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SF6 Gas Handling Guide for High-Voltage Equipment
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IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment IEEE Power & Energy Society Sponsored by the Substations Committee and Switchgear Committee IEEE 3 Park Avenue New York, NY 10016-5997 USA IEEE Std C37.122.3™-2011 9 January 2012 Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3™-2011 IEEE Guide for Sulphur Hexaflouride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Sponsor Substations Committee and Switchgear Committee of the IEEE Power & Energy Society Approved 2 November 2011 IEEE-SA Standards Board Approved 14 January 2013 American National Standards Institute Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. Grateful acknowledgment is made to CIGRE for the permission to use the following source material: CIGRE Brochure No. 276, Guide for preparation of customized “Practical SF6 handling instructions,” August 2005 edition. Abstract: Significant aspects of handling SF6 gas used in electric power equipment such as gas recovery, reclamation, recycling in order to keep the gas permanently in a closed cycle and avoiding any deliberate release in environment are described. The purpose of this guide is to provide state-of-the-art technologies and procedures to minimize SF6 gas emission to a minimum functional level for the electric power equipment to preserve the environment. This guide will include all the aspects for consideration during commissioning and recommissioning, topping up, refilling, checking the gas quality at site, sampling and shipment for off-site gas analysis, and recovering and reclaiming during normal operation and at the end of the life of power equipment while dismantling. This guide also presents the state-of-the art tools and measuring devices including the necessary personnel protective equipment. The basis for the preparation of this guide is CIGRE Brochure No. 276, Guide for preparation of customized “Practical SF6 handling instructions,” August 2005 edition, developed by the Study Committee B3, Task Force B3.02.01. Keywords: IEEE C37.122.3, SF6 analysis, SF6 handling, SF6 reclaiming, SF6 recovery, SF6 safety, SF6 transportation • The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright © 2012 by the Institute of Electrical and Electronics Engineers, Inc. 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Introduction This introduction is not part of IEEE Std C37.122.3-2011, IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment. The purpose of this document is to provide practical recommendations for a customized “Practical SF6 Handling Instruction Guide” that applies to all equipment and can become a standardized document containing standard information and procedures covering the following: ⎯ Commissioning or recommissioning ⎯ Topping-up ⎯ Refilling ⎯ Checking gas quality on-site ⎯ Sampling and shipment for off-site gas analysis ⎯ Recovery and reclaiming ⎯ Recovery and reclaiming at the end of life when the electric power equipment is dismantled The guide is organized in individual modules that can be bound together to form a customized “Practical SF6 Handling Instructions” manual. Such a standard manual describes the SF6 handling procedure according to the state-of-the-art technique. It is recommended that this guide be strictly followed in order to achieve operational, safety-at-work, and environmental benefits such as the following: ⎯ Safer operation of the equipment ⎯ Optimization of resources and tools required ⎯ Minimization of out-of-service time for equipment ⎯ Standard training of personnel handling SF6 ⎯ Reduction of the amount of gas released during handling operations down to the functional physical limit ⎯ Avoidance of any deliberate release, e.g., flushing to the atmosphere ⎯ Reduction of SF6 losses and emissions during commissioning, service, and operation to a minimum Notice to users Laws and regulations Users of these documents should consult all applicable laws and regulations. Compliance with the provisions of this standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. 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Further information may be obtained from the IEEE Standards Association. v Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. Participants At the time this guide was submitted to the IEEE-SA Standards Board for approval, the K1 T3 Working Group had the following membership: Gordon van der Zel, Chair Arun Arora, Vice Chair Hanna Abdallah George Becker Peter Blohm Lutz Boettger Phil Bolin Hugues Bosia John Brunke Wayne Cheng Paul Coventry Richard Crowdis Wolfgang Degen Pat Dilillo Ken Edwards Markus Etter Patrick Fitzgerald Ron Forster Noboru Fujimoto Peter Glaubitz Jack Gustin Chuck Hand Mel Hopkins Shin’ichi Imai Dick Jones Heinz-Willi Juelicher Sung Kim Hermann Koch Shawn Lav Bill Long Johny Luiz Venketesh Minsandram Bob Mueller Mike Muhlenhaupt Jeffrey Nelson Ted Olsen Deborah Ottinger Darin Penner Phillipe Ponchon Mansour Pourcyrous Vittal Rebbapragada Lukas Rothlisberger Alex Salinas Devki Sharma Robert Sicker Ryan Stone Ron Vance Ron Wamer Andreas Welsch Allen Xi The following members of the individual balloting committee voted on this guide. Balloters may have voted for approval, disapproval, or abstention. William J. Ackerman Michael Anderson Ficheux Arnaud Arun Arora Robert Barnett George Becker W. J. (Bill) Bergman Arvind K. Chaudhary Robert Christman Gary Donner Randall Dotson Dana Dufield Edgar Dullni Douglas Edwards Gary Engmann Markus Etter Patrick Fitzgerald Marcel Fortin Frank Gerleve David Giegel Jalal Gohari Edwin Goodwin James Graham Randall C. Groves David Harris Gary Heuston R. Jackson Gael Kennedy James Kinney Jospeh L. Koepfinger David Krause Jim Kulchisky Saumen Kundu Chung-Yiu Lam Stephen Lambert Hua Liu Greg Luri Jorge Marquez Peter Meyer Georges Montillet Jerry Murphy Jeffrey Nelson Michael S. Newman Ted Olsen Miklos Orosz Alexandre Parisot John Randolph Michael Roberts Anne-Marie Sahazizian Bartien Sayogo Devki Sharma Gil Shultz H. Smith James Smith Jerry Smith David Solhtalab Gary Stoedter Ryan Stone Michael Swearingen John Toth Joe Uchiyama John Vergis Kenneth White Brian Withers Xi Zhu vi Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. When the IEEE-SA Standards Board approved this guide on 2 November 2011, it had the following membership: Richard H. Hulett, Chair John Kulick, Vice Chair Robert M. Grow, Past Chair Judith Gorman, Secretary Masayuki Ariyoshi William Bartley Ted Burse Clint Chaplin Wael Diab Jean-Philippe Faure Alexander Gelman Paul Houzé Jim Hughes Joseph L. Koepfinger* David J. Law Thomas Lee Hung Ling Oleg Logvinov Ted Olsen Gary Robinson Jon Walter Rosdahl Sam Sciacca Mike Seavey Curtis Siller Phil Winston Howard L. Wolfman Don Wright *Member Emeritus Also included are the following nonvoting IEEE-SA Standards Board liaisons: Satish K. Aggarwal, NRC Representative Richard DeBlasio, DOE Representative Michael Janezic, NIST Representative Michelle D. Turner IEEE Standards Program Manager, Document Development Erin Spiewak IEEE Standards Program Manager, Technical Program Development vii Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. Contents 1. Overview .................................................................................................................................................... 1 1.1 Scope ................................................................................................................................................... 1 1.2 Purpose ................................................................................................................................................ 1 2. Normative references.................................................................................................................................. 2 3. Definitions .................................................................................................................................................. 2 4. General background modules ..................................................................................................................... 3 4.1 General ................................................................................................................................................ 3 4.2 Gas characteristics ............................................................................................................................... 3 4.3 Characteristics of electric power equipment........................................................................................ 5 4.4 Environmentally compatible SF6 policy .............................................................................................. 7 4.5 Toxicity................................................................................................................................................ 8 4.6 Gas categories...................................................................................................................................... 8 4.7 Safety during on-site SF6 handling .................................................................................................... 12 4.8 Training of personnel......................................................................................................................... 14 4.9 Storage and transportation ................................................................................................................. 15 4.10 Responsibilities................................................................................................................................ 17 5. Procedure description modules................................................................................................................. 17 5.1 General .............................................................................................................................................. 17 5.2 Commissioning or recommissioning of SF6 compartments............................................................... 18 5.3 Topping-up of SF6 prefilled compartments to the rated pressure/density.......................................... 19 5.4 Refilling of SF6 to the rated pressure/density .................................................................................... 21 5.5 Checking the SF6 quality in gas compartments on-site...................................................................... 22 5.6 Sampling and shipment of SF6 for off-site analysis........................................................................... 26 5.7 Recovery and reclaiming of non-arced and/or normally arced SF6 from compartments of controlled and/or closed-pressure systems............................................................. 27 5.8 Recovery and reclaiming of heavily arced SF6 from compartments of controlled and/or closed-pressure systems.......................................................................................................... 29 5.9 Recovery and reclaiming of SF6 at the end-of-life disposal when the electric power equipment is dismantled............................................................................................. 31 6. SF6 handling equipment description modules .......................................................................................... 33 6.1 General .............................................................................................................................................. 33 6.2 Gas reclaimers ................................................................................................................................... 34 6.3 Personal protective equipment........................................................................................................... 38 6.4 Devices for gas measurement on-site ................................................................................................ 39 6.5 Cylinder for gas samples ................................................................................................................... 41 6.6 Gas piping and pipe junctions in buildings or equipment.................................................................. 41 Annex A (normative) Theoretical considerations for SF6 handling ............................................................. 42 Annex B (informative) Moisture measurement units and conversions......................................................... 46 Annex C (informative) Bibliography............................................................................................................ 58 vii Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment IMPORTANT NOTICE: This standard is not intended to ensure safety, security, health, or environmental protection. Implementers of the standard are responsible for determining appropriate safety, security, environmental, and health practices or regulatory requirements. This IEEE document is made available for use subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at http://standards.ieee.org/IPR/disclaimers.html. 1. Overview 1.1 Scope This guide describes significant aspects of handling SF6 gas used in electric power equipment, such as gas recovery, reclamation, and recycling, in order to keep the gas permanently in a closed cycle and to avoid any deliberate release into the environment. 1.2 Purpose To provide state-of-the-art technologies and procedures to minimize SF6 gas emission to a minimum functional level for the electric power equipment to preserve the environment. This guide will include all the aspects for consideration during commissioning and recommissioning, topping up, refilling, checking the gas quality at site, sampling and shipment for off-site gas analysis, and recovering and reclaiming during normal operation and at the end of the life of power equipment while dismantling. This guide also presents the state-of-the art tools and measuring devices including the necessary personnel protective equipment. The basis for the preparation of this guide is CIGRE Brochure No. 276, Guide for preparation of customized “Practical SF6 handling instructions,” August 2005 edition, developed by the Study Committee B3, Task Force B3.02.01. 1 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 2. Normative references The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies. ASTM D2472-00, Standard Specification for Sulfur Hexafluoride. 1 IEC 60376, Specification of technical grade sulfur hexafluoride (SF6) for use in electrical equipment. 2 IEC 60480, Guidelines for the checking and treatment of sulfur hexafluoride (SF6) taken from electrical equipment and specification for its reuse. IEC 62271-1, High-voltage switchgear and controlgear―Part 1: Common specifications. IEC/TR 62271-303, High-voltage switchgear and controlgear―Part 303: Use and handling of sulphur hexafluoride (SF6). ISO 14040, Environmental management―Life cycle assessment―Principles and framework. 3 3. Definitions For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary: Glossary of Terms & Definitions [B10] should be referenced for terms not defined in this clause. 4, 5 energized: Qualifies a conductive part of the electrical equipment that has an electric potential difference with respect to a relevant reference. The reference potential is usually earth or an equipotential frame. evacuation: The transfer of air or nitrogen (N2) from the electric power equipment to the atmosphere or the transfer of SF6 from the electric power equipment to gas-handling equipment. pressure: Force divided by area. NOTE—In this document, pressures are given in terms of absolute units. 6 reclaimer: Device for purification and storage of used SF6 for the purpose of reuse. This device is also known as a gas cart. SF6 recovery: SF6 transfer from the electric power equipment into a reclaimer or a storage container. 1 ASTM publications are available from the American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA (http://www.astm.org/). 