SECTION 26 05 73 - ELECTRICAL SYSTEMS STUDIES AND ANALYSIS
PART 1 - GENERAL
1.1
RELATED DOCUMENTS
A.
1.2
Drawings and general provisions of the Contract, including General and Supplementary
Conditions and Division 01 Specification Sections, apply to this Section.
SUMMARY
A.
This Section includes computer-based, fault-current, are flash hazard analysis and overcurrent
protective device coordination studies. Protective devices shall be set based on results of the
protective device coordination study.
1.
1.3
Coordination of series-rated devices is permitted only where series ratings are allowed
and indicated on Drawings and/or schedules.
SUBMITTALS
A.
Product Data: For computer software program to be used for studies.
B.
Product Certificates: For coordination-study and fault-current-study computer software
programs, certifying compliance with IEEE 399.
C.
Qualification Data: Submittal information shall be signed and sealed by a registered
professional engineer (licensed in the State where project is located) indicating that the studies
and analysis are in compliance with applicable codes and the requirements of this specification.
Also refer to Section 1.4 “Quality Assurance” for qualification requirements.
D.
Other Action Submittals: The following submittals shall be made after the approval process for
system protective devices has been completed. Provide five (5) bound copies of complete final
report and CD in PDF format.
1.
2.
3.
4.
5.
6.
7.
E.
Coordination-study input data, including completed computer program input data sheets.
Study and Equipment Evaluation Reports.
Coordination-Study Report.
One-Line Diagrams.
Description, Purpose and Scope of the Study.
PPE Ratings.
Incident Energy and Flash Protection Boundary Calculations.
Study: The short-circuit and protective device coordination studies shall be submitted to the
design engineer prior to receiving final approval of the distribution equipment shop drawings
and/or prior to release of equipment drawings for manufacturing. If formal completion of the
studies may cause delay in equipment manufacturing, approval from the Design Engineer may
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be obtained for preliminary submittal of sufficient study data to ensure that the selection of
device and characteristics will be satisfactory. Protective device coordination in regards to
selective coordination is required prior to the applicable equipment review process.
1.4
QUALITY ASSURANCE
A.
Studies shall use computer programs that are distributed nationally and are in wide use.
Software algorithms shall comply with requirements of standards and guides specified in this
Section. Manual calculations are not acceptable.
B.
Coordination-Study Specialist Qualifications: An entity experienced in the application of
computer software used for studies, having performed successful studies of similar magnitude
on electrical distribution systems using similar devices.
1.
Professional Electrical Engineer, licensed in the state where Project is located, shall be
responsible for the study. All elements of the study shall be performed under the direct
supervision and control of engineer. The Registered Professional Engineer shall be a
full-time employee of the Engineering Services Organization.
C.
Comply with IEEE 242 for short-circuit currents and coordination time intervals.
D.
Comply with IEEE 399 for general study procedures.
E.
Comply with NFPA 70 and 70E.
PART 2 - PRODUCTS
2.1
COMPUTER SOFTWARE DEVELOPERS
A.
Computer Software Developers: Subject to compliance with requirements, provide products by
one of the following:
1.
2.
3.
4.
2.2
CGI CYME.
EDSA Micro Corporation.
ESA Inc.
SKM Systems Analysis, Inc.
COMPUTER SOFTWARE PROGRAM REQUIREMENTS
A.
Comply with IEEE 399.
B.
Analytical features of fault-current-study computer software program shall include
"mandatory," "very desirable," and "desirable" features as listed in IEEE 399.
C.
Computer software program shall be capable of plotting and diagramming time-currentcharacteristic curves as part of its output. Computer software program shall report device
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settings and ratings of all overcurrent protective devices and shall demonstrate selective
coordination by computer-generated, time-current coordination plots.
D.
Computer software program capable of performing an Arch Flash Hazard Analysis in
accordance with IEEE 1584 equations that are presented in NFPA 70E-2004, Annex D.
PART 3 - EXECUTION
3.1
EXAMINATION
A.
