Reliability Standard MOD-027-1

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

A. Introduction
1.

Title:
Verification of Models and Data for Turbine/Governor and Load Control
or Active Power/Frequency Control Functions

2.

Number:

3.

Purpose: To verify that the turbine/governor and load control or active
power/frequency control1 model and the model parameters, used in dynamic
simulations that assess Bulk Electric System (BES) reliability, accurately represent
generator unit real power response to system frequency variations.

4.

Applicability:

MOD-027-1

4.1. Functional entities
4.1.1

Generator Owner

4.1.2

Transmission Planner

4.2. Facilities
For the purpose of the requirements contained herein, Facilities that are directly
connected to the Bulk Electric System (BES) will be collectively referred to as an
“applicable unit” that meet the following:
4.2.1

Generation in the Eastern or Quebec Interconnections with the following
characteristics:
4.2.1.1 Individual generating unit greater than 100 MVA (gross nameplate
rating).
4.2.1.2 Individual generating plant consisting of multiple generating units
that are directly connected at a common BES bus with total
generation greater than 100 MVA (gross aggregate nameplate
rating).

4.2.2

Generation in the Western Interconnection with the following
characteristics:
4.2.2.1 Individual generating unit greater than 75 MVA (gross nameplate
rating).
4.2.2.2 Individual generating plant consisting of multiple generating units
that are directly connected at a common BES bus with total
generation greater than 75 MVA (gross aggregate nameplate
rating).

4.2.3

1

Generation in the ERCOT Interconnection with the following
characteristics:

Turbine/governor and load control or active power/frequency control:
a.

Turbine/governor and load control applies to conventional synchronous generation.

b.

Active power/frequency control applies to inverter connected generators (often found at variable energy plants).

Page 1 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

4.2.3.1 Individual generating unit greater than 50 MVA (gross nameplate
rating).
4.2.3.2 Individual generating plant consisting of multiple generating units
that are directly connected at a common BES bus with total
generation greater than 75 MVA (gross aggregate nameplate
rating).
5.

Effective Date:
5.1. For Requirements R1, and R3 through R5, the first day of the first calendar
quarter beyond the date that this standard is approved by applicable regulatory
authorities or as otherwise made effective pursuant to the laws applicable to such
ERO governmental authorities. In those jurisdictions where regulatory approval
is not required, the standard shall become effective on the first day of the first
calendar quarter beyond the date this standard is approved by the NERC Board of
Trustees, or as otherwise made effective pursuant to the laws applicable to such
ERO governmental authorities.
5.2. For Requirement R2, 30 percent of the entity’s applicable unit gross MVA for
each Interconnection on the first day of the first calendar quarter that is four years
following applicable regulatory approval or as otherwise made effective pursuant
to the laws applicable to such ERO governmental authorities, or in those
jurisdictions where no regulatory approval is required, on the first day of the first
calendar quarter that is four years following NERC Board of Trustees adoption or
as otherwise made effective pursuant to the laws applicable to such ERO
governmental authorities.
5.3. For Requirement R2, 50 percent of the entity’s applicable unit gross MVA for
each Interconnection on first day of the first calendar quarter that is six years
following applicable regulatory approval or as otherwise made effective pursuant
to the laws applicable to such ERO governmental authorities, or in those
jurisdictions where no regulatory approval is required, on the first day of the first
calendar quarter that is six years following NERC Board of Trustees adoption or
as otherwise made effective pursuant to the laws applicable to such ERO
governmental authorities.
5.4. For Requirement R2, 100 percent of the entity’s applicable unit gross MVA for
each Interconnection on the first day of the first calendar quarter that is 10 years
following applicable regulatory approval or as otherwise made effective pursuant
to the laws applicable to such ERO governmental authorities, or in those
jurisdictions where no regulatory approval is required, on the first day of the first
calendar quarter that is 10 years following NERC Board of Trustees adoption or
as otherwise made effective pursuant to the laws applicable to such ERO
governmental authorities.

Page 2 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

B. Requirements
R1.

R2.

