Prc-28-1

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

A. Introduction
1.

Title:
Resources

Disturbance Monitoring and Reporting Requirements for Inverter-Based

2.

Number:

PRC-028-1

3.

Purpose:
To have adequate data available from Inverter-Based Resources to
evaluate Inverter-Based Resource ride-through performance during System
Disturbances and to provide data for Inverter-Based Resource model validation.

4.

Applicability:
4.1. Functional Entities:
4.1.1. Generator Owner
4.2. Facilities:
4.2.1 BES Inverter-Based Resources
4.2.2 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

5.

Effective Date: See Implementation Plan

B. Requirements and Measures
R1. Each Generator Owner shall have sequence of event recording (SER) data for the
following Elements that it owns: [Violation Risk Factor: Lower] [Time Horizon: Longterm Planning]
1.1. Circuit breaker position (open/close) for circuit breakers associated with the
main power transformer(s) 1, collector bus(es), shunt static and dynamic reactive
device(s), and AC-DC and DC-AC converters, if any, in case of VSC HVDC system
with a dedicated connection to Inverter-Based Resource.
1.2. For IBR units 2 in commercial operation 3 after the effective date of this standard,
the following data shall be recorded when triggered by ride-through operation or
tripping of an IBR unit.
For the purpose of this standard, the main power transformer is the power transformer that steps up voltage from the
collection system voltage to the nominal transmission/interconnecting system voltage for Inverter-Based Resources. In case of
dedicated VSC HVDC system connecting to an Inverter-Based Resource, a transformer isolating the DC-AC converter from the
transmission system is also considered a main power transformer.
2 IBR unit includes the inverter, converter, wind turbine generator, or high voltage direct current converter connecting
generating resource to alternating current Transmission network.
3 Commercial operation means achievement of this designation indicating that the facility has received all approvals necessary
for operation after completion of initial start-up testing.
1

Page 1 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

1.2.1. All fault codes.
1.2.2. All fault alarms.
1.2.3. High and low voltage ride-through mode status.
1.2.4. High and low frequency ride-through mode status.
1.3. For IBR units in commercial operation before the effective date of this standard,
if capable, the following data shall be recorded when triggered by ride-through
operation or tripping of an IBR unit.
1.3.1. All fault codes.
1.3.2. All fault alarms.
1.3.3. High and low voltage ride-through mode status.
1.3.4. High and low frequency ride-through mode status.
M1. The Generator Owner has evidence (electronic or hard copy) of data, as applicable, as
specified in Requirement R1. Evidence may include, but is not limited to: (1) actual
data recordings; or (2) documents describing the device interconnections and
configurations which may include a single design standard as representative for
common installations; or (3) station or equipment drawings. The evidence to show IBR
unit capability to record fault codes, alarms, or ride-through mode status may include,
but is not limited to: (1) equipment specification, (2) letter from equipment
manufacturer, or (3) documents describing lack of recording capability.
R2. Each Generator Owner shall have triggered fault recording (FR) data to determine the
following electrical quantities for Elements that it owns: [Violation Risk Factor: Lower]
[Time Horizon: Long-term Planning]
2.1. High-side of the main power transformer FR data:
2.1.1. Phase-to-neutral voltage for each phase.
2.1.2. Each phase current and the residual or neutral current.
2.1.3. Real and Reactive Power expressed on a three-phase basis.
2.2. Collector feeder breaker FR data:
2.2.1. Phase-to-neutral voltage for each phase.
2.2.2. Each phase current and the residual or neutral current.
2.2.3. Real and Reactive Power expressed on a three-phase basis.
2.3. Shunt dynamic reactive device FR data:
2.3.1. Phase-to-neutral voltage for each phase.
2.3.2. Each phase current and the residual or neutral current.
2.3.3. Reactive Power output expressed on a three-phase basis.

Page 2 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

M2. The Generator Owner has evidence (electronic or hard copy) of FR data that is
sufficient to determine electrical quantities as specified in Requirement R2. Evidence
may include, but is not limited to: (1) actual data recordings or derivations; or (2)
documents describing the device specifications and configurations which may include
a single design standard as representative for common installations; or (3) station or
equipment drawings.
R3. Each Generator Owner shall have FR data as specified in Requirement R2 that meets
the following: [Violation Risk Factor: Lower] [Time Horizon: Long-term Planning]
3.1. High-side of the main power transformer FR data:
3.1.1. A single record or multiple records that include a pre-trigger record
length of at least two cycles and a total record length of at least 2.0
seconds for the same trigger point.
3.1.2. A minimum recording rate of 64 samples per cycle.
3.1.3. Trigger settings for at least the following:
3.1.3.1.

