamps even if they cost more? Q11 - Low Mercury? Consider Low Mercury? Type Count of Responses in Group Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total 5 1 % Using Low Mercury 1 20% 0 0% 1 1 100% 0 0% 14 2 11 79% 2 100% 3 21% 0 0% 23 15 65% 8 35% Using Low Mercury Considering Low Mercury % Considering Low Mercury 4 80% 1 100% Control of the on/off function of street lighting is performed predominately by a photocell located on each streetlight. Utilities tend to use the photocell more frequently (87% for IOUs and 83% for municipal utilities) than municipally owned street lighting (68%). Master controllers are the second most popular means of controlling streetlights (17%) although far behind photocells. Municipalities that own streetlights are more likely to use master controllers than other entities. See Table 8 for details. Table 8: How are streetlights controlled for on/off operation? Utility Types and Automatic Control Options Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility - Municipal Total Avg. of % Photocells 68% 20% 100% 87% 83% 82% Avg. of % - Time Clock 4% 0% 0% 0% 0% 1% Avg. of % - Master Controller 29% 80% 0% 12% 17% 17% The cobra head style streetlight fixture represents two-thirds of all streetlights owned by the survey respondents. This is to be expected because the cost of these fixtures is relatively low compared to any other streetlight fixture. As more areas within a 65 municipality or utility service area are receiving underground utilities, the use of post top, decorative and shoebox style streetlight fixtures are gaining popularity. For IOUs, the use of these three types of fixtures is split rather evenly (8% for post top, 10% for decorative and 11% for shoebox). Municipalities and municipal utilities tend to favor the post top fixture over decorative or shoe box as illustrated in Table 9. Table 9: What types of streetlight fixtures are used? Utility Types and Streetlight Fixture Types Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility Municipal Total Avg. of % - Cobra Avg. of % Head Post Top 74% 13% 90% 0% Avg. of % Decorative 6% 10% Avg. of % Shoebox 6% 0% 60% 67% 66% 2% 8% 20% 10% 10% 5% 28% 11% 9% 0% 5% 0% 69% 10% 8% 10% 3% Other 0% 0% Most (54%) of utilities and municipalities are now requiring full cutoff streetlight fixtures be installed. The remaining survey respondents (46%) believe full cutoff street lighting will be required soon. Table 10: Are you required to use full cutoff streetlight fixtures? Full Cutoff Required? Coming Soon? Type Municipality Utility - IOU Utility Municipal Total Count of % of responses % of responses Currently Required Responses in indicating indicating Required Soon Group Currently Required Required Soon 5 3 60% 2 40% 17 9 53% 8 47% 2 1 50% 1 50% 24 13 54% 11 46% It appears quality of streetlight fixtures matters more in their selection process than cost, availability, aesthetics, brand name or optics to IOUs and municipalities that own streetlights. However, municipal electric utilities care more about cost followed by quality. The order of importance is quality, cost, optics, aesthetics, availability and brand. 66 Table 11: Prioritize the selection criteria for fixtures and manufacturers. Utilities and the avg. ranking for Selection Criteria Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Average Average Average Average Ranking Ranking Ranking - Ranking Brand Aesthetics Optics Other Name 4.6 3.75 4.75 3.25 Average Average Average Ranking - Ranking - Ranking Quality Cost Availability 1.5 2.4 1 1 3 4 2 5 6 1.35 2 2.26 1.25 4.17 4.33 4 4.33 4.72 5.33 3.57 3.5 2 The type of material used in dedicated streetlight poles varies greatly (see Table 12). The primary type of pole listed as other was concrete. Wood (29%), aluminum (22%), fiber glass (15%) and concrete are all used extensively. The only type of streetlight pole used in infrequent locations is cast iron. Cast iron poles are the most expensive. Today’s cast aluminum poles can mimic the decorative design of cast iron at a fraction of the cost. Table 12: What types of dedicated streetlight poles are used? Utility Types and Averages of Streetlight Pole Percentages Avg. Fiberglass Type for Low Mounting Heights Municipality 0% Non-utility 0% Other Utility - Co- 38% Op Utility - IOU 18% Utility 12% Municipal Total 15% Avg. Wood for Low Mounting Heights 0% 0% Avg. Avg. Avg. Avg. Cast Wood for Aluminum Aluminum Iron for High for for High Other Decorative Mounting Decorative Mounting Fixtures Heights Fixtures Heights 25% 22% 9% 3% 41% 0% 0% 2% 0% 98% 0% 55% 0% 0% 0% 8% 5% 1% 28% 14% 13% 33% 4% 16% 1% 0% 25% 24% 3% 26% 16% 6% 1% 29% 67 Streetlight mounting heights, as depicted in Table 13, are relatively consistent across all types of street lighting entities. Overhead distribution mounting is approximately 28 feet, residential 17 feet, downtown area 24 feet and commercial 21 feet. Table 13: What is the standard mounting height (feet)? Utilities and Averages of Standard Pole Mounting Heights Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Overhead Distribution 30 Residential Downtown Neighborhoods 16.6 26 20 22.5 16 27.43 29.5 16.71 18.5 27.85 16.9 Decorative, Interstates Commercial 22.4 41.67 40 22.5 25 23.06 25.75 21 19 34.77 48.33 23.93 21.16 37.48 Most streetlight records are computerized (63%) with a large number of entities keeping both computer and paper records (32%). IOUs and municipal utilities are more likely to keep computerized records (70% and 60% respectively) than municipalities that own streetlights (43%) as is shown in Table 14. Table 14: How is streetlight records kept? Utilities and Method of Keeping Streetlight Records Type Municipality Non-utility Other Utility – CoOp Utility - IOU Utility – Municipal Total 7 1 % of % of % of responses responses responses Paper Both indicating indicating indicating Computerized Paper Both 3 43% 2 29% 2 29% 1 100% 0 0% 0 0% 2 1 50% 0 0% 1 50% 23 5 16 70% 3 60% 0 0% 0 0% 7 30% 2 40% 38 24 63% 2 5% 12 32% Count of Responses Computerized in Group Streetlight record keeping is depicted on Table 15. The information included on streetlight records varies by entity. All survey respondents indicated the records include the location of the streetlight. Most entities also keep records on fixture type, lamp type, lamp size, date of installation, voltage and pole type. For IOUs and municipal utility companies who rent lights to customers, the entity paying for the streetlight rental and the amount of the rental are also included in most record systems. 68 Table 15: What information is kept in streetlight records? % of Responses Indicating Location records kept Type Count of Responses in Group Municipality 7 7 100% 6 86% Non-utility Other 1 1 100% 0 0% Utility - Co-Op 2 2 100% 1 50% 24 24 100% 19 79% Utility - IOU Utility - Municipal Location 6 Lamp Type Type 6 100% % of Responses indicating Lamp Type records kept % of Responses indicating Fixture Type records kept Fixture Type 6 100% Lamp Size % of Responses Indicating Lamp Size records kept % of Responses Indicating Maintenance records kept Maintenance Municipality 6 86% 5 71% 4 57% Non-utility Other 0 0% 0 0% 0 0% Utility - Co-Op 1 50% 1 50% 1 50% 19 79% 23 96% 12 50% Utility - IOU Utility - Municipal 6 100% Date Initially Installed Type % of Responses indicating Date Initially Installed records kept 6 100% Date Replacement Fixture Installed 1 17% % of Responses indicating Date Replacement Fixture Installed Voltage % of Responses indicating Voltage Municipality 4 57% 4 57% 5 71% Non-utility Other 0 0% 0 0% 0 0% Utility - Co-Op 1 50% 0 0% 0 0% 19 79% 11 46% 16 67% Utility - IOU Utility - Municipal Type 5 83% Notes % of Responses Indicating Notes 1 17% % of Responses indicating Light Rental Payor 5 83% Pole Type % of Responses Indicating Pole Type Municipality 3 43% 14% 4 57% Non-utility Other 0 0% 0% 0 0% Utility - Co-Op 0 0% 100% 1 50% Utility - IOU 8 33% 79% 18 75% 1 17% 100% Utility - Municipal Type Rental Charge % of Responses indicating Rental Charge Special Options Installed 6 100% % of Responses indicating Special Options Installed Other % of Responses Indicating Other Municipality 0 0% 1 14% 0 0% Non-utility Other 0 0% 0 0% 0 0% Utility - Co-Op 2 100% 0 0% 0 0% 13 54% 7 29% 2 8% 1 17% 0 0% 0 0% Utility - IOU Utility - Municipal Table 16 indicates half of the respondents (50%) use the National Electrical Safety Code (NESC) when constructing streetlight facilities. IOUs (63%) and municipal utilities (56%) use NESC more so than