mm
Overview of SFC Emissions
Sources and Reduction Options
in Electric Power Systems
August 2018
The SFC Emission Reduction
Partnership for Electric Power
Systems is an innovative
voluntary program developed
jointly by the United States
Environmental Protection
Agency (EPA) and the electric
power industry to improve
equipment reliability while
reducing emissions of sulfur
hexafluoride (SF ), a potent
greenhouse gas that remains
in the atmosphere for
thousands of years.
AEPA
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Overview of SF6 Emissions Sources and
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Disclaimer
This overview report uses publicly available information in combination with information obtained through
direct contact with electric utilities and other stakeholders. EPA does not:
a. make any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or
usefulness of the information contained in this report, or that the use of any apparatus, method, or process
disclosed in this report may not infringe upon privately owned rights;
b. assume any liability with respect to the use of, or damages resulting from the use of, any information,
apparatus, method, or process disclosed in this report; or
c. imply endorsement of any technology supplier, product, or process mentioned in this report.
Acknowledgements
Thanks to all Partners of EPA's SFe Emission Partnership for Electric Power Systems for their continued support
to this program. A special thank you to the following Partners for providing feedback on and images for use in
this paper:
Sacramento Municipal Utility District (SMUD)
Consolidated Edison
DILO Company, Inc.
Pacific Gas and Electric (PG&E)
Toshiba
National Electrical Manufacturers Association (NEMA) and the NEMA Coalition
Southern California Edison
3M
Franklin Electric
Doble Engineering Company
ITC Holdings Group
Additional Resources
The EPA's SF6 Emission Reduction Partnership for Electric Power Systems website contains links to workshops
and partner meetings as well as case studies and research studies, including several references in this paper.
Please visit: https://www.epa.aov/f-aas-partnership-proarams/electric-power-svstems-partnership.
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Introduction
Understanding potential emissions sources is the first step to effectively managing them. In electric power
systems, as the industry's understanding of sulfur hexafluoride (SF ) emissions has evolved, so have practices
for handling and managing those emissions. The industry in the United States is much more efficient in
managing SF, emissions today than it was in the 1990s.1 This report provides an overview of SF emissions
sources and reduction opportunities throughout the gas's lifecycle in the power sector.
EPA's SF( Emission Reduction Partnership for Electric Power Systems
Established in 1999, the SF6 Emission Reduction Partnership for Electric Power Systems is a collaborative,
voluntary effort between EPA and the electric power industry to identify, recommend, and implement
cost-effective solutions to reduce or eliminate SFC emissions, The SFC emissions of Partners have reduced
b b
by 74% since 1999.
12,000,000
10,000,000
8,000,000
- 6,000,000
LL.
LO
4,000,000
2,000,000
14%
12%
10%
+-»
ru
CC
8% S
_o
lA
6% £
LU
4% ^
2%
0%
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
Total Emissions (lbs) Total Nameplate Capacity (lbs) ^•—Emission Rate (%)
Figure 1. SF Partnership accomplishments, 1999 to 2016.
In addition to voluntary action, some electric power systems are subject to EPA's Greenhouse Gas Reporting
Program. In December 2009, EPA published the Mandatory Greenhouse Gas Reporting Rule, codified at 40
CFR Part 98, that requires large U.S. greenhouse gas emitters and suppliers to monitor and report annual
greenhouse gas emissions.
HJ.S. Environmental Protection Agency (EPA). (2017). "Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2015." EPA 430-P-17-001.
Available at: https://www.epa.gov/eheemissions/inventorv-us-ereenhouse-gas-emissions-and-sinks-1990-2015. Accessed April 2018.
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Overview of the Electric Power Sector and SFC Use
o
Society's demand for electricity has been growing over time as people increasingly rely on electricity for
operating appliances, electronics, and vehicles. Utilities deliver electricity to customers through transmission
and distribution networks, which vary in voltage levels2 to minimize transmission losses and ensure service
reliability and safety. Within networks, voltage levels are changed with transformers, used to increase the
voltage to improve efficiency of transmission or to decrease the voltage to improve safety and direct supply.
In addition to transformers, networks rely on switchgear to protect electrical equipment against overload
and short circuit currents ("circuit breaking") as well as to interrupt the load current ("load breaking").
These types of electrical equipment are needed to ensure safety and service reliability at optimal operating
and capital costs. In the first half of the 20th century, different media including air, nitrogen, oil, and vacuum
were used for insulation and load breaking in transformers and circuit breakers. Since the 1950s, SF6 has
replaced those media in some applications, particularly for insulating high-voltage circuit breakers. Because
of its high electronegativity and density, SF, has excellent dielectric (insulating electricity) and arc-quenching
(extinguishing an electric arc) properties.3 The high density of SFg has also enabled the redesign of electrical
equipment, making it smaller, easier to maintain, and safer for higher-voltage loads.