Neutral (residual) overcurrent.

3.1.3.2.

AC phase overvoltage and undervoltage.

3.1.3.3.

Overfrequency and underfrequency

3.2. Collector feeder breaker FR data:
3.2.1. A single record or multiple records that include a pre-trigger record
length of at least two cycles and a total record length of at least 2.0
seconds for the same trigger point.
3.2.2. A minimum recording rate of 64 samples per cycle.
3.2.3. Trigger settings for at least the following:
3.2.3.1.

Neutral (residual) overcurrent, if applicable.

3.2.3.2.

AC phase overvoltage and undervoltage.

3.2.3.3.

Overfrequency and underfrequency.

3.3. Shunt dynamic reactive device FR data:
3.3.1. A single record or multiple records that include a pre-trigger record
length of at least two cycles and a total record length of at least 2.0
seconds for the same trigger point.
3.3.2. A minimum recording rate of 64 samples per cycle.
3.3.3. Trigger settings for at least the following:
3.3.3.1.

Neutral (residual) overcurrent.

3.3.3.2.

AC phase overvoltage and undervoltage.

Page 3 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

M3. The Generator Owner has evidence (electronic or hard copy) that FR data meets
Requirement R3. Evidence may include, but is not limited to: (1) actual data recordings
or derivations, or (2) documents describing the device specification and device
configuration or settings.
R4. Each Generator Owner shall have continuous dynamic disturbance recording (DDR)
data and storage to determine the following electrical quantities for each main power
transformer(s) it owns: [Violation Risk Factor: Lower] [Time Horizon: Long-term
Planning]
4.1. One phase-to-neutral or positive sequence voltage on high-side of the main
power transformer(s).
4.2. The phase current for the same phase at the same voltage corresponding to the
voltage in Requirement R4, Part 4.1, or the positive sequence current.
4.3. Real Power and Reactive Power flows expressed on a three-phase basis
corresponding to each main power transformer(s) where current measurements
are required.
4.4. Frequency of any one of the voltage(s) in Requirement R4, Part 4.1.
M4. The Generator Owner has evidence (electronic or hard copy) of continuous DDR data
recording and storage to determine electrical quantities as specified in Requirement
R4. Evidence may include, but is not limited to: (1) actual data recordings or
derivations; or (2) documents describing the device specifications and configurations,
which may include a single design standard as representative for common
installations; or (3) station drawings.
R5. Each Generator Owner responsible for DDR data for the electrical quantities identified
in Requirement R4 shall have DDR data that meet the following: [Violation Risk Factor:
Lower] [Time Horizon: Long-term Planning]
5.1. Input sampling rate of at least 960 samples per second.
5.2. Output recording rate of electrical quantities of at least 60 times per second.
M5. The Generator Owner has evidence (electronic or hard copy) that DDR data meets
Requirement R5. Evidence may include, but is not limited to: (1) documents describing
the device specification, device configuration, or settings (R5, Part 5.1; R5, Part 5.2); or
(2) actual data recordings (R5, Part 5.2).
R6. Each Generator Owner shall time synchronize all SER, FR, and DDR data to meet the
following: [Violation Risk Factor: Lower] [Time Horizon: Long-term Planning]
6.1. Synchronization to Coordinated Universal Time (UTC) with or without a local
time offset.
6.2. The IBR unit synchronized device clock accuracy within ± 100 milliseconds of
UTC. For all other devices, synchronized device clock accuracy within ± 1
milliseconds of UTC.

