Prc-024-4

Implementation Plan

Project 2020-02 Modifications to PRC-024 (Generator Ride-through)
Reliability Standards PRC-024-4 and PRC-029-1
Applicable Standard(s)
•

PRC-024-4 – Frequency and Voltage Protection Settings for Synchronous Generators, Type 1
and Type 2 Wind Resources, and Synchronous Condensers

•

PRC-029-1 – Frequency and Voltage Ride-through Requirements for Inverter-based
Generating Resources

Requested Retirement(s)
•

PRC-024-3 Frequency and Voltage Protection Settings for Generating Resources

Prerequisite Standard(s)
•

None

Applicable Entities
•

See subject Reliability Standards.

New Terms in the NERC Glossary of Terms

This section includes all newly defined, revised, or retired terms used or eliminated in the NERC
Reliability Standard. New or revised definitions listed below become approved when the proposed
standard is approved. When the standard becomes effective, these defined terms will be removed
from the individual standard and added to the Glossary.
Proposed New Definition(s):

Ride-through: The plant/facility remains connected and continues to operate through voltage or
frequency system disturbances.

Background

The purpose of Project 2020-02 is to modify Reliability Standard PRC-024-3 or replace it with a
performance-based Ride-through standard that ensures generators remain connected to the
Bulk Power System (BPS) during system disturbances. Specifically, the project focuses on using
disturbance monitoring data to substantiate inverter-based resource (IBR) ride-through performance
during grid disturbances. The project also ensures associated generators that fail to Ride-through
system events are addressed with a corrective action plan (if possible) and reported to necessary
entities for situational awareness.

RELIABILITY | RESILIENCE | SECURITY

The purpose for this project is based on the culmination of multiple analyses conducted by the ERO
Enterprise regarding widespread IBR tripping events. Furthermore, the NERC Inverter-Based Resource
Performance Subcommittee 1 has developed comprehensive recommendations for improved
performance of IBRs, including the recommendation to develop comprehensive ride-through
requirements.
In October 2023, FERC issued Order No. 901 2 which directs the development of new or modified
Reliability Standards that include new requirements for disturbance monitoring, data sharing, postevent performance validation, and correction of IBR performance. In January 2024, NERC submitted a
filing to FERC outlining a comprehensive work plan to address the directives within Order No. 901. 3
Within the work plan, NERC identified three active Standards Development projects that would need to
be filed for regulatory approval with FERC by November 4, 2024. These projects include 2020-02
Modifications to PRC-024 (Generator Ride-through) 4, 2021-04 Modifications to PRC-002-2 5, and 202302 Analysis and Mitigation of BES Inverter-based Resource Performance Issues 6.
Project 2020-02
Proposed Reliability Standard PRC-029-1 is a new Reliability Standard that includes Ride-through
requirements and performance requirements for IBRs. The scope of this project was adjusted to align
with associated regulatory directives from FERC Order No. 901 and the scope of the other projects
related to “Milestone 2” of the NERC work plan. The components of this project’s Standard
Authorization Request (SAR) that related to the inclusions of new data recording requirements are
covered in Project 2021-04 and the proposed new PRC-028-1 Reliability Standard. Components of this
project’s SAR that relate to analytics and corrective actions plans are covered in Project 2023-02 and the
proposed new PRC-030-1 Reliability Standard.
PRC-029-1 includes requirements for Generator Owner IBR to continue to inject current and perform
voltage support during a BPS disturbance. The standard also specifically requires Generator Owner IBR
to prohibit momentary cessation in the no-trip zone during disturbances.
PRC-024-4 includes modifications to revise applicable facility types to remove IBR, retain type 1 and
type 2 wind, and to include synchronous condensers.
See documents at the NERC IRPS website: https://www.nerc.com/comm/RSTC/Pages/IRPS.aspx and the previous Inverter-Based
Resource Performance Working Group website https://www.nerc.com/comm/RSTC/Pages/IRPWG.aspx
2 See FERC Order 901, Docket No. RM22-12-000; https://elibrary.ferc.gov/eLibrary/filelist?accession_number=202310193157&optimized=false; October 19, 2023
3 See INFORMATIONAL FILING OF THE NORTH AMERICAN RELIABILITY CORPORATION REGARDING THE DEVELOPMENT OF
RELIABILITY STANDARDS RESPONSIVE TO ORDER NO. 901
https://www.nerc.com/FilingsOrders/us/NERC%20Filings%20to%20FERC%20DL/NERC%20Compliance%20Filing%20Order%20No%2
0901%20Work%20Plan_packaged%20-%20public%20label.pdf; January 17, 2024
4 See NERC Standards Development Project page for Project 2002-02; https://www.nerc.com/pa/Stand/Pages/Project_202002_Transmission-connected_Resources.aspx
5 See NERC Standards Development Project page for Project 2021-04; https://www.nerc.com/pa/Stand/Pages/Project-2021-04Modifications-to-PRC-002-2.aspx
6 See NERC Standards Development Project page for Project 2023-02; https://www.nerc.com/pa/Stand/Pages/Project-2023-02Performance-of-IBRs.aspx
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Implementation Plan | PRC-024-4 and PRC-029-1
Project 2020-02 Modifications to PRC-024 (Generator Ride-through) | October 2024