municipal entities that own streetlights (23%). This should be expected since utilities, in general, abide by NESC for all their construction safety requirements. Because there are more responses to this survey question than there are responding organizations, it is possible the responses indicate that multiple safety codes are used within the same entity. Municipalities that own streetlights tend to use either the National Electrical Code (31%) or state safety codes (38%). However, large 69 percentages (23%) also use the NESC. Again the response from municipalities is in line with the code requirements for non-utility entities. Table 16: What safety standards are followed? Utility Types and Safety Standards Used Count of % % % % Responses NEC reporting NESC reporting State reporting Other reporting in Group NEC NESC State Other Municipality 13 4 31% 3 23% 5 38% 1 8% Non-utility 2 1 50% 0 0% 1 50% 0 0% Other Utility - Co4 2 50% 2 50% 0 0% 0 0% Op Utility - IOU 30 8 27% 19 63% 2 7% 1 3% Utility 9 0 0% 5 56% 3 33% 1 11% Municipal Total 58 15 26% 29 50% 11 19% 3 5% Type Installation and Installation Practices – Overhead Distribution of Survey Respondents Surprisingly, the majority (58%) of entities responding to who installs streetlights on overhead distribution facilities indicate they use qualified high voltage linemen. (see Table 17) High voltage linemen are expensive workers to install streetlights. Only 17% of IOUs and municipal utilities use dedicated low voltage linemen, normally a lower cost worker. Municipalities who own streetlights indicated they use low voltage linemen in 50% of the cases. This is expected because high voltage lineman are normally not required within municipalities. There are also a large number of streetlight entities (22%) that use either low or high voltage linemen. Table 17: What is the qualification of the overhead distribution streetlight installers? Utilities and Qualifications of Overhead Dist Installers Type Municipality Utility - CoOp Utility - IOU Utility Municipal Total % of responses indicating High Voltage Linemen 1 25% 2 100% Qualified Count of High Responses Voltage in Group Linemen 4 2 % of Qualified % of responses Low responses indicating Both Voltage indicating Low Voltage Linemen Both Linemen 2 50% 0 0% 1 25% 0 0% 24 6 13 54% 5 83% 4 17% 1 17% 7 29% 0 0% 36 21 58% 7 20% 8 22% Who pays for the installation of streetlights on overhead distribution facilities in new developments is depicted in Table 18. Overall, in 43% of the cases, the developer pays 70 for streetlight installation. However, in 40% of the cases, there is no charge for streetlight installations. There are dramatic differences on who pays based on the type of entity that owns the streetlights. For municipalities that own streetlights, developers pay for new streetlights 83% of the time with the municipality paying 17% of the time. In the case of IOUs, there is no charge 56% of the time and 30% of the time the developer is charged for new streetlights. Municipal utilities also favor the developer paying for new streetlights in 57% of the cases. Table 18: Who pays for streetlights in new developments on overhead distribution poles? Utility Type and Overhead Installation Payer % Count of % % reporting No reporting Type Responses Developer reporting Municipality Municipality Charge No in Group Developer Charge Municipality 6 5 83% 1 17% 0 0% Utility - Co2 1 50% 0 0% 1 50% Op Utility - IOU 27 8 30% 4 15% 15 56% Utility 7 4 57% 2 29% 1 14% Municipal Total 42 18 43% 7 17% 17 40% The issue of dedicated streetlight wiring versus streetlights served off of existing secondary distribution wires is split essentially evenly (49% vs. 51%) as indicated in Table 19. Municipalities that own streetlights and municipal utilities favor dedicated secondary wiring for streetlights (67% each) while IOUs favor serving streetlights off existing secondary distribution systems (60%). Table 19: Are separate/dedicated secondary wiring used for streetlights on overhead distribution poles? Utilities and Separate/Dedicated Secondary Wiring Type Municipality Utility - CoOp Utility - IOU Utility Municipal Total Uses Separate Does Not Use % or Dedicated Separate or responding Secondary Dedicated Uses Wiring Secondary Wiring 6 4 67% 2 2 1 50% 1 Count of Responses in Group % responding Does Not Use 33% 50% 25 6 10 40% 4 67% 15 60% 2 33% 39 19 49% 20 51% Streetlight grounding practices on overhead distribution systems vary by the type of entity owning the streetlights (see Table 20). It appears utilities favor bonding the streetlight neutral only to the secondary neutral conductor of the secondary distribution system (45% for IOUs and 83% for municipal utilities). This practice may be linked to 71 the use of the NESC by many utilities. Twenty-one percent of IOUs responding to the survey also use a ground rod at each overhead pole and bond both the streetlight neutral conductor and the equipment ground to the grounding rod. Municipalities that own streetlights appear to favor the NEC grounding requirements to bond to an equipment ground. Again, this may be due to their use of the NEC in their construction practices. Table 20: What type of grounding practices are employed for streetlights on overhead distribution systems? Count of % reporting Secondary Responses in Secondary Neutral Group Neutral Municipality 5 1 20% Utility - Co2 1 50% Op Utility - IOU 33 15 45% Utility 6 5 83% Municipal Total 46 22 48% % reporting Neutral and Neutral and Type Ground None Ground Together Together Municipality 1 20% 0 Utility - Co0 0% 0 Op Utility - IOU 7 21% 5 Utility 1 17% 0 Municipal Total 9 19% 5 Type Driven Rod % reporting % reporting Equipment Driven Rod Equipment 1 20% 1 50% 2 40% 0 0% 3 9% 0 0% 2 6% 0 0% 5 11% 4 9% % reporting None Other % reporting Other 0% 0% 0 0% 0 0% 15% 0% 1 3% 0 0% 11% 1 2% Installation and Installation Practices – Underground/Direct Buried Distribution of Survey Respondents There is a consistency of responses from municipalities that own streetlights and municipal utilities as to who installs streetlights on both overhead and underground distribution systems. By comparing the responses on Table 17 (Overhead Distribution Installers) and Table 21 below, we see identical percentages for municipalities that own streetlights, 25% installed by high voltage linemen, 50% installed by low voltage linemen or splicers and 25% installed by a mixture of either high or low voltage linemen. The percentages are close to being the same for municipal utilities for both overhead and underground distribution systems. IOUs have a shift from 54% using high voltage linemen on overhead distribution systems to install streetlights to 25% on underground systems. The shift is toward using either high or low voltage personnel (29% for overhead to 42% for underground). 72 Table 21: What are the qualifications of the underground streetlight installers? Utilities and Qualifications of Underground Dist Installers Type % of % of responses High Low % of responses % of responses Count of indicating High Voltage indicating Voltage indicating Low responses Mixture Responses High Voltage Cable Linemen/ Voltage indicating High in Group Voltage Linemen Splicers Voltage Splicers Linemen/Splicers Mixture Cable Linemen Splicers Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total 4 1 0 0% 0 0% 1 25% 0 0% 2 50% 1 100% 1 25% 0 0% 2 0 0% 2 100% 0 0% 0 0% 24 6 2 8% 0 0% 6 25% 4 67% 5 21% 1 17% 10 42% 1 17% 37 2 5% 13 35% 9 24% 12 32% Table 22 indicates where conduit is used for streetlight wiring in underground distribution systems. Municipalities that own streetlights have more of a tendency to use conduit all the time (50%) followed by municipal utilities at 40% and then IOUs at 25%. If not using conduit all the time, the entities have a tendency to use conduit under pavement and within downtown areas. The use of conduit for streetlight wiring in residential areas occurs only 15% of the time according to the survey respondents. Table 22: Is conduit used for underground streetlight wiring? Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility Municipal Total Type Municipality Non-utility Other Utility - Co-Op Utility - IOU Utility Municipal Total Count of % reporting Always Responses in Always Underground Group Underground 10 5 50% 1 1 100% 3 36 10 % reporting Never Underground 0 0% 0 0% Never Underground 0 0% 9 25% 4 40% 0 0% 0 0% 0 0% 60 19 32% 0 0% % reporting Under % reporting % reporting Under Downtown Residential Pavement Downtown Residential Pavement 1 10% 2 20% 2 20% 0 0% 0 0% 0 0% 1 33% 12 33% 3 30% 1 33% 10 28% 2 20% 1 33% 5 14% 1 10% 17 28% 15 25% 9 15% 73 The dominant response as to who is responsible for installing street lighting conduit in new developments is the developer (56%) followed by the utility (36%) according to the results of the survey as shown on Table 23 below. When the municipality owns the streetlights, the developer has the responsibility for the conduit installation 86% of the time. Municipal utilities also lean toward the developer installing the conduit (67%). IOUs are relatively evenly split between developers (47%) and the utility (41%) as to who will install the conduit. Table 23: Who is responsible for the installation of any required conduit in new construction developments? Utilities and New Const Conduit Install Responsibility Count of % % % reporting Developer reporting Responses Utility reporting Municipality Municipality in Group Utility Developer Municipality 7 1 14% 0 0% 6 86% Non-utility 1 0 0% 0 0% 1 100% Other Utility - Co2 1 50% 0 0% 1 50% Op Utility - IOU 34 14 41% 4 12% 16 47% Utility 6 2 33% 0 0% 4 67% Municipal Total 50 18 36% 4 8% 28 56% Type The responsibility for excavation in new developments for the installation of streetlight wiring in underground distribution areas follows closely the results found for who is responsible for installing conduits in underground distribution areas as shown in Table 23. Table 24 shows the same percentages for who is responsible for excavation as is shown in Table 23 when the municipality owns the streetlights. For municipal utilities and IOUs, there is a slight shift toward the utility doing the excavation. Table 24: Who is responsible for the excavation for the installation of streetlights and streetlight wiring in new construction developments? Utilities and Excavation Responsibility in New Construction Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Count of % % reporting Responses in Utility reporting Municipality Municipality Group Utility 7 1 14% 0 0% 1 0 0% 0 0% Developer % reporting Developer 6 86% 1 100% 2 1 50% 0 0% 1 50% 29 7 15 52% 3 43% 3 10% 0 0% 11 38% 4 57% 46 20 43% 3 7% 23 50% 74 The utility is most likely (70%) to provide and install the streetlight wiring in underground distribution area (see Table 25 below). The exception to this response is where the municipality owns the streetlights. In this case, the developer of the new development is more likely to provide and install the streetlight wiring (57%) with the utility installing the wiring 43% of the time. Table 25: Who is responsible for providing and installing the underground wiring for streetlights? Utilities and Provide & Install Underground Wires Count of % % % reporting Developer reporting Responses Utility reporting Municipality Municipality in Group Utility Developer Municipality 7 3 43% 0 0% 4 57% Non-utility 1 0 0% 0 0% 1 100% Other Utility - Co2 2 100% 0 0% 0 0% Op Utility - IOU 30 23 77% 3 10% 4 13% Utility 6 4 67% 0 0% 2 33% Municipal Total 46 32 70% 3 6% 11 24% Type Most entities (80%) that own streetlights in underground distribution areas install separate or dedicated wires to the streetlights as depicted in Table 26. Table 26: Are separate/dedicated secondary wiring used for streetlights in underground distribution areas? Utilities and Secondary or Dedicated Underground Wiring Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Uses Separate Does Not Use % or Dedicated Separate or responding Secondary Dedicated Uses Wiring Secondary Wiring 7 7 100% 0 1 1 100% 0 Count of Responses in Group % responding Does Not Use 0% 0% 3 2 67% 1 33% 24 6 18 75% 5 83% 6 25% 1 17% 41 33 80% 8 20% In new developments with underground electric distribution systems, the property developer is most likely to pay for the installation of the streetlights in total (56%) or the differential cost between overhead and underground streetlights (15%). Only for 8% of the IOUs responses are no charges assessed. In some instances (12%), the municipality 75 pays for the installation of streetlights in new developments in underground distribution areas. (See Table 27) Table 27: Who pays for the installation of streetlights in new developments with underground distribution? Utilities and Underground New Dev Installation Payer Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total % Count of % % % % reporting No reporting Responses Utility reporting Developer reporting Municipality Differential reporting Municipality Charge No in Group Utility Developer Differential Charge 7 1 0 0% 0 0% 6 86% 1 100% 1 14% 0 0% 0 0% 0 0% 0 0% 0 0% 3 1 33% 1 33% 0 0% 0 0% 1 33% 36 5 5 14% 0 0% 16 44% 5 100% 5 14% 0 0% 3 8% 0 0% 7 19% 0 0% 52 6 12% 29 55% 6 12% 3 6% 8 15% When the installation of streetlights shifts to existing streets in underground electric distribution areas, the entity responsible for costs associated with the installation of the streetlights also shifts. Municipalities are more likely to pay any installation costs associated with streetlights (40%) followed by the developer (29%). Table 28: Who pays for the installation of streetlights on existing streets with underground distribution? Utilities and Underground Existing Streets Install Payer Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total % Count of % % % % reporting No reporting Responses Utility reporting Developer reporting Municipality Differential reporting Municipality Charge No in Group Utility Developer Differential Charge 6 1 0 0% 0 0% 2 33% 1 100% 4 67% 0 0% 0 0% 0 0% 0 0% 0 0% 4 0 0% 0 0% 2 50% 1 25% 1 25% 35 6 5 14% 1 17% 10 29% 2 33% 12 34% 3 50% 3 9% 0 0% 5 14% 0 0% 52 6 12% 15 29% 21 40% 4 7% 6 12% Municipalities that own streetlights are most likely to use driven ground rods at each streetlight within underground distribution areas (80%). IOUs and municipal utilities are less likely to use grounding rods (38% and 50% respectively) as Table 29 illustrates. The use of ground rods may be tied to which safety code is used by the streetlight entity. Municipalities that own streetlights tend to follow the NEC while utilities tend to use NESC. 76 Table 29: Are driven ground rods used for streetlights in underground areas? Utilities and Driven Ground Type Count of Responses in Group Yes Municipality 5 4 Non-utility Other 1 0 Utility - Co-Op 2 0 Utility - IOU 21 8 Utility - Municipal 6 3 Total 35 15 % reporting Yes No % reporting No 80% 1 20% 0% 1 100% 0% 2 100% 38% 13 62% 50% 3 50% 43% 20 57% For those entities that use grounding rods, the impedance to ground varies as described in Table 30. Given the small response to this question, it is difficult to imply any statistically significant conclusions. Table 30: If driven grounds are used, what are the impedance requirements? Utilities and Impedance of Driven Ground Type Municipality Utility - IOU Utility Municipal Total Count of Responses in Group <= 25 % reporting <= 50 % reporting No % reporting ohm <= 25 ohm ohm <= 50 ohm Req. No Req. 1 5 1 1 100% 1 20% 0 0% 0 0% 2 40% 0 0% 0 0% 2 40% 1 100% 7 2 29% 2 29% 3 42% Table 31 indicates the number of conductors distributed to streetlights in underground distribution areas. There is no dominant answer as to how many conductors. Thirty-six percent of respondents use a two wire conductor with a hot leg and neutral, 22% use a three wire conductor with hot, neutral and ground and 42% use two hot legs and the neutral. Table 31: When serving underground fed streetlights, how many conductors are installed between the transformer and the streetlight pole? Utilities and No. Conductors for Underground Fed Streetlights % Count of Hot Leg reporting Type Responses and Hot Leg in Group Neutral and Neutral Municipality 5 0 0% Utility - Co2 2 100% Op Utility - IOU 23 8 35% Utility 6 3 50% Municipal Total 36 13 36% 77 Hot Leg, % reporting Two Hot % reporting Neutral Hot Leg, Legs Two Hot and Neutral and and Legs and Ground Ground Neutral Neutral 2 40% 0 0% 3 60% 0 0% 5 22% 1 17% 10 43% 2 33% 8 22% 15 42% Fuses are used by most of the streetlight entities (91%) responding to the survey as shown on Table 32. The location of the fuse varies widely from the transformer or controller (23%), the hand hole or streetlight pole base (48%) to a two location scheme of the transformer and the pole base (20%). Municipalities that own streetlights and municipal utilities prefer the hand hole or the pole base (100% and 57% respectively) while IOUs have no preference. Table 32: Where are the