NERC requirements for setting load-dependent power plant protection: PRC-025-1

As a result of the NERC analysis of the 2003 blackout, NERC has proposed “voltage ride through” criteria that have resulted in two standards. Transmission line protection loadability and low voltage “ride through” has been addressed in Standard PRC-023-2. NERC PRC-025-1 addresses loadability of power plant protection and is much more complicated to apply than the transmission loadability requirements outlined in PRC-023-2. PRC-025-1 addresses the effects of generator field forcing. As discussed in this paper, PRC-025-1 has many options and calculation methods to establish stress point limits. The adoption of PRC-025-1 will result in limiting generator remote backup protection for transmission system faults on lines exiting power plants. It will require that transmission line protection for lines exiting power plants to have delineated primary and backup protection and local breaker failure because in most cases remote backup will not be possible.