For electric system reliability, generators should remain connected to the grid during defined frequency and voltage excursions. In order to do so, Bulk Electric System Generators are required to set any installed frequency or voltage protective relays in accordance with NERC Reliability Standard PRC-024-2. The standard includes charts and settings parameters that define the “No Trip Zone” for setting the relays. While the frequency relay settings verification is mostly straightforward, for voltage relays, the verification of compliance is not that simple. The voltage relay “No Trip Zone” in Requirement 2 of the Standard is based upon the Point of Interconnection (POI). Distance and impedances between the POI and the voltage relay trip point location must be factored in the evaluation of settings compliance. Also, any volts per hertz relays have to be evaluated for both frequency and voltage settings.
To assist registered entities in evaluating voltage relay settings compliance, NERC has published a very good compliance guidance document titled, “PRC-024 R2 Generator Frequency and Voltage Protective Relay Settings”. This document is located on NERC’s website at https://www.nerc.com/pa/comp/guidance/Pages/default.aspx under the ERO Enterprise-Endorsed Implementation Guidance heading. Proven Compliance Solutions Inc. (PCS) recommends registered entities review the guidance document prior to evaluating their generator voltage relay settings. For new generating facility construction, engineering teams or contractors should reference the guidance document when determining coordinated relay settings.
If you have questions or need assistance with your PRC-024-2 compliance or other NERC compliance concerns, PCS can help. Please contact Dale Zahn at firstname.lastname@example.org or (262) 436-4116 for further information.