fuses located on underground street lighting circuits? Utilities and Fuse Locations on Underground Circuits Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total % Hand % % reporting % reporting reporting Count of Transformer Hole Transformer No reporting Transformer Hand Transformer or Responses or and pole No or and pole Fuses Hole or in Group Controller Pole base Fuses Controller Pole base Base Base 5 1 0 0% 0 0% 0 0% 0 0% 5 100% 1 100% 0 0% 0 0% 2 0 0% 1 50% 1 50% 0 0% 29 7 4 14% 0 0% 8 28% 1 14% 10 34% 4 57% 7 24% 2 29% 44 4 9% 10 23% 21 48% 9 20% Street Lighting Maintenance Practices Table 33 delineates who performs routine streetlight maintenance for the different streetlight owning entities. All entities favor the use of dedicated streetlight maintenance crews (56% for municipalities that own streetlights, 44% for IOUs and 71% for municipal utilities). IOUs are also more likely than the other street lighting entities to use contractors to maintain their streetlights (32%). Table 33: Who performs routine maintenance on streetlights? Utilities and Performers of Routine Maintenance % % Count of Regular reporting Dedicated reporting % reporting Type Responses Line Regular Contractors Crews Dedicated Contractors in Group Crews Line Crews Crews Municipality 9 5 56% 3 33% 1 11% Non-utility 1 0 0% 1 100% 0 0% Other Utility - Co3 1 33% 1 33% 1 33% Op Utility - IOU 34 15 44% 8 24% 11 32% 78 Utilities and Performers of Routine Maintenance Type Utility – Municipal Total % % Count of Regular reporting Dedicated reporting % reporting Responses Line Regular Contractors Crews Dedicated Contractors in Group Crews Line Crews Crews 7 5 71% 1 14% 1 14% 54 26 48% 14 26% 14 26% Of the streetlight maintenance personnel used, 50% are fully qualified high voltage linemen, 39% are low voltage linemen, 9% are other and 2% have no special qualifications. Utilities, both IOUs and municipal, are more likely to use high voltage linemen (52% and 71% respectively) than are municipalities that own streetlights (14%). Municipalities that own streetlights tend to use low voltage linemen. Table 34: What are the qualifications of personnel maintaining the streetlights? Utilities and Qualifications of Maintenance Personnel % % Count of reporting reporting HV LV Type Responses Other Linemen HV Linemen LV in Group Linemen Linemen Municipality 7 1 14% 4 57% 2 Non-utility 1 0 0% 0 0% 1 Other Utility - Co2 2 100% 0 0% 0 Op Utility - IOU 27 14 52% 11 41% 1 Utility 7 5 71% 2 29% 0 Municipal Total 44 22 50% 17 39% 4 % % reporting No Special reporting No Special Qualification Other Qualification 29% 100% 0 0% 0 0% 0% 0 0% 4% 0% 1 4% 0 0% 9% 1 2% Table 35 indicates most streetlight entities do not perform group relamping, 62% - no vs. 38% - yes. Municipalities that own streetlights are more likely to group relamp than the other entities. The average group relamping cycle is 4.1 years. It does not differ greatly from the average replacement cycle of those entities that report they do not group relamp. Table 35: Is group relamping performed? If group relamping, what is the interval between relamping? Utilities and Group Relamping Type Municipality Non-utility Other Count of % % Responses in Yes reporting No reporting Group Yes No 8 1 4 50% 1 100% 4 50% 0 0% 79 Avg. Interval Reported by those responding "Yes" Avg. Interval Reported by those responding "No" 4 6 4 Utilities and Group Relamping Type Utility - CoOp Utility - IOU Utility Municipal Total Count of % % Responses in Yes reporting No reporting Group Yes No 2 0 0% Avg. Interval Reported by those responding "Yes" Avg. Interval Reported by those responding "No" 2 100% 25 10 40% 6 1 17% 15 60% 5 83% 4 3 4.5 42 16 38% 26 62% 4.1 4.3 A secondary method of examining the question of group relamping is by the number of streetlights owned rather than the type of entity owning the streetlights. The low (less than 10,000 streetlights) number of streetlights owned group appears to group relamp more so that the other size entities. Table 35A Streetlights Owned and Group Relamping Number of Streetlights Less than 10,000 10,000 to 50,000 50,000 to 100,000 More than 100,000 Total Count of % % Responses Yes reporting No reporting in Group Yes No Avg. Interval Reported by those responding "Yes" Avg. Interval Reported by those responding "No" 4 2 50% 2 50% 5 8 1 12% 7 88% 4 4 13 6 46% 7 54% 3.5 4 17 7 41% 10 59% 4.33 5 42 16 38% 26 62% 4.1 4.3 Most entities that own streetlights conduct an inventory either at the time of group relamping (16%) or as a separate activity (55%). Only 29% do not conduct any type of inventory of installed streetlights. (see Table 36 below) However, IOUs are more likely to conduct inventories of installed streetlights (83%) than are either municipalities that own streetlights (50%) or municipal utilities (60%). 80 Table 36: Is inventorying of streetlight conducted periodically? Utilities and Streetlight Inventory Practices % % % Count of Part of reporting Conducted reporting No reporting Type Responses Group Part of Separately Conducted Inventory No in Group Relamping Group Separately Inventory Relamping Municipality 6 1 17% 2 33% 3 50% Non-utility 1 0 0% 0 0% 1 100% Other Utility - Co2 0 0% 1 50% 1 50% Op Utility - IOU 24 5 21% 15 62% 4 17% Utility 5 0 0% 3 60% 2 40% Municipal Total 38 6 16% 21 55% 11 29% The majority (79%) of streetlight owning entities responding to the survey, as depicted in Table 37, do not inspect streetlight wiring for deterioration, shorts or wear. However, 50% of municipalities that own streetlights do inspect their streetlight wiring. Of the entities that do inspect wiring, the average frequency is 6.67 years. Table 37: Is regular inspection of streetlight wiring for deterioration, shorts or wear performed? Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Count of Responses in Group 6 1 % % reporting No reporting Yes No 3 50% 3 50% 0 0% 1 100% 2 0 0% 24 6 4 17% 1 17% 20 83% 5 83% 7.5 39 8 21% 31 79% 6.67 Yes Avg Frequency Reported by those responding "Yes" 5 2 100% Given the number of responses to the question of who reports streetlight outages, it is obvious that many streetlight owning entities have multiple groups reporting outages. The most frequent group that reports streetlight outages are the general public at 55%. Police and people within the streetlight owning entity at 21% each also play key roles in reporting streetlight outages. 81 Table 38: What is the primary method for streetlight outage reporting? Utilities and Primary Method of Outage Reports Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Count of Responses in Group 13 1 2 % % % Dedicated reporting Customers reporting Police reporting % Person Dedicated Report Customers Report Police Other reporting Reports Person Outages Report Outages Report Other Outages Reports Outages Outages Outages 7 54% 2 15% 4 31% 0 0% 1 100% 0 0% 0 0% 0 0% 2 100% 0 0% 0 0% 0 0% 44 11 23 52% 6 55% 11 25% 2 18% 8 18% 3 27% 2 5% 0 0% 71 39 55% 15 21% 15 21% 2 3% Survey respondents reported only replacing streetlight fixtures, poles and wiring upon failure of the asset. (see Table 39 below) Table 39: How often are streetlight fixtures, poles and wiring replaced? Utilities and Fixture, Pole & Wiring Replaceme Type Number Reporting Replaced on Fixture Failure Only Number Reporting Replaced on Pole Failure Only 1 6 1 6 1 2 2 2 24 6 23 6 23 6 39 38 38 Municipality 6 Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Number Reporting Replaced on Wiring Failure Only The annual cost to maintain streetlights on a per streetlight basis is depicted on Table 40 below. There was a wide range of costs per streetlight per year reported in the survey with municipalities that own streetlights reporting a higher cost than the utilities. An expected cost might be in the $40 range based on spot relamping with a fully qualified high voltage lineman and replacement every four years. 