Examine Project overcurrent protective device submittals for compliance with electrical
distribution system coordination requirements and other conditions affecting performance.
1.
3.2
Proceed with coordination study only after relevant equipment submittals have been
assembled. Overcurrent protective devices that have not been submitted and approved
prior to coordination study may not be used in study.
POWER SYSTEM DATA
A.
Gather and tabulate the following input data to support coordination study:
1.
2.
3.
Product Data for overcurrent protective devices specified in other Division 26 Sections
and involved in overcurrent protective device coordination studies. Use equipment
designation tags that are consistent with electrical distribution system diagrams,
overcurrent protective device submittals, input and output data, and recommended device
settings. The Contractor shall expedite collection of the data to assure completion of the
studies as required for final approval of the distribution equipment shop drawings and/or
prior to the release of the equipment for manufacturing.
Maximum available fault current and impedance of utility service entrance.
Electrical Distribution System Diagram: In hard-copy and electronic-copy formats,
showing the following:
a.
b.
c.
d.
e.
f.
g.
4.
Circuit-breaker and fuse-current ratings and types.
Relays and associated power and current transformer ratings and ratios.
Transformer kilovolt amperes, primary and secondary voltages, connection type,
impedance, and X/R ratios.
Generator kilovolt amperes, size, voltage, and source impedance.
Cables: Indicate conduit material, sizes of conductors, conductor material,
insulation, and length.
Busway ampacity and impedance.
Motor horsepower and code letter designation according to NEMA MG 1.
Data sheets to supplement electrical distribution system diagram, cross-referenced with
tag numbers on diagram, showing the following:
a.
Special load considerations, including starting inrush currents and frequent starting
and stopping.
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b.
c.
d.
e.
f.
g.
h.
i.
j.
3.3
Transformer characteristics, including primary protective device, magnetic inrush
current, and overload capability.
Motor full-load current, locked rotor current, service factor, starting time, type of
start, and thermal-damage curve.
Generator thermal-damage curve.
Ratings, types, and settings of utility company's overcurrent protective devices.
Special overcurrent protective device settings or types stipulated by utility
company.
Time-current-characteristic curves of devices indicated to be coordinated.
Manufacturer, frame size, interrupting rating in amperes rms symmetrical, ampere
or current sensor rating, long-time adjustment range, short-time adjustment range,
and instantaneous adjustment range for circuit breakers.
Manufacturer and type, ampere-tap adjustment range, time-delay adjustment range,
instantaneous attachment adjustment range, and current transformer ratio for
overcurrent relays.
Panelboards, switchboards, motor-control center ampacity, and interrupting rating
in amperes rms symmetrical.
FAULT-CURRENT STUDY
A.
Calculate the maximum available short-circuit current in amperes rms symmetrical at circuitbreaker positions of the electrical power distribution system. The calculation shall be for a
current immediately after initiation and for a three-phase bolted short circuit at each of the
following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Switchgear bus
Medium voltage controller
Motor control center
Switchboard bus.
Distribution panelboard.
Branch circuit panelboard.
Elevator controllers.
Mechanical equipment starters/controllers
Fire pump controller.
Automatic and/or manual transfer switches.
Standby generator.
B.
Study electrical distribution system from normal and alternate power sources throughout
electrical distribution system for Project. Include studies of system-switching configurations
and alternate operations that could result in maximum fault conditions.
C.
Calculate momentary and interrupting duties on the basis of maximum available fault current.
D.
Calculations to verify interrupting ratings of overcurrent protective devices shall comply with
IEEE 241 and IEEE 242.
1.
Transformers:
a.
ANSI C57.12.10
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b.
c.
d.
e.
2.
3.
4.
E.
2.
Show calculated X/R ratios and equipment interrupting rating (1/2-cycle) fault currents
on electrical distribution system diagram.
Show interrupting (5 cycle) and time delayed currents (6 cycles and above) on medium
voltage breakers as needed to set relays and access the sensitivity of overcurrent relays.
Equipment Evaluation Report:
1.
2.
3.
3.4
Low-Voltage Circuit Breakers: IEEE 1015 and ANSI C37.13.
