Reliability Standard MOD-026-1

Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions
A. Introduction

1.

Title:
Verification of Models and Data for Generator Excitation Control System
or Plant Volt/Var Control Functions

2.

Number:

3.

Purpose: To verify that the generator excitation control system or plant volt/var
control function1 model (including the power system stabilizer model and the
impedance compensator model) and the model parameters used in dynamic simulations
accurately represent the generator excitation control system or plant volt/var control
function behavior when assessing Bulk Electric System (BES) reliability.

4.

Applicability:

MOD-026-1

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 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).

1

Excitation control system or plant volt/var control function:
a.

For individual synchronous machines, the generator excitation control system includes the generator,
exciter, voltage regulator, impedance compensation and power system stabilizer.

b.

For an aggregate generating plant, the volt/var control system includes the voltage regulator & reactive
power control system controlling and coordinating plant voltage and associated reactive capable resources.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions

4.2.3

Generation in the ERCOT Interconnection with the following
characteristics:
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).

4.2.4

For all Interconnections:


5.

A technically justified2 unit that meets NERC registry criteria but is
not otherwise included in the above Applicability sections 4.2.1, 4.2.2,
or 4.2.3 and is requested by the Transmission Planner.

Effective Date:
5.1. For Requirements R1, and R3 through R6, 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

2

Technical justification is achieved by the Transmission Planner demonstrating that the simulated unit or plant
response does not match the measured unit or plant response.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions

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.
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 excitation control system or plant volt/var
control function models that are acceptable to the Transmission Planner for use in
dynamic simulation,



Instructions on how to obtain the dynamic excitation control system or plant
volt/var 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
excitation control system or plant volt/var control function contained in the
Transmission Planner’s dynamic database from the current (in-use) models,
including generator MVA base.

Each Generator Owner shall provide for each applicable unit, a verified generator
excitation control system or plant volt/var control function model, including
documentation and data (as specified in Part 2.1) to its Transmission Planner in
accordance with the periodicity specified in MOD-026 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 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.

Documentation demonstrating the applicable unit’s model response
matches the recorded response for a voltage excursion from either a staged
test or a measured system disturbance,

2.1.2.

Manufacturer, model number (if available), and type of the excitation
control system including, but not limited to static, AC brushless, DC
rotating, and/or the plant volt/var control function (if installed),

2.1.3.

Model structure and data including, but not limited to reactance, time
constants, saturation factors, total rotational inertia, or equivalent data for
the generator,

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions

R3.

2.1.4.

Model structure and data for the excitation control system, including the
closed loop voltage regulator if a closed loop voltage regulator is installed
or the model structure and data for the plant volt/var control function
system,

2.1.5.

Compensation settings (such as droop, line drop, differential
compensation), if used, and

2.1.6.

Model structure and data for power system stabilizer, if so equipped.

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 R6) that the excitation control system or plant volt/var control
function model is not usable,



Written comments from its Transmission Planner identifying technical
concerns with the verification documentation related to the excitation control
system or plant volt/var control function model, or



Written comments and supporting evidence from its Transmission Planner
indicating that the simulated excitation control system or plant volt/var control
function model response did not match the recorded response to a
transmission system event.

The written response shall contain either the technical basis for maintaining the current
model, the model changes, or a plan to perform model verification3 (in accordance with
Requirement R2). [Violation Risk Factor: Lower] [Time Horizon: Operations
Planning]
R4.

3
4

Each Generator Owner shall provide revised model data or plans to perform model
verification4 (in accordance with Requirement R2) for an applicable unit to its
Transmission Planner within 180 calendar days of making changes to the excitation
control system or plant volt/var control function that alter the equipment response
characteristic.5 [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

If verification is performed, the 10-year period as outlined in MOD-026 Attachment 1 is reset.

Ibid

5

Exciter, voltage regulator, plant volt/var or power system stabilizer control replacement including software alterations that alter
excitation control system equipment response, plant digital control system addition or replacement, plant digital control system
software alterations that alter excitation control system equipment response, plant volt/var function equipment addition or
replacement (such as static var systems, capacitor banks, individual unit excitation systems, etc), a change in the voltage control
mode (such as going from power factor control to automatic voltage control, etc), exciter, voltage regulator, impedance
compensator, or power system stabilizer settings change. Automatic changes in settings that occur due to changes in operating
mode do not apply to Requirement R4.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions
R5.

