Reliability Standard VAR-001-4

VAR-001-4 — Voltage and Reactive Control
A. Introduction
1.

Title:

2.

Number: VAR-001-4

3.

Purpose: To ensure that voltage levels, reactive flows, and reactive resources are monitored,
controlled, and maintained within limits in Real-time to protect equipment and the
reliable operation of the Interconnection.

4.

Applicability:

5.

Voltage and Reactive Control

4.1.

Transmission Operators

4.2.

Generator Operators within the Western Interconnection (for the WECC Variance)

Effective Date:
5.1.

The standard shall become effective on the first day of the first calendar quarter
after the date that the standard is approved by an applicable governmental
authority or as otherwise provided for in a jurisdiction where approval by an
applicable governmental authority is required for a standard to go into effect.
Where approval by an applicable governmental authority is not required, the
standard shall become effective on the first day of the first calendar quarter after
the date the standard is adopted by the NERC Board of Trustees or as otherwise
provided for in that jurisdiction.

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VAR-001-4 — Voltage and Reactive Control
B. Requirements and Measures
R1.

Each Transmission Operator shall specify a system voltage schedule (which is either a range or a
target value with an associated tolerance band) as part of its plan to operate within System
Operating Limits and Interconnection Reliability Operating Limits. [Violation Risk Factor: High] [Time
Horizon: Operational Planning]
1.1. Each Transmission Operator shall provide a copy of the voltage schedules (which is either a
range or a target value with an associated tolerance band) to its Reliability Coordinator and
adjacent Transmission Operators within 30 calendar days of a request.

M1. The Transmission Operator shall have evidence that it specified system voltage schedules using
either a range or a target value with an associated tolerance band.
For part 1.1, the Transmission Operator shall have evidence that the voltage schedules (which is
either a range or a target value with an associated tolerance band) were provided to its Reliability
Coordinator and adjacent Transmission Operators within 30 days of a request. Evidence may include,
but is not limited to, emails, website postings, and meeting minutes.
R2. Each Transmission Operator shall schedule sufficient reactive resources to regulate voltage levels
under normal and Contingency conditions. Transmission Operators can provide sufficient reactive
resources through various means including, but not limited to, reactive generation scheduling,
transmission line and reactive resource switching, and using controllable load. [Violation Risk Factor:
High] [Time Horizon: Real-time Operations, Same-day Operations, and Operational Planning]
M2. Each Transmission Operator shall have evidence of scheduling sufficient reactive resources based on
their assessments of the system. For the operational planning time horizon, Transmission Operators
shall have evidence of assessments used as the basis for how resources were scheduled.
R3. Each Transmission Operator shall operate or direct the Real-time operation of devices to regulate
transmission voltage and reactive flow as necessary. [Violation Risk Factor: High] [Time Horizon:
Real-time Operations, Same-day Operations, and Operational Planning]
M3. Each Transmission Operator shall have evidence that actions were taken to operate capacitive and
inductive resources as necessary in Real-time. This may include instructions to Generator Operators
to: 1) provide additional voltage support; 2) bring resources on-line; or 3) make manual adjustments.
R4. The Transmission Operator shall specify the criteria that will exempt generators from: 1) following a
voltage or Reactive Power schedule, 2) from having its automatic voltage regulator (AVR) in service
or from being in voltage control mode, or 3) from having to make any associated notifications.
[Violation Risk Factor: Lower] [Time Horizon: Operations Planning]
4.1 If a Transmission Operator determines that a generator has satisfied the exemption criteria, it
shall notify the associated Generator Operator.
M4. Each Transmission Operator shall have evidence of the documented criteria for generator
exemptions.
For part 4.1, the Transmission Operator shall also have evidence to show that, for each generator in
its area that is exempt from: 1) following a voltage or Reactive Power schedule, 2) from having its