Page 4 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

M6. The Generator Owner has evidence (electronic or hard copy) of time synchronization
described in Requirement R6. Evidence may include, but is not limited to: (1)
documents describing the device specification, configuration, or setting; (2) time
synchronization indication or status; or 3) station drawings.
R7. Each Generator Owner shall provide all requested SER, FR, and DDR data to its
Transmission Planner, Planning Coordinator, Transmission Operator, Balancing
Authority, Reliability Coordinator, Regional Entity, or NERC in accordance with the
following: [Violation Risk Factor: Lower] [Time Horizon: Long-term Planning]
7.1. Data shall be retrievable for the period of 20 calendar days, inclusive of the day
the data was recorded.
7.2. Data subject to Part 7.1 shall be provided within 15 calendar days of a request
unless an extension is granted by the requestor.
7.3. SER data shall be provided in ASCII 4 Comma Separated Value (CSV) format
following Attachment 1.
7.4. FR data shall be provided either in CSV format with appropriate headers or in
electronic files that are formatted in conformance with C37.111, IEEE Standard
Common Format for Transient Data Exchange (COMTRADE), revision C37.1111999 or later.
7.5. DDR data shall be provided either in CSV format with appropriate headers or in
electronic files that are formatted in conformance with C37.111, IEEE Standard
Common Format for Transient Data Exchange (COMTRADE), revision C37.1111999 or later.
7.6. Data files shall be named in conformance with C37.232, IEEE Standard for
Common Format for Naming Time Sequence Data Files (COMNAME), revision
C37.232-2011 or later.
M7. The Generator Owner has evidence (electronic or hard copy) that data was submitted
upon request in accordance with Requirement R7. Evidence may include, but is not
limited to: (1) actual data recordings; (2) dated transmittals to the requesting entity
with formatted records; or (3) documents describing data storage capability, device
specification, configuration, or settings.
R8. Each Generator Owner shall, upon the discovery of a failure of the recording capability
for the SER, FR, or DDR data: [Violation Risk Factor: Lower] [Time Horizon: Long-term
Planning]

4

•

Restore the recording capability within 90 calendar days, or

•

Submit a Corrective Action Plan (CAP) to the Regional Entity within 90 calendar
days and then implement it according to CAP timeline.

American Standard Code for Information Interchange

Page 5 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

M8. The Generator Owner has dated evidence (electronic or hard copy) that meets
Requirement R8. Evidence may include, but is not limited to: (1) dated reports of the
discovery of a failure, (2) documentation noting the date the data recording was
restored, (3) SCADA records, or (4) dated Corrective Action Plan transmittals to the
Regional Entity and evidence of Corrective Action Plan implementation.

C. Compliance
1.

Compliance Monitoring Process
1.1. Compliance Enforcement Authority: “Compliance Enforcement Authority”
means NERC or the Regional Entity, or any entity as otherwise designated by an
Applicable Governmental Authority, in their respective roles of monitoring
and/or enforcing compliance with mandatory and enforceable Reliability
Standards in their respective jurisdictions.
1.2. Evidence Retention:
The following evidence retention periods identify the period of time an entity is
required to retain specific evidence to demonstrate compliance. For instances
where the evidence retention period specified below is shorter than the time
since the last audit, the Compliance Enforcement Authority may ask an entity to
provide other evidence to show that it was compliant for the full time period
since the last audit.
The Generator Owner shall keep data or evidence to show compliance as
identified below unless directed by its Compliance Enforcement Authority to
retain specific evidence for a longer period of time as part of an investigation:
The Generator Owner shall retain evidence, as per Requirements R1 through
R8, for three calendar years.
If a Generator Owner is found non-compliant, it shall keep information related to
the non-compliance until mitigation is completed and approved or for the time
specified above, whichever is longer.
The Compliance Enforcement Authority shall keep the last audit records, and all
requested and submitted subsequent audit records.
1.3. Compliance Monitoring and Enforcement Program: As defined in the NERC
Rules of Procedure, “Compliance Monitoring and Enforcement Program” refers
to the identification of the processes that will be used to evaluate data or
information for the purpose of assessing performance or outcomes with
associated Reliability Standard.

Page 6 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

Violation Severity Levels
R#

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL

R1

Each Generator Owner as
directed by Requirement
R1 to have the required
SER data had more than 80
percent, but less than 100
percent of the circuit
breaker(s) identified in
Requirement R1.

Each Generator Owner as
directed by Requirement R1
to have the required SER
data had more than 70
percent, but less than or
equal to 80 percent of the
circuit breaker(s) identified
in Requirement R1.

Each Generator Owner as
directed by Requirement
R1 to have the required
SER data had more than 60
percent, but less than or
equal to 70 percent of the
circuit breaker(s) identified
in Requirement R1.

Each Generator Owner as
directed by Requirement
R1 to have the required
SER data had less than or
equal to 60 percent of the
circuit breaker(s) identified
in Requirement R1.

