Setting and verification of generation protection to meet NERC reliability standards

NERC has recently published several reliability standards PRC-019, PRC-024 and PRC-026. Together with the existing standards PRC-001 and PRC-025, these standards set out the generation and generation interconnection relays reliability requirements for Bulk Electric System (BES). The protection relays are required not only to provide adequate protection to generators, step-up power transformers and unit auxiliary transformers, but also to comply with these standards to avoid tripping off generators during various power system disturbances. This paper first reviews these standards, and studies their impact to the protection functions, such as: To identify the generation and generation interconnection protection relays that are subject to the various NERC standards; How to set and verify the distance/loss-of-field/out-of-step protection elements for stable power swing compliance; How to set and verify the under-and over-frequency voltage protection elements for generator protection and to satisfy the NERC frequency and voltage ride through requirements; How to set and verify the over-excitation and loss-of-field protection elements to coordinate with generator excitation limiters. The paper then analyzes a few cases where the protection relay settings do not meet the reliability standards due to commonly overlooked items, such as the voltage drop, voltage tap position on the step-up transformer and relay over-excitation curve selection.