By Rich Heidorn Jr.
NERC stakeholders have until 8 p.m. ET Friday to weigh in on proposed changes to reliability standard PRC-024-2 concerning inverter-based generation resources.
The proposal is intended to ensure that generator owners (GOs), operators, developers and equipment manufacturers understand how their plants are expected to respond to grid disturbances. It was based on disturbance analyses and the Inverter-Based Resource Performance Task Force’s PRC-024-2 Gaps Whitepaper. (See NERC to Try Again on Inverter Rules.)
One of the most significant changes is in section 4.1.2., in which NERC proposes expanding applicability to include transmission owners “that own a bulk electric system generator step-up (GSU) transformer or collector transformer.”
It also requires inverters not to trip or “enter momentary cessation” — an interruption in their injection of current into the grid — within the “no trip zone,” except for “documented and communicated regulatory or equipment limitations.”
The unofficial comment form references two issues that the standard drafting team (SDT) said must be addressed to ensure the reliability intent of the PRC-024 is achieved.
It notes that the existing standard refers only to “generator protective relaying,” which suggests the setting of voltage and frequency protection relays on the GSU transformers on synchronous generators are excluded.
“Because the GSU and the generator are connected to the same bus and have the same source (the generator), they see the same voltage (and frequency). Consequently, the voltage and frequency protection settings applied to the relays on the GSU must be included in the standard as the operation of those relays would result in tripping the generator, thus defeating the reliability intent of the standard,” it said.
Another issue identified by the SDT is that the standard applies only to GOs, excluding TOs that own GSUs or collector transformer and associated voltage and frequency protective relays.
However, none of those who had filed comments as of Monday said they knew of any GSU owners that were registered as a TO but not as a GO.
Commenters should use the Standards Balloting and Commenting System to submit feedback.