R2

The Generator Owner had
FR data as directed by
Requirement R2, Parts 2.1,
2.2, and 2.3 that covers
more than 80 percent, but
less than 100 percent of
the total required
electrical quantities, which
is the product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

The Generator Owner had
FR data as directed by
Requirement R2, Parts 2.1,
2.2, and 2.3 that covers
more than 70 percent, but
less than or equal to 80
percent of the total
required electrical
quantities, which is the
product of the total number
of monitored Elements and
the number of specified
electrical quantities for
each Element.

The Generator Owner had
FR data as directed by
Requirement R2, Parts 2.1,
2.2, and 2.3 that covers
more than 60 percent, but
less than or equal to 70
percent of the total
required electrical
quantities, which is the
product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

The Generator Owner had
FR data as directed by
Requirement R2, Parts 2.1,
2.2, and 2.3 that covers
less than or equal to 60
percent of the total
required electrical
quantities, which is the
product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

R3

The Generator Owner had
FR data that meets more

The Generator Owner had
FR data that meets more

The Generator Owner had
FR data that meets more

The Generator Owner had
FR data that meets less
Page 7 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

than 80 percent, but less
than 100 percent of the
total recording parameters
as specified in
Requirement R3.

than 70 percent, but less
than or equal to 80 percent
of the total recording
parameters as specified in
Requirement R3.

than 60 percent, but less
than or equal to 70
percent of the total
recording parameters as
specified in Requirement
R3.

than or equal to 60
percent of the total
recording parameters as
specified in Requirement
R3.

R4

The Generator Owner had
DDR data as directed by
Requirement R4, Parts 4.1
through 4.4 that covered
more than 80 percent, but
less than 100 percent of
the total required
electrical quantities, which
is the product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

The Generator Owner had
DDR data as directed by
Requirement R4, Parts 4.1
through 4.4 for more than
70 percent, but less than or
equal to 80 percent of the
total required electrical
quantities, which is the
product of the total number
of monitored Elements and
the number of specified
electrical quantities for
each Element.

The Generator Owner had
DDR data as directed by
Requirement R4, Parts 4.1
through 4.4 for more than
60 percent, but less than
or equal to 70 percent of
the total required
electrical quantities, which
is the product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

The Generator Owner had
DDR data as directed by
Requirement R4, Parts 4.1
through 4.4 for less than or
equal to 60 percent of the
total required electrical
quantities, which is the
product of the total
number of monitored
Elements and the number
of specified electrical
quantities for each
Element.

R5

The Generator Owner had
DDR data that meets more
than 80 percent, but less
than 100 percent of the
total recording parameters
as specified in
Requirement R5.

The Generator Owner had
DDR data that meets more
than 70 percent, but less
than or equal to 80 percent
of the total recording
properties as specified in
Requirement R5.

The Generator Owner had
DDR data that meets more
than 60 percent, but less
than or equal to 70
percent of the total
recording properties as
specified in Requirement
R5.

The Generator Owner had
DDR data that meets less
than or equal to 60
percent of the total
recording properties as
specified in Requirement
R5.

Page 8 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

R6

The Generator Owner had
time synchronized SER, FR,
or DDR data per
Requirement R6, Parts 6.1
and 6.2 for more than 90
percent, but less than 100
percent of the Elements.

The Generator Owner had
time synchronized SER, FR,
or DDR data per
Requirement R6, Parts 6.1
and 6.2 for more than 80
percent, but less than or
equal to 90 percent of the
Elements.

The Generator Owner had
time synchronized SER, FR,
or DDR data per
Requirement R6, Parts 6.1
and 6.2 for more than 70
percent, but less than or
equal to 80 percent of the
Elements.

The Generator Owner
failed to have time
synchronized SER, FR, or
DDR data per Requirement
R6, Parts 6.1 and 6.2 for
less than or equal to 70
percent of the Elements.

R7

The Generator Owner as
directed by Requirement
R7 provided more than 90
percent, but less than 100
percent of the requested
data.

The Generator Owner as
directed by Requirement R7
provided more than 80
percent, but less than or
equal to 90 percent of the
requested data.

The Generator Owner as
directed by Requirement
R7 provided more than 70
percent, but less than or
equal to 80 percent of the
requested data.

The Generator Owner as
directed by Requirement
R7 failed to provide less
than or equal to 70
percent of the requested
data.

OR

OR

OR

OR

The Generator Owner as
directed by Requirement
R7, Part 7.2 provided the
requested data one to 10
calendar days late.

The Generator Owner as
directed by Requirement
R7, Part 7.2 provided the
requested data 11 to 20
calendar days late.