Each Transmission Planner shall provide the following requested information to the
Generator Owner within 90 calendar days of receiving a written request: [Violation
Risk Factor: Lower] [Time Horizon: Operations Planning]


Instructions on how to obtain the list of turbine/governor and load control or active
power/frequency control system models that are acceptable to the Transmission
Planner for use in dynamic simulation,



Instructions on how to obtain the dynamic turbine/governor and load control or
active power/frequency control function model library block diagrams and/or data
sheets for models that are acceptable to the Transmission Planner, or



Model data for any of the Generator Owner’s existing applicable unit specific
turbine/governor and load control or active power/frequency control system
contained in the Transmission Planner’s dynamic database from the current (in-use)
models.

Each Generator Owner shall provide, for each applicable unit, a verified
turbine/governor and load control or active power/frequency control model, including
documentation and data (as specified in Part 2.1) to its Transmission Planner in
accordance with the periodicity specified in MOD-027 Attachment 1. [Violation Risk
Factor: Medium] [Time Horizon: Long-term Planning]
2.1. Each applicable unit’s model shall be verified by the Generator Owner using one
or more models acceptable to the Transmission Planner. Verification for
individual units rated less than 20 MVA (gross nameplate rating) in a generating
plant (per Section 4.2.1.2, 4.2.2.2, or 4.2.3.2) may be performed using either
individual unit or aggregate unit model(s) or both. Each verification shall include
the following:
2.1.1.

2.1.2.

Documentation comparing the applicable unit’s MW model response to
the recorded MW response for either:


A frequency excursion from a system disturbance that meets
MOD-027 Attachment 1 Note 1 with the applicable unit on-line,



A speed governor reference change with the applicable unit online, or



A partial load rejection test,2

Type of governor and load control or active power control/frequency
control3 equipment,

2

Differences between the control mode tested and the final simulation model must be identified, particularly when analyzing
load rejection data. Most controls change gains or have a set point runback which takes effect when the breaker opens. Load or
set point controls will also not be in effect once the breaker opens. Some method of accounting for these differences must be
presented if the final model is not validated from on-line data under the normal operating conditions under which the model is
expected to apply.
3

Turbine/governor and load control or active power/frequency control:

Page 3 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

R3.

2.1.3.

A description of the turbine (e.g. for hydro turbine - Kaplan, Francis, or
Pelton; for steam turbine - boiler type, normal fuel type, and turbine type;
for gas turbine - the type and manufacturer; for variable energy plant type and manufacturer),

2.1.4.

Model structure and data for turbine/governor and load control or active
power/frequency control, and

2.1.5.

Representation of the real power response effects of outer loop controls
(such as operator set point controls, and load control but excluding AGC
control) that would override the governor response (including blocked or
nonfunctioning governors or modes of operation that limit Frequency
Response), if applicable.

Each Generator Owner shall provide a written response to its Transmission Planner
within 90 calendar days of receiving one of the following items for an applicable unit.


Written notification, from its Transmission Planner (in accordance with
Requirement R5) that the turbine/governor and load control or active
power/frequency control model is not “usable,”



Written comments from its Transmission Planner identifying technical
concerns with the verification documentation related to the turbine/governor
and load control or active power/frequency control model, or



Written comments and supporting evidence from its Transmission Planner
indicating that the simulated turbine/governor and load control or active
power/frequency control response did not approximate the recorded response
for three or more transmission system events.

The written response shall contain either the technical basis for maintaining the current
model, the model changes, or a plan to perform model verification4 (in accordance with
Requirement R2). [Violation Risk Factor: Lower] [Time Horizon: Operations
Planning]
R4.

Each Generator Owner shall provide revised model data or plans to perform model
verification5 (in accordance with Requirement R2) for an applicable unit to its
Transmission Planner within 180 calendar days of making changes to the
turbine/governor and load control or active power/frequency control system that alter
the equipment response characteristic6. [Violation Risk Factor: Lower] [Time
Horizon: Operations Planning]

a.

Turbine/governor and load control applies to conventional synchronous generation.

b.

Active power/frequency control applies to inverter connected generators (often found at variable energy plants).

4

If verification is performed, the 10 year period as outlined in MOD-027 Attachment 1 is reset.

5

Ibid.

6

Control replacement or alteration including software alterations or plant digital control system addition or replacement, plant
digital control system software alterations that alter droop, and/or dead band, and/or frequency response and/or a change in the
frequency control mode (such as going from droop control to constant MW control, etc).

Page 4 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions
R5.