2 IEC publications are available from the Central Office of the International Electrotechnical Commission, 3, rue de Varembé, P.O. Box 131, CH-1211, Geneva 20, Switzerland (http://www.iec.ch/). IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, USA (http://www.ansi.org/). 3 ISO publications are available from the ISO Central Secretariat, 1, ch. de la Voie-Creuse, Case Postale 56, CH-1211, Geneva 20, Switzerland (http://www.iso.org/). IEC publications are available from the Central Office of the International Electrotechnical Commission, 3, rue de Varembé, P.O. Box 131, CH-1211, Geneva 20, Switzerland (http://www.iec.ch/). 4 The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/. 5 The numbers in brackets correspond to those of the bibliography in Annex C. 6 Notes in text, tables, and figures of a standard are given for information only and do not contain requirements needed to implement this standard. 2 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment tight drilling system: When connection to SF6 compartment via available openings (e.g., filling points, pressure gauge) is not provided, then a tight drilling system should be used. This generally consists of a drill fitted with a hollow bit connected to hoses with appropriate gasket systems to avoid leakage during and after drilling. 4. General background modules 4.1 General This clause provides general background information about SF6, related equipment, environmental considerations, and safety, organized as modules. 4.2 Gas characteristics The following subclauses describe the main properties and characteristics of SF6 gas. 4.2.1 General Sulfur hexafluoride (SF6) is a synthetic gas formed by six atoms of fluorine gathered around a centrally situated atom of sulfur. The chemical formula is SF6 and the molecular weight is 146.05 g/mol. The chemical bond between fluorine and sulfur is known as one of the most stable existing atomic bonds. Six of these bonds grant the molecule very high chemical and thermal stability. In addition, the compatibility of SF6 with material used in electric constructions is similar to that of nitrogen (N2), up to temperatures of about 180 °C (356 °F). Since the early 1960s, SF6 has been successfully used by the electric industry in power equipment for the high-voltage (HV) transmission and medium-voltage (MV) distribution of electricity (e.g., gas-insulated substations, ring main units, circuit breakers, transformers, and cables). For electrical equipment, SF6 offers excellent electric insulation and switching properties. Today’s high performance of HV switchgear in voltage level and current switching capability cannot be reached with any other gas. Other gases under consideration for application in HV switchgear have shown better insulating performance or switching performance, but not both. Most of these gases do not offer long-term stability. Additionally, they are often toxic or cost prohibitive. Other non-electrical industrial applications of SF6 include metallurgy, electronics, scientific equipment, ocular surgery, and military applications. The maximum tolerable moisture level for the gas in the equipment is specified by IEC 62271-1. 7 Purity requirements for SF6 as it comes from the supplier are specified by ASTM D2472-00 and IEC 60376. Purity requirements for reuse of reclaimed SF6 are specified by IEC 60480. 7 Information on references can be found in Clause 2. 3 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 4.2.2 Physical Pure SF6 is odorless, tasteless, non-toxic, non-corrosive, non-flammable, and chemically inert at ambient temperature. It does not support combustion. Although the gas is non-toxic, it does not support life, as it is not oxygen. Equipment containing SF6 should not be entered without adequate ventilation and personal protection equipment. The solubility of SF6 in water (7000 ppmv) is four times lower than that of air. 4.2.3 Thermodynamic At normal room temperatures and pressures [20 °C and 100 kPa (68 °F and 14.5 psi)], SF6 is about five times heavier than air. 8 Its density is 6.139 g/L (0.382 lb/ft3). As the gas is heavier than air, areas below ground level, poorly-ventilated areas, or unventilated areas (e.g., cable ducts, trenches, inspection pits, and drainage systems), may remain full of SF6. Personnel should be aware of the danger of asphyxiation in such places. As the critical temperature and pressure of SF6 are 45.54 °C and 3.759 MPa (113.97 °F and 545.197 psi) respectively, it can be liquefied by compression and is usually transported as a liquid in cylinders or containers. Given that the gas is delivered in the form of compressed liquid, if large quantities of the gas are released rapidly, the temperature of both the gas and the container will fall quickly. Frost and ice may form on metal parts. If this occurs, gas filling should be immediately stopped until ice and frost are gone. Filling of SF6 should always be performed slowly. Personnel should be aware of the danger of freeze burns when touching iced and/or frozen metal parts. The heat capacity of one mole of SF6 is around three times greater than air. 4.2.4 Electric SF6 is strongly electronegative (i.e., it tends to attract free electrons). It has a unique combination of physical properties, including high dielectric strength (about three times that of air), high thermal interruption capabilities (about 10 times that of air), and high heat transfer performance (about twice that of air). 4.2.5 Environmental SF6 does not harm the ecosystem; biological accumulation in the food chain does not occur. It is an inert gas with very low solubility in water and therefore presents no danger to surface water, ground water, or the soil. SF6 has no impact on the stratospheric ozone layer―its ozone depletion potential (ODP) is 0. However, SF6 is a potent greenhouse gas with a global warming potential (GWP) of 23 900. It is also a persistent greenhouse gas with an atmospheric life time (ALT) of 650 to 3200 years. The difference in the figures is a consequence of the adoption of different calculation models. 8 In this document, pressures are given in terms of absolute units. 4 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment The GWP of SF6 alone is not adequate to measure the environmental impact of electric power equipment based on SF6 technology. The environmental impact of any specific application should be evaluated and/or compared using the life-cycle assessment (LCA) approach, as regulated by ISO 14040. SF6 has to be used in a closed cycle. When gas removal from containment is needed, a proper handling procedure should be implemented to avoid any deliberate release into the atmosphere. The yearly SF6 emission rate from the overall electric industry represents 0.1% of the yearly emission rate of man-made global warming gases. As just one example, emissions from European manufacturers and users contribute only by 0.008%. 4.3 Characteristics of electric power equipment The tightness of certain older installed gas-insulated power equipment, especially for HV systems, could be a significant issue for environmental impact. Nevertheless, it has to be kept in mind that handling SF6 during installation, on-site testing, and maintenance activities may contribute significantly to the overall emissions. State-of-the-art electric power equipment is designed and manufactured for tightness so that it is compatible with environmental protection guidelines. This implies the following: ⎯ Very-low leakage rates due to the quality of the encapsulation, including its material, the machining process, the design of gaskets, the sealing material itself, and the factory testing procedures ⎯ Very-low handling losses due to smaller gas compartments, reduced maintenance frequency, more sophisticated tools and instruments to handle and to check the gas quality, and specific training of designated personnel In addition to these items noted, procedures for installation, service, maintenance, repair, and proper disposal should be described by the manufacturer in as detailed a manner as possible. Specially trained personnel should carry out the practical work. 4.3.1 Controlled pressure systems (obsolete) In controlled pressure systems, a volume is automatically replenished from an external or internal gas source. The volume may consist of several permanently connected gas-filled compartments. Controlled pressure systems are no longer used in new equipment, because of their high leakage rate. It is recommended that controlled pressure systems in old equipment be replaced by closed-pressure systems, because of the unacceptable leakage rate. 4.3.2 Closed-pressure systems In closed-pressure systems, a volume is replenished only periodically by manual connection to an external gas source. High-voltage (above 72.5 kV) SF6 single-pressure circuit breakers are examples of closedpressure systems. It is recommended that: ⎯ The leakage rate be kept lower than 0.5% per annum (p.a.) per gas compartment. ⎯ When SF6 conditions are checked, that gas be recaptured from analysis equipment. ⎯ Appropriate record-keeping procedures are used. 5 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 4.3.3 Sealed-pressure system Sealed-pressure systems have gas volumes that are completely sealed. It is not expected that any gas or vacuum processing will be performed over the expected operating life. Sealed-pressure systems are completely assembled and tested in the factory. Much state-of-the-art MV electric power equipment uses a sealed-pressure system. These systems are commercially designated “sealed for life,” as they require no on-site gas handling for their entire life duration, typically 40 years. End-of-life disposal is performed under the responsibility of the user and is supported by the manufacturer. Third parties, such as service companies, may also carry out end-of-life disposal. During the product life of these systems, SF6 is handled in a controlled environment only twice: for gas filling at the beginning and for gas recovery at the end. Given the limited handling, handling losses can be considered to be of the same order of magnitude as leakage losses. Today a typical leakage rate is lower than 0.1% p.a. per gas compartment. 4.3.4 Description of the installed system Among all characteristics defined by the current IEC Standards in force and given in the instruction manual from the manufacturer, those most relevant to SF6 handling are highlighted in Table 1. They are, at least, as shown in Table 1. Table 1 —Equipment characteristics related to SF6 handling Equipment characteristic SF6 mass per compartment/substation Volume per compartment/substation Rated SF6 filling pressure at 20 °C (68 °F) Leakage rate in % p.a. per gas compartment Designation of different compartments (e.g., breaker, disconnector, and bus bar) Number of separate compartments Location of safety overpressure control means System used to observe the pressure in each containment Precautions when handling SF6 containments Record-keeping Typical time between two consecutive maintenance operations in years Typical time between two consecutive SF6 measurements in years Location of SF6 valves Location of gas tight spacers Pressure levels and number of alarms/indicators Closed-pressure systems X Sealed-pressure systems X X X X X X X X X X X X X X X X When relevant ― When relevant X ― Required ― X X X When relevant When relevant When relevant 6 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 4.3.5 Description of the monitoring system for controlled and closed-pressure systems In order to operate safely, switchgear needs a minimum gas pressure/density. In the case of controlled or closed-pressure systems, visual indications and/or acoustic alarms are set as a function of that threshold. If the gas pressure/density reaches its minimum threshold, standard operations can no longer be maintained and, according to specific users’ requirements, appropriate counter measures (e.g., alarm, automatic lockout, or switching features) come into effect. Common gas-monitoring systems provide an alarm or indication when 5% to 10% of the gas has been released. The system has been designed to operate safely under these conditions and still keeps a safety margin. In the case of compartments containing a small amount of gas, the impact on the environment is very small. On the contrary, in the case of large compartments, such as long bus-bar ducts, the amount of gas released before reaching the threshold is significant for the environment. Therefore, it is recommended that the gas pressure/density of each compartment is monitored, whenever technically reasonable, to enable early detection of small leaks. State-of-the-art monitoring systems continuously monitor gas pressure/density allowing for early detection of small leaks. In addition to the above, appropriate corrective measures to locate and eliminate the leak should be immediately arranged. 4.4 Environmentally compatible SF6 policy SF6 should be handled in a closed cycle to avoid any deliberate release to the environment. Among all the voluntary initiatives, gas recovery and recycling have the highest priority. Voluntary agreements involving manufacturers and users have been signed in some countries with the aim of controlling and reducing emissions of SF6 from electric power equipment. In general, it is mentioned in such agreements that for the development, manufacturing, installation, operation, maintenance, and end-oflife disposal of SF6 electric power equipment, state-of-the-art technologies, procedures, and training should be applied to minimize SF6 emissions. The following voluntary actions are typically performed by users of SF6: ⎯ Systematically reusing, reprocessing, and disposing of SF6 in a closed cycle process ⎯ Monitoring of SF6-filled gas compartments to ensure that leaks are detected and eliminated at an early stage (controlled and closed-pressure systems) ⎯ Reusing SF6 recovered from electric power equipment directly on-site, as much as possible ⎯ Keeping non-reusable SF6 in a closed cycle for further processing off-site ⎯ Regularly training personnel handling SF6, so that SF6 is only handled by properly qualified personnel ⎯ Recording SF6 consumption and inventories ⎯ Providing the authorities SF6-relevant statistical data as a basis for regional/national SF6 monitoring 7 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment The following voluntary actions are typically performed by equipment manufacturers and SF6 producers: ⎯ Producing and guaranteeing that electric power equipment will have a leakage rate lower than 0.5% p.a. for each compartment (controlled and closed-pressure systems) ⎯ Providing electric power equipment that has a leakage rate lower than 0.1% p.a. for each compartment (sealed-pressure systems) ⎯ Accepting returns of non-reusable SF6 for reprocessing or reduction to environmentally compatible end products ⎯ Keeping statistics of the SF6 quantities produced and sold ⎯ Providing the authorities SF6-relevant statistical data as a basis for regional/national SF6 monitoring If SF6 handling is performed as described above, LCA studies demonstrate that SF6 technology applied to electric power equipment minimizes the impact on the environment. 4.5 Toxicity Pure SF6 is not toxic (see 4.2.2). Toxic gaseous and/or solid decomposition products may arise during the operation of gas-insulated electric equipment. They are fully described in IEC/TR 62271-303. Design rules and operational procedures are implemented to handle both the gas and the equipment according to safety rules, in order to eliminate any potential harmful effects. 4.6 Gas categories SF6 contains contaminants. These originate from the industrial manufacturing process as well as from use of the gas in electric power equipment. Depending on the nature and the amount of the contaminants, the following gas categories have been defined: ⎯ Gas from gas suppliers (meeting the specification for either purchased gas or technical grade gas) ⎯ Non-arced gas ⎯ Normally arced gas ⎯ Heavily arced gas ⎯ Gas suited for the complete range of use pressures ⎯ Gas suited for the low range of use pressures ⎯ Gas not suited for reuse The following subclauses provide additional details. 