NERC PRC Standards Overview
Compliance Reporting Support using CAPE
With the increasing number of regulatory requirements being imposed on utilities, it is important to have a relay protection simulation software package that can assist with meeting these voluminous requirements. CAPE offers support for a number of NERC PRC standards, including: PRC-001 (System Protection Coordination), PRC-002-2 Identifying Required BES Buses for Events Recording (SER) and Fault Recording (FR) Data, PRC-019-1 (Coordination of Generator Voltage Regulator Controls with Unit Capabilities and Protection), PRC-023-2 (Transmission Relay Loadability), NERC PRC-024-2 (Generator Frequency and Voltage Protective Relay Settings), PRC-025-1 (Generator Relay Loadability), PRC-026-1 (Stable Power Swing Relay Loadability), and PRC-027-1 (Protection System Coordination for Performance During Faults).
NERC PRC-001 – System Protection Coordination
NERC PRC-001 requires the Generator Operator and Transmission Operator to coordinate with each other’s protection: “each Generator Operator and Transmission Operator shall have…revised fault analysis study…or other equivalent evidence that will be used to confirm that there was coordination of new protective systems or changes…”
Electrocon developed a macro to evaluate coordination between the primary distance element on a line and backup overcurrent element at a generator, in small increments out to the reach point of the primary element. This macro was originally written at the request of a CAPE user and is now included in the CAPE software for all customers.
NERC PRC-002-2 – Disturbance Monitoring and Reporting Requirements
The purpose of PRC-002-2 is to have adequate data available to facilitate analysis of Bulk Electric System (BES) Disturbances. To comply with NERC PRC-002-2, it is required that the Transmission Owners “identify BES buses for which sequence of events recording (SER) and fault recording (FR) data is required by using the methodology in PRC-002-2, Attachment 1,” with the purpose of having adequate data available to facilitate analysis of Bulk Electric System (BES) disturbances.
Electrocon has developed a macro in CAPE that implements the methodology for finding and reporting which BES buses are required to have SER and FR data available.
NERC PRC-019 – Coordination of Generating Unit or Plant Capabilities, Voltage Regulating Controls, and Protection
NERC PRC-019 requires verification of generator voltage regulating controls, limit functions, equipment capabilities, and protection system settings. The verification study must be done at least every five years or within 90 days of making relevant settings or equipment changes.
PRC-019 requires that evidence of verification should include equipment capabilities and the operating region for limiters and protection functions. The evidence may be in the form of
• P-Q diagram
• R-X diagram
• Inverse-time diagram
• Equivalent tables
Supporting features in CAPE include a Database Engine tool for digitizing capability and limiter curves, CG P-Q & R-X displays of capability, limiter, SSSL curves, CAPE-TS Link™ module for LOF simulation, and models for V/Hz and PSB/OOS relay elements.
NERC PRC-023 – Transmission Relay Loadability
NERC PRC-023 requires that “protective relay settings shall not limit transmission loadability…” The regulation requires that “each Transmission Owner, Generator Owner, and Distribution Provider shall evaluate relay loadability at 0.85 per unit voltage and a power factor angle of 30 degrees…” The regulation further states that “each Transmission Owner…shall set its out-of-step blocking elements to allow tripping of phase protective relays for faults that occur during the loading conditions used to verify…relay loadability...”
CAPE macros to evaluate and report relay loadability have evolved since 2004. The latest version may be accessed through the CAPE Sensitivity Checking macros in the System Simulator module. A macro for switch-onto-fault (SOTF) evaluation is also included in CAPE.
The CAPE-TS Link module evaluates the behavior of OOS blocking elements together with the distance elements that should operate. This may be more than the standard demands, but combined with CAPE’s detailed relay models, this is arguably the most convincing analysis available.
NERC PRC-024-2 – Generator Frequency and Voltage Protective Relay Settings
NERC PRC-024-2 was written to “ensure Generator Owners set their generator protective relays such that generating units remain connected during defined frequency and voltage excursions.” The frequency and voltage protection characteristics do not touch the area marked up as “no trip zone” from Attachment 1 and 2 in the standard. Each Region has different criteria for generator performance during frequency excursions. The CAPE PRC-024-2 application allows the user to select the appropriate Region when determining the frequency excursions. PRC-024-2 replaces PRC-024-1.
NERC PRC-025 – Generator Relay Loadability
NERC PRC-025 requires the Generator Owner, Transmission Owner, and Distribution Provider to set load-responsive relays associated with generation at a level to prevent tripping during a disturbance that does not pose a risk of damage “while maintaining reliable fault protection.”
This standard is supported in CAPE through a Relay Setting macro that incorporates loadability criteria.
Specifically, for distance relays looking toward transmission system:
? If on generator side of GSU, must not operate for impedance derived from:
115% of (1 + j1.5) * rated MW (Opt. 7a, 7b), or
115% of (1*rated MW + j1*gross MVar) (Opt. 7c – field forcing)
? If on high side of GSU, must not operate for impedance derived from:
115% of (1 + j1.2) * rated MW (Opt. 14a), or
115% of (1*rated MW + j1*gross MVar) (Opt. 14b – field forcing)
NERC PRC-026 – Relay Performance During Stable Power Swingc
The purpose of this standard is to “ensure that load-responsive protective relays are expected to not trip in response to stable power swings during non-fault conditions.” Compliance must be demonstrated on BES elements within 12 months of [annual] notification by Planning Coordinator, unless this was done in the previous five years.
The CAPE macro for plotting swing trajectories has been significantly upgraded to support PRC-026 with advice from a senior member of the PRC-026 development committee.
The CAPE-TS Link module, in combination with the detailed PSB/OOS relay models of CAPE, can prove likely operation/non-operation in critical cases.
NERC PRC-027 – Coordination of Protection System Performance During Faults
The purpose of the as-yet-unratified standard PRC-027-1 is “To maintain the coordination of Protection Systems installed for the purpose of detecting Faults on BES Elements and isolating those faulted Elements, such that the Protection Systems operate in the intended sequence during Faults.” To achieve this purpose, several requirements are laid out which include: (1) reviewing and updating the data used in the calculation of relay settings; (2) reviewing the relay settings themselves to verify that desired coordination is achieved, and (3) communicating proposed protection settings with other entities (neighbors) that need to coordinate with the devices.
One part of the standard states that relay settings should be reviewed if (1) 6 calendar years have passed or (2) the bus fault current deviates by 15% or more from the time when the settings were established. Knowing if 6 years have passed is easy. All you need is the settings calculated date, which can already be stored with the relay in CAPE. The second criteria is more difficult since it requires knowing the bus fault current at the time when the settings were generated.
Several macros have been created to perform various tasks to help fulfill requirements of PRC-027-1. The macro “PRC_027_1_FAULT_STUDY_CREATE” allows creating a new fault study and storing fault results for all buses in a bus set. The macro “PRC_027_1_FAULT_STUDY_UPDATE” will modify the fault values stored with an existing fault study.
The macro “PRC_027_1_COMPARE_AGAINST_BASELINE” allows comparing the present SC network fault results with a stored fault study. The macro “PRC_027_1_COMPARE_2_STUDIES” allows comparing results from two stored fault studies.
The macro “PRC_027_1_COMPARE_SUBSTATION” allows comparing SC results for the presently built SC network with the “baseline” fault results associated with each device in the selected substation.
Future NERC PRC Standards
CAPE is constantly being updated to provide support for future NERC PRC standards and other regulatory requirements faced by our customers. Contact Electrocon for the latest information on NERC PRC compliance support within CAPE.