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FERC Approves Interpretations to Reliability Standards PRC-004-1 and PRC-005-1

On September 26, 2011, in Docket No. RD11-5, FERC issued an order approving interpretations to Reliability Standards PRC-004-1 and PRC-005-1, which address maintenance, testing, and analysis of transmission and generation protection systems.  Specifically, NERC interprets “transmission Protection System,” as it appears in Requirements R1 and R3 of PRC-004-1 and Requirements R1 and R2 of PRC_005-1, to mean “any Protection system that is installed for the purpose of detecting faults on transmission elements (lines, buses, transformers, etc.). identified as being included in the Bulk Electric system and trips an interrupting device that interrupts current supplied directly from the BES.”

Therefore, regarding the question of whether a radially connected transformer would be considered part of a “transmission Protection System” NERC’s interpretation states that “[a] Protection System for a radially connected transformer energized from the BES would be considered a transmission Protection System and subject to these standards only if the protection trips an interrupting device that interrupts current supplied directly from the BES and the transformer is a BES element.” To view the Order approving NERC’s interpretation, click here.