Each Transmission Planner shall provide a written response to the Generator Owner
within 90 calendar days of receiving the turbine/governor and load control or active
power/frequency control system verified model information in accordance with
Requirement R2 that the model is usable (meets the criteria specified in Parts 5.1
through 5.3) or is not usable.
5.1. The turbine/governor and load control or active power/frequency control function
model initializes to compute modeling data without error,
5.2. A no-disturbance simulation results in negligible transients, and
5.3. For an otherwise stable simulation, a disturbance simulation results in the
turbine/governor and load control or active power/frequency control model
exhibiting positive damping.
If the model is not usable, the Transmission Planner shall provide a technical
description of why the model is not usable. [Violation Risk Factor: Medium] [Time
Horizon: Operations Planning]

C. Measures
M1. The Transmission Planner must have and provide the dated request for instructions or

data, the transmitted instruction or data, and dated evidence of a written transmittal
(e.g., electronic mail message, postal receipt, or confirmation of facsimile) as evidence
that it provided the request within 90 calendar days in accordance with Requirement
R1.
M2. The Generator Owner must have and provide dated evidence it verified each generator

turbine/governor and load control or active power/frequency control model according
to Part 2.1 for each applicable unit and a dated transmittal (e.g., electronic mail
message, postal receipt, or confirmation of facsimile) as evidence it provided the
model, documentation, and data to its Transmission Planner, in accordance with
Requirement R2.
M3. Evidence for Requirement R3 must include the Generator Owner’s dated written

response containing the information identified in Requirement R3 and dated evidence
of transmittal (e.g., electronic mail message, postal receipt, or confirmation of
facsimile) of the response.
M4. Evidence for Requirement R4 must include, for each of the Generator Owner’s

applicable units for which system changes specified in Requirement R4 were made,
dated revised model data or dated plans to perform a model verification and dated
evidence of transmittal (e.g., electronic mail message, postal receipt, or confirmation of
facsimile) within 180 calendar days of making changes.
M5. Evidence of Requirement R5 must include, for each model received, the dated response

indicating the model was usable or not usable according to the criteria specified in
Parts 5.1 through 5.3 and for a model that is not useable, a technical description is the
model is not usable, and dated evidence of transmittal (e.g., electronic mail messages,
postal receipts, or confirmation of facsimile) that the Generator Owner was notified
within 90 calendar days of receipt of model information in accordance with
Requirement R5.

Page 5 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

D. Compliance
1.

Compliance Monitoring Process
1.1. Compliance Enforcement Authority
The Regional Entity shall serve as the Compliance Enforcement Authority unless
the applicable entity is owned, operated, or controlled by the Regional Entity. In
such cases the ERO or a Regional entity approved by FERC or other applicable
governmental authority shall serve as the CEA.
1.2. Data 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 and Transmission Planner shall each 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 Transmission Planner shall retain the information/data request and
provided response evidence of Requirements R1 and R5, Measures M1 and
M5 for 3 calendar years from the date the document was provided.



The Generator Owner shall retain the latest turbine/governor and load control
or active power/frequency control system model verification evidence of
Requirement R2, Measure M2.



The Generator Owner shall retain the information/data request and provided
response evidence of Requirements R3, and R4 Measures M3 and M4 for 3
calendar years from the date the document was provided.

If a Generator Owner or Transmission Planner is found non-compliant, it shall
keep information related to the non-compliance until mitigation is complete 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 Assessment Processes
Compliance Audit
Self-Certification
Spot Checking
Compliance Investigation
Self-Reporting
Complaint

Page 6 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

1.4. Additional Compliance Information
None

Page 7 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions

2.
R#

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL

R1

The Transmission Planner
provided the instructions and data
to the Generator Owner more than
90 calendar days but less than or
equal to 120 calendar days of
receiving a written request.

The Transmission Planner provided
the instructions and data to the
Generator Owner more than 120
calendar days but less than or equal
to 150 calendar days of receiving a
written request.

The Transmission Planner provided
the instructions and data to the
Generator Owner more than 150
calendar days but less than or equal
to 180 calendar days of receiving a
written request.

The Transmission Planner failed to provide
the instructions and data to the Generator
Owner within 180 calendar days of
receiving a written request.

