FAQs > Rule Subparts > Subpart DD. Electrical Transmission and Distribution Equipment Use > Q831. Can “hermetically sealed-pressure switchgear” under Subpart DD in 40 CFR Part 98 be interpreted consistently with the definitions of “hermetically sealed gas-insulated switchgear” adopted by the Massachusetts and the California?
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Q831. Can “hermetically sealed-pressure switchgear” under Subpart DD in 40 CFR Part 98 be interpreted consistently with the definitions of “hermetically sealed gas-insulated switchgear” adopted by the Massachusetts Department of Environmental Protection (MDEP) and the California Air Resources Board (CARB)?

A831. Yes.  For purposes of reporting under subpart DD, electric power systems may interpret “hermetically sealed-pressure switchgear” consistently with how MDEP and CARB define “hermetically sealed gas-insulated switchgear.” CARB defines “hermetically sealed gas insulated switchgear” as “switchgear that is designed to be gas-tight and sealed for life.  This type of switchgear is pre-charged with SF6, sealed at the factory, and is not refillable by its user.”  Similarly, MDEP defines “hermetically sealed gas-insulated switchgear” as “switchgear that is designed to be gas-tight and sealed for life.  This type of switchgear is pre-charged with SF6, sealed at the factory, and cannot be refilled by its user.”

EPA does not define “hermetically sealed-pressure switchgear” in Part 98 but has previously indicated its intent to be consistent with definitions of similar terms that are in wide use in the electric power transmission and distribution industry.  For example, in the preamble to the December 9, 2016 final rule (81 FR 89233), EPA noted the similarity between the definition of ‘‘sealed pressure systems’’ or ‘‘sealed-for-life equipment’’ in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (‘‘equipment that does not require any refilling (topping up) with gas during its lifetime and which generally contains less than 5 kg of gas per functional unit”) and EPA’s previous observation in the preamble to the April 10, 2010 proposed rule (75 FR 18652), that sealed-pressure equipment, unlike closed-pressure equipment, generally does not require periodic refilling (topping up) with gas during its lifetime.  These statements were not intended to preclude the use of the MDEP or CARB definitions. EPA believes that the MDEP and CARB definitions of “hermetically sealed gas-insulated switchgear” are also reasonable interpretations of the term “hermetically sealed-pressure switchgear” as used in subpart DD of Part 98.


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