4.6.1 Gas from gas suppliers Gas obtained from the gas supplier should meet specifications for either purchased gas (as defined in ASTM D2472-00) or technical grade gas (as defined in IEC 60376). The concept of technical grade gas was established to provide SF6 that is pure enough for the electric industry. 8 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment The maximum acceptable impurity levels for purchased gas and technical grade gas are given in Table 2 and Table 3, respectively. Table 2 —Maximum acceptable impurity levels for purchased gas (ASTM D2472-00) Impurity Specification Air (expressed as N2) Carbon tetrafluoride (CF4) H2O (expressed in dew point) Hydrolysable fluorides (expressed in the concentration of hydrofluoric acid) a 0.5 g/kg 0.5 g/kg –62 °C (–79.6 °F) a 0.3 mg/kg –62 °C (–79.6 °F) is equivalent to a water content of 8.0 ppmv at 101 k Pa (14.696 psi). Table 3 —Maximum acceptable impurity levels for technical grade gas (IEC 60376) Impurity Specification Air CF4 H2O Mineral oil Total acidity expressed in hydrogen fluoride (HF) 2 g/kg a 2400 mg/kg b 25 mg/kg c 10 mg/kg 1 mg/kg d a 2 g/kg is equivalent to 1% v under ambient conditions [100 kPa and 20 °C (14.5 psi and 68 °F)]. b 2400 mg/kg is equivalent to 4000 µl/l (microliters per liter) under ambient conditions [100 kPa and 20 °C (14.5 psi and 68 °F)]. c 25 mg/kg is equivalent to 200 µl/l and to a dew point of –36 °C (–32.8 °F), measured at ambient conditions [100 kPa and 20 °C (14.5 psi and 68 °F)]. d 1 mg/kg is equivalent to 7.3µl/l under ambient conditions [100 kPa and 20 °C (14.5 psi and 68 °F)]. Due to the maximum impurity levels that can be present in SF6, the SF6 amount in a container (measured in the liquid phase) should be higher than 99.7% for technical grade gas or 99.8% for purchased gas. 4.6.2 Non-arced gas If the volume concentration of the indicator gases SO2 + SOF2 (sulfur dioxide plus thionyl fluoride) is lower than 100 ppmv, then the gas is non-arced. Non-arced gas is to be expected at the following: ⎯ Insulation testing in the factory ⎯ Insulation testing on-site during erection/commissioning ⎯ Routine maintenance of insulation compartments ⎯ Repair of insulation compartments after malfunction without arcing ⎯ Retrofitting of insulation compartments ⎯ Decommissioning of insulation compartments in which arcing has not occurred ⎯ Any kind of compartment after filling but prior to energizing 9 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment The major contaminants in non-arced gas may be air (mainly introduced by handling) and moisture (mainly desorbed from inner surfaces). Small quantities of reactive gaseous decomposition products (approximately 100 ppmv) may also be present when strong partial discharges have occurred in the gas. 4.6.3 Normally arced gas Normally arced gas is gas that has been recovered from switchgear compartments after normal switching operations. In practice, if the volume concentration of the indicator gases SO2 + SOF2 is between 100 ppmv and 1%, then the gas is normally arced. Normally arced gas is to be expected at the following: ⎯ Maintenance and repair of switching devices after normal (load or fault) operation ⎯ Interruption testing during switchgear development ⎯ Decommissioning of switchgear Normally arced gas may contain, in addition to air and moisture, the following: ⎯ The inert gas CF4, generated by arc erosion of polymers ⎯ Corrosive gaseous decomposition products (approximately 100 ppmv to 200 ppmv) as residues ⎯ Solid decomposition products, mainly metal fluorides and tungsten oxifluorides, usually referred to as switching dust 4.6.4 Heavily arced gas Heavily arced gas is gas that has been recovered from equipment in which failure arcing has occurred. In practice, if the volume concentration of the indicator gases SO2 + SOF2 is greater than 1%, then the gas is heavily arced. Heavily arced gas is to be expected from the following: ⎯ Circuit breakers after interruption failure ⎯ Insulation compartments after internal arcing failure ⎯ Any kind of arcing failure In this case, high levels of solid and gaseous contaminants should be expected. The gaseous contaminants may reach levels of several percentage points of the volume, of which a substantial fraction can be highly reactive, toxic, and/or corrosive. 4.6.5 Suited for the complete range of use pressures Gas that is suited for the complete range of use pressures is used SF6 gas that is stored in cylinders, tagged with the “orange collar,” compliant with a standard for used gas (such as IEC 60480), and that can be reused in any electric power equipment without any limitations. The maximum acceptable impurity levels are given in Table 4. 10 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 4 —Maximum acceptable impurity levels for reuse of SF6 at all use pressures (IEC 60480) Impurity Air and/or CF4 H2O Mineral oil Total reactive gaseous decomposition products Specification 3% volume a 25 ppmw b (see NOTE 1) 10 ppmw (see NOTE 2) 50 µl/l total or 12 µl/l for (SO2 + SOF2) or 25 µl/l HF NOTE 1―Converted to ppmv these levels should also apply to mixtures until a suitable standard becomes available. NOTE 2―If gas-handling equipment (e.g., pump or compressor) containing oil is used, it may be necessary to measure the oil content of the SF6. If all equipment in contact with the SF6 is oil-free, then it is not necessary to measure oil content. a In case of SF6 mixtures, the equipment manufacturer should specify the levels for these gases. b 25 mg/kg (25 ppmw) is equivalent to 200 ppmv (200 µl/l) and to a dew point of –36 °C (–32.8 °F), measured at 100 kPa and 20 °C (14.5 psi and 68 °F). 4.6.6 Suited for the low range of use pressures Gas that is suited for the low range of use pressures is used SF6 gas that is stored in cylinders, tagged with the “orange collar,” compliant with a standard for used gas (such as IEC 60480), and that can be reused in any electric power equipment having an SF6 rated filling pressure not exceeding a certain limit [e.g., 200 kPa (29 psi)]. The maximum acceptable impurity levels are given in Table 5. Table 5 —Maximum acceptable impurity levels for reuse of SF6 at low range of use pressures (IEC 60480) Impurity Specification a Air and/or CF4 H2O Mineral oil Total reactive gaseous decomposition products 3% volume 95 ppmw b (see NOTE 1) 10 ppmw (see NOTE 2) 50 µl/l total or 12 µl/l for (SO2 + SOF2) or 25 µl/l HF NOTE 1―Converted to ppmv these levels should also apply to mixtures until a suitable standard becomes available. NOTE 2―If gas-handling equipment (e.g., pump or compressor) containing oil is used, it may be necessary to measure the oil content of the SF6. If all equipment in contact with the SF6 is oil-free, then it is not necessary to measure oil content. a In case of SF6 mixtures, the equipment manufacturer should specify the levels for these gases. 95 mg/kg (95 ppmw) is equivalent to 750 ppmv (750 µl/l) and to a dew point of –23 °C (–9.4 °F), measured at 100 kPa and 20 °C (14.5 psi and 68 °F). b 4.6.7 Not suited for reuse Gas that is not suited for reuse is used SF6 gas that does not comply with a standard for used gas, such as IEC 60480. This gas requires further treatment, usually off-site. If further treatment is unsuccessful, the gas will require final disposal. 11 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 4.7 Safety during on-site SF6 handling Before starting any maintenance/service work in SF6 power equipment, the detailed state and condition of the equipment should be inspected and reported in detail. This subclause contains general safety guidelines for handling SF6. Utility procedures and operating instruction manuals from equipment manufacturers should always be followed. 4.7.1 General safety rules and recommendations Table 6 lists the major issues to consider when working on SF6 switchgear. Table 6 —Considerations when working with SF6 switchgear Item SF6 material safety data sheet/operational manuals Training Gas-handling equipment Cleaning equipment Personal protection equipment Flames Welding/smoking Drinking/eating Working in the vicinity of switchgear (operation, visual check, or room cleaning) ― Mandatory Opening of SF6 gas compartments or working on open compartments Mandatory Mandatory (see NOTE) ― ― ― Mandatory Mandatory ― ― Mandatory Mandatory Mandatory Mandatory ― ― ― Not allowed Not allowed ― Not allowed Not allowed Not allowed Filling, recovering, or evacuation of SF6 gas compartments NOTE―General information should be specified according to type of work and installation. In addition to 4.2.2 and 4.2.3, as with any gas but oxygen, a concentration greater than 19% of SF6 in the air presents the potential risk of asphyxiation. This is because it reduces the oxygen concentration down to 16%, which is usually considered as the clinical threshold for asphyxiation. As a consequence, it is recommended that the oxygen content in the gas compartment be measured prior to entering or accessing. In addition, the oxygen content in the ambient air may be checked when working in confined spaces. Switching dust (which might be present inside the gas compartment after opening), as well as the adsorbents, contain acidic compounds and should be treated as special chemical waste according to local regulations. This applies also to any tool or equipment (e.g., vacuum cleaner, cleaning paper, and protective clothes) that has been in contact with the switching dust. 4.7.2 Protection of personnel Safety measures are mandatory when accessing and/or entering a gas compartment. The type and extent of protection depends on the category of the gas in the compartment (see 4.6). Details are given in Table 7. 12 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 7 —Safety precautions when entering an SF6 compartment Item Potential risk Open compartment before first SF6 filling ⎯ ⎯ ⎯ Open compartment that contained non-arced SF6 Fumes of cleaning material O2 starvation Remaining SF6 or other gas from production process ⎯ ⎯ ⎯ Fumes of cleaning material O2 starvation Remaining gas Safety precaution ⎯ ⎯ Ventilation Measurement of O2 concentration when entering ⎯ ⎯ Ventilation Measurement of O2 concentration when entering Safety equipment and tools ⎯ Suction ventilator or vacuum cleaner O2 concentration measuring device ⎯ Suction ventilator or vacuum cleaner O2 concentration measuring device ⎯ ⎯ Open compartment that contained either normally arced or heavily arced SF6 ⎯ Fumes of cleaning material ⎯ O2 starvation ⎯ Remaining gas ⎯ Residual reactive gaseous decomposition products ⎯ Switching dust and adsorbents ⎯ Removal of switching dust and adsorbents ⎯ Ventilation ⎯ Measurement of O2 concentration when entering ⎯ Wearing of personal protective equipment ⎯ Suction ventilator or vacuum cleaner ⎯ O2 concentration measuring device ⎯ Single-use protective clothes, shoe covers, and hair cap ⎯ Acid-proof safety gloves ⎯ Full-face mask (preferred) or, at least, breathing protective mask ⎯ Protective goggles 4.7.3 Personal hygiene Eating, drinking, and smoking are not allowed when handling SF6 or when accessing an open gas compartment. It is recommended that clothes be changed and skin washed to prevent irritation or burns after handling solid or gaseous decomposition products. 4.7.4 Handling of contaminated safety equipment/tools Safety equipment and tools that have been in contact with switching dust or adsorbents should be considered contaminated. They should be collected afterwards and placed in plastic bags. The plastic bags should be sealed with tape and labeled. Reusable safety equipment and tools should be washed and neutralized in a saturated solution of water and sodium bicarbonate (baking soda), then washed with clean water. Single-use safety equipment and tools should be placed in a plastic bag for further disposal according to local regulations. They should be considered special waste. 13 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Disposal of both the water/soda solution and the washing water is done according to the local regulations. 4.7.5 Pressurized equipment and tools/measuring devices All equipment and tools used during SF6 handling potentially contain gaseous or liquid SF6 under high pressure. They should be handled with extreme caution. 4.8 Training of personnel Work on electric power equipment involving SF6 handling (e.g., manufacturing, testing, erection, commissioning, maintenance, service, and dismantling at the end of life) should be performed either by trained personnel or under the supervision of trained personnel. For the personnel involved, training is mandatory. Training can be delivered in different locations (e.g., special training center of the user, in the factory, or on-site during erection, commissioning, and maintenance of installed SF6 equipment). In all cases, the training should be based on the operating instruction manual from the original equipment manufacturer (OEM) if the training is on equipment such as electric power equipment, tools, and instruments. The training should be based on datasheets if the training is on products such as (e.g., SF6 gas or cleaning agents). Training courses should consist of both theoretical and practical sessions. Training should include at least the following topics: a) SF6: 1) Physical, chemical, and environmental characteristics of SF6 2) Application of SF6 used in electric power equipment (e.g., insulation and arc quenching) 3) Standards 4) Personnel safety i) Asphyxiation ii) Contamination iii) Decomposition products, both solid and gaseous b) c) 5) Environmental impact 6) Disposal of SF6 and its gaseous and/or solid decomposition products Electric power equipment 1) Design and functionality 2) SF6 handling on-site during erection, commissioning, maintenance, and dismantling at the end of life 3) Benefits of SF6 technology in electric power equipment 4) Troubleshooting of electric power equipment utilizing SF6 Handling of SF6 in electric power equipment 1) Evacuation of gas compartments 2) Filling of gas compartments 14 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 3) Proper recovery, reclaiming, and storage of SF6 4) Proper handling of maintenance equipment 5) Working on open gas compartments 6) Checking the gas quality 4.9 Storage and transportation Storage and transportation of SF6 shall be performed according to international and local regulations. The measures given in the material safety data sheet (MSDS) should be followed. 4.9.1 Gas categories With respect to storage and transportation, five gas categories are distinguished, as follows: ⎯ Purchased gas or technical grade gas (i.e., SF6 complying with ASTM D2472-00 or IEC 60376, respectively) ⎯ SF6 suited for reuse in electric power equipment (i.e., SF6 complying with IEC 60480) ⎯ SF6 not suited for reuse in electric power equipment and containing neither toxic nor corrosive gaseous decomposition products (i.e., SF6 not complying with IEC 60480 and containing CF4 and/or air and/or N2) ⎯ SF6 not suited for reuse in electric power equipment and containing toxic gaseous decomposition products (i.e., SF6 not complying with IEC 60480 and containing HF and SOF2) ⎯ SF6 not suited for reuse in electric power equipment and containing both toxic and corrosive gaseous decomposition products (i.e., SF6 not complying with IEC 60480 and containing HF and SOF2) 4.9.2 Storage of SF6 Table 8 gives an overview of typical storage methods. Table 8 —Methods for storage of SF6 Method Gaseous Requirements Typical pressure lower than 2 MPa (290 psi) Gas remains in the gaseous state Liquid-cooling assisted Typical pressure equal to 3 MPa (435 psi) Employs additional cooling system to cool SF6 after compression, which allows SF6 to be stored in liquid form Liquid-pressure only Typical pressure equal to 5 MPa (725 psi) Gas compressed to 5 MPa (725 psi) liquefies by pressure only Features Requires relatively small recovery pressure differential (typically 100:1) but needs larger storage volumes Gas cannot be liquefied in cylinders for transportation; therefore, it is limited to small quantities [200 kg (441 lb)] and stationary use Requires relatively small recovery pressure differential (700:1) but needs cooling aggregate, the performance of which can influence processing speed Additional maintenance requirements Limited storage volume required Generally not suitable for transportation Requires recovery differential of 1000:1 but eliminates the need of additional aggregates Can be used with any storage vessel rated 5 MPa (725 psi) or higher 15 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment When used SF6 has to be stored on-site, the storage containers for this purpose should comply with the local pressure vessel regulations and should be labeled in compliance with the regulations given in 4.9.3. For practical reasons, it is recommended that transportable storage containers be used wherever possible. 