R2

The Generator Owner provided its
verified model(s) to its
Transmission Planner after the
periodicity timeframe specified in
MOD-027 Attachment 1 but less
than or equal to 90 calendar days
late;

The Generator Owner provided its
verified model(s) to its Transmission
Planner more than 90 calendar days
but less than or equal to 180 calendar
days late as specified by the
periodicity timeframe in MOD-027
Attachment 1;

The Generator Owner provided its
verified model(s) to its Transmission
Planner more than 180 calendar days
but less than or equal to 270 calendar
days late as specified by the
periodicity timeframe in MOD-027
Attachment 1;

The Generator Owner provided its verified
model(s) more than 270 calendar days late
to its Transmission Planner in accordance
with the periodicity specified in MOD-027
Attachment 1;

OR

OR

OR

The Generator Owner provided the
Transmission Planner a verified
model that omitted one of the five
Parts identified in Requirement R2,
Subparts 2.1.1, through 2.1.5.

The Generator Owner provided the
Transmission Planner a verified
model that omitted two of the five
Parts identified in Requirement R2,
Subparts 2.1.1, through 2.1.5.

The Generator Owner provided the
Transmission Planner verified
models that omitted three of the five
Parts identified in Requirement R2,
Subparts 2.1.1, through 2.1.5.

Page 8 of 16

OR
The Generator Owner failed to use model(s)
acceptable to the Transmission Planner as
specified in Requirement R2, Part 2.1;
OR
The Generator Owner provided the
Transmission Planner verified model(s) that
omitted four or more of the five Parts
identified in Requirement R2, Subparts
2.1.1, through 2.1.5.

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions
R#
R3

Lower VSL
The Generator Owner provided a
written response more than 90
calendar days but less than or equal
to 120 calendar days of receiving
written notice.

Moderate VSL
The Generator Owner provided a
written response more than 120
calendar days but less than or equal
to 150 calendar days of receiving
written notice.

High VSL
The Generator Owner provided a
written response more than 150
calendar days but less than or equal
to 180 calendar days of receiving
written notice.

Severe VSL
The Generator Owner failed to provide a
written response within 180 calendar days
of receiving written notice;
OR
The Generator Owner's written response
failed to contain either the technical basis
for maintaining the current model, or a list
of future model changes, or a plan to
perform another model verification.

R4

The Generator Owner provided
revised model data or plans to
perform model verification more
than 180 calendar days but less
than or equal to 210 calendar days
of making changes to the
turbine/governor and load control
or active power/frequency control
system that alter the equipment
response characteristic.

The Generator Owner provided
revised model data or plans to
perform model verification more than
210 calendar days but less than or
equal to 240 calendar days of making
changes to the turbine/governor and
load control or active
power/frequency control system that
alter the equipment response
characteristic.

The Generator Owner provided
revised model data or plans to
perform model verification more than
240 calendar days but less than or
equal to 270 calendar days of making
changes to the turbine/governor and
load control or active
power/frequency control system that
alter the equipment response
characteristic.

Page 9 of 16

The Generator Owner failed to provide
revised model data or failed to provide
plans to perform model verification within
270 calendar days of making changes to the
turbine/governor and load control or active
power/frequency control system that altered
the equipment response characteristic.

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions
R#
R5

Lower VSL

Moderate VSL

High VSL

Severe VSL

The Transmission Planner
provided a written response to the
Generator Owner indicating
whether the model is usable or not
usable, including a technical
description if the model is not
usable, more than 90 calendar days
but less than or equal to 120
calendar days of receiving verified
model information;

The Transmission Planner provided a
written response to the Generator
Owner indicating whether the model
is usable or not usable, including a
technical description if the model is
not usable, more than 120 calendar
days but less than or equal to 150
calendar days of receiving the
verified model information;

The Transmission Planner provided a
written response to the Generator
Owner indicating whether the model
is usable or not usable, including a
technical description if the model is
not usable, more than 150 calendar
days but less than or equal to 180
calendar days of receiving the
verified model information;

The Transmission Planner failed to provide
a written response to the Generator Owner
within 180 calendar days of receiving the
verified model information;

OR

OR

OR

The Transmission Planner’s written
response omitted confirmation for
one of the specified model criteria
listed in Requirement R5, Parts 5.1
through 5.3;

The Transmission Planner’s written
response omitted confirmation for
two of the specified model criteria
listed in Requirement R5, Parts 5.1
through 5.3;

OR

OR

The Transmission Planner provided a
written response to the Generator
Owner indicating that the model is
not usable, but did not include a
technical description and provided
the response more than 90 calendar
days but less than or equal to 120
calendar days of receiving verified
model information.