R6.

Each Generator Owner shall provide a written response to its Transmission Planner,
within 90 calendar days following receipt of a technically justified6 unit request from
the Transmission Planner to perform a model review of a unit or plant that includes one
of the following: [Violation Risk Factor: Lower] [Time Horizon: Operations
Planning]


Details of plans to verify the model (in accordance with Requirement R2), or



Corrected model data including the source of revised model data such as
discovery of manufacturer test values to replace generic model data or
updating of data parameters based on an on-site review of the equipment.

Each Transmission Planner shall provide a written response to the Generator Owner
within 90 calendar days of receiving the verified excitation control system or plant
volt/var control function model information in accordance with Requirement R2 that
the model is usable (meets the criteria specified in Parts 6.1 through 6.3) or is not
usable.
6.1. The excitation control system or plant volt/var control function model initializes
to compute modeling data without error,
6.2. A no-disturbance simulation results in negligible transients, and
6.3. For an otherwise stable simulation, a disturbance simulation results in the

excitation control and plant volt/var control function 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 instructions 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

excitation control system or plant volt/var control function 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

6

Technical justification is achieved by the Transmission Planner demonstrating that the simulated unit or plant
response does not match the measured unit or plant response.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions

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, a
dated revised model data or plans to perform a model verification and dated evidence
(e.g., electronic mail message, postal receipt, or confirmation of facsimile) it provided
the revised model and data or plans within 180 calendar days of making changes.
M5. Evidence for Requirement R5 must include the Generator Owner’s dated written

response containing the information identified in Requirement R5 and dated evidence
(e.g., electronic mail message, postal receipt, or confirmation of facsimile) it provided
a written response within 90 calendar days following receipt of a technically justified
request.
M6. Evidence of Requirement R6 must include, for each model received, the dated response

indicating the model was usable or not usable according to the criteria specified in
Parts 6.1 through 6.3 and for a model that is not usable, a technical description; and
dated evidence of transmittal (e.g., electronic mail message, postal receipt, or
confirmation of facsimile) that the Generator Owner was notified within 90 calendar
days of receipt of model information.
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 R6, Measures M1 and
M6 for three calendar years from the date the document was provided.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control
System or Plant Volt/Var Control Functions


The Generator Owner shall retain the latest excitation control system or plant
volt/var control function model verification evidence of Requirement R2,
Measure M2.



The Generator Owner shall retain the information/data request and provided
response evidence of Requirements R3 through R5, and Measures M3 through
M5 for three 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 or
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
Complaints
1.4. Additional Compliance Information
None

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

2.

Violation Severity Levels

R#

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), including
documentation and data to its
Transmission Planner after the
timeframe specified in MOD-026
Attachment 1 but less than or equal
to 90 calendar days late;

The Generator Owner provided its
verified model(s), including
documentation and data 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-026 Attachment 1.

The Generator Owner provided its
verified model(s), including
documentation and data 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-026 Attachment 1.

The Generator Owner provided its
verified model(s), including
documentation and data more than
270 calendar days late to its
Transmission Planner in accordance
with the periodicity specified in
MOD-026 Attachment 1.

OR

OR

The Generator Owner provided the
Transmission Planner verified
models that omitted two of the six
Parts identified in Requirement R2,
Parts 2.1.1 through 2.1.6.

The Generator Owner provided the
Transmission Planner verified
models that omitted three of the six
Parts identified in Requirement R2,
Parts 2.1.1 through 2.1.6.

OR
The Generator Owner provided the
Transmission Planner verified
models that omitted one of the six
Parts identified in Requirement R2,
Parts 2.1.1 through 2.1.6.

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) but omitted four or more of
the six parts identified in
Requirement R2, Subparts 2.1.1
through 2.1.6.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var 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 excitation
control system or plant volt/var
control function that altered 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 excitation
control system or plant volt/var
control function that altered 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 excitation
control system or plant volt/var
control function that altered the
equipment response characteristic.

