Calculating SF6-insulated Equipment

Calculating SF6-insulated Equipment

This piece was originally published in the March 2017 issue of electroindustry.

Jonathan Stewart, Government Relations Manager, NEMA

Jonathan Stewart, NEMA government relations manager, addressed SF6 reporting challenges at an EPA workshop. Photo by Karla Trost, G&W Electric

NEMA Government Relations Manager Jonathan Stewart spoke in January on behalf of the Electric Transmission and Distribution SF6 Coalition at an Environmental Protection Agency (EPA) workshop on SF6 emission reduction strategies in Burlingame, California. The coalition is made up of representatives from the equipment manufacturers and SF6 producers and distributors and is administered by NEMA.

SF6 is the chemical notation for sulfur hexafluoride, the gas used to insulate medium- and high-voltage electric transmission and distribution equipment to prevent electrical arcing. It is a potent greenhouse gas. The EPA’s Greenhouse Gas Reporting Program, as well as regulatory agencies in California and Massachusetts, requires users of SF6-insulated equipment to calculate and report emissions annually.

All three regulatory agencies rely on the same equation to calculate emissions. One variable in that equation is nameplate capacity (i.e., how many pounds of gas the equipment will hold when properly insulated with SF6). Equipment in use, however, usually does not have precisely the same mass of gas that is listed on the nameplate; when the nameplate figure is greater than the amount of SF6 in the equipment, users are forced to report “phantom” emissions.

Mr. Stewart identified common scenarios that can lead to phantom emissions and discussed how to avoid them. He also spoke about the need for a regulatory solution to allow reporting entities to use a figure other than the nameplate designation for reporting purposes.

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