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
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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
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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
•
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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
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Implementers of the standard are responsible for observing or referring to the applicable regulatory
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compliance with applicable laws, and these documents may not be construed as doing so.
iv
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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).
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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
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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.
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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.
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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.
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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.
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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).
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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.
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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
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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
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(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.
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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
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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
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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
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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
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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
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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)
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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)
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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
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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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
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