Duke Energy (NYSE:DUK), Hydro One and Ontario’s Independent Electric System Operator (IESO) said the proposed revisions to NERC’s definition of the bulk electric system (BES) adequately eliminate subjectivity and regional variation in characterizing bulk electric system facilities.
Duke Energy on Aug. 31 and Hydro One and the IESO on Aug. 30 submitted comments in response to FERC’s June 21 notice of proposed rule-making (NOPR) for proposed revisions to NERC’s definition of the bulk electric system (Docket Nos. RM12-6 and RM12-7).
Duke Energy, Hydro One and the IESO all submitted comments on Exclusion E3, which deals with characteristics of local networks.
According to the exclusion, a local network is defined as “a group of contiguous transmission elements operated at or above 100 kV but less than 300 kV that distribute power to load rather than transfer bulk power across the interconnected system.”
Local networks emanate from multiple points of connection at 100-kV or higher to improve the level of service to retail customer load and not to accommodate bulk power transfer across the interconnected system, the definition continues.
Hydro One and the IESO said that certain systems greater than 300-kV should also be able to qualify for an exception.
“We believe that the 300 kV cap associated with the applicability of Exclusion E3 is not justifiable on technical grounds, and submit that certain systems with greater than 300 kV should be able to qualify for exclusion E3 based on their own merits,” they said. “It appears that the 300 kV voltage cap applied to exclusion E3 for a local network was established because of the threshold between extra high voltage and high voltage and not a technical justification. A radial or a local network below 300 kV can be as much or more impactive on the reliability of the interconnected BES than a local network operating at 300 kV or above depending upon its location and configuration.”
Duke Energy asked for further clarification regarding Exclusion E3b, which stipulates that power flows only into the local network, and that the local network not transfer energy originating outside of it for delivery through it.
“While Duke Energy agrees with NERC’s comment that prohibitions on outbound power flow beyond the local network apply in both normal and contingent conditions, we believe that ‘contingent’ should be further clarified as limited to N-1 contingencies for the bright line BES definition,” Duke Energy said. “If entities are required to analyze layers of multiple contingencies, then Exclusion E3 would become difficult if not impossible to administer.”
Exclusion E3a places limitations on connected generation, stipulating that the local network and its underlying elements not include generation resource identified in Inclusion I3 and do not have an aggregate capacity of nonretail generation greater than 75 MVA.
Exclusion E3c indicates that a local network is not part of a flowgate or transfer path, does not contain a monitored facility of a permanent flowgate in the Eastern Interconnection, a major transfer path in the Western Interconnection, or a comparable monitored facility in ERCOT or in the Quebec Interconnections. A local network also may not be a monitored facility included in an interconnection reliability operating limit (IROL)
Hydro One and the IESO, which filed comments jointly, said that cranking paths and the elements comprising them should not be included in NERC’s definition of the bulk electric system.
Cranking paths “do not provide or increase the reliability of the power system and the probability of these elements being unavailable is significantly lower than that of a blackstart unit after a major contingency event,” they said. “We do not believe there is a reliability gap with regards to cranking paths. Cranking paths are subject to change so it is not appropriate to label all elements in a cranking path to be BES. The elements in a cranking path should be assessed on their own merit using the BES core definition and its inclusions and exclusions.”
Among other comments, Hydro One and the IESO said radial lines that have connections only with generation facilities and those that have connections with generation facilities and load serving facilities would not have an adverse reliability impact to the bulk electric system. These exclusions (E1a and E1b) apply to radial systems that have less than 75 MVA aggregate non-retail generation, a threshold which Hydro One and the IESO said was consistent with the registration requirements for generation facilities.