4.9.3 Containers for transportation of SF6 Each of the five gas categories requires a specific type of container, as specified in Table 9. Table 9 —Required container types for SF6 transportation Gas category Purchased gas or technical grade gas SF6 suited for reuse SF6 not suited for reuse and containing neither toxic nor corrosive gaseous decomposition products SF6 not suited for reuse and containing toxic gaseous decomposition products SF6 not suited for reuse and containing both toxic and corrosive gaseous decomposition products Container type Suitable for liquefied gas up to a pressure of 7 MPa (1015 psi). (See NOTE 1) Recommendation: Containers should be marked with a green label or the container should be painted green according to DIN EN 1089-3. Same type of container as for new or technical grade SF6. (See NOTE 2 and NOTE 3) Recommendation: Containers should be specially colored to avoid confusion between used and purchased gas (an orange band on the upper third of the cylinder is suggested). Same as for SF6 suited for reuse. Same as for SF6 suited for reuse. Special containers approved for storing and transportation of corrosive gases [such as hydrofluoric acid (HCl)] with a corrosion-proof valve and adapter. NOTE 1—The filling factor for purchased gas is up to 1.04 kg/L (64.92 lbm/ft3). NOTE 2—Due to the inert gas content (N2, O2, etc.), the filling factor is smaller than 0.8 kg/L (49.94 lbm/ft3). NOTE 3—The filling factor is the weight of SF6 contained in the container divided by the container volume and is usually specified in kg/L. Each of the five gas categories requires a specific type of labeling and documentation, as specified in Table 10. 16 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 10 —Required labeling and documentation for shipment of SF6 Item UN number (see NOTE 1) Class Danger label Final classification Transport document (see NOTE 2) Purchased gas or technical grade gas a UN 1080 liquefied gas 2A 2.2 UN 1080 liquefied gas, n.o.s. (not otherwise specified) 2.2 UN 1080 liquefied gas, n.o.s (SF6), 2.2 SF6 suited for reuse UN 3163 liquefied gas 2A 2.2 UN 3163 liquefied gas, n.o.s. 2.2 UN 3163 liquefied gas, n.o.s. (SF6 and air or N2 or CF4), 2.2 SF6 not suited for reuse and containing neither toxic nor corrosive gaseous decomposition products UN 3163 liquefied gas 3162 liquefied toxic gas 2A 2.2 UN 3163 liquefied gas, n.o.s. 2.2 2T 2.3 UN 3162 liquefied gas, n.o.s. 2.3 SF6 not suited for reuse and containing both toxic and corrosive gaseous decomposition products UN 3308 liquefied toxic and corrosive gas 2TC 2.3 + 8 UN 3308 liquefied gas, n.o.s. 2.3 + 8 UN 3163 liquefied gas, n.o.s. (SF6 and air or N2 or CF4), 2.2 UN 3162 liquefied gas, toxic, n.o.s. (SF6 and HF and SOF2), 2.3 UN 3308 liquefied gas, toxic, corrosive, n.o.s. (SF6 and HF and SOF2), 2.3 + 8 SF6 not suited for reuse and containing toxic gaseous decomposition products NOTE 1—UN numbers or UN IDs are four-digit numbers that identify dangerous goods, hazardous substances, and hazardous articles (such as explosives, flammable liquids, toxic substances) in the framework of international transport. They are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. NOTE 2—Only the two most abundant contaminants have to be specified. a Any contamination of packaging exclusively dedicated to new SF6 should be avoided. 4.10 Responsibilities The owner of the SF6 electric power equipment is responsible for the proper use, transportation, and disposal of both the equipment and the gas. The owner is also responsible for record keeping regarding SF6 banked in equipment and/or stored in cylinders, as well as emission rates on a yearly basis. This is supported by the equipment manufacturer and the gas producer with basic information. 5. Procedure description modules 5.1 General This clause covers the different situations where SF6 will be handled on-site, including the following: ⎯ Commissioning or recommissioning of SF6 compartments ⎯ Topping-up or refilling of SF6 compartments to the rated pressure/density ⎯ Checking the SF6 quality in gas compartments ⎯ Sampling and transportation of SF6 ⎯ Recovery and reclaiming of SF6 at maintenance or repair ⎯ Recovery and reclaiming of SF6 at the end-of-life disposal when the electric power equipment is dismantled 17 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 5.2 Commissioning or recommissioning of SF6 compartments This module applies to compartments of controlled and/or closed-pressure systems that currently contain a gas different from SF6 (typically air or N2) at ambient pressure or slight overpressure [typically 100 kPa to 150 kPa (14.5 psi to 21.8 psi)]. This module does not apply to compartments of controlled and closed-pressure systems that currently contain SF6 at a pressure above the atmosphere [typically 120 kPa to 150 kPa (17.4 psi to 21.8 psi)]. These compartments should be topped-up as described in 5.3. This module does not apply to the refilling of leaking compartments of controlled and/or closed-pressure systems to assure continuity of service. These compartments should be refilled as described in 5.4. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for air/N2 evacuation and SF6 filling in each compartment should be performed according to Figure 1. Additional details are given in Table 11. Figure 1 —Commissioning or recommissioning of SF6 compartments 18 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 11 —Commissioning or recommissioning SF6 compartments Step Procedure 1 Prepare gas-handling equipment 2 Adsorbent installation 3 Evacuation 4 Residual air and/or moisture content 5 Documentation 6 Filling with SF6 7 Documentation 8 Pressure/density sensor inspection 9 Tightness inspection 10 SF6 quality checking 11 Documentation Check that the gas reclaimer is working properly and the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Quickly insert the adsorbents in the compartment. Start evacuation immediately afterwards. Connect the vacuum pump and leave it running until a vacuum level smaller than 2kPa (0.29 psi) for at least 1 h is reached in the gas compartment. a Detach the vacuum pump and read the pressure gauge. The vacuum level should be smaller than 2kPa (0.29 psi). Record at least the serial number or other identifying information for the gas compartment, the vacuum level of the residual air content, ambient temperature, and date for further reference. Connect the SF6 container and fill the compartment until the SF6 rated filling pressure is reached. Use a safety valve and a calibrated gauge to avoid overfilling. b, c Record at least the serial number or other identifying information for the gas compartment, the final filling pressure, ambient temperature, and date for further reference. Check the functionality of the pressure/density sensor. The operation can be performed during the filling operation. Check the tightness of at least all permanent connections made onsite. Wait at least 12 h after the filling operation and then measure the moisture content and the SF6 content of the gas in the compartment. Record at least the serial number or other identifying information for the gas compartment, the functionality of the pressure/density sensor, the moisture content, the SF6 content, ambient temperature, and date for further reference. a The residual pressure of air in the gas compartment should remain smaller than 2kPa (0.29 psi) for at least 1 h, see Annex A. b SF6 gas to be introduced into the gas compartment should comply with one of the following gas categories as defined in 4.6: ⎯ Purchased gas or technical grade gas ⎯ Suited for the complete range of reuse pressures ⎯ Suited for the low range of reuse pressures only in the case that the SF6 rated filling pressure of the equipment does not exceed the reuse limit, i.e., 200 kPa (29 psi) c No gas check is required if the gas comes from the supplier in sealed cylinders or containers. In all other cases, the gas quality should be checked prior to the filling operation. The gas quality check should comprise moisture content, SF6 percentage, and residual acidity content. 5.3 Topping-up of SF6 prefilled compartments to the rated pressure/density This module applies to compartments of controlled and/or closed-pressure systems that contain SF6 at above atmospheric pressure [typically 120 kPa to 150 kPa (17.4 psi to 21.8 psi)]. This is typically done for the purpose of shipping prefilled new equipment. This module does not apply to compartments of controlled and/or closed-pressure systems that currently contain a gas different from SF6 (typically air or N2) at ambient pressure or slight overpressure [typically 100 kPa to 150 kPa (14.5 psi to 21.8 psi)]. These compartments should be commissioned or recommissioned as described in 5.2. 19 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment This module does not apply to the refilling of leaking compartments of controlled and/or closed-pressure systems to assure continuity of service. These compartments should be refilled as described in 5.4. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for SF6 topping-up in each prefilled compartment should be performed according to Figure 2. Additional details are given in Table 12. Figure 2 —Topping-up of SF6 prefilled compartments to the rated pressure/density Table 12 —Topping-up SF6 prefilled compartments to the rated pressure/density Step Procedure 1 Prepare gas-handling equipment 2 Topping-up with SF6 3 Documentation 4 Pressure/density sensor inspection 5 Tightness inspection Check that the gas reclaimer is working properly and the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Connect the SF6 container and fill the compartment until the SF6 rated filling pressure is reached. Use a safety valve and a calibrated gauge to avoid overfilling. a, b Record at least the serial number or other identifying information for the gas compartment, the final filling pressure, ambient temperature, and date for further reference. Check the functionality of the pressure/density sensor. The operation can be performed during the filling operation. Check the tightness of at least all permanent connections made on-site. 20 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 12―Topping-up SF6 prefilled compartments to the rated pressure/density (continued) 6 Step SF6 quality checking 7 Documentation Procedure Wait at least 12 h after the filling operation and then measure the moisture content and the SF6 content of the gas in the compartment. Record at least the serial number or other identifying information for the gas compartment, the functionality of the pressure/density sensor, the moisture content, the SF6 content, ambient temperature, and date for further reference. a SF6 gas to be introduced into the gas compartment should comply with one of the following gas categories as defined in 4.6: ⎯ Purchased gas or technical grade gas ⎯ Suited for the complete range of reuse pressures ⎯ Suited for the low range of reuse pressures only in the case that the SF6 rated filling pressure of the equipment does not exceed the reuse limit, i.e., 200 kPa (29 psi) b No gas check is required if the gas comes from the supplier in sealed cylinders or containers. In all other cases, the gas quality should be checked prior to the filling operation. The gas quality check should comprise moisture content, SF6 percentage, and residual acidity content. 5.4 Refilling of SF6 to the rated pressure/density This module applies to the refilling of leaking compartments (usually indicated by the first alarm/indication of the pressure/density monitor) of controlled and/or closed-pressure systems to maintain continuity of service. In this case, appropriate corrective measures to locate and eliminate the leak should be immediately arranged. This module does not apply to leaking energized compartments. The operating instruction manual from the equipment manufacturer should be observed. This module does not apply to compartments of controlled and closed-pressure systems that currently contain a gas different from SF6 (typically air or N2) at ambient pressure or slight overpressure [typically 100 kPa to 150 kPa (14.5 psi to 21.8 psi). These compartments should be commissioned or recommissioned as described in 5.2. This module does not apply to compartments of controlled and/or closed-pressure systems that contain SF6 at a pressure above the atmosphere [typically 120 kPa to 150 kPa (17.4 psi to 21.8 psi)]. These compartments should be topped-up as described in 5.3. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for gas refilling in each compartment should be performed according to Figure 3. Additional details are given in Table 13. 21 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Figure 3 —Refilling SF6 compartments to the rated pressure/density Table 13 —Refilling SF6 compartments to the rated pressure/density Step Procedure 1 Prepare gas-handling equipment 2 Refilling with SF6 3 Documentation Check that the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Connect the SF6 container and fill the compartment until the SF6 rated filling pressure is reached. Use a safety valve and a calibrated gauge to avoid overfilling. a, b, c Record at least the serial number or other identifying information for the gas compartment, the final filling pressure, ambient temperature, and date for further reference. a SF6 gas to be introduced into the gas compartment should comply with one of the following gas categories as defined in 4.6: ⎯ Purchased gas or technical grade gas ⎯ Suited for the complete range of reuse pressures ⎯ Suited for the low range of reuse pressures only in the case that the SF6 rated filling pressure of the equipment does not exceed the reuse limit, i.e., 200 kPa (29 psi) b No gas check is required if the gas comes from the supplier in sealed cylinders or containers. In all other cases, the gas quality should be checked prior to the filling operation. The gas quality check should comprise moisture content, SF6 percentage, and residual acidity content. c As the amount of gas used for refilling is very small in comparison to the amount of gas in the related compartment, it is not necessary to perform a SF6 gas quality check after the refilling operation. 5.5 Checking the SF6 quality in gas compartments on-site Measurement of the SF6 quality is usually done on-site, using portable equipment. Off-site analysis may be performed to cross-check unsatisfactory on-site results, by sampling the gas and sending it to a qualified chemical laboratory. Depending on the category of the SF6 contained in the gas compartment or container, different physical characteristics (e.g., moisture content, SF6 content, or residual equivalent acidity) should be checked. The minimum requirements for quality checks are given in Table 14. 22 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 14 —Minimum on-site SF6 quality checks SF6 category Non arced gas Normally arced gas Heavily arced gas SF6 characteristics Moisture, SF6 content Moisture, SF6 content, residual acidity content Moisture, SF6 content, residual acidity content The residual acidity content should be checked first to prevent damage of other instruments, if normally or heavily arced gas is expected. 5.5.1 Measurement of the moisture content/dew point of SF6 on-site This module applies to the on-site measurement of moisture content/dew point of SF6-filled compartments of controlled and/or closed-pressure systems or SF6-filled containers. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for an on-site SF6 moisture check should be performed according to Figure 4. Additional details are given in Table 15. Characteristics of portable dew-point meters are given in 6.4.1. Figure 4 —On-site measurement of SF6 moisture content/dew point 23 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 15 —On-site measurement of SF6 moisture content/dew point Step Procedure 1 Prepare measuring equipment 2 Connect the dew-point meter 3 Read the dew-point meter 4 5 Disconnect the dew-point meter Documentation Check that the dew-point meter is working properly; and the gas connections are clean and dry to avoid any false measurements. Check the validity of the calibration of instruments subject to calibration. Use short connections to minimize SF6 release. Attach the dew-point meter. Make tight connections and establish gas flow. Refer to the operating instruction manual provided by the instrument manufacturer. Stop the gas flow and detach the dew-point meter. Record at least the serial number or other identifying information for the gas compartment, the reading, and the date for further reference. 5.5.2 Measurement of the SF6 content/quantity of inert gases on-site This module applies to the on-site measurement of SF6 content/quantity of SF6-filled compartments of controlled and/or closed-pressure systems or SF6-filled containers. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for an on-site measurement of the SF6 content/quantity of inert gases should be performed according to Figure 5. Additional details are given in Table 16. Characteristics of portable SF6 content measuring devices are given in 6.4.2. Figure 5 —On-site measurement of SF6 content/quantity of inert gases 24 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 16 —On-site measurement of SF6 content/quantity of inert gases Step Procedure 1 Prepare measuring equipment 2 Connect the SF6 content measuring device Read the SF6 content 3 4 5 Disconnect the SF6 content measuring device Documentation Check that the SF6 content measuring device is working properly and the gas connections are clean and dry to avoid any false measurements. Check the validity of the calibration of instruments subject to calibration. Use short connections to minimize SF6 release. Attach the SF6 content measuring device. Make tight connections and establish the gas flow. Refer to the operating instruction manual provided by the instrument manufacturer. Stop the gas flow and detach the SF6 content measuring device. Record at least the serial number or other identifying information for the gas compartment, the reading, and the date for further reference. 5.5.3 Measurement of the residual quantity of reactive gaseous decomposition products/residual acidity content on-site This module applies to the on-site measurement of the residual quantity of reactive gaseous decomposition products/residual acidity of SF6-filled compartments of controlled and/or closed-pressure systems or SF6filled containers. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for an on-site measurement of the residual quantity of reactive gaseous decomposition products/residual acidity content should be performed according to Figure 6. Additional details are given in Table 17. Portable analyzers of reactive gaseous decomposition products are described in 6.4.3. Figure 6 —On-site measurement of residual quantity of reactive gaseous decomposition products/residual acidity 25 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 17 —On-site measurement of residual quantity of reactive gaseous decomposition products/residual acidity 1 2 3 4 5 Step Prepare measuring equipment Connect the analyzer of reactive gaseous decomposition products Read the analyzer of reactive gaseous decomposition products Documentation Disconnect the analyzer of reactive gaseous decomposition products Procedure Check that the analyzer of reactive gaseous decomposition products is working properly and the gas connections are clean and dry to avoid any false measurements. Check the validity of the calibration of instruments subject to calibration. Use short connections to minimize SF6 release. Attach the analyzer of reactive gaseous decomposition products. Make tight connections and establish gas flow. Refer to the operating instruction manual provided by the instrument manufacturer. Record at least the serial number or other identifying information for the gas compartment, the reading, and the date for further reference. Stop the gas flow and detach the analyzer of reactive gaseous decomposition products. 5.6 Sampling and shipment of SF6 for off-site analysis This module applies to the collection of gas samples from SF6-filled compartments of controlled and/or closed-pressure systems or SF6-filled containers for off-site analysis. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for gas sampling and shipment should be performed according to Figure 7. Additional details are given in Table 18. Characteristics of cylinders for gas samples are described in 6.5. Figure 7 —Gas sampling and shipment 26 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 18 —Gas sampling and shipment a Step Procedure 1 Prepare gas-sampling equipment 2 Documentation 3 Connect the sampling cylinder 4 5 Disconnect the sampling cylinder Shipment Evacuate the sampling cylinder.a Check that the gas connections are clean and dry to avoid contamination of the sample and use short connections to minimize SF6 release. Tag the sampling cylinder with at least the following information: the serial number of the gas compartment, date, pressure, and ambient temperature. Attach the sampling cylinder. Make tight connections and establish gas flow. Stop gas flow and detach the sampling cylinder. Transportation to the laboratory shall be done in accordance to international and local regulations, as described in 4.9.3. Stainless steel cylinders with a volume smaller than 1 L (1.06 qt) should be used. 5.7 Recovery and reclaiming of non-arced and/or normally arced SF6 from compartments of controlled and/or closed-pressure systems This module applies to compartments of controlled and/or closed-pressure systems that contain non-arced or normally arced SF6 to be recovered for maintenance or end-of-life disposal when the equipment is dismantled. This module does not apply to compartments of controlled and/or closed-pressure systems that contain heavily arced SF6 to be recovered and reclaimed. These compartments should be handled as described in 5.8. This module does not apply to compartments of sealed-pressure systems. These compartments should be handled as described in 5.9.2. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for recovery of non-arced and normally arced gas from each compartment should be performed according to Figure 8. Additional details are given in Table 19. The safety rules given in 4.7 should be followed. 27 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Figure 8 —Recovery and reclaiming of non-arced or normally arced SF6 from compartments Table 19 —Recovery and reclaiming of non-arced or normally arced SF6 from compartments 1 Step Prepare gas-handling equipment 2 Connect filters 3 Gas recovery 4 Minimize residual SF6 content 5 Documentation Procedure Check that the gas reclaimer is properly working, the filters and pre-filters are still active, and the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Connect the pre-filter between the gas compartment and the compressor and the filter between the compressor and the storage container. Connect the SF6 compartment. Use the main compressor stage as soon as the SF6 residual pressure in the compartment approaches the pressure in the storage container. Use a safety valve and a calibrated gauge to avoid overfilling of the storage container.a Connect the auxiliary compressor stage when the SF6 residual pressure in the compartment approaches 100 kPa (14.5 psi) and leave it running until a pressure smaller than 2 kPa (0.29 psi) is reached.b Record at least the serial number or other identifying information for the gas compartment, the reading, and the date for further reference. Record any SF6 emissions, if required. 28 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 19―Recovery and reclaiming of non-arced or normally arced SF6 from compartments (continued) 6 Step Flooding with air 7 Open the gas compartment 8 Remove switching dust and adsorbents when present 9 Neutralization, if required Procedure Detach the compressor and let the air enter slowly into the gas compartment. Carefully open the gas compartment. Apply safety rules according to 4.7. Immediately use vacuum cleaner or wipe with a clean lintfree rag to collect the dust, if present. Place adsorbents in a plastic bag. Seal the plastic bag with tape and tag it. If switching dust was collected, use a saturated solution of water and sodium bicarbonate (baking soda) to wash and neutralize all parts and then wash with clean water. a In the case of liquid storage, the weight of the storage container should be controlled in order to avoid overfilling. The filling factor is smaller than 0.8 kg/L (49.94 lbm/ft3) for safety reasons. b If a leak in the gas compartment prevents evacuation to a pressure smaller than 2 kPa (0.29 psi), stop the evacuation process and consider alternative measures to capture the residual gas. 5.8 Recovery and reclaiming of heavily arced SF6 from compartments of controlled and/or closed-pressure systems This module applies to compartments of controlled and/or closed-pressure systems that contain heavily arced SF6 to be recovered for maintenance or at the end-of-life disposal when the equipment is dismantled. This module does not apply to compartments of controlled and/or closed-pressure systems that contain nonarced or normally arced SF6 to be recovered and reclaimed. These compartments should be handled as described in 5.7. This module does not apply to compartments of sealed-pressure systems. These compartments should be handled as described in 5.9.2. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for recovery of heavily arced gas from each compartment should be performed according to Figure 9. Additional details are given in Table 20. The safety rules given in 4.7 should be followed. 29 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Figure 9 —Recovery and reclaiming of heavily arced SF6 from compartments Table 20 —Recovery and reclaiming of heavily arced SF6 from compartments 1 Step Prepare gas-handling equipment 2 Connect filters 3 Connect additional pre-filter 4 Gas recovery 5 Minimize residual SF6 content 6 Documentation 7 Flooding with air Procedure Check that the gas reclaimer is properly working, the filters and pre-filters are still active, and the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Connect the pre-filter between the gas compartment and the compressor and the filter between the compressor and the storage cylinder. Connect an additional pre-filter at the inlet of the gas reclaimer. Connect the SF6 compartment. Use the main compressor stage as soon as the SF6 residual pressure in the compartment approaches the pressure in the storage container. Use a safety valve and a calibrated gauge. Use an external storage container and avoid its overfilling. a Connect the auxiliary compressor stage when the SF6 residual pressure in the compartment approaches 100 kPa (14.5 psi) and leave it running until a pressure smaller than 2 kPa (0.29 psi) is reached. b Record at least the serial number or other identifying information for the gas compartment, the reading, and the date for further reference. Record any SF6 emissions, if required. Detach the compressor and let the air enter slowly into the gas compartment. 30 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 20―Recovery and reclaiming of heavily arced SF6 from compartments (continued) 8 Step Settling down of switching dust 9 Open the gas compartment 10 Remove switching dust, adsorbents, and removable parts 11 Neutralization 12 Documentation Procedure Wait at least 1 h to give enough time for the remaining switching dust to settle down in the gas compartment. Carefully open the gas compartment. Apply safety rules according to 4.7. Immediately use a vacuum cleaner to collect the dust. Place adsorbents and removable parts in plastic bags. Seal plastic bags with tape and tag them. Use 10% soda solution or equivalent to wash and neutralize all parts and then wash with clean water. Record all relevant information concerning the internal fault. Include some pictures. a In the case of liquid storage, the weight of the storage container should be controlled in order to avoid overfilling. The filling factor is smaller than 0.8 kg/L (49.94 lbm/ft3) for safety reasons. b If a leak in the gas compartment prevents evacuation to a pressure smaller than 2 kPa (0.29 psi), stop the evacuation process and consider alternative measures to capture the residual gas. 5.9 Recovery and reclaiming of SF6 at the end-of-life disposal when the electric power equipment is dismantled This module covers the different phases where SF6 should be handled during the end-of-life disposal when dismantling is chosen for the end of life of electric power equipment. End-of-life disposal/dismantling is performed under the user’s responsibility and supported by the manufacturer. Third parties, such as qualified service companies, may also carry out end-of-life disposal/dismantling. When the equipment is dismantled, its material components will typically be metal materials (such as aluminum, copper, and aluminum casting components), insulation components, low-voltage components, hydraulic fluid, and grease. Additionally, SF6 gas and its gaseous and solid decomposition products will be present. Almost 90% of all materials can be reused. The materials have to be sorted before delivering to the waste collector. Electrical switchgear dismantling and related treatment of polluted gas, enclosures, powders, adsorbents, and effluents shall be conducted with due regard to personnel and environment safety, as described in 4.7 and also in IEC 62271-303. In particular, SF6 gas should be recovered, reclaimed, and recycled using an appropriate procedure before any other dismantling operations. Then, any contaminants in the remaining part of the switchgear should be removed, if necessary. After treatment, the equipment can be recycled as normal electrical waste. 5.9.1 Closed and controlled pressure systems For this equipment, the gas recovery takes place either on-site or off-site. Corresponding procedures are given in 5.7 (non-arced or normally arced SF6) and 5.8 (heavily arced SF6). 31 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 5.9.2 Sealed-pressure systems Generally, sealed-pressure systems are collected for destruction before removal of SF6, as this operation is typically conducted by service companies. These companies should implement the necessary handling and storage means to avoid any shocks that may crack or break the enclosure, in particular resin-based enclosures. Experience shows that the risk of the SF6 gas being dispersed in the environment during handling and transportation is low, if the manufacturer’s transportation instructions are followed. The devices to be dismantled may come from a number of places. For this reason, the residual quantity of gaseous and solid decomposition products sometimes cannot be determined prior to opening of the equipment. In these cases, the gas should be considered as heavily arced and the procedure in 5.8 should be applied. When it can be demonstrated that the SF6 is non-arced or normally arced (i.e., SF6 has not been exposed to current breaking and/or internal arc) then the procedure in 5.7 can be applied. When sealed-pressure systems are fitted with connecting facilities, dedicated tools according to manufacturer instructions should preferably be used for the gas recovery. If not, then tight drilling systems should be used. Unless otherwise specified by the equipment manufacturer in the operating instruction manual, the following detailed sequence of operations for SF6 handling at the end-of-life disposal, when the sealedpressure systems is dismantled, should be performed according to Figure 10. Additional details are given in Table 21. The safety rules given in 4.7 should be followed. Figure 10 —SF6 recovery at the end-of-life disposal for a sealed-pressure system 32 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 21 —SF6 recovery at the end-of-life disposal for a sealed-pressure system Step Procedure 1 Organization 2 Disconnection of equipment Make arrangements with the manufacturer or a qualified service company for off-site SF6 recovery/end-of-life disposal of the equipment, if required. Disconnect primary and secondary wiring. 