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 excitation
control system or plant volt/var
control function that altered the
equipment response characteristic.

R5

The Generator Owner provided a
written response more than 90
calendar days but less than or equal
to 120 calendar days to the
Transmission Planner following
receipt of a technically justified
request to perform a model review of
an applicable unit.

The Generator Owner provided a
written response more than 120
calendar days but less than or equal
to 150 calendar days to the
Transmission Planner following
receipt of a technically justified
request to perform a model review of
an applicable unit.

The Generator Owner provided a
written response more than 150
calendar days but less than or equal
to 180 calendar days to the
Transmission Planner following
receipt of a technically justified
request to perform a model review of
an applicable unit.

The Generator Owner failed to
provide a written response to the
Transmission Planner within 180
calendar days following receipt of a
technically justified request to
perform a model review of an
applicable unit.
OR
The Generator Owner’s written
response failed to include one of the
sub bullets of Requirement R5.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

R#
R6

Lower VSL

Moderate VSL

High 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;

OR

OR

OR

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.

The Transmission Planner’s written
response omitted confirmation for
one of the specified model criteria
listed in Requirement R6, Parts 6.1
through 6.3;

The Transmission Planner’s written
response omitted confirmation for
two of the specified model criteria
listed in Requirement R6, Parts 6.1
through 6.3;

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.

Severe VSL
The Transmission Planner failed to
provide a written response to the
Generator Owner within 180
calendar days of receiving the
verified model information;
OR
The Transmission Planner’s written
response omitted confirmation for all
specified model criteria listed in
Requirement R6, Parts 6.1 through
6.3;
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.

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation
Control System or Plant Volt/Var Control Functions

E. Regional Variances

None.
F. Associated Documents

None.
Version History
Version

Date

Action

1

February 7, 2013

1

March 20, 2014

Adopted by NERC Board of
Trustees
FERC Order issued approving
MOD-026-1. (Order becomes
effective for R1, R3, R4, R5, and
R6 on 7/1/14. R2 becomes
effective on 7/1/18.)

1

May 7, 2014

NERC Board of Trustees
adopted revisions to VSLs in
Requirement R6.

1

November 26,
2014

FERC issued a letter order
approved revisions to VSLs in
Requirement R6.

Change Tracking
New

Revisions

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation
Control System or Plant Volt/Var Control Functions

G. References

The following documents contain technical information beyond the scope of this
Standard on excitation control system functionality, modeling, and testing.
1. IEEE 421.1 Definitions for Excitation Systems for Synchronous Machines
2. IEEE 421.2 Guide for Identification, Testing, and Evaluation of the Dynamic
Performance of Excitation Control Systems
3. IEEE 421.5 IEEE Recommended Practice for Excitation System Models for
Power System Stability Studies
4. K. Clark, R.A. Walling, N.W. Miller, "Solar Photovoltaic (PV) Plant Models in
PSLF," IEEE/PES General Meeting, Detroit, MI, July 2011
5. M. Asmine, J. Brochu, J. Fortmann, R. Gagnon, Y. Kazachkov, C.-E. Langlois, C.
Larose, E. Muljadi, J. MacDowell, P. Pourbeik, S. A. Seman, and K. Wiens,
“Model Validation for Wind Turbine Generator Models”, IEEE Transactions on
Power System, Volume 26, Issue 3, August 2011
6. A. Ellis, E. Muljadi, J. Sanchez-Gasca, Y. Kazachkov, “Generic Models for
Simulation of Wind Power Plants in Bulk System Planning Studies,” IEEE PES
General Meeting 2011, Detroit, MI, July 24-28
7. N.W. Miller, J. J. Sanchez-Gasca, K. Clark, J.M. MacDowell, “Dynamic
Modeling of GE Wind Plants for Stability Simulations,” IEEE PES General
Meeting 2011, Detroit, MI, July 24-28
8. A. Ellis, Y. Kazachkov, E. Muljadi, P. Pourbeik, J.J. Sanchez-Gasca, Working
Group Joint Report – WECC Working Group on Dynamic Performance of Wind
Power Generation & IEEE Working Group on Dynamic Performance of Wind
Power Generation, “Description and Technical Specifications for Generic WTG
Models – A Status Report,” Proc. IEEE PES 2011 Power Systems Conference and
Exposition (PSCE), March 2011, Phoenix, AZ
9. K. Clark, N.W. Miller, R.A. Walling, "Modeling of GE Solar Photovoltaic (PV)
Plants for Grid Studies," version 1.1, April 2010

