Sulfur Hexafluoride From Electric Power Sources
Proposed Rule: Mandatory Reporting of Greenhouse Gases
Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or
operators of electric power transmission and distribution systems that include electrical
equipment with a total nameplace capacity that exceeds 17,820 Ibs (7,838 kg) of sulfur
hexafluoride (SF$) and/or perfluorocarbons (PFCs) would report emissions ofSF$ and/or PFCs
from electric power transmission and distribution systems. Owners or operators would collect
emission data, calculate GHG emissions, and follow the specified procedures for quality
assurance, missing data, recordkeeping, and reporting.
How Is This Source Category Defined?
Under the proposal, electric power systems include electric power transmission and distribution systems
that operate gas-insulated substations, circuit breakers, switchgear, gas-insulated lines, or power
transformers.
What GHGs Would Be Reported?
The proposal calls for each electric power system to report total SF6 and PFC emissions (including
emissions from equipment leaks, installation, servicing, decommissioning, and disposal, and from storage
cylinders) from the following types of equipment:
• Gas-insulated substations
• Circuit breakers
• Switchgear
• Electrical transformers
• Gas-insulated lines
How Would GHG Emissions Be Calculated?
Under the proposal, owners or operators of electric power systems would calculate SF6 and PFC
emissions for each electric power sytem using a mass-balance approach that takes into account the
following:
• Decrease in SF^ Inventory: The SF6 stored in containers at the beginning of the year minus the
SF6 stored in containers at the end of the year.
• Acquisitions of SF^: The amount of SF6 purchased from chemical producers, bulk distributors,
equipment manufacturers, or distributors minus the amount of SF6 returned to site after offsite
recycling.
• Disbursements of SF^: The sum of the amount of SF6 in bulk and contained in equipment that is
sold to other entities, returned to suppliers, and sent offsite for recycling or destruction. Facilities
returning cylinders to storage or to the supplier would either weigh the cylinders themselves or
have the supplier weigh the cylinders, obtaining a detailed monthly account (within 1 percent)
from the supplier. In either case, the scale would have to be certified to be accurate within 1
percent of the true weight and recalibrated at least annually.
• Net Increase in Total Nameplate Capacity of Equipment: The nameplate capacity of new
equipment minus the nameplate capacity of retiring equipment. Nameplate capacity refers to the
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Environrnsntal Protection
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full and proper charge of gas specified by the equipment manufacturer rather than the actual
charge, which may reflect leakage.
Emissions = Decrease in SF6 Inventory + Acquisitions of SF6 - Disbursements of SF6
- Net Increase in the Nameplate Capacity of Equipment
• PFC emissions (e.g., from transformers that formerly used CFC-113) would be calculated in the
same way, substituting the PFC for SF6 in the equation above.
What Information Would Be Reported?
In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for
each electric power system to report:
• Nameplate capacity of equipment containing SF6 and PFCs at the beginning of the year, of new
equipment purchased during the year and of equipment retired during the year.
• Transmission miles (length of lines carrying voltages at or above 34.5 kilovolts [kV]).
• SF6 and PFC sales and purchases.
• SF6 and PFCs sent off site for destruction.
• SF6 and PFCs sent off site for recycling.
• SF6 and PFCs returned from off site after recycling.
• SF6 and PFCs stored in containers at the beginning and end of the year.
• SF6 and PFCs with or inside new equipment purchased in the year.
• SF6 and PFCs with or inside equipment sold to other entities.
• SF6 and PFCs returned to suppliers.
For More Information
This series of information sheets is intended to assist reporting facilities/owners in understanding key
provisions of the proposed rule. However, these information sheets are not intended to be a substitution
for the rule. Visit EPA's Web site (www.epa.gov/climatechange/emissions/ghgrulemaking.html) for more
information, including the proposed preamble and rule and additional information sheets on specific
industries, or go to to access the rulemaking docket (EPA-HQ OAR-2008-
0508). For questions that cannot be answered through the Web site or docket, call 1-877-GHG-l 188.
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