82 Table 40: What is the cost for maintenance per streetlight per year? Utilities and Cost for Maintenance per Streetlight per Yr Type Municipality Utility - IOU Utility - Municipal Range-Low $85 $10 $25 Range-High $400 $50 $382 Average $260.50 $27 $203.50 Training There is some kind of training provided to most people involved in the design of streetlight systems. However, the majority of the training (57%) is on the job. Some street lighting owning entities (23%) provide classroom training in addition to on the job training. Table 41: What type of training is given to the people designing streetlight systems? Utilities and Streetlight System Designer Training % Count of % On % reporting Type Classroom reporting Other Responses None reporting The On The in Group None Job Classroom Job Municipality 9 0 0% 6 67% 2 22% 1 Non-utility 1 0 0% 1 100% 0 0% 0 Other Utility - Co2 0 0% 1 50% 0 0% 1 Op Utility - IOU 30 2 7% 16 53% 7 23% 5 Utility 7 0 0% 4 57% 2 29% 1 Municipal Total 49 2 4% 28 57% 11 23% 8 % reporting Other 11% 0% 50% 17% 14% 16% Installers of street lighting equipment also receive some type of training. Thirty-seven percent receive low voltage training and another 37% receive special training on the installation of streetlight equipment. 83 Table 42: What type of training is given to people installing streetlights? Utilities and Streetlight Installer Training Type Municipality Non-utility Other Utility - CoOp Utility - IOU Utility Municipal Total Count of Responses in Group 5 1 % % Special reporting % % Low reporting Correct Special None reporting Other reporting Voltage Low Install Correct None Other Voltage Training Install Training 0 0% 2 40% 2 40% 1 20% 0 0% 0 0% 0 0% 1 100% 2 0 0% 0 0% 0 0% 2 100% 24 6 2 8% 1 17% 11 46% 1 17% 9 38% 3 50% 2 8% 1 17% 38 3 8% 14 37% 14 37% 7 18% The number of responses to the question regarding streetlight inspectors indicates some of the streetlight owners do not have dedicated streetlight inspectors. Fifty-five percent of those that do have inspectors do provide some type of formal training. (see Table 43 below) Table 43: What type of training is given to inspectors of streetlight systems? Utilities and Dedicated Inspector Training Type Municipality Utility - IOU Utility Municipal Total Count of Responses in Group None % reporting % reporting % reporting Some Other None Some Other 4 13 3 0 0% 5 38% 2 67% 3 75% 7 54% 1 33% 1 25% 1 8% 0 0% 20 7 35% 11 55% 2 10% 84 APPENDIX B Table of Code References Organization California Public Utility Commission Standard General Order #95 American National Standard Practice for Roadway Lighting National Fire Protection National Agency Electrical Code (NEC) National American National Electrical Standards Institute/ Safety Code Institute of Electrical (NESC) and Electronic Engineers American National Standards Institute/ Illumination Engineering Society of North America American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers National Fire Protection Agency Rule 58.5, 78.3, et al RP-8-00 Addressing Requirements for street and decorative lighting in the State of California. Basic design guide of fixed lighting for roadways, adjacent bikeways, and pedestrian ways. 90.2(A)(2) Installation of electric conductors along public and private premises. C2-2002 Basic safeguard of persons from hazards arising from installation, operation, or maintenance of electric supply and communication lines and associated equipment. Establishes the NESC as the rules governing public or private utilities. National Electrical Safety Code (NESC) 011.A National Electrical Safety Code (NESC) 011.B Defines the applicability of NESC rules. 90.1(A) Defines the purpose of the NEC. 90.2(B)(5) Defines the point of demarcation between the NESC and NEC rules. 011 Defines the point of demarcation between the NEC and NESC rules. National Electrical Code (NEC) National Fire Protection National Agency Electrical Code (NEC) National American National Electrical Standards Institute/ Safety Code Institute of Electrical (NESC) and Electronic Engineers 87 Organization American National Standards Institute/ Institute of Electrical and Electronic Engineers National Fire Protection Agency Standard National Electrical Safety Code (NESC) Rule Part 1, Section 2 Definitions Addressing Defines terms qualified person, service point, and utility. 100. Definitions Defines the term service point. 210.8 Ground- fault circuit- interrupter protection for personnel. 232.B.4 Clearances of wires, conductors, cables, equipment, and support arms mounted on supporting structures for street and area lighting. Table 2322 Vertical clearances of equipment cases, support arms, platforms, braces and unguarded rigid live parts above ground, roadway, or water surfaces. 011.C Defines NESC as the rules covering street and area lighting under the exclusive control of utilities or other qualified persons. 1910.269 This provision establishes a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment. National Electrical Safety Code (NESC) 092.B.1 Alternating current systems that are to be grounded, 750 volts and below. National Electrical Safety Code (NESC) 097.A.2 Separation of grounding conductors. National Electrical Code (NEC) National Fire Protection National Agency Electrical Code (NEC) National American National Electrical Standards Institute/ Safety Code Institute of Electrical (NESC) and Electronic Engineers National American National Electrical Standards Institute/ Safety Code Institute of Electrical (NESC) and Electronic Engineers National American National Electrical Standards Institute/ Safety Code Institute of Electrical (NESC) and Electronic Engineers 29 CFR Part Occupational Safety 1910 and Health Occupational Administration Safety and (OSHA) Health Standards American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers 88 Organization American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers National Fire Protection Agency American National Standards Institute/ Institute of Electrical and Electronic Engineers Standard National Electrical Safety Code (NESC) Rule 097.B.2 Addressing Exception to separation of grounding conductors. National Electrical Safety Code (NESC) 093.C.7 Bonding of equipment frames and closures. National Electrical Safety Code (NESC) 384.A & B Effectively grounding conductive cases and closures of equipment. National Electrical Safety Code (NESC) 215.C.1 Effectively grounding metal or metal reinforced supporting structures including lamp posts. National Electrical Safety Code (NESC) 314.B Conductive lighting poles shall be effectively grounded. National Electrical Safety Code (NESC) 093.C.8 Grounding conductor ampacity limits. National Electrical Safety Code (NESC) 093.A Composition of grounding conductor. National Electrical Code (NEC) National Electrical Safety Code (NESC) 250.66 Size of alternating current grounding electrode conductor. Table 2356 Clearances in direction from line conductors to supports and to vertical or lateral conductors, span, or guy wires attached to the same support. 89 Organization American National Standards Institute/ Institute of Electrical and Electronic Engineers American National Standards Institute/ Institute of Electrical and Electronic Engineers Standard National Electrical Safety Code (NESC) Rule 350.F Addressing Bonding of all above ground metallic power and communications equipment separated by a distance of six feet or less. National Electrical Safety Code (NESC) 441.A.1.a, b, and c Minimum approach distances, deenergizing and grounding of lines above 300 volts unless insulated from the energized part. 90 APPENDIX C Electric Shock and the Human Being This section discusses contact incidents; it explains methods of protection against and the process the body goes through during such an occurrence. This section is intended to inform the reader of the dangers of accidental contact and methods of protection that can be utilized to protect one’s life. These concepts can be brought forward into street lighting practices to help achieve the best system possible for safeguarding the public. The human body, particularly the heart, is very vulnerable to electrical current. Muscle contraction, paralysis, or heart stoppage can result from the flow of current through the body. Burns of the skin may also occur. These effects depend upon the amount of current and the path which the current takes through the body. The length of time during which the current flows through the body is also a significant factor. At currents ranging from 0.0001 to 0.001 ampere, a person my start to sense that current flow is present. A current level of 0.001 to 0.005 ampere may cause the arm muscles to contract and pain to begin. A current level of 0.01 ampere induces both pain and muscle contraction. Uncontrolled contraction of muscles results from current between 0.01 and 0.02 ampere. Thus, a person cannot let go of an energized conductor. If the current level is above 0.03 ampere, loss of voluntary controls over respiratory muscles may occur causing breathing to stop. Normal respiration generally resumes if