KEY:
Subtransmission System
29-69kV
Distribution System
7-34.5kv
Transmission System
Distribution System
¦M
a
r i
a
Distribution
Substation
Figure 2. Basic structure of electric power system. Adapted from DOE (2014)" and (2015).5
2ln the United States, electric power systems are nationally classified according to the following voltage classes, per ANSI CS4.1-2016:
• Low Voltage: 1,000 volts or less
• Medium Voltage: greater than 1,000 volts and less than 100 kV
• High Voltage: greater than 100 kV and equal to or less than 230 kV
• Extra-High Voltage: greater than 230 kV but less than 1,000 kV
• Ultra-High Voltage: equal to or greater than 1,000 kV.
(Some states have different approaches to classifying electric power systems),
3ln the United States, SF6 is contained primarily in transmission and distribution equipment rated above 34.5 kV.
"U.S. Department of Energy (DOE). (2014). "Infographic: Understanding the Grid." Available at: https://energy.gov/articles/infographic-
understandina-grid. Accessed April 2018.
5U.S. Department of Energy (DOE). (2015). "United States Electricity Industry Primer." Available at: https://www.energv.gov/sites/prod/
files/2015/12/f28/united-states-electricitv-industrv-primer.pdf. Accessed April 2018.
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Despite its efficiency and effectiveness, use of SF, has some drawbacks and operational constraints.
First, to maintain the required dielectric properties for the circuit breaker to operate, SF must be kept at
minimum functional pressure (density). If the pressure of SF, decreases in a piece of switchgear equipment
due to leaking or loss, operators must purchase additional gas to replace the emitted SF_. This is an added
cost to facilities that can be avoided through better handling practices. Next, the gas' exposure to moisture
must be minimized, since moisture not only affects the dielectric properties of SF;, but can also react
with decomposed S.F, creating dangerous by-products such as hydrofluoric acid (HF). Finally, SFg is a
highly potent greenhouse gas (22,800 times more potent than CO in trapping heat over 100 years), which
can enter into the atmosphere and remain there for 3,200 years.6 To minimize emissions of SF to the
atmosphere, the industry continues to focus on improving its SF. handling practices.
SF6 in Switchgear
In electric power systems, SFs gas is used in medium voltage and high voltage switchgear for insulation (such
as in gas-insulated switchgear and ring main units) and breaking (in circuit breakers and load break switches).
Additionally, less common uses of SFg in electric power systems include high voltage gas-insulated lines,
outdoor gas-insulated instrument transformers, and other equipment.
Transmission
Distribution
n
34564 657
7 56
65 4
1. Ground wire
2. Overhead lines
3. Transformer for
measurement of electric
voltage
4. Disconnect switch
5. Circuit breaker
6. Current transformer
7. Lightning arrester
8. Main transformer
9. Control building
10. Security fence
Figure 3. Gas-insulated switchgear in a typical electric power transmission and distribution system.
Adapted from IESL (2013)7 to display an assembly of gas-insulated switchgear (GIS) and air-insulated
transmission lines installed to control the transmission and distribution of electric power.
intergovernmental Panel on Climate Change (IPCC), (2007). [S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L.
Miller (eds.)]. "Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergov-
ernmental Panel on Climate Change." Cambridge University Press. Cambridge, United Kingdom, pp 996.
7The Institution of Engineers Sri Lanka (IESL). (2013). "Gas-Insulating Substation (GIS) at the Norochcholai Coal Power Plant in Sri Lanka." Available
at: http://www.iesl.lk/paee-1668324. Accessed April 2018.
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Gas insulated equipment (GIE) can be divided into two major categories8,9 (although in reality equipment in the
field can vary and be of hybrid types):
• Sealed-pressure systems (also known as 'hermetically sealed-pressure systems' or 'sealed-for-life'
equipment) include gas-insulated circuit breakers and gas-insulated switchgear from 1 to 52 kV, and are
most commonly used in distribution. These are smaller pieces of equipment that are meant to be operated
without maintenance for the operating life of the GIE, Equipment typically arrives at operating pressure
and requires no refilling, or topping off, of gas. Gas handling only takes place during manufacture and
decommissioning. Hermetically sealed-pressure equipment typically contains several pounds (lbs.) of SF£.
• Closed-pressure systems include switchgear above 52 kV and may have the capacity to contain hundreds
of pounds of SF_. During its lifetime, such switchgear might require replenishing with SFf by manual
connection to an external gas source to ensure that the gas is at the minimally functional pressure.