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General Considerations

This implementation plan recognizes the urgent need for Reliability Standards to address IBR ride
through performance, as demonstrated by multiple event reports of the last decade, while providing a
reasonable period of time for entities to develop the necessary procedures and change their protection
and control settings to meet the new requirements. The ERO Enterprise acknowledges that there are
IBRs currently in operation and unable to meet voltage Ride-through requirements due to their inability
to modify their coordinated protection and control settings. Consistent with FERC Order No. 901, a
limited and documented exemption process for those IBR is appropriate and included within this
Implementation Plan. Other NERC Standards Development projects will be pursued to address ongoing
identification and mitigation of any potential reliability impacts to the BPS for such exemptions.
This implementation plan also recognizes that certain requirements (Requirements R1, R2, and R3) call
for entities to “ensure the design and operation” of their IBR units meets certain criteria. Design
elements may be implemented more expeditiously than operation requirements; the latter of which
will require entities to show compliance through use of actual disturbance monitoring data. Therefore,
this implementation plan provides staggered timeframes by which entities shall first ensure the design
of their IBR units meets the criteria (12 months following regulatory approval). Subsequent compliance
with the “operation” elements of these requirements shall become due as entities install disturbance
monitoring equipment on each applicable IBR in accordance with the implementation plan for proposed
Reliability Standard PRC-028-1 Disturbance Monitoring and Reporting Requirements for Inverter-based
Resources.
The ERO Enterprise acknowledges that Generator Owners and Generator Operators owning or
operating Bulk Power System connected IBRs that do not meet NERC’s current definition of Bulk Electric
System (“BES”) will be registered no later than May 2026 in accordance with the IBR Registration
proceeding in FERC Docket No. RR24-2. To ensure an orderly registration and compliance process for
these entities, as well as fairness and consistency in the standard’s application among similar asset
types, this implementation plan provides additional time for both new and existing registered entities to
come into compliance with Reliability Standard PRC-029-1’s requirements for their applicable IBRs not
meeting the BES definition. In so doing, this implementation plan advances an orderly process for new
registrants while allowing existing entities to focus their immediate efforts on their assets posing the
highest risk to the reliable operation of the Bulk Power System.