The Transmission Planner provided a
written response to the Generator
Owner indicating that the model is
not usable, but did not include a
technical description and provided
the response more than 120 calendar
days but less than or equal to 150
calendar days of receiving verified
model information.

The Transmission Planner
provided a written response to the
Generator Owner within 90
calendar days indicating that the
model is not usable; but did not
include a technical description

Page 10 of 16

OR
The Transmission Planner provided a
written response without including
confirmation of all specified model criteria
listed in Requirement R5, Parts 5.1 through
5.3;
OR
The Transmission Planner provided a
written response to the Generator Owner
indicating that the model is not usable, but
did not include a technical description and
provided the response more than 150
calendar days after receiving verified model
information.

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

E. Regional Variances
None.
F. Associated Documents
None.

Version History
Version

Date

Action

1

February 7,
2013

Adopted by NERC Board of Trustees

1

March 20,
2014

FERC Order issued approving MOD027-1. (Order becomes effective for R1,
R3, R4, and R5 on 7/1/14. R2 becomes
effective 7/1/18.)

1

May 7, 2014

NERC Board of Trustees adopted
revisions to VSLs in Requirement R5.

1

November 26,
2014

FERC issued a letter order approved
revisions to VSLs in Requirement R5.

Change Tracking
New

Revisions

G. References
The following documents contain technical information beyond the scope of this Standard on
turbine/governor and load control or active power/frequency control system functionality,
modeling, and testing.
1) IEEE Task Force on Generator Model Validation Testing of the Power System
Stability Subcommittee, “Guidelines for Generator Stability Model Validation
Testing,” IEEE PES General Meeting 2007, paper 07GM1307
2) L. Pereira "New Thermal Governor Model Development: Its Impact on Operation and
Planning Studies on the Western Interconnection" IEEE POWER AND ENERGY
MAGAZINE, MAY/JUNE 2005
3) D.M. Cabbell, S. Rueckert, B.A. Tuck, and M.C. Willis, "The New Thermal
Governor Model Used in Operating and Planning Studies in WECC," in Proc. IEEE
PES General Meeting, Denver, CO, 2004
4) S. Patterson, "Importance of Hydro Generation Response Resulting from the New
Thermal Modeling-and Required Hydro Modeling Improvements," in Proc. IEEE
PES General Meeting, Denver, CO, 2004
5) L. Pereira, D. Kosterev, D. Davies, and S. Patterson, "New Thermal Governor Model
Selection and Validation in the WECC," IEEE Trans. Power Syst., vol. 19, no. 1, pp.
517-523, February 2004

Page 11 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions

6) L. Pereira, J. Undrill, D. Kosterev, D. Davies, and S. Patterson, "A New Thermal
Governor Modeling Approach in the WECC," IEEE Trans. Power Syst., vol. 18, no.
2, pp. 819-829, May 2003
7) P. Pourbeik, C. Pink and R. Bisbee, “Power Plant Model Validation for Achieving
Reliability Standard Requirements Based on Recorded On-Line Disturbance Data”,
Proceedings of the IEEE PSCE, March, 2011

Page 12 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions

MOD-027 Attachment 1
Turbine/Governor and Load Control or Active Power/Frequency Control Model Periodicity

Row
Number
1

Verification Condition
Establishing the initial verification date for an applicable unit.
(Requirement R2)

Required Action
Transmit the verified model, documentation and data to the Transmission
Planner on or before the Effective Date.
Row 5 applies when calculating generation fleet compliance during the
10year implementation period.
See Section A5 for Effective Dates.

2

Subsequent verification for an applicable unit.
(Requirement R2)

3

Applicable unit is not subjected to a frequency excursion per Note
1 by the date otherwise required to meet the dates per Rows 1, 2,
4, or 6.
(This row is only applicable if a frequency excursion from a
system disturbance that meets Note 1 is selected for the
verification method and the ability to record the applicable unit’s
real power response to a frequency excursion is installed and
expected to be available).

Transmit the verified model, documentation and data to the Transmission
Planner on or before the 10-year anniversary of the last transmittal (per Note
2).