Both categories of equipment have typical lifetimes of more than 30 to 40 years.
f-
{a
10 -9
11
1. Busbar
2. Disconnector
3. Maintenance Earthing Switch
4. Current Transformer
5. Circuit breaker
6. Current Transformer
7. Maintenance Earthing Switch
8. Disconnector
9. Earthing Switch
10. Voltage Transformer
11. Bushing
Figure 4. Example of gas-insulated switchgear. Reproduced with permission from Toshiba (2017).10
intergovernmental Panel on Climate Change (IPCC). (2006). [Eggleston H.S., Buendia L., Miwa K., Ngara T.( and Tanabe K. (eds)]. "2006 IPCC Guide-
lines for National Greenhouse Gas Inventories - Chapter S: Other Product Manufacture and Use." Vol.3. Prepared by the National Greenhouse Gas
Inventories Programme. Published by the Institute for Global Environmental Strategies (IGES), Japan. Available at: http://www.iPcc-nggip.iges.or.ip/
public/2006gl/pdf/3 Volume3/V3 8 Ch8 Other Product.pdf. Accessed April 2018.
'International Electrotechnical Commission (IEC), (2017). "IEC 62271-1: 2007: High-voltage Switchgear and Controlgear- Part 1: Common
Specifications." Switzerland, October 2007.
"Toshiba. (2017). "GIS/GCB Gas Insulated Switchgear: GIS (550kV and Over)." Available at: http://www.toshiba-tds.com/tandd/products/
giswitchgear/en/gis550.htm. Accessed April 2018.
KEY:
SF6 Gas
Insulators
Live Parts
Current/Potential Transformer
Earthed Parts
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SF6 Emissions in Electric Power Systems
Potential sources of SFg emissions occur from 1) losses through poor gas handling practices during equipment
installation, maintenance, and decommissioning and 2) leakage from SFg-containing GIE.11
Closed-pressure equipment is the category of GIE that is the most susceptible to SFg emissions. Emissions
associated with sealed-pressure equipment mostly occur during the manufacturing process and at disposal.
Below is an overview of potential sources of SFg in transmission and distribution equipment, focusing on
closed-pressure equipment. At the disposal stage, all equipment can release SFg. Therefore, proper disposal
procedures are critical to reduce emissions of SF into the atmosphere.
Retiring,
disposal, and/or
recycling
Manufacturing
of electrical
equipment
KEY:
Storage
SFe can be used
in a closed cycle
OEM/Gas
Supplier Processes
Electric Power
System Processes
Possible Leakage
Emissions
Equipment
Operation/
Servicing
Installation
of
equipment
Figure 5. SF emissions in the lifecycle process of switchgear.
"Estimating emissions using the 2006 IPCC Guidelines Tier 3 mass-balance method consists of four sub-calculations (A,B,C,D) and a final total emis-
sions estimate (E), which is calculated by taking the decrease in inventory (A) + purchases/acquisitions (B) - Disbursements (C) - Net increase in total
nameplate capacity (D). While this method will not reveal the exact process or piece of equipment that is the source of emissions, it will provide
an estimate of total emissions. Having accurate inputs on the quantities associated with all gas flows and inputs to the mass balance equation will
prevent over- or under-estimating emissions.
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Potential sources of SFg emissions at various stages in the lifecycle of transmission and distribution equipment
are as follows:
• Manufacturing of electrical equipment: Before switchgear is acquired by utilities, manufacturers produce,
assemble, and test components, fill equipment, and, in some cases, test assembled equipment. Release
of SFg by manufacturers may occur at this stage. SFg volumetric tightness testing is one method used by
manufacturers to test a circuit breaker's ability to retain pressurized SFg gas.
12
• Shipping of equipment and/or SFg cylinders: Properly sealed equipment or equipment shipped with dry
gas should not leak during shipping when transported in a secure position. Cylinders, when containing SFg
above certain pressure (29 pounds per square inch gauge (PSIG) at 68°F), must meet packaging, shipping,
documentation, and driver-licensing requirements established by the U.S. Department of Transportation.
Accidental release of SFg can occur at this stage; however, requesting the manufacturer to ship closed-
pressure GIE using dry gas instead of SFg can minimize emissions during shipping.
• Installation of equipment: While hermetically sealed-pressure switchgear is completely filled with SFg
at the factory prior to shipping, closed-pressure switchgear is partially filled with SFg or N2 at a pressure
slightly above atmospheric for shipping. It is completely filled to the required pressure when installing
equipment. During the installation process of closed-pressure systems, emissions of SFg can occur,
especially if staff are not properly trained or are operating faulty refilling equipment.
• Equipment operation: As closed-pressure GIE seals wear out as a result of normal operation, gas leaks can
occur in several locations, such as at the flanges, fittings, seals, or bushings, as well as from the casting.1314
GIE can deteriorate and result in emissions of SFg if subject to:
o high ambient temperatures and heat produced by the current passing through the circuit breaker;
o chemical changes resulting from arcing due to current interruptions (e.g., SFg by-products reacting with
the gasket material), if water is present to mix with by-products;
° corrosion due to the external environment, such as salt spray from the ocean and pollution;15 or
o lightning, fires, storms, or other catastrophic events that can also cause sudden and severe damage
to equipment.