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VAR-001-4 — Voltage and Reactive Control
automatic voltage regulator (AVR) in service or from being in voltage control mode, or 3) from having
to make any notifications, the associated Generator Operator was notified of this exemption.
R5. Each Transmission Operator shall specify a voltage or Reactive Power schedule (which is either a
range or a target value with an associated tolerance band) at either the high voltage side or low
voltage side of the generator step-up transformer at the Transmission Operator’s discretion.
[Violation Risk Factor: Medium] [Time Horizon: Operations Planning]
5.1. The Transmission Operator shall provide the voltage or Reactive Power schedule (which is
either a range or a target value with an associated tolerance band) to the associated Generator
Operator and direct the Generator Operator to comply with the schedule in automatic voltage
control mode (the AVR is in service and controlling voltage).
5.2. The Transmission Operator shall provide the Generator Operator with the notification
requirements for deviations from the voltage or Reactive Power schedule (which is either a
range or a target value with an associated tolerance band).
5.3. The Transmission Operator shall provide the criteria used to develop voltage schedules Reactive
Power schedule (which is either a range or a target value with an associated tolerance band) to
the Generator Operator within 30 days of receiving a request.
M5. The Transmission Operator shall have evidence of a documented voltage or Reactive Power Schedule
(which is either a range or a target value with an associated tolerance band).
For part 5.1, the Transmission Operator shall have evidence it provided a voltage or Reactive Power
schedule (which is either a range or a target value with an associated tolerance band) to the
applicable Generator Operators, and that the Generator Operator was directed to comply with the
schedule in automatic voltage control mode, unless exempted.
For part 5.2, the Transmission Operator shall have evidence it provided notification requirements for
deviations from the voltage or Reactive Power schedule (which is either a range or a target value
with an associated tolerance band). For part 5.3, the Transmission Operator shall have evidence it
provided the criteria used to develop voltage schedules or Reactive Power schedule (which is either a
range or a target value with an associated tolerance band) within 30 days of receiving a request by a
Generator Operator.
R6.

After consultation with the Generator Owner regarding necessary step-up transformer tap changes
and the implementation schedule, the Transmission Operator shall provide documentation to the
Generator Owner specifying the required tap changes, a timeframe for making the changes, and
technical justification for these changes. [Violation Risk Factor: Lower] [Time Horizon: Operations
Planning]

M6. The Transmission Operator shall have evidence that it provided documentation to the Generator
Owner when a change was needed to a generating unit’s step-up transformer tap in accordance with
the requirement and that it consulted with the Generator Owner.

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VAR-001-4 — Voltage and Reactive Control
C. Compliance

1.

Compliance Monitoring Process:
1.1. Compliance Enforcement Authority:
As defined in the NERC Rules of Procedure, “Compliance Enforcement Authority” refers to NERC or
the Regional Entity in their respective roles of monitoring and enforcing compliance with the NERC
Reliability Standards.
1.2. Evidence Retention:
The following evidence retention periods identify the period of time a registered entity is required
to retain specific evidence to demonstrate compliance. For instances in which the evidence
retention period specified below is shorter than the time since the last audit, the Compliance
Enforcement Authority may ask the registered entity to provide other evidence to show that it
was compliant for the full time period since the last audit.
The Transmission Operator shall retain evidence for Measures 1 through 6 for 12 months. The
Compliance Monitor shall retain any audit data for three years.
1.3. Compliance Monitoring and Assessment Processes:
“Compliance Monitoring and Assessment Processes” 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 the associated reliability standard.
1.4. Additional Compliance Information:
None

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VAR-001-4 — Voltage and Reactive Control
Table of Compliance Elements
R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

R1

Operational
Planning

High

R2

Real-time
Operations,
Same-day
Operations,
and
Operational
Planning

High

R3

Real-time
Operations,
Same-day
Operations,
and
Operational
Planning

High

Moderate VSL

High VSL

Severe VSL

N/A

N/A

N/A

N/A

N/A

The Transmission
Operator does not
schedule sufficient
reactive resources as
necessary to avoid
violating an SOL.

The Transmission
Operator does not
specify a system voltage
schedule (which is
either a range or a
target value with an
associated tolerance
band).
The Transmission
Operator does not
schedule sufficient
reactive resources as
necessary to avoid
violating an IROL.

N/A

N/A

The Transmission
Operator does not
operate or direct any
real-time operation of
devices as necessary to
avoid violating an SOL.

The Transmission
Operator does not
operate or direct any
real-time operation of
devices as necessary to
avoid violating an IROL.

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VAR-001-4 — Voltage and Reactive Control

R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

R4

Operations
Planning

Lower

R5

Operations
Planning

Medium

N/A

N/A

Moderate VSL
N/A

High VSL

The Transmission
Operator has
exemption criteria and
notified the Generator
Operator, but the
Transmission Operator
does not have
evidence of the
notification to the
Generator Operator.
The Transmission
The Transmission
Operator does not
Operator does not
provide the criteria for provide voltage or
voltage or Reactive
Reactive Power
Power schedules
schedules (which is
(which is either a range either a range or a
or a target value with
target value with an
an associated
associated tolerance
tolerance band) after
band) to all Generator
30 days of a request.
Operators.

Severe VSL
The Transmission
Operator does not have
exemption criteria.