the current is interrupted. Current flow through the heart muscle will cause ventricular fibrillation. During this condition, the muscles of the heart operate in a disorganized manner and do not pump blood. Current levels as low as 0.075 ampere can cause this condition, but the human body can normally tolerate this for a short time. The threshold for 60 Hz current is proportional to body weight and inversely proportional to the square root of shock duration time. A current of 1 ampere through the heart muscle for 1/60 of a second will cause fibrillation.9 When a person touches an energized conductor, current flows through the body to the ground. Some of the current may flow through the heart, depending upon how contact occurred. The amount of current that flows depends upon the resistance of the skin, the voltage on the energized conductor, and the ground resistance. The skin typically provides a resistance on the order of 1500 to 5000 ohms. Skin puncture, which can result from burns caused by electrical current flow, reduces the resistance to as low as 500 ohms.10 9 “A range of Body Impedance Values for Low Voltage, Low source Impedance systems of 60 Hz”, M. S. Hammam, R. S. Baishiki, IEEE Transactions on Power Apparatus and Systems, Vol. PAS-102, May, 1983, pp 1097 – 1105 10 “Downed Power Lines: Why They Can’t Always Be Detected”, D. R. Volzka et al., IEEE Power Engineering Society, February 22, 1989, p23 93 Now consider what happens when a person touches a 120 volt conductor. The typical skin resistances noted above permit a current flow of approximately 0.024 to 0.080 amperes which can be enough to cause fibrillation given sufficient time. When a person touches a 480 volt conductor, the current flow would be 0.096 to 0.320 amps. It should be noted that a breaker or a fuse can not distinguish between these currents and those of load currents and will not operate to protect the person. GFI (Ground Fault Interrupter) outlets are designed to operate for faults of 0.005 amps and do provide protection from electric shock.11 Figure 5 shows how skin resistance and voltage affect current flow through the body, and the effects of these currents. This figure shows that contact with an energized power line conductor is likely to cause ventricular fibrillation or cardiac standstill. These effects will occur faster than the fault can be detected and the circuit isolated.12 The effects of current flowing through the body depend primarily on the frequency, magnitude, duration, and path of the current through the body. On the basis of safety, the 50-60 Hz range of frequencies used by utilities is not a good choice for power systems, because it is in the same range of frequency as the human heart. The body is capable of surviving much higher levels of current at either lower or higher frequencies. The higher threshold at higher frequencies is apparently due to the tendency of the current to remain near the skin’s surface and away from the heart region. Research indicates that current magnitude is not the only important factor, the shock impulse to the heart must occur during a certain window of the heartbeat to cause ventricular fibrillation. The duration of the shock increases the probability that the shock impulse to the heart will occur during this window. Some experiments also indicate that physiological factors, such as age and gender, may be more important than body weight. Thus, the following equation yields the tolerable body current that is recommended for all body weights: 0.116 Amperes ts IB = rms magnitude of the current through the body (Amps) ts = duration of the shock (seconds) IB = Individual cases needs to be considered when determining risk, but how a person contacts the electrical equipment and other factors can influence the level of risk. There are three types of accidental shock circuits that are normally studied: Touch Potential = voltage differences between hand and feet Step Potential = voltage differences from foot-to-foot 11 “Downed Power Lines: Why They Can’t Always Be Detected”, D. R. Volzka et al., IEEE Power Engineering Society, February 22, 1989, p23 12 “Downed Power Lines: Why They Can’t Always Be Detected”, D. R. Volzka et al., IEEE Power Engineering Society, February 22, 1989, p23 94 Figure 5 Effects of Electricity on Humans 95 Metal-to-Metal Touch Potential = voltage potential difference between one hand and the other hand For Touch Potential and Step Potential it is necessary to be able to model the resistance of the feet to the earth. The foot is represented as a perfectly conducting circular metallic disk (ignore the resistance of shoes and shocks). The equation for the resistance of the foot on uniform soil is Rf = ρ ohms 4b ρ = the resistivity of soil directly beneath the foot, in ohm-m b = equivalent radius of the foot, in meters If b is assumed to be 0.08m (3 in.), then Rf is approximately 3ρ in ohms. Though an equation is given for the mutual resistance between the feet, it has negligible effects. Thus, the resistance of two feet in parallel (touch circuit), is approximately Rf /2 in ohms.13 Soil resistivity varies based on the type of soil and moisture content. Dry asphalt has an average dry resistivity of 16,000,000 ohm-meters, but when wet it can be as low as 10,000 ohm-meters. Concrete has a low resistivity when wet, 21 to 63 ohm-meters. (Note: these values for soil resistivity are typical values only). 14 The tolerable touch potential voltages can be computed for each shock situation by multiplying the tolerable body current by the appropriate equivalent shock circuit impedance.15 The touch potential occurs when a person touches the pole and his feet are approximately three feet from the pole. Step potential is normally only considered in areas of high fault currents, such as electric power substations. Touch potential is the metal-to-metal touch voltage. For practical purposes, the grounding system, and all objects bonded to it, may be considered at the same potential. Understanding Grounding To create a circuit, a voltage potential causes current to flow through a conductor (hot leg) to an appliance or load and return on another conductor. The voltage at the receiving end (at the appliance) is different than at the sending end because of the voltage drop in 13 “Tennessee Valley Public Power Association Research and Development Grounding Manual”, Allen & Hoshall, Inc., May 1996, page 46 14 “Tennessee Valley Public Power Association Research and Development Grounding Manual”, Allen & Hoshall, Inc., May 1996, page 49, Table 4.1 15 “Tennessee Valley Public Power Association Research and Development Grounding Manual”, Allen & Hoshall, Inc., May 1996, page 50 96 the conductor (V=IR). The amount of voltage drop is dependent on the amount of current and the resistance of the conductor. In the example circuit below, Figure 6, only a grounded circuit conductor (system neutral) and a hot leg are run to a blender and a disposal in a kitchen. The case of each device is tied directly or indirectly to remote ground. When the disposal is turned on and current flows through the hot leg to the disposal and back through the neutral, there is a voltage drop in the hot leg and a voltage drop in the neutral conductor. With the neutral isolated from the case ground, no voltage potential will be measured between the grounded cases. However, if a volt meter was placed on the load end of each neutral, a voltage potential would be measured which will equal the voltage drop from the return current in the neutral. The typical voltage drop allowed by the NEC is only 4 volts. Blender 120 V Disposal 120 V Figure 6 Example Circuit, Equipment Case Remotely Grounded Another situation to be concerned about occurs when the there is a short circuit in the disposal. This would occur if the hot leg is tied or shorted to the case. In this instance, the potential difference between the disposal case and blender case is very near the full 120 volt. The actual voltage will depend on the resistance of each case ground. In this instance, assuming the ground resistance of the disposal case ground is 20 ohms, the resulting fault current is 6 amps (I=V/R). This current may or may not be of a sufficient magnitude to trip a breaker or fuse. Another possible way to ground the cases is to bond the neutral conductor to the case, as shown in Figure 7. This time there is no ground connection at each case. With no current flowing, the voltage between the case of the blender and the