Additionally, poor maintenance, poor construction, and component failure can also cause leaks in
operating GIE.
• Equipment servicing: Servicing the equipment to repair leaks and refilling to operating pressure creates
opportunity for potential emissions. For example, hoses on gas filling carts can wear out and create leaks
during top offs, so all equipment and equipment parts should be checked prior to use. Similarly, faulty
12Hermosillo, V., Broglio, M., and Keller, J. (2017). "Recent Advancements in Productions Testing of AC High-Voltage Outdoor Circuit Breakers."
Excerpt from a paper presented at the 21st Annual Circuit Breaker Test & Maintenance Training Conference, October 2015. Pittsburgh, Pennsylvania,
USA.
13Campbell, E. (2006). "SF6 Accounting Practices." DILO summary paper.
"Blackman, J., Averyt, M., and Taylor, Z. (2006). "SF6 Leak Rates from High Voltage Circuit Breakers - U.S. EPA Investigates Potential Greenhouse Gas
Emissions Source." Proceedings of the 2006 IEEE Power Engineering Society General Meeting, June 2006. Montreal, Quebec, Canada. Available at:
https://www.eDa.gov/sites/Droduction/files/2016-02/documents/leakrates circuitbreakers.pdf. Accessed April 2018.
15Bessede, J., Buescher, A., Marshall, R., Montillet, G., Stelter, A. (2006). "Limiting SF6 Gas Emission by Optimization of Design and Handling over the
Life Cycle of HV Switchgear." EPA Conference on SF and the Environment. San Antonio, USA.
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recovery equipment can result in gas losses. Some companies routinely analyze the SFg in serviced
equipment to detect any harmful by-products, but even though safety control protocols, such as safety
integrity level (SIL) or performance level d (PLd), can help to reduce the risk, this kind of analysis also
releases SFg. Even when leaking equipment is prioritized for repair or replacement, delays due to extreme
weather or inability to take equipment off-line may impede timely repair and replacement.
• Storage: It is common for companies to keep a stock of SFg cylinders; additionally, partially-filled GIE that
are recently purchased and not yet installed may be stored temporarily on-site. Storage cylinders or de-
energized GIE present another potential SFg emissions source.
• Decommissioning, disposal, or recycling: All equipment, including hermetically sealed-pressure, has to
be decommissioned properly to reduce emissions of SFg. The gas must be either recycled or destroyed,
either by the gas producer or a specialized service. When closed-pressure equipment is opened, SFg can be
released to the atmosphere, especially if decommissioning staff are not properly trained to handle SFg and
prevent its release. Emissions from sealed-pressure equipment can occur when staff decommissioning such
equipment are not aware that it contains SFg or that the SFg should be recovered. This risk is greater when
different service teams manage closed-pressure and sealed-pressure equipment, and only the former are
trained to handle SF .1S
6
Owners and operators of electric power systems and manufacturers and refurbishers of electric power systems
equipment report their emissions of SFg to EPA's Greenhouse Gas Reporting Program (GHGRP)17 if they exceed
certain thresholds. This reported data can be helpful in estimating the relative percent of emissions from most
stages of the SFg lifecycle. While emissions from shipping and storage of SFg cylinders and equipment could
not be estimated at this time, emissions from these stages are understood to be minimal. Review of 2016
GHGRP reported data shows that SFg emissions from manufacturing of electrical equipment are estimated to
be 12 percent of the total SFg emissions, while installation of equipment combined with equipment operation
and servicing represent 76 percent of total reported emissions. Emissions from retiring, disposing, and
recycling of equipment are estimated to constitute 12 percent. These data show that equipment installation,
operation, and servicing account for the largest portion of emissions of the SFg lifecycle. However, it is
important to remember that this breakdown of total emissions by lifecycle is only an estimation based on one
year of reported data. In addition, emissions at different lifecycle stages can vary year to year, and utilities
may experience different percent losses at each lifecycle stage due to different equipment types, operating
conditions, practices, and other circumstances.
Reducing Emissions of SF6 in Electric Power Systems
Over the last two decades, the industry has made significant progress in reducing SFg leakage rates and
handling losses, based on improved understanding of practices and technologies for managing SFg. This
overview of approaches for reducing SFg losses is based on experiences shared by participants in EPA's SFg
"Globally, about 50% of sealed medium voltage equipment is not sold to utilities but, rather, to a diverse set of other industries for which the fate
of equipment at end-of-life is less understood and emissions are presumed to be substantially higher because of the lack of awareness and training.
These other industries include: commercial buildings such as supermarkets; industry and infrastructure such as hospitals; and high power industries
such as mining.