3 Removal of the equipment Remove the sealed-pressure system. 4 Shipping of the equipment 5 Prepare gas-handling equipment 6 Connect filters 7 8 Connect additional pre-filter (only for heavily arced SF6) Connect SF6 compartment 9 Gas recovery 10 Reduce residual SF6 content 11 Flooding with air 12 Settling down of switching dust (only for heavily arced SF6) Open the gas compartment Transportation to the manufacturer or to the qualified service company shall be done in accordance to international and local regulations, as described in 4.9.3. Check that the gas reclaimer is working properly, the filters and pre-filters are still active, and the gas connections are clean and dry to avoid contamination. Check the validity of the calibration of instruments subject to calibration. Connect the pre-filter between the gas compartment and the compressor and the filter between the compressor and the storage container. Connect an additional pre-filter at the inlet of the gas reclaimer. Use dedicated tools and follow the manufacturer’s instructions to connect the SF6 compartment. In other cases, tight drilling systems should be used. Use the main compressor stage to transfer the gas to the storage container. Use a safety valve and a calibrated gauge. Use an appropriate external storage container and avoid its overfilling. a Connect the auxiliary compressor stage and leave it running until a pressure smaller than 2 kPa (0.29 psi) is reached. Detach the compressor and let the air enter slowly into the gas compartment. Wait at least 1 h until the remaining switching dust has settled down in the gas compartment. Carefully open the gas compartment. Apply safety rules according to 4.7. Immediately use vacuum cleaner or wipe with a clean lintfree rag to collect the dust, if present. Place adsorbents and removable parts in a plastic bag. Seal the plastic bags with tape and tag them. If switching dust was collected, use 10% soda solution or equivalent to wash and neutralize all parts and then wash with clean water. Record at least the serial number or other identifying information for the gas compartment, the date of dismantling, and the quantity of gas recovered in kg. 13 14 Remove switching dust, removable parts, and adsorbents, when present 15 Neutralization, if required 16 Documentation a In the case of liquid storage, the weight of the storage container should be controlled in order to avoid overfilling. The filling factor is smaller than 0.8 kg/L (49.94 lbm/ft3) for safety reasons. 6. SF6 handling equipment description modules 6.1 General This clause provides guidelines for the specifications, minimum functionality, and performance criteria for SF6 handling equipment and specific components. 33 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 6.2 Gas reclaimers The appropriate type and size of the reclaimer should be chosen according to the gas quantity to be handled. The typical functions of a standard SF6 reclaimer include the following: ⎯ Evacuation of air from the gas compartment ⎯ Filling of SF6 in the gas compartment ⎯ Recovery of SF6 from the gas compartment ⎯ Storage and filtering of SF6 ⎯ Flooding of the gas compartment with ambient air The typical characteristics to examine when selecting or specifying a reclaimer include the following: ⎯ Residual recovery pressure pres (residual pressure in equipment down to which the gas can be recovered and compressed to the rated storage pressure pst) ⎯ Recovery pressure differential [performance indicator of compressor(s)]: pst/pres ⎯ Recovery speed: Time required recovering a specific gas volume down to the specified residual recovery pressure pres ⎯ Evacuation speed: Time required to evacuate a specific gas volume down to a residual air pressure of 2 kPa (0.29 psi) ⎯ Refill speed: Time required filling gas from the storage container at rated storage pressure into the equipment at its rated operating pressure ⎯ Failsafe operation control (to avoid gas contamination by incorrect handling) ⎯ Filter exchange/handling/disposal facilities Figure 11 shows the basic functional scheme of a general purpose SF6 reclaimer. The requirements for each component of a SF6 reclaimer are discussed in the following subclauses. 34 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Figure 11 —Functional scheme of a general purpose SF6 reclaimer 6.2.1 Pre-filtering unit A pre-filtering unit, either stand-alone or internal, is required to recover both normally and heavily arced SF6. The reactive gaseous decomposition products are acid compounds and could damage the gas reclaimer or the gas storage container. The requirements of the pre-filtering unit are essentially the same as those of the filtering units installed in the gas-handling device, but the pre-filtering capacity could be considerably higher. Recommended major characteristics are as follows: ⎯ Pore size 10 μm (low through-flow resistance) ⎯ Residual moisture lower than 200 ppmv ⎯ Residual reactive gaseous decomposition products lower than 200 ppmv 6.2.2 Filtering unit Filtering units are required to remove the reactive gaseous decomposition products before they are stored, allowing for the reuse of SF6. These filtering units are installed in the SF6 reclaimer. Table 22 shows typical filter types used during SF6 reclaiming. 35 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table 22 —Typical filter types used during SF6 reclaiming Filter type Particle filter Gas/moisture filter Oil filter Tasks Removes solid decomposition products and other particles at the reclaimer inlet Removes reactive gaseous decomposition products and moisture Removes oil, when required Major characteristics Pore size 1 μm Residual moisture lower than 100 ppmv Residual SO2 + SOF2 lower than 12 ppmv Particle retention ability Special filter utilizing active charcoal The following subclauses provide further details. 6.2.2.1 Particle filter Some decomposition products, which are generated during switching operations, are made up of fine solid particles (e.g., metal particles or switching dust). The inner side of the particle filter consists of paper or a suitable bonded fabric that is able to retain the particles in a range up to 1 µm. Normally, the particle filter is installed at the inlet and upstream from the outlet of the gas reclaimer to protect parts of the plant as well as the gas storage container. 6.2.2.2 Gas/moisture filters Appropriate filters can absorb moisture and reactive gaseous decomposition products. They are mainly used in combination with the particle filter. Molecular sieves with a pore size smaller than 0.5 nm are used. If a bigger pore size is used, under certain conditions thermodynamic reactions can occur, resulting in severe filter overheating. Soda lime (NaCO3) should not be used as a filter material for SF6 as it produces CO2 upon contact with certain reactive gaseous decomposition products. CO2 is difficult to remove from SF6. 6.2.2.3 Oil filter An oil trap should be inserted in the SF6 cycle if an oil-lubricated machine is used or if an oil-insulated electric component is included in the electric power equipment utilizing SF6. The oil removal is achieved in several steps to avoid diffusion of the oil. 6.2.3 Vacuum pump The vacuum pump is used to evacuate gases other than SF6 (typically air or N2) from the gas compartment, container, or sample cylinders. The residual pressure at the inlet of the vacuum pump should be lower than 2 kPa (0.29 psi). In order to speed the evacuation of gas compartments, it is recommended that vacuum pumps with a residual pressure at the inlet lower than 10 Pa (0.0015 psi) be used. The capacity of the vacuum pump should be suitable for the volume of the gas compartment and the evacuation time. The connecting diameter is also of great importance. For example, for a gas compartment with a volume of 1000 L (264 gal), a connecting diameter of 20 mm (¾ in) is recommended. If smaller diameters are used, the evacuation process is considerably extended and the use of a vacuum pump with a higher capacity is not effective. 36 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment The vacuum pump is equipped with a vacuum pressure gauge. It is recommended that the resolution of the vacuum pressure gauge be lower than 10 Pa (0.0015 psi); however, at minimum, it should be lower than 100 Pa (0.015 psi). Vacuum gauges independent of the gas type are generally recommended. A valve is recommended to shut off the connection between the gas compartment and the vacuum pump. The valve should close at least manually (automatically is recommended) after having turned off the vacuum pump. Closing the valve avoids oil diffusion into the gas compartment. 6.2.4 Compressor When the SF6 pressure in the gas compartment is higher than the pressure in the storage container, it is quickest to allow direct gas expansion. In all other cases, a compressor is required to recover the gas. A 2.5 MPa (362.6 psi) rated outlet pressure of the compressor is sufficient to store SF6 in a gaseous form [5 MPa (725.2 psi) pressure is recommended]. An additional cooling device may be used to speed gas recovery. A very important parameter for choosing a compressor is the pressure at the outlet divided by the pressure at the inlet (compression ratio). State-of-the-art compressor stages are optimized for a compression ratio of 1:100 for technological reasons. As the pressure in the gas compartment may vary within a very wide range, a dual compressor should be used, as follows: ⎯ The main compression stage, usually employing a piston-type compressor, operates between a gas inlet pressure about 100 kPa (14.5 psi), typically higher than 50 kPa (7.25 psi), and the pressure in the gas storage container. Almost all kinds of piston-type compressors can be used; however, those that are dry-running and hermetically sealed are preferred to reduce the possibility of SF6 leaks and oil contamination. ⎯ The auxiliary compression stage, connected in series when needed, operates between the pressure in the gas compartment and the pressure at the inlet of the main compressor. 6.2.5 Storage container Commercial pressure vessels or special storage containers for used SF6 are available. They are mobile, stationary, or installed in the gas reclaimer. Only specially approved storage containers or gas cylinders for storage and/or transportation of used SF6 are allowed. These are described in 4.9. The maximum pressure of the storage container should be suitable for the final pressure of the compressor. Local regulations for the operation of pressure vessels shall be observed. For storage containers with liquid SF6 storage, a rated pressure of 5 MPa (725 psi) is recommended. 6.2.6 Evaporator/heater If SF6 is stored in liquid form and used as a gas, icing/frosting of the storage container takes place when large gas quantities are handled in a short time. Cylinder heaters and evaporators are commercially available. The evaporator receives liquid SF6 from the storage container and should be designed so that no liquid can reach the gas compartment. The storage container heaters should be designed to avoid accidental overheating. It is recommended that the gas temperature is always kept lower than 60 °C (140 °F). 37 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 6.2.7 Gas and hose connections The reclaimer, the gas storage container, and the electric power equipment are connected via flexible hose connections. Particular care should be exercised to avoid the presence of air or other compounds inside the hoses in order to reduce the possibility of contaminating the gas. For this reason, hose connections with both self-closing and vacuum-tight couplings are required. Suitable hoses, typically made of polytetrafluoroethylene (PTFE) or flexible stainless steel, and able to withstand vacuum and permeation are required. 6.2.8 Gas piping and pipe junctions Gas piping and pipe junctions should be designed to avoid leaks and corrosion. For that purpose, copper and brass are typically used. The design of both piping and connections should take vibration into account, so that periodic operations (such as retightening of fittings) are not required. 6.2.9 Control instruments Control gauges should be provided to show information such as the gas pressure in the gas compartment, the vacuum level, and the gas temperature. The gauges should be placed in a position so that they can be observed when initiating operations of the gas-handling device. Accuracy and resolution of the gauges should be adequate to support the necessary operations. 6.2.10 Safety valves Safety valves should be used in the SF6 cycle for pressure relief. Local safety regulations shall be followed. Safety valves that do not directly release SF6 to the atmosphere are recommended. 6.3 Personal protective equipment Safety shoes and helmets should be used according to local safety regulations. In addition, equipment that protects against SF6 decomposition products when accessing a gas compartment is briefly described in the following subclauses. 6.3.1 Skin protection Protective gloves should be resistant to solvents, acids, and liquid tight. They are usually made of nitril rubber or neoprene. In addition to protective gloves, the use of protective creams is recommended. 6.3.2 Eye protection Safety goggles provide protection against gas and fine dust. 38 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 6.3.3 Breathing protection 6.3.3.1 Dust mask A dust mask protects the nose and mouth against dust. 6.3.3.2 Full-face mask A full-face mask is gas-tight and protects the eyes, nose, and mouth from by-products with a changeable active-charcoal filter. 6.3.4 Overall protection Single-use dust-proof protective clothes to wear over normal clothes, shoe covers, and hair cap provide overall protection. 6.4 Devices for gas measurement on-site Pressure/density gauges are used to compare the SF6 pressure in the gas compartment to the SF6 rated filling pressure of each compartment. The ambient temperature should be taken into account to permit proper comparison. Table 23 provides a survey of the SF6 control instruments, including recommended measuring range and minimum accuracy. Table 23 —On-site SF6 measuring devices Device Quantity SF6 pressure gauge Pressure Thermometer Temperature Dew-point meter Moisture SF6 content-measuring device Reaction tubes SF6/N2 SF6/air SO2 Oil mist Range 0 to 1 MPa (0 to 145.04 psi) –25 °C to 50 °C (–13 °F to 122 °F) Dew point: –50 °C to 0 °C (–58 °F to 32 °F) 0% to 100% by volume Minimum accuracy ±10 kPa (± 1.45 psi) 1 ppmv to 25 ppmv 0.16 ppmv to 1.6 ppmv ± 15% ±1 °C (± 1.8 °F) ±2 °C (± 3.6 °F) ±1% volume Gas quality measurements can be made under laboratory conditions and on-site. The following sublauses describe the most commonly applied on-site control instruments for the determination of the following: ⎯ Moisture content/dew point ⎯ SF6 content/quantity of inert gases ⎯ Residual quantity of reactive gaseous decomposition products/residual acidity content 39 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment 6.4.1 Dew-point meters The moisture content can be measured with different measuring principles and measuring instruments. It is mainly expressed as dew point. Desirable features of dew-point meters include the following: ⎯ A sensor that is resistant to oil traces and corrosive gases ⎯ Permeation-resistant connecting pipes that use self-sealing valve connections ⎯ Portability ⎯ Calibrated or capable of field calibration ⎯ SF6 gas release less than approximately 6 g (0.2 oz) per measurement ⎯ Average time to obtain the readout of less than 5 min 6.4.2 SF6 content measuring devices Devices that compare the speed of sound or the thermal conductivity of the SF6 gas mixture with pure SF6 are used to determine the SF6 content. Speed-of-sound based systems are fast (response time less than 1 min), accurate to ±1%, do not need recalibration, and use only a minimal amount of gas. Their readout is the SF6 concentration in percent volume. They are mostly calibrated for mixtures of SF6 and N2 and/or air. Devices that measure the concentration of the non-reactive gases (such as oxygen sensors) and then calculate the percentage of SF6 should not be used, as other non-reactive gases (such as N2 or CF4) may be present. Desirable features of SF6 content measuring devices include the following: ⎯ A response time of less than 1 min ⎯ No recalibration required ⎯ Portability ⎯ SF6 gas release less than 3 g (0.1 oz) per measurement 6.4.3 Analyzers of reactive gaseous decomposition products Desirable features for analyzers of reactive gaseous decomposition products include the following: ⎯ Calibration for SO2 and SOF2 ⎯ Connecting pipes that are resistant to reactive gaseous decomposition products and use self-sealing valve connections ⎯ Portability ⎯ SF6 gas release less than approximately 6 g (0.2 oz) per measurement 6.4.3.1 Reaction tubes Reaction tubes sensitive to SO2 should be used, as the gas remains for quite a long time in the SF6 environment. These portable field instruments change their initial color if SF6 containing SO2 is fed through them. SO2 reaction tubes are also sensitive to SOF2. A small amount of SF6 from the equipment [~6 g 40 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment (0.2 oz)] is needed. The gas sample is then released through the reaction tube to perform the measurement. A measuring range from 0 to 25 ppmv is recommended. Reaction tubes sensitive to HF should not be used, as this gas reacts quickly with all metals to form metal fluorides. 