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation
Control System or Plant Volt/Var Control Functions

10. K. Clark, N.W. Miller, J. J. Sanchez-Gasca, “Modeling of GE Wind TurbineGenerators for Grid Studies,” version 4.5, April 16, 2010, Available from GE
Energy
11. R.J. Piwko, N.W. Miller, J.M. MacDowell, “Field Testing & Model Validation of
Wind Plants,” in Proc. IEEE PES General Meeting, Pittsburg, PA, July 2008
12. N. Miller, K. Clark, J. MacDowell and W. Barton, “Experience with Field and
Factory Testing for Model Validation of GE Wind Plants,” in Proc. Eur. Wind
Energy Conf. Exhib., Brussels, Belgium, March/April 2008
13. 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
14. W.W. Price and J. J. Sanchez-Gasca, “Simplified Wind Turbine Generator
Aerodynamic Models for Transient Stability Studies,” in PROC IEEE PES 2006
Power Systems Conf. Expo. (PSCE), Atlanta, GA, October 1, 2006, p. 986-992
15. J.J. Sanchez-Gasca, R.J. Piwko, N. W. Miller, W. W. Price, “On the Integration of
Wind Power Plants in Large Power Systems,” Proc. X Symposium of Specialists
in Electric and Expansion Planning (SEPOPE), Florianopolis, Brazil, May 2006
16. N. W. Miller, J. J. Sanchez-Gasca, W. W. Price, R. W. Delmerico, “Dynamic
Modeling of GE 1.5 and 3.6 MW Wind Turbine-Generators for Stability
Simulations,” Proc. IEEE Power Engineering Society General Meeting, Toronto,
Ontario, July 2003
17. 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

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

MOD-026 Attachment 1
Excitation Control System or Plant Volt/Var Function Model Verification Periodicity

Row Number
1

Verification Condition

Required Action

Establishing the initial verification date for an applicable
unit.

Transmit the verified model, documentation and data to the Transmission
Planner on or before the Effective Date.

(Requirement R2)

Row 4 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

Initial verification for a new applicable unit or for an
existing applicable unit with new excitation control system
or plant volt/var control function equipment installed.

Transmit the verified model, documentation and data to the Transmission
Planner on or before the 10-year anniversary of the last transmittal (per Note
1).
Transmit the verified model, documentation and data to the Transmission
Planner within 365 calendar days after the commissioning date.

(Requirement R2)

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

MOD-026 Attachment 1
Excitation Control System or Plant Volt/Var Function Model Verification Periodicity

Row Number
4

Verification Condition
Existing applicable unit that is equivalent to another 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)
5

The Generator Owner has submitted a verification plan.
(Requirement R3, R4 or R5)

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

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Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

MOD-026 Attachment 1
Excitation Control System or Plant Volt/Var Function Model Verification Periodicity

Row Number
6

Verification Condition

Required Action

New or existing applicable unit does not include an active
closed loop voltage or reactive power control function.

Requirement 2 is met with a written statement to that effect transmitted to
the Transmission Planner.

(Requirement R2)

Perform verification per the periodicity specified in Row 3 for a “New
Generating Unit” (or new equipment) only if active closed loop function is
established.
See Footnote 1 (see Section A.3) for clarification of what constitutes an
active closed loop function for both conventional synchronous machines
(reference Footnote 1a) and aggregate generating plants (reference Footnote
1b).

7

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-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-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 16 of 17

Standard MOD-026-1 — Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control
Functions

MOD-026 Attachment 1
Excitation Control System or Plant Volt/Var Function Model Verification Periodicity

Row Number

Verification Condition

Required Action

NOTES:
NOTE 1: Establishing the recurring 10-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 2: Consideration for early compliance:
Existing generator excitation control system or plant volt/var control function 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 17 of 17