"EPA (2017) Greenhouse Gas Reporting Program (GHGRP). Aggregation of Reported Facility Level Data under Subpart DD -Use of Electric Transmission
and Distribution Equipment for Calendar Year 2016. U.S. Environmental Protection Agency, Washington, D.C. Available at: https://www3.epa.eov/
enviro/facts/ehg/search.html.
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Emission Reduction Partnership for Electric Power Systems. For a number of these approaches, several utilities
are also able to work with their service providers to improve practices for handling gas and reducing emissions
related to gas handling.
1. Companies' policies, protocols, and standard operating procedures: Understanding emissions sources is
the first step to better managing SFg gas in electric power systems. However, improving that understanding
and being able to act on it depends on companies' policies, protocols, and standard operating procedures.
Such company documents can establish a lifecycle approach to SFg management, which can help ensure
that employees track inventories of SFg, detect and repair leaks, properly recover SFg from circuit breakers,
recycle SFg, and dispose of equipment and gas, as well as take advantage of other options for reducing
SFg emissions. Ideally, company policies establish a process for continuous improvement and training on
SFg management and emphasize that senior management supports the goal of reducing emissions. As
a general example, some companies make their standard operating procedures available online to all
employees, who, in the process of applying them, can recommend changes and improvements, which are
then taken to leadership for buy-in and implementation. Some utilities incentivize the goal of reducing SFg
emissions (e.g., by tying it to performance metrics) and incorporate these targets as part of their larger
environmental management plans.18 Developing company policies and programs that are comprehensive,
allow for innovation, clearly designate responsible parties, and train and empower employees is a powerful
approach that can create a solid foundation for successful SFg management. For example, Consolidated
Edison has established "Fix-lt-Now" (FIN) teams that consist of dedicated management and union
personnel that work to improve the timeliness and effectiveness of maintenance repairs to address SFg
related equipment deficiencies. The program takes a centralized view of all equipment conditions and a
structured approach to the current repair program.19
2. Gas inventory, accounting, and tracking procedures and systems: Procedures and systems for gas
accounting, tracking, and management can monitor all SFg activities, such as purchases, cylinder rentals,
recycling, and disbursals. It is imperative that any residual SFg gas from cylinders be accounted for either
by physical removal of SFg from a facility or by removal from inventory when the cylinders are returned
to the suppliers. Protocols work best if they designate and instruct employees to measure SFg at every
installation and handling and to document activities undertaken during the year. Tracking procedures can
include labelling and inventorying of gas cylinders, use of warehouse cylinder log sheets, and inventorying
of all GIE, including sealed-pressure equipment.20 Tracking leak history of GIE also creates awareness and
allows for the preparation of prioritization plans for equipment repair and/or replacement.21 Utilities hiring
contractors to manage their SFg could include such SFg handling procedures as part of their scopes of work
18Slezak, M. (2014). "SF6 - A Utility Perspective on Sustaining Low SF6 Gas Emission Rate." ComEd presentation at the 2014 Workshop on SF6
Emission Reduction Strategies. Long Beach, California, USA. Available at: https://www.epa.eov/sites/production/files/2016-02/documents/
slezak-comed-presentation-2014-wkshp.pdf. Accessed April 2018.
19Blute, M., Szabo, J., and Dilillo, P. "Con Edison Emissions Reduction Program." Presented at EPA's 2012 Workshop on SF6 Emission Reduction
Strategies, April 2012. Available at: https://www.epa.gov/sites/production/files/2017-02/documents/blute presentation 2017 workshop.pdf.
Accessed April 2018.
20U.S. Environmental Protection Agency (EPA). (2006). "Reducing SF6 Emissions Means Better Business for Utilities." Partner Pacific Gas and Electric
case study, April 2006. Available at: https://www.epa.eov/sites/production/files/2016-02/documents/pee casestudv.pdf. Accessed April 2018.
21McNulty, M. and Jasinski, J. (2012). "SF6 Equipment Maintenance, Repair, and Replacement and Emission Programs." ITC Holdings Group.
Presented at EPA's 2012 Workshop on SF6 Emission Reduction Strategies, April 2012. Available at: https://www.epa.eov/sites/production/
files/2016-02/documents/confl2 mcnultv.pdf. Accessed April 2018.
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and specifications. Multiple robust SF„ data tracking systems, such as TrackRef, TrackAbout, and DirectTrack,
offer a number of features:
• automated cylinder barcode scanning and other direct upload features to reduce manual keying errors;
• customizable report capabilities that include real-time tracking of leak rates to make GIE owners
instantaneously aware of effective leak rates;
• predictive functionality to forecast and project trends and identify chronic leakers; and
• validation features to track inconsistent data or outliers.22
Bl Main Menu - SF6 Forms
J
VJUHIIKN CAUTONM*.
