Modules · Modeling studies · Module 030
PRC-024-4 Frequency and Voltage Protection Settings
Evidence that frequency and voltage protection settings do not trip synchronous generators, Type 1 and Type 2 wind resources or synchronous condensers inside the PRC-024-4 no-trip zones.
About this module
What this module covers.
This module covers activities needed in support of compliance with NERC PRC-024-4, which requires Generator Owners and Transmission Owners to set frequency, voltage and volts per hertz protection so that it does not cause the Facility to trip within the "no trip zone" of Attachment 1 (frequency) or Attachment 2 (voltage). PRC-024-4 applies to synchronous generators, Type 1 and Type 2 wind resources and synchronous condensers, including the protection applied to their step-up and main power transformers and to the high side of their unit auxiliary transformers. Protection may be set to trip within a portion of a no-trip zone only for a regulatory or equipment limitation that is documented and communicated under Requirement R3. PRC-024-4 took effect October 1, 2026 and replaced PRC-024-3.
Ride-through for inverter-based resources is covered by PRC-029-2.
Module: 030
Kind: Modeling studies
Governing body: NERC
Applies to: Operating plants
Typical time: Two to three weeks, all in, including your review
Dashboard capabilities
- Automated Compliance Workflow for PRC-024-4
Support services
What GridStrong does inside this module.
- Gather the as-left frequency, voltage and volts per hertz protection settings that PRC-024-4 covers, whether provided by relays or by functions within associated control systems, for the generators, wind turbines or synchronous condensers, their step-up and main power transformers, and the high side of their unit auxiliary transformers.
- Overlay each frequency setting on the PRC-024-4 Attachment 1 no-trip zone.
- Overlay each voltage setting on the PRC-024-4 Attachment 2 no-trip zone at the high side of the generator step-up (GSU) or main power transformer, or on the voltage recovery characteristics of a location-specific Transmission Planner study where the Transmission Planner allows less stringent settings.
- Flag each setting that would trip inside a no-trip zone and identify whether a regulatory or equipment limitation supports it. A limitation caused by the setting capability of the protective relay itself does not qualify.
- Document each known regulatory or equipment limitation with its basis, such as study results, experience from an actual event or manufacturer's advice, ready for the communication to the Planning Coordinator and Transmission Planner that R3 requires within 30 calendar days.
- Compile the setting sheets, no-trip zone overlays and limitation documentation into a PRC-024-4 evidence package.
Final deliverables
- PRC-024-4 evidence package: protection setting summary, Attachment 1 and Attachment 2 overlays, and documentation of each regulatory or equipment limitation.
What we need from you
- Single line diagram showing the generators, wind turbines or synchronous condensers, GSU or main power transformer(s), unit auxiliary transformers and the protection that trips them.
- Nameplate data and tap settings for the GSU or main power transformer(s), so voltage settings can be referred to the high side.
- Relay setting files or setting sheets for the frequency, voltage and volts per hertz protection, including protection functions within associated control systems.
- Any known regulatory or equipment limitations with their supporting study results, event records or manufacturer's advice, and any Transmission Planner study that allows less stringent voltage settings.
Assumptions and considerations
How the scope is bounded.
- All protection settings and equipment information you supply are accurate and represent the as-left settings and installed equipment.
- We use engineering judgment and best practices where specific information is not available from you; the timeline assumes you supply all necessary information.
- Other information required to complete the scope of work for this project may be requested during the execution of this project, as deemed necessary.
- This scope includes one round with the Generator Owner, Transmission Owner or OEMs to resolve settings questions; further rounds are additional support at the agreed hourly rate, approved in writing.
Other modules
Every module runs on the same record.
Run this module on one site.
Tell us the plant and the deadline. An engineer confirms the inputs, the schedule and what the Dashboard needs from you.