Low-Voltage Fuses: IEEE C37.46.
Medium voltage circuit breakers: IEEE C37.010
Study Report:
1.
F.
ANSI C57.12.40
ANSI C57.12.22.
IEEE C57.96.
IEEE C57.12.00.
For 600-V overcurrent protective devices, ensure that interrupting ratings are equal to or
higher than calculated 1/2-cycle symmetrical fault current.
For devices and equipment rated for asymmetrical fault current, apply multiplication
factors listed in the standards to 1/2-cycle symmetrical fault current.
Verify adequacy of phase conductors at maximum three-phase bolted fault currents;
verify adequacy of equipment grounding conductors and grounding electrode conductors
at maximum ground-fault currents. Ensure that short-circuit withstand ratings are equal
to or higher than calculated 1/2-cycle symmetrical fault current.
COORDINATION STUDY
A.
Perform coordination study using approved computer software program. Prepare a written
report using results of fault-current study. Comply with IEEE 399.
1.
2.
3.
Calculate the maximum and minimum 1/2-cycle short-circuit currents.
Calculate the maximum and minimum ground-fault currents.
Calculate the maximum and minimum interrupting duty (5 cycles to 2 seconds) short
circuit current.
B.
Comply with IEEE 241 and IEEE 242 recommendations for fault currents and time intervals.
C.
Transformer Primary Overcurrent Protective Devices:
1.
Device shall not operate in response to the following:
a.
b.
c.
D.
Inrush current when first energized.
Self-cooled, full-load current or forced-air-cooled, full-load current, whichever is
specified for that transformer.
Permissible transformer overloads according to IEEE C57.96 if required by
unusual loading or emergency conditions.
Motors served by voltages more than 600 V shall be protected according to IEEE 620
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E.
Conductor Protection: Protect cables against damage from fault currents according to ICEA P32-382, ICEA P-45-482, and conductor melting curves in IEEE 242. Demonstrate that
equipment withstands the maximum short-circuit current for a time equivalent to the tripping
time of the primary relay protection or total clearing time of the fuse. To determine
temperatures that damage insulation, use curves from cable manufacturers or from listed
standards indicating conductor size and short-circuit current.
F.
Coordination-Study Report:
coordination study:
1.
Tabular Format of Settings Selected for Overcurrent Protective Devices:
a.
b.
c.
d.
e.
2.
Prepare a written report indicating the following results of
Device tag.
Relay-current transformer ratios; and tap, time-dial, and instantaneous-pickup
values.
Circuit-breaker sensor rating; and long-time, short-time, and instantaneous
settings.
Fuse-current rating and type.
Ground-fault relay-pickup and time-delay settings.
Coordination Curves: Prepared to determine settings of overcurrent protective devices to
achieve selective coordination. Graphically illustrate that adequate time separation exists
between devices installed in series, including power utility company's upstream devices.
Prepare separate sets of curves for the switching schemes and for emergency periods
where the power source is local generation. Show the following information:
a.
b.
c.
d.
e.
f.
g.
Device tag.
Voltage and current ratio for curves.
Three-phase and single-phase damage points for each transformer.
No damage, melting, and clearing curves for fuses.
Cable damage curves.
Transformer inrush points.
Maximum fault-current cutoff point.
G.
Completed data sheets for setting of overcurrent protective devices.
H.
The protective device coordination study shall determine the final selection of protective devices
that are required to provide selective coordination per the 2008 National Electric Code, in
accordance with the following articles:
NEC 620.62
NEC 700.27
NEC 701.18
Elevators, Dumbwaiters, Escalators, Moving Walks, Wheelchair and Stairway Lifts
Emergency Systems
Legally Required Standby Systems
In addition to the above code requirements, provide selective coordination of protective devices for
the following:
Normal and Emergency power distribution system from main service equipment to, and including,
the next level downstream protective devices within the electrical equipment
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All modifications to the electrical distribution system and protective devices required to ensure
selective coordination are to be determined by this study and are the responsibility of the electrical
contractor. These modifications are to be implemented by the contractor at no additional cost to the
Owner. Notify Architect, in writing, as part of the Submittal, where selective coordination is
unachievable. Provide the best solution that achieves coordination over the long term and short
term ranges.