EDISON
SF Forms
~0®
Form Version 3
Data Version: 2012-04-09 7:00
Update Data [Internet req.)
Gassing/Removing
i«y
Gas Consolidation
fcl
Quarterly Inventory Report
View Submitted Forms (All types)
View SAP SF6 Report Data
Cylinder Storage Log
(Ins and Outs)
Figure 6. Example of a field tool for tracking SFs gas handling,
Southern California Edison's SFe smart form tracking tool.23
3. Management ofSF6 acquisitions and gas inventory: Several utilities have found that improving management
of their SFg acquisitions and gas inventory can offer several benefits. Utilities that consolidate their storage
inventory and/or select a single vendor have found that it simplifies the tracking of their gas flows, increases
transparency of costs, and offers other benefits such as cylinder inventory support from the vendor. Vendors
can also support practices such as using the correct cylinder size and customizing the cylinder delivery system
to minimize handling, limit cylinder inventories, and maximize gas utilization from each cylinder.24 This can also
make supplying gas easier, safer, and more cost-effective. Timely calibration of scales and other measurement
devices can also help to ensure any issues are detected correctly when gas measurements are taken.
22Helak, M. (2018). Feedback on draft paper titled Overview Opportunities for Electric Power Systems. Representative from Sacramento Municipal
Utility District (SMUD). April 13, 2018.
"Preston, R. (2012). "An Asset Management Approach for EPA/CARB SF6 Regulations. Southern California Edison. Available at: https://www.epa.gov/
sites/production/files/2016-02/documents/confl2 llovd2.pdf. Accessed April 2018. Note: This tool is used by Southern California Edison's crews to
enter gas handling data and ensure accuracy of tracking SF6~containing GIE and cylinders.
24Mueller, R. (2005). "10 Steps to Help Reduce SF6 Emissions in T&D." Airgas Inc. Available at: http://www.airgas.com/medias/Utilitv-Automa-
tion-Ten-Steps-to-Reduce-SF6-Emissionspdf?context=bWFzdGVvfHJvb3R8MiAzNTIlfGFwcGxpY2F0aW9uL3BkZnxoMzQvaDBiLzExNDg2MzevNig2M-
iM4LnBkZnw4ZDdhODQ3MiQlNTk3NTEzOTZkYzklNzFhYWFiYTIkMGYONDBIOWYwYzUxNDFIY2UzZilmNTUOY2NkZmQlZml4. Accessed April 2018.
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4. Training: Training is a vita! ingredient for successfully managing SFg emissions at all phases of the life-
cycle. Training raises awareness of emissions, environmental and health impacts of SF and by-products,
and potential reduction options, but training also enables employees to follow procedures and protocols
properly. Employees involved in handling gas should be specifically trained in SF_ handling and using
equipment for performing this task on a routine basis (e.g., annual refresher trainings). For example,
Consolidated Edison requires all field employees whose responsibilities involve handling SF, to complete an
on-the-job training course for handling SF,. It is common for companies to maintain in-house certification
requirements and develop specialized training courses as part of a broader program. SMUD, for example,
promotes rigorous cylinder management practices, which include not allowing SF, cylinders to be dropped
or rolled, not applying direct heat, and prohibiting cylinder temperature to exceed 122 degrees Fahrenheit.
Figure 7. A gas cart can enable employees to more efficiently handle SFe.
5. Recycling of SFe gas: Commonly practiced in the United States, recycling of SF, gas allows utilities to
capture used gas that otherwise would be vented to the atmosphere. For example, Consolidated Edison
utilizes three zero-waste DILO SFg pass-through gas analyzers for sampling, which exhaust into Tedlar
bags that reclaim all of the sampled SF gas. Consolidated Edison has had significant success in reducing
emissions with this process as compared to traditional units. Utilities can reduce emissions further by
ensuring that they use and maintain recovery equipment, or gas service carts, properly. Gas cart operation
and maintenance is key to SFg emission reduction programs. Companies have found that gas carts can
enable employees to efficiently handle SF , such as when off-loading and transferring SF. for maintenance
and recycling.25 In order to minimize emissions during the service or disposal of equipment, SF, must be
25Rothiisberger, L. (2009). "SF6 Emission Reductions through Recovery/Recycling/Reuse." Presented at EPA's 2009 Workshop on SF6 Emission
Reduction Strategies, February 2009. Available at: https://www.epa.gov/sites/production/files/2016-02/documents/conf09 rothlisbereer.pdf.
Accessed April 2018.