Effective Date and Phased-in Compliance Dates

The effective dates for the proposed Reliability Standards are provided below. Where the standard
drafting team identified the need for a longer implementation period for compliance with a particular
section of a proposed Reliability Standard (i.e., an entire Requirement or a portion thereof), the
additional time for compliance with that section is specified below. The phased-in compliance dates for
those particular sections represent the date that entities must begin to comply with that particular
section of the Reliability Standard, even where the Reliability Standard goes into effect at an earlier
date.
PRC-024-4

Implementation Plan | PRC-024-4 and PRC-029-1
Project 2020-02 Modifications to PRC-024 (Generator Ride-through) | October 2024

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Where approval by an applicable governmental authority is required, Reliability Standard PRC-024-4
shall become effective on the first day of the first calendar quarter that is twelve months after the
effective date of the applicable governmental authority’s order approving the standard, or as otherwise
provided for by the applicable governmental authority.
Where approval by an applicable governmental authority is not required, the Reliability Standard PRC024-4 shall become effective on the first day of the first calendar quarter that is twelve months after the
date the standard is adopted by the NERC Board of Trustees, or as otherwise provided for in that
jurisdiction.
PRC-029-1 and definition of Ride-through

Where approval by an applicable governmental authority is required, Reliability Standard PRC-029-1
and the definition of Ride-through shall become effective on the first day of the first calendar quarter
that is twelve months after the effective date of the applicable governmental authority’s order
approving the standard, or as otherwise provided for by the applicable governmental authority.
Where approval by an applicable governmental authority is not required, the Reliability Standard PRC029-1 and the definition of Ride-through shall become effective on the first day of the first calendar
quarter that is twelve months after the date the standard is adopted by the NERC Board of Trustees, or
as otherwise provided for in that jurisdiction.
PRC-029-1 Phased-in Compliance Dates

Requirements R1, R2, and R3
Capability-Based Elements
Bulk Electric System IBRs
Entities shall comply with the portion of Requirements R1, R2, and R3 relating to the design of their
BES IBRs to meet the requirements by the effective date of the standard.
Applicable Non-BES IBRs 7
Entities shall not be required to comply with Requirements R1, R2, and R3 relating to the design of
their applicable non-BES IBRs until the later of: (1) January 1, 2027; or (2) the effective date of the
standard.
Performance-Based Elements (all applicable IBRs)
Entities shall not be required to comply with the portion of Requirements R1, R2, and R3 relating to
the operation of IBRs to meet the requirements until the entity has established the required

The standard defines such as IBRs as “Non-BES Inverter-Based Resources that either have or contribute to an aggregate nameplate
capacity of greater than or equal to 20 MVA, connected through a system designed primarily for delivering such capacity to a
common point of connection at a voltage greater than or equal to 60 kV.”

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Implementation Plan | PRC-024-4 and PRC-029-1
Project 2020-02 Modifications to PRC-024 (Generator Ride-through) | October 2024

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disturbance monitoring equipment capabilities for those IBRs in accordance with the
implementation plan for Reliability Standard PRC-028-1.
Requirement R4
Bulk Electric System IBRs
Entities shall comply with Requirement R4 for their BES IBRs by the effective date of the standard.
Applicable Non-BES IBRs
Entities shall not be required to comply with Requirement R4 or their non-BES IBRs until the later of:
(1) January 1, 2027; or (2) the effective date of the standard.

Retirement Date
PRC-024-3

Reliability Standard PRC-024-3 shall be retired immediately prior to the effective date of Reliability
Standards PRC-024-4 and PRC-029-1 in the particular jurisdiction in which the revised standard is
becoming effective.

Equipment Limitations and Process for Requirement R4

Consistent with FERC Order No. 901, a limited and documented exemption for some legacy IBR with
certain documented equipment limitations are acceptable. Per the Order, these IBRs are
“…typically older IBR technology with hardware that needs to be physically replaced and whose
settings and configurations cannot be modified using software updates – may be unable to
implement the voltage ride though performance requirements.” 8
To ensure compliance with Requirement R4 and alignment with FERC Order No. 901, only those IBR that
are in operation as of the effective date of PRC-029-1 may be considered for potential exemption.
Further, only those IBR that are unable to meet ride-through requirements due to their inability to
modify their coordinated protection and control settings may be considered for potential exemption.

8

Order No. 901 at p. 193.

Implementation Plan | PRC-024-4 and PRC-029-1
Project 2020-02 Modifications to PRC-024 (Generator Ride-through) | October 2024

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