disposal is zero. When the disposal is turned on, the voltage difference between the disposal case and the blender case is the voltage drop from the current in the system neutral (V=IR). The potential difference is often too low to present a shock hazard to persons or affect operation of conventional electrical load equipment.16 It should be noted that while this small potential difference may not be a shock hazard to people, a similar situation within 16 “IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems”, Gordon S. Johnson et al., 1992, page 39 97 a dairy barn, can result in a voltage potential of sufficient level to be detected by livestock. In this same connection, if the hot leg shorted to the case of the disposal a closed circuit is formed from the hot leg to the case and back to the source through a low impedance path (the neutral conductor). This low impedance path will result in high currents which will quickly trip a breaker or fuse. There will be voltage potential between each case. This is a result of the voltage drop from the fault current returning to the source through the system neutral. Because the fault current is many times higher than the load current, the potential difference can pose a hazard to humans. However, the low impedance path will help to de-energize the fault quickly. If one touches both cases during the fault, an alternate return path is established through the individual’s body (metal-to-metal touch potential). Standing next to the disposal and touching it during a short circuit results in an alternate path to ground through the body (touch potential). As long as the impedance in the body and the remote ground (resistance beneath the feet) is sufficiently high, the shock potential is limited but is still a cause for concern. Blender 120 V 120 V Disposal Figure 7 Example Circuit, Equipment Case Bonded to System Neutral To avoid the problems shown in Figures 4 and 5, the NEC requires that a separate grounding conductor be run in addition to the grounded circuit conductor (neutral). For this system, the grounding conductor is tied to neutral at the service entrance and the grounding conductor is tied to each case. Each case can also have a direct connection to the earth via a separate ground rod or tied to other grounding sources such as metallic water pipes or structural steel in a building. The neutral is not connected or bonded to the case. In fact, the neutral is treated like the hot leg and isolated from the case and from the grounding conductor at all locations except at the service entrance. The connection is shown in Figure 8. 98 Blender 120 V 120 V Disposal Figure 8 Example Circuit, Equipment Case Remotely Grounded and Bonded to System Neutral When load current is flowing to the disposal, the cases are at ground potential because there is no return current in the grounding conductor. A voltmeter would measure a voltage potential between the load ends of each neutral. During a short circuit at the disposal (the hot leg tied to the case ground), the low impedance path to the source will result in sufficient fault current to trip a breaker or fuse. There will still be a voltage potential during the fault between the case of the disposal and the case of the blender. The NEC sets parameters to ensure that the impedance of the grounding conductor is low enough to accept the available line-to-ground-fault current without creating a hazardous impedance (IR) voltage drop. Thus the available ground-fault current of the supply system will have a direct bearing on the equipment-grounding conductor requirements.17 The NEC also provides protection from a circuit fault by requiring ground fault interrupters (GFI) in bathrooms, kitchens near water sources, and outside. These devices compare the current on the hot leg to the current on the neutral conductor. If there is a difference, the device de-energizes the circuit. The comparison of the currents allows the device to operate very fast for very small differences in currents (less than .005 amps). This speed and sensitivity is necessary to protect humans from electric shock. The example based discussion to understanding grounding is critical to the design of safe and reliable systems. These examples show how systems react under different grounding and bonding situations, and help show advantages and disadvantages to each system. Without this understanding, all protections available to safeguard the public may not be utilized. 17 “IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems”, Gordon S. Johnson et al., 1992, page 81 99 APPENDIX D Street Lighting Design Basics and Inspection Techniques Presented by Hi-Line Engineering, LLC Training Prerequisite Participants involved in this training segment must have a demonstrated knowledge of the basic concepts of electrical theory, grounding practices and principles, a minimum of 6 months construction experience, ability to interpret electrical codes, are familiar with map and diagram reading, familiarity with the National Electrical Code and National Electrical Safety Code. Seminar Goals The intent of this training is to provide inspectors, linemen, and technicians with the techniques and tools required to safely, efficiently and effectively inspect street lighting systems to protect the public and personnel. Insight gained from the inspection process will benefit linemen and technicians who can later apply innovative techniques in the field. This will be accomplished by explaining the basic concepts of street lighting, how to apply codes and standards, verification of wiring, and bonding and grounding requirements. Also, discussion will be held on current technology available for the protection of the public, such as, breakaway poles and wiring. Proper wiring is paramount for the protection of life, methods of wiring verification will be discussed and simple measures shown for checking wiring. It is assumed those attending the course are familiar with wiring techniques, electrical theory, grounding and bonding practices and concepts, and electrical codes. The ability to read maps and diagrams, as well as, construction experience will help the student absorb the material more easily. Training Objective • Verification techniques for compliance with all applicable electrical codes and utility specifications with regards to street light installation. • Recognition of source side hot wire reversal. • Recognition of wiring in compliance with construction drawings. • Purpose of grounding and bonding techniques, as required by codes, to protect employees and the public from touch potential and ground plane differential voltages. • Introduction to the basic theory overview of lighting concepts including lighting levels, veiling luminance, glare, etc. • Application of standards for offset distances from roadways and standards for breakaway pole foundations and wiring requirements. • Inspection techniques for concrete street lighting foundations will be explored with common problems identified. 103 • Comprehension of design specifications including reading maps and diagrams, and code references. Terminal Objectives • The student will be able to apply codes and utility specifications to an inspection and provide feedback as to the condition of the installation. • The student will be capable of verifying proper wiring and check for lead reversal utilizing techniques learned. • The student will utilize techniques from the class to verify the grounding and bonding per applicable codes and specifications. The student shall utilize their class experience of bonding concepts to identify possible areas of concern to be brought forth to the design engineer. • The student will use skills from class to aid in identifying areas where lighting levels may not be sufficient or areas of shadows occur and bring forth these concerns to the design engineer. • The student will be capable of determining if street lighting poles proximity to the roadway may pose a hazard to the public and bring concerns forward to a design engineer. • The student will utilize techniques obtained through training to analyze the concrete structure for basic compliance with specifications. The student will utilize knowledge gained in the seminar to check for common problems found in concrete foundations. • The student may utilize his training on breakaway pole and wiring systems, obtained from class, to verify proper operation of the scheme. The student will be able to recognize different types of breakaway poles and wiring schemes and verify their proper operation. • The student will be able to read a plan, verify proper locations and installation in accordance to the plan. Training Strategies Audience Specific Effective training takes into consideration the characteristics of the audiences being trained and what those audiences need to learn. A seminar can be created that is tailored to the training needed for the intended audience to transfer the knowledge and skills identified in this analysis. Hands-On The participants will acquire new skills and will practice those skills throughout training to ensure knowledge retention. The training will allow participants to see, hear and do (practice) the actions they will be expected to perform. 