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recovered to the correct "blank-off pressure," ensuring that very little SF, remains in the equipment when
it is opened to the atmosphere. When the equipment is evacuated only to atmospheric pressure, 20% or
more of the SFg may remain; a vacuum must be generated to remove the remaining gas to appropriate
blank-off pressures.26 It is critical to follow correct procedures, including verifying that residual SF. is
removed using mass flow scales or weight scales; referring to temperature/pressure curves; and using
properly functioning recovery equipment, gauges, and scales. Because purchase of gas carts could be a
large capital expense, another option is to rent equipment. Renting gas carts has advantages, as rental
costs can be recorded as operating expenses rather than as capital expenditures, the renting service takes
responsibility for maintenance, and carts can be onsite only when needed, saving space.27 Used gas can be
recycled either through processing using gas carts or by partnering with a supplier that takes it to offsite
processing facilities. In some cases, suppliers or specialized services offer technical assistance and mobile
equipment for onsite purification.
Figure 8. Thermal imaging cameras help visualize the leak of SF6.
An example camera arid an example image captured by the camera are shown above.
6. Leak detection and repair (LDAR): LDAR is a vital strategy to managing SF, emissions. Components of
LDAR are included below.
• Leak detection techniques identify gas leaks from SF -insulated equipment. Leak detection methods
vary from simple techniques such as soap and water solutions to more sophisticated techniques such as
thermal imaging cameras that visualize the source of SF leaks. Such cameras exploit the strong infrared
absorption of SF. to detect it. Thermal imaging cameras can detect minor, chronic leaks that are not
detectable with conventional methods (i.e. soapy water or halogen leak detectors) without the need
26Rothlisberger, L. (2012). "SF5 Management Challenges Version 2016 & Beyond." Presented at Dilo's 2016 SF6 Gas Management Seminar, November
2016, Available at: http://www.dilo.com/2016-seminar-aeenda-and-slides/. Accessed April 2018.
"Mueller, R. (2005). "10 Steps to Help Reduce SF6 Emissions in T&D." Airgas Inc. Available at: http://www.airgas.com/medias/Utilitv-Automa-
tion-Ten-Steps-to-Reduce-SF6-Emissions.pdf?context=bWFzdGVvfHJvb3R8MiAzNTIlfGFwcGxpY2F0aW9uL3BkZnxoMzQvaDBiLzExNDg2MzgvNig2M-
iM4LnBkZnw4ZDdhODQ3MiQlNTk3NTEzOTZkYzklNzFhYWFiYTIkMGYONDBIOWYwYzUxNDFIY2UzZilmNTUOY2NkZmQlZml4. Accessed April 2018.
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to take equipment out of service. A limitation to thermal imaging is having the correct background to
insure image visibility. A more cost-effective method for chronic leaks is bagging. This method takes
plastic lining taped to various sections of the switchgear to trap any escaped gas. Upon waiting several
hours, a user can slide the wand of a standard halogen leak detector under the plastic. All detection
methods have relative advantages and disadvantages in terms of cost, outage times, and efficacy (e.g.,
false positives).28 A number of Partners utilize an optical gas imaging camera to immediately detect
small SF leaks.
6
• Monitoring programs also identify leaks and help understand the specific characteristics of company's
equipment at various locations. Leak detection frequency and strategies can vary. Some companies
have established leak detection teams that are equipped with such technologies as thermal imaging
cameras and sniffers to identify leaks. Such teams regularly inspect switchgear with available tools.
Technologies are available to provide real-time monitoring of SFg leaks and to identify and prioritize
leaking components that require the most immediate repair.29 For example, SMUD institutes an
inspection and maintenance program that includes monthly visual inspections to check for gas pressure.
• Leak repair on identified leaks is typically handled by applying a sealing material to the component
that is leaking. Leak repair should be done using new gaskets and desiccant, as well as lubricant for
flanges and o-rings. Kits are usually available from the manufacturer. Equipment should always be
tested before and after repairs, using proper SFg recovery procedures and equipment. Some leak repair
technology is available that uses clamps and sealant injection. This method reduces down time of the
equipment, which reduces costs by avoiding loss of transmission. Leak repair requires planning ahead.
Several utilities have leak prioritization plans that address worst performers first. GIE replacement can
be the more effective mitigation strategy for the worst performers.30
7. Equipment upgrade and replacement: Upgrading and replacing equipment is a successful strategy that
can significantly reduce emissions. Over time, engineering design changes have reduced the amount of SFg
necessary for the operation of switchgear and increased the tightness of equipment, resulting in smaller
leakage amounts and less frequent leakage over time. Low and medium voltage systems can use C02,
a vacuum, and "Clean Air" (i.e., N2 and 02) as base gases. For medium and high voltage systems, more
non-gas filled and vacuum equipment is now on the market. Specifically, vacuum technology for 72.5 kV
has been available in the United States since 2007. For high-voltage systems, equipment with alternative
insulating gases (including clean air as well as fluoronitrile and fluoroketone which typically use C02 as
the base gas in switchgear) is scheduled to become available in 2018 for vacuums between 72.5 kV and
28Wolf, M. "SF6 Leak Management, Repairs, and Considerations." Presented at DILO 2nd Annual SF6 Gas Management Seminar, November 2017.