6.4.3.2 Electronic and electrochemical SO2 sensors Electronic and electrochemical SO2 sensors have been developed but have not yet been tested in SF6insulated power technology. 6.4.3.3 Ion mobility spectrometers A new commercially-available method is based on an ion mobility spectrometer (IMS) and is calibrated to detect the total quantity of reactive gaseous decomposition products as a whole, rather than only the sum of SO2 and SOF2. 6.5 Cylinder for gas samples Stainless-steel cylinders with a volume smaller than 1 L (1.06 qt) are recommended for collecting gas samples. The gas quantity should be not smaller than 6 g (0.2 oz). The gas should be sampled directly from the container (e.g., gas compartment or storage container of the gas reclaimer) using suitable fittings. If the pressure in the gas container exceeds the maximum allowable pressure of the cylinder, then a pressure regulator and a pressure gauge should be used. 6.6 Gas piping and pipe junctions in buildings or equipment For piping installed at electrical equipment or in buildings, piping and fittings made of copper, aluminum, or stainless steel can be used. Stainless-steel piping and fittings are recommended if normally arced or heavily arced gas is handled. Piping connections are a common source of SF6 leaks; therefore, it is recommended that connections be regularly checked for leakage. 41 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Annex A (normative) Theoretical considerations for SF6 handling A.1 Overview The following subclauses present some theoretical considerations for best practices for SF6 handling. The focus is on both air and SF6 residual pressure in gas compartments versus SF6 dilution and handling losses, respectively. A.2 Air residual pressure versus SF6 dilution and moisture content Maintenance of a compartment requires the recovery of the contained SF6 gas, flooding with air, and subsequent evacuation of the compartment down to residual pressure. The reused SF6 gas is diluted by the remaining air so that after some number of handling operations, the recovered gas reaches the maximum air content permitted for reused gas. The following subclause describes how to calculate the maximum number of handling operations until the gas no longer meets the purity requirements for reuse. The following information is relevant when calculating the maximum number of handling operations: ⎯ While it is possible to separate air from SF6, this requires more expensive gas reclaimers that are not typically used on-site. ⎯ Technical grade gas, as defined in IEC 60376, allows up to 1% volume air and 0.4% volume CF4 (i.e., 1.4% volume for the sum of both inert gases). ⎯ The purity requirements for SF6 reuse and recycling, which are specified by IEC 60480, allow up to 3% volume for the sum of both air and CF4. ⎯ Each time a gas compartment is evacuated down to the air residual pressure pair and filled with SF6 p up to the SF6 rated filling pressure9 pSF6, the gas is diluted by a factor 1 − air . pSF6 In the case of many complete handling operations, which include both evacuation and filling, the following equation applies: ⎛ p 1 − c f = (1 − ci )⎜1 − air ⎜ pSF6 ⎝ ⎞ ⎟ ⎟ ⎠ n where ci is the IEC 60376 limit for air and CF4 (1.4%) cf is the IEC 60480 limit for air and CF4 (3.0%) pSF6 is the SF6 rated filling pressure pair is the air residual pressure after evacuation n is the number of complete handling operations 9 Typical SF6 rated filling pressures are: 100 kPa to 150 kPa for MV insulation, ~300 kPa for MV breakers, ~500 kPa for HV insulation, and ~700 kPa for HV breakers. 42 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table A.1 gives the number of handling operations, starting from “technical grade SF6,” to reach the SF6 reuse limit specified by IEC 60480, as a function of the air residual pressure and the SF6 rated filling pressure. Table A.1—Maximum number of handling operations Air residual pressure (Pa) (# of times) 100 200 300 400 500 600 700 800 1000 100 SF6 rated filling pressure (kPa) 150 300 500 700 16 24 49 81 114 8 5 4 3 2 2 2 1 12 8 6 4 4 3 3 2 24 16 12 9 8 7 6 4 40 27 20 16 13 11 10 8 57 38 28 22 19 16 14 11 Sealed-pressure systems (commercially designated as sealed for life), require no SF6 handling on-site. Therefore, Table A.1 does not apply to sealed-for-life systems. The vacuum level for evacuation is set to be smaller than 2 kPa for at least 1 h in order to remove sufficient moisture from each gas compartment. Figure A.1 and Figure A.2 show the evacuation experiment in gas compartment of 200 L, containing 20 cm3 of water. Looking from the observation window into the gas compartment, it is possible to notice the following: ⎯ The water starts to boil around 1300 Pa ⎯ The pressure remains around 500 Pa for a short time and the moisture level is reduced ⎯ When the pressure is smaller than 300 Pa the water is no longer visible in the gas compartment The top limit concerning the residual pressure in any kind of gas compartment prior to filling is deduced from IEC 62271-1: dew point not higher than –5 °C (23 °F), corresponding to a moisture partial pressure of 400 Pa. 43 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Figure A.1—Correlation between the pressure in a typical gas compartment and the evacuation time during air evacuation Figure A.2—Schematic of evacuation experiment 44 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment A.3 SF6 residual pressure versus SF6 handling losses The SF6 handling loss per handling operation can be easily evaluated, as it is the ratio between the SF6 residual pressure and the SF6 rated filling pressure. This is given in Table A.2. Table A.2—SF6 handling loss in % per handling operation SF6 residual pressure (Pa) (% vol.) 100 100 200 500 1000 2000 5000 10000 20000 0.10 0.20 0.50 1.00 2.00 5.00 10.00 20.00 SF6 rated filling pressure (kPa) 150 300 500 0.07 0.13 0.33 0.67 1.67 3.33 6.67 16.7 0.03 0.07 0.17 0.33 0.67 1.67 3.33 6.67 0.02 0.04 0.10 0.20 0.40 1.00 2.00 4.00 700 0.01 0.03 0.07 0.14 0.29 0.71 1.43 2.86 State-of-the-art MV equipment requires no SF6 handling on-site. A SF6 residual pressure not higher than 2 kPa is required to assure reaching a target of 2% handling losses at the end-of-life disposal when the equipment is dismantled (assuming a SF6 rated filling pressure of approximately 100 kPa). The same SF6 residual pressure of 2 kPa is suggested for MV closed-pressure systems. HV equipment with a typical rated filling pressure of 500 kPa and a SF6 residual pressure of 2 kPa can achieve 0.4% handling losses. However, state-of-the-art handling equipment is capable of recovering SF6 down to less than 100 Pa in the gas compartment, achieving a further environmental benefit. 45 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Annex B (informative) Moisture measurement units and conversions B.1 Overview Several physical quantities and units are used to measure the amount of moisture in a GIS compartment, as follows: ⎯ Moisture partial pressure, usually in pascal (Pa) ⎯ Moisture volume concentration, usually in parts per million by volume (ppmv) ⎯ Moisture mass concentration, usually in part per million by weight (ppmw) ⎯ Dew point, usually in degree centigrade (°C) ⎯ Absolute humidity, usually in grams per cubic meter (g/m3) ⎯ Relative humidity, usually in percentage (%) The following subclauses define and give a short explanation of each measure. Conversion formulas and tables are also given. B.2 Moisture partial pressure (Pa) The primary physical quantity characterizing the moisture level in a gas compartment is the moisture partial pressure. This is a linear measure of the moisture level and is independent of the pressure of the background gas, as well as its nature. As the moisture partial pressure is a pressure, the unit is pascal (Pa). The law of perfect gases can be successfully applied, as shown in Equation (B.1): pH 2 O = nH 2 O V RT = mH 2 O R V M H 2O (B.1) T where pH2O is the moisture partial pressure (Pa) nH2O is the number moles of moisture contained in the gas compartment V is the volume of the gas compartment (m3) J is the universal constant of perfect gases R = 8.3143 mol K T is the absolute temperature (K) to which the moisture partial pressure is referred, typically 293.16 K, corresponding to 20 °C mH 2 O = is the mass of moisture contained in the gas compartment (g) M H 2 O = 18 g is the molar mass of water mol 46 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment B.3 Absolute humidity (g/m3) The absolute humidity (AH) is the mass of moisture contained in the gas compartment divided by the volume of the gas compartment. This is a linear measure of the moisture level and is independent of the pressure of the background gas, as well as its nature. As the AH is a mass density, the unit is (g/m3). Equation (B.2) applies: AH = mH 2 O V = pH 2 O M H 2 O T (B.2) R where AH is the absolute humidity (g/m3) mH 2 O is the mass of moisture contained in the gas compartment (g) V is the volume of the gas compartment (m3) pH2O is the moisture partial pressure (Pa) T is the absolute temperature (K) to which the moisture partial pressure is referred, typically 293.16 K, corresponding to 20 °C g is the molar mass of water M H 2 O = 18 mol J is the universal constant of perfect gases R = 8.3143 mol K B.4 Moisture volume concentration (ppmv) The moisture volume concentration cV is the volume occupied by the moisture contained in the gas compartment at the SF6 rated filling pressure divided by the volume of the gas compartment. This is also the ratio between the moisture partial pressure and the SF6 rated filling pressure. The recommended unit is parts per million by volume (ppmv). See Equation (B.3). cV = VH 2 O V = RT nH 2 O 3 pH 2 O 3 nH 2 O 6 mH 2 O M SF6 10 = 10 = 10 = 103 V pSF6 pSF6 nSF6 mSF6 M H 2 O (B.3) where cV is the moisture volume concentration (ppmv) VH2O is the volume occupied by the moisture contained in the gas compartment at the SF6 rated filling pressure (cm3) V is the volume of the gas compartment (m3) J is the universal constant of perfect gases R = 8.3143 mol K T is the absolute temperature (K) to which both the SF6 rated filling pressure and the moisture partial pressure are referred, typically 293.16 K, corresponding to 20 °C nH2O is the number moles of moisture contained in the gas compartment pSF6 is the SF6 rated filling pressure (kPa) pH2O is the moisture partial pressure (Pa) nSF6 is the number moles of SF6 contained in the gas compartment mH2O is the mass of moisture contained in the gas compartment (g) mSF6 is the mass of SF6 contained in the gas compartment (kg) 47 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment g is the molar mass of SF6 mol g is the molar mass of water = 18 mol M SF6 = 146 M H 2O B.5 Moisture mass concentration (ppmw) The mass concentration cM is the ratio between the mass of the moisture and the SF6 contained in the gas compartment. The most common unit is parts per million by weight (ppmw). See Equation (B.4). cM = mH 2 O mSF6 103 = pH 2 O M H 2 O pSF6 M SF6 103 = M H 2O M SF6 cV (B.4) where cM is the mass concentration (ppmw) mH2O is the mass of moisture contained in the gas compartment (g) mSF6 is the mass of SF6 contained in the gas compartment (kg) pH2O is the moisture partial pressure (Pa) pSF6 is the SF6 rated filling pressure (kPa) g M H 2 O = 18 is the molar mass of water mol g M SF6 = 146 is the molar mass of SF6 mol cV is the moisture volume concentration (ppmv) B.6 Dew point (°C) Condensation of moisture as liquid or solid occurs when the moisture partial pressure reaches a critical value, termed the moisture saturation pressure. The moisture saturation pressure is a non-linear function of the temperature only. It has no relation to the pressure of the background gas or its nature. The moisture saturation pressure versus dew point is an experimental curve. It is used to relate the dew point and moisture partial pressure. The Smithsonian Meteorological Tables define the worldwide interpolation curves, depending on the temperature interval: For temperatures ranging between –100 °C and 0 °C, use Equation (B.5): log10 ⎛ 273.16 ⎞ pw Tw ⎞ 273.16 ⎛ + 0.876793⎜1 − = −9.09718⎜⎜ − 1⎟⎟ − 3.56654 log10 ⎟ 610.71 Tw ⎝ 273.16 ⎠ ⎠ ⎝ Tw (B.5) For temperatures ranging between 0 and +100 °C, use Equation (B.6): log10 ⎛ 373.16 ⎞ pw 373.16 + = −7.90298⎜⎜ − 1⎟⎟ + 5.02808 log10 101325.6 Tw ⎠ ⎝ Tw − 1.3816 ⋅10 ⎛ −3.49149⎛⎜ 373.16 −1⎞⎟ ⎞ ⎛ 11.344⎛⎜1− Tw ⎞⎟ ⎞ ⎜ ⎟ ⎟ ⎜ T ⎟ 3 − 373 . 