104 Focused Content The seminar will focus on street lighting inspection process. The course will not cover basic knowledge of electricity, plan reading, or code implementation. The training will focus on essential skills and concepts necessary to safeguard the public and personnel from improper street light installation. While a training program must teach individuals the building blocks to garner an overall perception of street lighting, this program is not intended to make street light designers out of the students. The participant will be required to interpret portions of design standards to be effective. A good example highlighting this concept is the need for a participant to know distances from roadways in which breakaway poles or wiring may be required. Supporting materials, in printed format, will contain tables, charts and diagrams needed to perform an inspection. Several real world inspection problems will be given in the classroom as a joint exercise. In addition, individual problems will be assigned for completion. Due to the highly visual nature of the trainees and the dominant mode of learning, the presentation material will include photos and repetition of the material content. Good example problems and situations will also be presented in both group exercises and individual exercise. The repetition of the examples helps to reinforce the new design skills. Interactive Participants involved in training will find the classroom interaction enjoyable and valuable. The give and take of classroom interaction, permits trainees to address unique concerns that could not be covered using more rigid training methods. The training materials will use creative approaches including a variety of presentation styles, methods of instruction, realistic examples, and frequent opportunity for trainees to assess their understanding of a topic. Surveys of the class will help all participants to learn from their peers in their geographic area. The methods used and lessons learned by the individuals and their utilities will be discussed as it relates to street lighting safety, inspection techniques, and inspection timetables. Throughout the training, the trainee will work on sample problems followed by a group review to give the trainee immediate feedback informing them the answer they gave was correct. Modular A modular approach to training should be used, grouping the information given in logical and easy to understand format. This pertains to the instructional design elements and provides flexibility in organizing and presenting the training. This logical step by step approach will lead the trainee from the simple concepts to the 105 Modular complex design techniques employed and there importance to the task of street light inspection. Timely Delivery Ideally training should occur prior to the required use of the information, as refresher training or support a continuous training program. The trainees who will attend the training seminar will already have experience in construction type activities, plan reading, basic electricity and familiarity with applicable electrical codes and utility standards. The seminar will be designed for those new to the inspection of street lighting, preparing the student for exposure to varying types, styles and design concepts. It will also be useful as a refresher training seminar for those who have been in the field performing these services already. Real-Life Scenarios Abstract explanations and far-fetched examples will be avoided in favor of concrete, real-life scenarios. Street lighting wiring diagrams, utility standards, and other sources, from actual utilities, will be utilized to show real world designs. The testing for lead reversal on a street light, proper grounding and bonding, and adherence to standards are all real life situations faced by inspectors. The information will be pertinent thereby increasing retention and recall when called upon to perform the task in the field. Trainee Skill Assessment Trainee skill assessments will be conducted informally during the course through class and individual problems. Each course will include exercises for participants to complete specific tasks on their own. These exercises give the user immediate feedback and allow for clarification of concepts prior to advancing to other topics. Trainee feedback is an important function in developing training. The instructor will ask for feedback during and at the end of training. A written evaluation is essential to judge if the terminal objectives were met. Modifications can be made to the curriculum to improve participation and retention. Course Evaluations Training Curriculum The course lesson overview/ outline are provided in this section. The following information provides a summary of the lessons and topics for the seminar. The curriculum is designed to meet the objectives of the training seminar. I. Electric Shock and the Human Body A. Affects of Electricity on the Body i. Level of Current Required to Affect the Heart Muscle ii. How Voltage Levels Affect Current Flow B. Resistance of the Human Body i. Hand to Hand Contact 106 II. III. IV. V. VI. VII. VIII. ii. Hand to Foot Contact iii. Other Contact Methods Understanding Grounding A. Grounding Versus Bonding B. NEC, NESC Requirements C. Effectively Grounded Bonding A. Touch Potential B. Step Voltage C. Proximity to Other Objects D. Effectively Grounded Code Implementation A. NEC, NESC, OSHA, DOT B. Case studies Roadway Lighting Design A. Identify Roadway Types i. Expressway ii. Major iii. Collector iv. Local B. Luminance Levels C. Design Techniques D. Light Trespass E. Pole Offsets i. Breakaway Pole Requirements ii. Breakaway Wiring Requirements F. Pedestrian Conflict Areas Map and Diagram Reading A. Knowledge of Symbols B. Interpreting Schematic Diagram C. Verify the Construction to the Drawing (Conceptualization) Wiring and Construction Standards A. Equipment Utilized i. Type Poles ii. Type Fixtures iii. Wattage of Fixture iv. Type Bulb B. Voltage Levels C. Wiring Methods D. Mounting and Aiming E. Methods of Control i. Understand How This Affects Safety of Personnel and Public Inspection Requirements A. Verification of Proper Wiring i. Check for Lead Reversal ii. Use of Multimeter 107 iii. Falls Within Utility or Applicable Safety Code iv. Are Connections Proper With No insulation Exposed v. Understand the Operation and Connections Required for Breakaway Poles and Wiring B. Adherence to Utility Specifications i. All Applicable Codes C. Determining Proper Grounding and Bonding i. Some Form of Grounding or Bonding Present ii. Neutral Tied to Ground Rod D. Structural Support is Installed Properly i. Base is Secure and Meets all Requirements of Applicable Codes and Utility Specifications 1. Concrete Base Properly Formed and Reinforcing Rod Present E. Proximity to Roadway i. Breakaway Pole and Wiring Required F. Safety Inspection Checklist i. Verify All Safety Critical Items are Properly Installed G. Understand What to Look for in an Inspection i. Perform a Mock Inspection and Critique the Process IX. Certification Test and Practical Exam 108 BIBLIOGRAPHY American Association of State Highway and Transportation Officials. 2003 Interim Revisions to the Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. 4th Edition. Washington: American Association of State Highway and Transportation Officials, 2003. ---. An Information Guide for Roadway Lighting. Washington: American Association of State Highway and Transportation Officials, 1984. American Association of State Highway and Transportation Officials/Associated General Contractors/American Road and Transportation Builders Association. 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