Requirement 2 is met with a written statement to that effect transmitted to
the Transmission Planner. Transmit the verified model, documentation and
data to the Transmission Planner on or before 365 calendar days after a
frequency excursion per Note 1 occurs and the recording equipment captures
the applicable unit’s real power response as expected.

(Requirement R2)
4

Initial verification for a new applicable unit or for an existing
applicable unit with new turbine/governor and load control or
active power/frequency control equipment installed.

Transmit the verified model, documentation and data to the Transmission
Planner within 365 calendar days after the commissioning date.

(Requirement R2)

Page 13 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions

MOD-027 Attachment 1
Turbine/Governor and Load Control or Active Power/Frequency Control Model Periodicity

Row
Number
5

Verification Condition
Existing applicable unit that is equivalent to another applicable
unit(s) at the same physical location;
AND
Each applicable unit has the same MVA nameplate rating;
AND

Required Action
Document circumstance with a written statement and include with the
verified model, documentation and data provided to the Transmission
Planner for the verified equivalent unit.
Verify a different equivalent unit during each 10-year verification period.
Applies to Row 1 when calculating generation fleet compliance during the
10-year implementation period.

The nameplate rating is ≤ 350 MVA;
AND
Each applicable unit has the same components and settings;
AND
The model for one of these equivalent applicable units has been
verified.
(Requirement R2)
6

The Generator Owner has submitted a verification plan.
(Requirement R3 or R4)

Transmit the verified model, documentation and data to the Transmission
Planner within 365 calendar days after the submittal of the verification plan.

Page 14 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions

MOD-027 Attachment 1
Turbine/Governor and Load Control or Active Power/Frequency Control Model Periodicity

Row
Number
7

Verification Condition
Applicable unit is not responsive to both over and under frequency
excursion events (The applicable unit does not operate in a
frequency control mode, except during normal start up and shut
down, that would result in a turbine/governor and load control or
active power/frequency control mode response.);

Required Action
Requirement 2 is met with a written statement to that effect transmitted to
the Transmission Planner.
Perform verification per the periodicity specified in Row 4 for a “New
Generating Unit” (or new equipment) only if responsive control mode
operation for connected operations is established.

OR
Applicable unit either does not have an installed frequency control
system or has a disabled frequency control system.
(Requirement R2)
8

Existing applicable unit has a current average net capacity factor
over the most recent three calendar years, beginning on January 1
and ending on December 31 of 5% or less.
(Requirement R2)

Requirement 2 is met with a written statement to that effect transmitted to
the Transmission Planner.
At the end of this 10 calendar year timeframe, the current average three year
net capacity factor (for years 8, 9, and 10) can be examined to determine if
the capacity factor exemption can be declared for the next 10 calendar year
period. If not eligible for the capacity factor exemption, then model
verification must be completed within 365 calendar days of the date the
capacity factor exemption expired.
For the definition of net capacity factor, refer to Appendix F of the GADS
Data Reporting Instructions on the NERC website.

Page 15 of 16

Standard MOD-027-1 — Verification of Models and Data for Turbine/Governor and Load Control or Active Power/Frequency
Control Functions

MOD-027 Attachment 1
Turbine/Governor and Load Control or Active Power/Frequency Control Model Periodicity

Row
Number

Verification Condition

Required Action

NOTES:
NOTE 1: Unit model verification frequency excursion criteria:


≥ 0.05 hertz deviation (nadir point) from scheduled frequency for the Eastern Interconnection with the applicable unit operating in a frequency
responsive mode



≥ 0.10 hertz deviation (nadir point) from scheduled frequency for the ERCOT and Western Interconnections with the applicable unit operating in a
frequency responsive mode



≥ 0.15 hertz deviation (nadir point) from scheduled frequency for the Quebec Interconnection with the applicable unit operating in a frequency
responsive mode

NOTE 2: Establishing the recurring ten year unit verification period start date:


The start date is the actual date of submittal of a verified model to the Transmission Planner for the most recently performed unit verification.

NOTE 3: Consideration for early compliance:
Existing turbine/governor and load control or active power/frequency control model verification is sufficient for demonstrating compliance for a 10 year period
from the actual transmittal date if either of the following applies:




The Generator Owner has a verified model that is compliant with the applicable regional policies, guidelines or criteria existing at the time of model
verification
The Generator Owner has an existing verified model that is compliant with the requirements of this standard

Page 16 of 16