3.5
ARC FLASH HAZARD ANALYSIS
A.
The arc flash hazard analysis shall be performed according to the IEEE 1584 equations that are
presented in NFPA70E-2004, Annex D.
B.
The short circuit calculations and the clearing times of the phase overcurrent devices will be
retrieved from the short circuit and coordination study model.
C.
The flash protection boundary and the incident energy shall be calculated at all significant new
equipment locations in the electrical distribution system (transformers, switchboards, automatic
transfer switches, distribution panelboards and panelboards) where work could be performed on
energized parts.
D.
The Arc-Flash Hazard Analysis shall include all significant locations in 208 volt systems fed from
transformers equal to or greater than 75 kVA.
E.
Safe working distances shall be specified for calculated fault locations based upon the calculated
arc flash boundary considering an incident energy of 1.2 cal/cm2.
F.
The Arc Flash Hazard analysis shall include calculations for maximum and minimum contributions
of fault current magnitude. The minimum calculation shall assume that the utility contribution is at
a minimum and shall assume a minimum motor load. Conversely, the maximum calculation shall
assume a maximum contribution from the utility and shall assume motors to be operating under
full-load conditions.
G.
Arc flash computation shall include both line and load side of main breaker calculations, where
necessary.
H.
Arc Flash calculations shall be based on actual over current protective device clearing time.
Maximum clearing time will be capped at 2 seconds based on IEEE 1584-2002 section B1.2. The
arch flash analysis shall be based on the lowest clearing time setting of the over current protective
device to minimize the incident energy level without compromising selective coordination.
3.6
FIELD ADJUSTMENT
A.
Adjust protective device settings according to the recommended settings table provided by the
coordination study. Field adjustments to be completed by the engineering service division of
the equipment manufacturer under the Startup and Acceptance Testing contract portion.
B.
Make minor modifications to equipment as required to accomplish conformance with short circuit
and protective device coordination studies.
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C.
Notify Project Office in writing of any required major equipment modifications.
D.
Following completion of all studies, acceptance testing and startup by the field engineering service
division of the equipment manufacturer, a two-year warranty shall be provided on all components
manufactured by the engineering service parent manufacturing company.
3.7
ARC FLASH WARNING LABELS
A.
The vendor shall provide a 3.5 in. x 5 in. thermal transfer type label of high adhesion polyester for
each work location device analyzed.
B.
The label shall have an orange header with the wording, “WARNING, ARC FLASH HAZARD”,
and shall include the following information:
1.
2.
3.
4.
5.
6.
7.
8.
Location designation
Nominal voltage
Flash protection boundary
Hazard risk category
Incident energy range
Working distance
Engineering report number, revision number and issue date.
PPE Ratings/classification
C.
Labels shall be machine printed, with no field markings.
D.
Arc flash labels shall be provided in the following manner and all labels shall be based on
recommended overcurrent device settings.
1.
2.
3.
4.
E.
3.8
For each 480 and applicable 208 volt panelboards, one arc flash label shall be provided.
For each low voltage switchboard, one arc flash label shall be provided.
For each distribution panelboard, one flash label shall be provided.
For each panelboard, one flash label shall be provided.
Labels shall be field installed by the engineering service division of the equipment manufacturer
under the Startup and Acceptance Testing contract portion.
ARC FLASH HAZARD TRAINING
A.
The equipment vendor shall train Owner’s personnel of the potential arc flash hazards associated
with working on energized equipment (minimum of 8 hours). Maintenance procedures in
accordance with the requirements of NFPA 70E, Standard for Electrical Safety Requirements for
Employee Workplaces, shall be provided in the equipment manuals. The training shall be certified
for continuing education units (CEUs) by the International Association for Continuing Education
Training (IACET). Provide the video of the training recorded on DVD to the Owner.
END OF SECTION 26 05 73
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