Tampa, Florida, USA. Available at: http://www.dilo.com/wp-content/uploads/2017/ll/DILQ-Version-SF6-Leak-Manaeement-and-Repair-Techniaues-
Wolf.pdf. Accessed April 2018.
29Examples include: 1) Hoffman, R. (2009). "SF6 Emission Monitoring: State-of-the-Art SF6 Tracking." EPA Workshop, February 2009. Phoenix, Arizona,
USA. Available at: https://www.epa.gov/sites/production/files/2016-02/documents/conf09 hoffman.pdf. Accessed April 2018; and 2) Wacker, J.
(2014). "Continuous Emissions Monitoring of Substation Assets: Spotlight on Sulfur Hexafluoride (SF6)." Energy Utility & Environment Conference
(EUEC), February 2014. Phoenix, Arizona, USA. Available at: https://www.epa.eov/sites/production/files/2016-02/documents/wacker-incon-presen-
tation-2014-wkshp.pdf. Accessed April 2018.
30McNulty, M. and Jasinski, J. (2012). "SF6 Equipment Maintenance, Repair, and Replacement and Emission Programs." ITC Holdings Group. Present-
ed at EPA's 2012 Workshop on SF6 Emission Reduction Strategies, April 2012. Available at: https://www.epa.gov/sites/production/files/2016-02/
documents/confl2 mcnultv.pdf. Accessed April 2018.
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145 kV.31,32 These alternatives have lower GWPs ranging from less than one to 2,100.33 SF, alternatives
are promising but might require some industry adaption, including new equipment and maintenance
procedures that will necessitate training and adjustments to manage systems with different insulating
mediums. A systematic approach to identifying and anticipating equipment replacement and repair needs
can significantly reduce overall emissions.
Figure 9. Example of C02-based switchgear. Image from Toshiba (2018).
8. Proper decommissioning: At the end of life, all SF equipment, including hermetically sealed-pressure
switchgear, should be properly decommissioned to avoid emissions. Any remaining gas should be fully
extracted using recovery systems that achieve acceptable blank-off pressure (i.e., vacuum generated during
the recovery process to levels of 35 Torr and lower depending on the size of the GIE). Used SFg should
be purified either on-site or off-site. Heavily arced, contaminated gas that is non-reusable can be sent to
specialized incineration plants for destruction.34 Proper handling and disposing of non-reusable SFg gas is
important for safety reasons and can help to avoid emissions of contaminated gas. Although it might not
be obvious, proper decommissioning also applies to hermetically sealed-pressure switchgear, which will
eventually breakdown and release SF if not properly disposed.
31Helak, M. and Rak, T. Feedback on draft paper titled Overview Opportunities for Electric Power Systems. Representatives from Pacific Gas and
Electric (PG&E) and Sacramento Municipal Utility District (SMUD). April 2018.
32Rak, T. "SF6 Free HV GIS and Breakers." Pacific Gas and Electric (PG&E). Presented at EPA's 2017 Workshop on SF6 Emission Reduction Strategies,
January 2017. Available at: https://www.epa.gov/sites/production/files/2017-02/documents/rak presentation 2017 workshop.pdf.
Accessed April 2018.
33Nyberg, D. "3M™ Novec™ Dielectric Fluids SF. Alternatives for Power Utilities: Workshop for SF. Emission Reduction Strategies." 3M. Presented at
EPA's 2017 Workshop on SF6 Emission Reduction Strategies, January 2017. Available at: https://www.epa.gov/sites/production/files/2017-02/docu-
ments/nvberg presentation 2017 workshop.pdf. Accessed April 2018.
34The maximum tolerable impurity level of SF6 contaminants for reuse is 50 parts per million by volume (ppmv), which translates into a reading of
12 ppmv if the sum concentration of SO and SOF is measured (IEC 60480 and CIGRE TFB3.01.01/2004).
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Figure 10. Reclaimed cylinders can be rented or a specialized service can ensure
that your equipment is properly decomissioned.
Conclusion
As the world moves towards electrification, electric power systems have become major users of SFg and
sources of SF emissions. Tracking SF from leaking equipment and better gas handling techniques are
crucial for reducing the impact of the industry on the environment, since there are many sources of fugitive
emissions in the life cycle of electrical transmission and distribution equipment. By relying on best practices
and technologies in managing SF . electric power industries will be able to lower their SFg emissions, while also
reducing costs from purchases of replacement SF&.
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SEPA
United States
Environmental Protection
Agency
Climate Change Division (6207J)
EPA 430-R-18-004
https://www.epa.gov/f-gas-partnership-programs/electric-power-systems-partnership
August 2018
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