The Generator Owner as
directed by Requirement
R7, Part 7.2 provided the
requested data 21 to 30
calendar days late.

The Generator Owner as
directed by Requirement
R7, Part 7.2 provided the
requested data more than
30 calendar days late.

OR

OR

OR

OR

The Generator Owner as
directed by Requirement
R7, Parts 7.3 through 7.6
provided more than 90
percent of the data, but
less than 100 percent of

The Generator Owner as
directed by Requirement
R7, Parts 7.3 through 7.6
provided more than 80
percent of the data, but less
than or equal to 90 percent

The Generator Owner as
directed by Requirement
R7, Parts 7.3 through 7.6
provided more than 70
percent of the data, but
less than or equal to 80

The Generator Owner as
directed by Requirement
R7, Parts 7.3 through 7.6
provided less than or equal
to 70 percent of the data
in the proper data format.

Page 9 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

R8

the data in the proper data of the data in the proper
format.
data format.

percent of the data in the
proper data format.

The Generator Owner as
directed by Requirement
R8 was unable to restore
recording capability within
90 calendar days and
provided a Corrective
Action Plan to the Regional
Entity more than 90
calendar days, but less
than or equal to 100
calendar days after
discovery of the failure.

The Generator Owner as
directed by Requirement
R8 was unable to restore
recording capability within
90 calendar days and
provided a Corrective
Action Plan to the Regional
Entity more than 110
calendar days, but less
than or equal to 120
calendar days after
discovery of the failure.

The Generator Owner as
directed by Requirement R8
was unable to restore
recording capability within
90 calendar days and
provided a Corrective
Action Plan to the Regional
Entity more than 100
calendar days, but less than
or equal to 110 calendar
days after discovery of the
failure.

OR
The Generator Owner as
directed by Requirement
R8 submitted a Corrective
Action Plan to the Regional
Entity but failed to
implement it.

The Generator Owner as
directed by Requirement
R8 was unable to restore
recording capability within
90 calendar days and
provided a Corrective
Action Plan to the Regional
Entity more than 120
calendar days after
discovery of the failure.
OR
Generator Owner as
directed by Requirement
R8 failed to restore the
recording capability within
90 calendar days and failed
to submit a Corrective
Action Plan to the Regional
Entity.

Page 10 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

D. Regional Variances
None.

E. Interpretations
None.

F. Associated Documents
NERC Reliability Standard PRC-028-1: Implementation Plan.
NERC Reliability Standard PRC-028-1: Technical Rationale.

G. References
IEEE C37.111: Common format for transient data exchange (COMTRADE) for power
Systems.
IEEE C37.232-2011: IEEE Standard for Common Format for Naming Time Sequence Data
Files (COMNAME). Standard published 11/09/2011 by IEEE.
IEEE Std 2800-2022: IEEE Standard for Interconnection and Interoperability of InverterBased Resources (IBRs) Interconnecting with Associated Transmission Electric Power
Systems.
Multiple Solar PV Disturbances in CAISO, Joint NERC and WECC Staff Report, April 2022.
NERC Reliability Standard PRC-002-5.
Odessa Disturbance, Texas Events: May 9, 2021 and June 26, 2021, Joint NERC and Texas RE
Event Report, September 2021.
Odessa Disturbance, Texas Event: June 4, 2022, Joint NERC and Texas RE Event Report,
December 2022.

Page 11 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

Version History
Version
1

Date
October 8, 2024

Action

Change
Tracking

Adopted by NERC Board of Trustees

Page 12 of 13

PRC-028-1 – Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources

Attachment 1
Sequence of Events Recording (SER) Data Format
(Requirement R7, Part 7.3)
Date, Time, Local Time Code, Plant Name, Device 5, State 6
08/27/23, 23:58:57.110, -5, Plant name 1, Breaker 1, Close
08/27/23, 23:58:57.082, -5, Plant name 2, Breaker 2, Close
08/27/23, 23:58:57.217, -5, Plant name 1, IBR unit 1, undervoltage ride-through mode
08/27/23, 23:58:57.214, -5, Plant name 2, IBR unit 2, dc overcurrent trip

Device name may include specific names of breakers or IBR units as appropriate.
Breaker status and any other terminology such as TRIP, TRIP TO LOCKOUT, RECLOSE, etc. is acceptable. For IBR unit level data,
fault codes, alarms, change in operating mode etc., are also acceptable.

5

6

Page 13 of 13