16 w ⎠ − 1⎟ ⎠ − 1 + 8.1328 ⋅10 ⎜10 ⎝ ⎝ ⎟ ⎜10 ⎜⎜ ⎟⎟ ⎟ ⎜ ⎠ ⎝ ⎝ ⎠ −7 ⎜ (B.6) 48 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment where pw is the moisture saturation pressure (Pa) Tw is the absolute dew point (K); Tw = 273.16 + t w where tw is the dew point in °C Table B.1 gives the non-linear relationship between the dew point and the moisture saturation pressure in the temperature range –60 °C to +60 °C in steps of 1 °C. Table B.1—Moisture saturation pressure Dew point tw (°C) –60 –59 –58 –57 –56 –55 –54 –53 –52 –51 –50 –49 –48 –47 –46 –45 –44 –43 –42 –41 –40 –39 –38 –37 –36 –35 –34 –33 –32 –31 –30 –29 –28 –27 –26 –25 –24 –23 –22 –21 –20 Moisture saturation pressure pw (Pa) 1.1 1.2 1.4 1.6 1.8 2.1 2.4 2.7 3.1 3.5 3.9 4.4 5.0 5.7 6.4 7.2 8.1 9.1 10.2 11.5 12.8 14 16 18 20 22 25 28 31 34 38 42 47 52 57 63 70 77 85 94 103 Moisture saturation pressure pw (Pa) 103 114 125 137 151 165 181 198 217 238 260 284 310 338 368 401 437 476 517 562 611 657 705 758 813 872 935 1 001 1 072 1 147 1 227 1 312 1 402 1 497 1 598 1 704 1 817 1 937 2 063 2 196 2 337 Dew point tw (°C) –20 –19 –18 –17 –16 –15 –14 –13 –12 –11 –10 –9 –8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Dew point tw (°C) 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Moisture saturation pressure pw (Pa) 2 337 2 486 2 643 2 809 2 983 3 167 3 361 3 565 3 780 4 006 4 243 4 493 4 755 5 031 5 320 5 624 5 942 6 276 6 626 6 993 7 378 7 780 8 202 8 642 9 103 9 586 10 089 10 616 11 166 11 740 12 340 12 970 13 620 14 300 15 010 15 750 16 520 17 320 18 150 19 020 19 930 49 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment B.7 Relative humidity (%) The ratio between the partial pressure and the saturation pressure of moisture, at the same reference temperature, is the relative humidity (RH). The RH is an implicit and non-linear function of the temperature only. It has no relation to the pressure of the background gas or its nature. The typical unit is percentage (%). See Equation (B.7). RH = 100 pH 2 O (B.7) pw where pH2O is the moisture partial pressure (Pa) at the reference temperature t pw is the moisture saturation pressure (Pa) at the reference temperature t B.8 Maximum moisture content in equipment IEC 62271-1 states that the dew point in electric power equipment, at the SF6 rated filling pressure, is not higher than –5 °C for a measurement at 20 °C. Therefore, the moisture partial pressure in electric power equipment, at the SF6 rated filling pressure, should not exceed the limit of 401 Pa (see Table B.1). The conversion to the recommended unit, given by Equation (B.3), is an inverse function of the SF6 rated filling pressure. It is given in Table B.2 for a SF6 rated filling pressure range of 100 kPa to 850 kPa in steps of 10 kPa. Table B.2—Maximum moisture content versus SF6 rated filling pressure SF6 rated filling pressure pSF6 (kPa) 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 Maximum moisture content (ppmv) 4010 3650 3340 3080 2860 2670 2510 2360 2230 2110 2010 1910 1820 1740 1670 1600 1540 1490 1430 Maximum moisture content (ppmv) 1145 1115 1085 1055 1030 1005 980 955 935 910 890 870 855 835 820 800 785 770 755 SF6 rated filling pressure pSF6 (kPa) 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 SF6 rated filling pressure pSF6 (kPa) 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 780 Maximum moisture content (ppmv) 670 655 645 635 625 615 610 600 590 580 575 565 555 550 540 535 530 520 515 50 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.2―Maximum moisture content versus SF6 rated filling pressure (continued) Maximum moisture content (ppmv) 1380 1340 1290 1250 1220 1180 1150 SF6 rated filling pressure pSF6 (kPa) 290 300 310 320 330 340 350 Maximum moisture content (ppmv) 745 730 715 705 690 680 670 SF6 rated filling pressure pSF6 (kPa) 540 550 560 570 580 590 600 SF6 rated filling pressure pSF6 (kPa) 790 800 810 820 830 840 850 Maximum moisture content (ppmv) 510 500 495 490 485 475 470 B.9 Conversion to moisture volume concentration (ppmv) B.9.1 From moisture partial pressure (Pa) to moisture volume concentration (ppmv) Equation (B.3) applies, as shown in Equation (B.8): cV = pH 2 O pSF6 103 (B.8) where cV is the moisture volume concentration (ppmv) pH2O is the moisture partial pressure (Pa) pSF6 is the SF6 rated filling pressure (kPa) The conversion to the moisture volume concentration is given in Table B.3. Table B.3—Conversion from moisture partial pressure (Pa) to moisture volume concentration (ppmv) Moisture partial pressure (Pa) (ppmv) 1 1.5 2 3 4 5 7 10 15 20 30 40 50 70 100 150 200 300 400 100 10.0 15.0 20.0 30.0 40.0 50.0 70.0 100 150 200 300 400 500 700 1000 1500 2000 3000 4000 150 6.67 10.0 13.3 20.0 26.7 33.3 46.7 66.7 100 133 200 267 333 467 667 1000 1330 2000 2670 SF6 rated filling pressure (kPa) 200 300 400 500 600 5.00 3.33 2.50 2.00 1.67 7.50 5.00 3.75 3.00 2.50 10.0 6.67 5.00 4.00 3.33 15.0 10.0 7.50 6.00 5.00 20.0 13.3 10.0 8.00 6.67 25.0 16.7 12.5 10.0 8.33 35.0 23.3 17.5 14.0 11.7 50.0 33.3 25.0 20.0 16.7 75.0 50.0 37.5 30.0 25.0 100 66.7 50.0 40.0 33.3 150 100 75.0 60.0 50.0 200 133 100 80.0 66.7 250 167 125 100 83.3 350 233 175 140 117 500 333 250 200 167 750 500 375 300 250 1000 667 500 400 333 1500 1000 750 600 500 2000 1330 1000 800 667 700 1.43 2.14 2.86 4.29 5.71 7.14 10.0 14.3 21.4 28.6 42.9 57.1 71.4 100 143 214 286 429 571 850 1.18 1.76 2.35 3.53 4.71 5.88 8.24 11.8 17.6 23.5 35.3 47.1 58.8 82.4 118 176 235 353 471 51 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment B.9.2 From absolute humidity (g/m3) to moisture volume concentration (ppmv) By substituting Equation (B.2) in Equation (B.3), Equation (B.9) is obtained: cV = 103 R T AH M H 2 O pSF6 (B.9) where cV is the moisture volume concentration (ppmv) J is the universal constant of perfect gases R = 8.3143 mol K g M H 2 O = 18 is the molar mass of water mol T is the absolute temperature (K) to which the SF6 rated filling pressure is referred, typically 293.16 K, corresponding to 20 °C pSF6 is the SF6 rated filling pressure (kPa) AH is the absolute humidity (g/m3) Substituting the values for R and MH2O we obtain: cV = 103 (273.16 + t ) AH 8.3143 (273.16 + t ) AH = 461.91 18 pSF6 pSF6 (B.10) where cV is the moisture volume concentration (ppmv) t is the ambient temperature (°C) pSF6 is the SF6 rated filling pressure (kPa) AH is the absolute humidity (g/m3) Equation (B.9) at the ambient temperature of 20 °C becomes Equation (B.11): cV = 135410 AH pSF6 (B.11) where cV is the moisture volume concentration (ppmv) pSF6 is the SF6 rated filling pressure (kPa) AH is the absolute humidity (g/m3) The conversion to the moisture volume concentration is given in Table B.4. 52 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.4—Conversion from absolute humidity (g/m3) to moisture volume concentration (ppmv) Absolute humidity (g/m3) (ppmv) 0.007 0.01 0.015 0.02 0.03 0.04 0.05 0.07 0.1 0.15 0.2 0.3 0.4 0.5 0.7 1 1.5 2 3 100 9.48 13.5 20.3 27.1 40.6 54.2 67.7 94.8 135 203 271 406 542 677 948 1350 2030 2710 4060 150 6.32 9.03 13.5 18.1 27.1 36.1 45.1 63.2 90.3 135 181 271 361 451 632 903 1350 1810 2710 SF6 rated filling pressure (kPa) 200 300 400 500 600 4.74 3.16 2.37 1.90 1.58 6.77 4.51 3.39 2.71 2.26 10.2 6.77 5.08 4.06 3.39 13.5 9.03 6.77 5.42 4.51 20.3 13.5 10.2 8.12 6.77 27.1 18.1 13.5 10.8 9.03 33.9 22.6 16.9 13.5 11.3 47.4 31.6 23.7 19.0 15.8 67.7 45.1 33.9 27.1 22.6 102 67.7 50.8 40.6 33.9 135 90.3 67.7 54.2 45.1 203 135 102 81.2 67.7 271 181 135 108 90.3 339 226 169 135 113 474 316 237 190 158 677 451 339 271 226 1020 677 508 406 339 1350 903 677 542 451 2030 1350 1020 812 677 700 1.35 1.93 2.90 3.87 5.80 7.74 9.67 13.5 19.3 29.0 38.7 58.0 77.4 96.7 135 193 290 387 580 850 1.12 1.59 2.39 3.19 4.78 6.37 7.97 11.2 15.9 23.9 31.9 47.8 63.7 79.7 112 159 239 319 478 B.9.3 From moisture mass concentration (ppmw) to moisture volume concentration (ppmv) Equation (B.4) applies, as shown in Equation (B.12): cV = M SF6 M H 2O cM = 146 cM = 8.1111cM 18 (B.12) The conversion table between the moisture mass concentration and the moisture volume concentration is given in Table B.5. 53 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.5—Conversion from moisture mass concentration (ppmw) to moisture volume concentration (ppmv) Moisture concentration Mass Volume (ppmv) (ppmv) 0.1 0.811 0.15 1.22 0.2 1.62 0.25 2.03 0.3 2.43 0.35 2.84 0.4 3.24 0.45 3.65 0.5 4.06 0.55 4.46 0.6 4.87 0.65 5.27 0.7 5.68 0.75 6.08 0.8 6.49 0.85 6.89 0.9 7.30 0.95 7.71 1 8.11 1.5 12.2 2 16.2 2.5 20.3 3 24.3 3.5 28.4 4 32.4 4.5 36.5 5 40.6 5.5 44.6 6 48.7 6.5 52.7 7 56.8 7.5 60.8 Moisture concentration Mass Volume (ppmv) (ppmv) 7.5 60.8 8 64.9 8.5 68.9 9 73.0 9.5 77.1 10 81.1 15 122 20 162 25 203 30 243 35 284 40 324 45 365 50 406 55 446 60 487 65 527 70 568 75 608 80 649 85 689 90 730 95 771 100 811 150 1220 200 1620 250 2030 300 2430 350 2840 400 3240 450 3650 500 4060 B.9.4 From dew point (°C) to moisture volume concentration (ppmv) Table B.1 can be used to obtain the moisture partial pressure, and then Table B.3 can be used to obtain the moisture volume concentration. The final result is given in Table B.6. This can be used for direct conversion between the dew point (°C) and the moisture volume concentration (ppmv) using the SF6 rated filling pressure (kPa) as a parameter. 54 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.6—Conversion from dew point (°C) to moisture volume concentration (ppmv) Dew point (°C) (ppmv) –60 –59 –58 –57 –56 –55 –54 –53 –52 –51 –50 –49 –48 –47 –46 –45 –44 –43 –42 –41 –40 –39 –38 –37 –36 –35 –34 –33 –32 –31 –30 –29 –28 –27 –26 –25 –24 –23 –22 –21 –20 –19 –18 –17 –16 –15 –14 –13 100 10.8 12.4 14.1 16.1 18.4 20.9 23.8 27.0 30.7 34.8 39.3 44.5 50.3 56.7 63.9 72.0 81.0 91.0 102 115 128 144 161 179 200 223 249 277 308 342 380 421 467 517 572 632 698 771 850 937 1032 1140 1250 1370 1510 1650 1810 1980 150 7.2 8.2 9.4 10.7 12.3 13.9 15.9 18.0 20.4 23.2 26.2 29.7 33.5 37.8 42.6 48.0 54.0 60.7 68.1 76.4 85.5 95.8 107 120 133 149 166 185 205 228 253 281 311 345 381 422 466 514 567 625 688 757 832 914 1000 1100 1210 1320 SF6 rated filling pressure (kPa) 200 300 400 500 600 5.4 3.6 2.7 2.2 1.8 6.2 4.1 3.1 2.5 2.1 7.1 4.7 3.5 2.8 2.4 8.1 5.4 4.0 3.2 2.7 9.2 6.1 4.6 3.7 3.1 10.5 7.0 5.2 4.2 3.5 11.9 7.9 5.9 4.8 4.0 13.5 9.0 6.8 5.4 4.5 15.3 10.2 7.7 6.1 5.1 17.4 11.6 8.7 7.0 5.8 19.7 13.1 9.8 7.9 6.6 22.2 14.8 11.1 8.9 7.4 25.1 16.8 12.6 10.1 8.4 28.4 18.9 14.2 11.3 9.5 32.0 21.3 16.0 12.8 10.7 36.0 24.0 18.0 14.4 12.0 40.5 27.0 20.2 16.2 13.5 45.5 30.3 22.7 18.2 15.2 51.1 34.0 25.5 20.4 17.0 57.3 38.2 28.6 22.9 19.1 64.2 42.8 32.1 25.7 21.4 71.8 47.9 35.9 28.7 23.9 80.3 53.5 40.2 32.1 26.8 89.7 59.8 44.9 35.9 29.9 100 66.7 50.1 40.0 33.4 112 74.4 55.8 44.7 37.2 124 82.9 62.2 49.8 41.5 138 92.3 69.2 55.4 46.1 154 103 77.0 61.6 51.3 171 114 85.5 68.4 57.0 190 127 95.0 76.0 63.3 211 140 105 84.3 70.2 233 156 117 93.4 77.8 258 172 129 103 86.2 286 191 143 114 95.3 316 211 158 126 105 349 233 175 140 116 385 257 193 154 128 425 283 213 170 142 468 312 234 187 156 516 344 258 206 172 568 378 284 227 189 624 416 312 250 208 686 457 343 274 229 753 502 376 301 251 826 551 413 330 275 905 604 453 362 302 992 661 496 397 331 700 1.5 1.8 2.0 2.3 2.6 3.0 3.4 3.9 4.4 5.0 5.6 6.4 7.2 8.1 9.1 10.3 11.6 13.0 14.6 16.4 18.3 20.5 22.9 25.6 28.6 31.9 35.5 39.6 44.0 48.9 54.3 60.2 66.7 73.9 81.7 90.3 99.8 110 121 134 147 162 178 196 215 236 259 283 850 1.3 1.5 1.7 1.9 2.2 2.5 2.8 3.2 3.6 4.1 4.6 5.2 5.9 6.7 7.5 8.5 9.5 10.7 12.0 13.5 15.1 16.9 18.9 21.1 23.6 26.3 29.3 32.6 36.2 40.3 44.7 49.6 54.9 60.8 67.3 74.4 82.2 90.7 100 110 121 134 147 161 177 194 213 233 55 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.6―Conversion from dew point (°C) to moisture volume concentration (ppmv) (continued) Dew point (°C) (ppmv) –12 –11 –10 –9 –8 –7 –6 –5 100 2170 2380 2600 2840 3100 3380 3680 4010 150 1450 1580 1730 1890 2060 2250 2460 2680 SF6 rated filling pressure (kPa) 200 300 400 500 600 1090 724 543 434 362 1190 792 594 475 396 1300 866 649 519 433 1420 946 709 567 473 1550 1030 774 619 516 1690 1130 845 676 563 1840 1230 921 737 614 2010 1340 1000 803 669 700 310 339 371 405 442 483 526 574 850 255 279 306 334 364 398 433 472 B.9.5 From relative humidity (%) for moisture volume concentration (ppmv) Table B.1 is used to obtain the moisture saturation pressure at the reference temperature and then Equation (B.7) is used to calculate the moisture partial pressure. Finally, Equation (B.8) is applied. Table B.7 and Table B.8 can be used for converting the RH (%) at 0 °C and 20 °C, respectively, to the moisture volume concentration (ppmv) as a function of the SF6 rated filling pressure (kPa). Table B.7—Conversion from relative humidity (%) at 0 °C and moisture volume concentration (ppmv) Relative humidity (%) at 0 °C (ppmv) 5 10 15 20 25 30 35 40 45 50 55 60 65 70 100 305 611 916 1220 1530 1830 2140 2440 2750 3050 3360 3660 3970 4270 150 204 407 611 814 1020 1220 1420 1630 1830 2040 2240 2440 2650 2850 SF6 rated filling pressure (kPa) 200 300 400 500 600 153 102 76 61 51 305 204 153 122 102 458 305 229 183 153 611 407 305 244 204 763 509 382 305 254 916 611 458 366 305 1070 712 534 427 356 1220 814 611 489 407 1370 916 687 550 458 1530 1020 763 611 509 1680 1120 840 672 560 1830 1220 916 733 611 1980 1320 992 794 662 2140 1420 1070 855 712 700 44 87 131 174 218 262 305 349 393 436 480 523 567 611 850 36 72 108 144 180 216 251 287 323 359 395 431 467 503 56 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Table B.8—Conversion from relative humidity (%) at 20 °C and moisture volume concentration (ppmv) Relative humidity (%) at 20 °C (ppmv) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 100 230 470 700 930 1170 1400 1640 1870 2100 2300 2600 2800 3000 3300 3500 3700 4000 4200 150 156 310 470 620 780 930 1090 1250 1400 1560 1710 1870 2000 2200 2300 2500 2600 2800 SF6 rated filling pressure (kPa) 200 300 400 500 600 117 78 58 47 39 230 156 117 93 78 350 230 175 140 117 470 310 230 187 156 580 390 290 230 195 700 470 350 280 230 820 550 410 330 270 930 620 470 370 310 1050 700 530 420 350 1170 780 580 470 390 1290 860 640 510 430 1400 930 700 560 470 1520 1010 760 610 510 1640 1090 820 650 550 1750 1170 880 700 580 1870 1250 930 750 620 1990 1320 990 790 660 2100 1400 1050 840 700 700 33 67 100 134 167 200 230 270 300 330 370 400 430 470 500 530 570 600 850 27 55 82 110 137 165 192 220 250 270 300 330 360 380 410 440 470 490 57 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment Annex C (informative) Bibliography Bibliographical references are resources that provide additional or helpful material but do not need to be understood or used to implement this standard. Reference to these resources is made for informational use only. [B1] Capiel, Cradle-to-Grave Inventory Methodology for SF6 Insulated Electrical High Voltage Switchgear in Europe, EPA Conference, Nov. 2002. [B2] CIGRE TF 23-02.01, “Handling of SF6 and its decomposition products in Gas Insulated Switchgears (GIS),” ELECTRA, pp. 136 and 137, 1991. [B3] CIGRE TF B3-02.01, “SF6 Recycling Guide. Reuse of SF6 gas in electrical power equipment and final disposal (Revision 2003),” CIGRE Brochure 234, 2003. [B4] CIGRE WG B3-02, “Template for Voluntary agreement on the use of SF6 and on measures for SF6 emission reduction in the national, regional electric industry,” 2003. [B5] IEC 61640, Rigid high-voltage, gas-insulated transmission lines for rated voltage of 72.5 kV and above. 10 [B6] IEC 62271-100, High-voltage switchgear and controlgear―Part 100: Alternating current circuit breakers. [B7] IEC 62271-102, High-voltage switchgear and controlgear―Part 102: Alternating current disconnectors and earthing switches. [B8] IEC 62271-200, A.C. metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV. [B9] IEC 62271-203, High-voltage switchgear and controlgear―Part 203: Gas-insulated metal-enclosed switchgear for rated voltages above 52 kV. [B10] IEEE Standards Dictionary: Glossary of Terms & Definitions. 11 [B11] IEEE Std C37.04™, IEEE Standard Rating Structure for AC High-Voltage Circuit Breakers. 12, 13 [B12] IEEE Std C37.100.1™, IEEE Standard of Common Requirements for High Voltage Power Switchgear Rated Above 1000 V. [B13] IEEE Std C37.122™, IEEE Standard for High Voltage Gas-Insulated Substations Rated Above 52 kV [B14] Intergovernmental Panel on Climate Change (IPCC), Third Assessment Report: Climate Change 2001, 2001. [B15] Owens, J. G., “Calculation of the Global Warming Potential for sulfur hexafluoride using the updated Atmospheric Lifetime from Moore, et al.,” Gaseous Dielectrics IX, pp. 91–92, 2001. 10 IEC publications are available from the Central Office of the International Electrotechnical Commission, 3, rue de Varembé, P.O. Box 131, CH-1211, Geneva 20, Switzerland (http://www.iec.ch/). IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, USA (http://www.ansi.org/). 11 The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/ 12 IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854, USA (http://standards.ieee.org). 13 The IEEE standards or products referred to in Annex C are trademarks owned by the Institute of Electrical and Electronics Engineers, Incorporated. 58 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply. IEEE Std C37.122.3-2011 IEEE Guide for Sulphur Hexafluoride (SF6) Gas Handling for High-Voltage (over 1000 Vac) Equipment [B16] Project Group ABB, PreussenElektra, RWE, Siemens, and Solvay. Electricity supply using SF6 technology. In B. Zahn and E. Ruess, “Economical and ecological system comparison for the electricity supply of an urban area,” CIGRE SC23.99 (COLL) IWD, Zurich, 1999. Management Support: SF6-GIS-Technologie in der Energieverteilung― [B17] Solvay Mittelspannung. Life Cycle Assessment study (in German, abstract and summary available in English), commissioned by ABB, Areva T&D, EnBW Regional, e.on Hanse, RWE, Siemens, and Solvay Fluor und Derivate. Solvay: Hannover/Germany, 2003. 59 Copyright © 2012 IEEE. All rights reserved. Authorized licensed use limited to: OAKLAND UNIVERSITY . Downloaded on January 01,2015 at 07:12:12 UTC from IEEE Xplore. Restrictions apply.
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