The Transmission
Operator does not
provide voltage or
Reactive Power
schedules (which is
either a range or a
target value with an
associated tolerance
band) to any Generator
Operators.
Or
The Transmission
Operator does not
provide the Generator
Operator with the
notification
requirements for
deviations from the

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VAR-001-4 — Voltage and Reactive Control

R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL
voltage or Reactive
Power schedule (which
is either a range or a
target value with an
associated tolerance
band).

R6

Operations
Planning

Lower

The Transmission
Operator does not
provide either the
technical justification or
timeframe for changing
generator step-up tap
settings.

N/A

N/A

The Transmission
Operator does not
provide the technical
justification and the
timeframe for changing
generator step-up tap
settings.

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Application Guidelines
D. Regional Variances

The following Interconnection-wide variance shall be applicable in the Western Electricity
Coordinating Council (WECC) and replaces, in their entirety, Requirements R4 and R5. Please
note that Requirement R4 is deleted and R5 is replaced with the following requirements.
Requirements
E.A.13

E.A.14

Each Transmission Operator shall issue any one of the following types of voltage
schedules to the Generator Operators for each of their generation resources that are
on-line and part of the Bulk Electric System within the Transmission Operator Area:
[Violation Risk Factor: Medium] [Time Horizon: Operations Planning and Same-day
Operations]
•

A voltage set point with a voltage tolerance band and a specified period.

•

An initial volt-ampere reactive output or initial power factor output with a voltage
tolerance band for a specified period that the Generator Operator uses to
establish a generator bus voltage set point.

•

A voltage band for a specified period.

Each Transmission Operator shall provide one of the following voltage schedule
reference points for each generation resource in its Area to the Generator Operator.
[Violation Risk Factor: Medium] [Time Horizon: Operations Planning and Same-day
Operations]
•

The generator terminals.

•

The high side of the generator step-up transformer.

•

The point of interconnection.

•

A location designated by mutual agreement between the Transmission Operator
and Generator Operator.

E.A.15

Each Generator Operator shall convert each voltage schedule specified in
Requirement E.A.13 into the voltage set point for the generator excitation system.
[Violation Risk Factor: Medium] [Time Horizon: Operations Planning and Same-day
Operations]

E.A.16

Each Generator Operator shall provide its voltage set point conversion methodology
from the point in Requirement E.A.14 to the generator terminals within 30 calendar
days of request by its Transmission Operator. [Violation Risk Factor: Lower] [Time
Horizon: Operations Planning]

E.A.17

Each Transmission Operator shall provide to the Generator Operator, within 30
calendar days of a request for data by the Generator Operator, its transmission
equipment data and operating data that supports development of the voltage set
point conversion methodology. [Violation Risk Factor: Lower] [Time Horizon:
Operations Planning]

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Application Guidelines
E.A.18

Each Generator Operator shall meet the following control loop specifications if the
Generator Operator uses control loops external to the Automatic Voltage Regulators
(AVR) to manage MVar loading: [Violation Risk Factor: Medium] [Time Horizon: Realtime Operations]
E.A.18.1. Each control loop’s design incorporates the AVR’s automatic voltage
controlled response to voltage deviations during System Disturbances.
E.A.18.2. Each control loop is only used by mutual agreement between the Generator
Operator and the Transmission Operator affected by the control loop.

Measures1
M.E.A.13 Each Transmission Operator shall have and provide upon request, evidence that it
provided the voltage schedules to the Generator Operator. Dated spreadsheets,
reports, voice recordings, or other documentation containing the voltage schedule
including set points, tolerance bands, and specified periods as required in
Requirement E.A.13 are acceptable as evidence.
M.E.A.14 The Transmission Operator shall have and provide upon request, evidence that it
provided one of the voltage schedule reference points in Requirement E.A.14 for
each generation resource in its Area to the Generator Operator. Dated letters, email, or other documentation that contains notification to the Generator Operator
of the voltage schedule reference point for each generation resource are acceptable
as evidence.
M.E.A.15 Each Generator Operator shall have and provide upon request, evidence that it
converted a voltage schedule as described in Requirement E.A.13 into a voltage set
point for the AVR. Dated spreadsheets, logs, reports, or other documentation are
acceptable as evidence.
M.E.A.16 The Generator Operator shall have and provide upon request, evidence that within
30 calendar days of request by its Transmission Operator it provided its voltage set
point conversion methodology from the point in Requirement E.A.14 to the
generator terminals. Dated reports, spreadsheets, or other documentation are
acceptable as evidence.
M.E.A.17 The Transmission Operator shall have and provide upon request, evidence that
within 30 calendar days of request by its Generator Operator it provided data to
support development of the voltage set point conversion methodology. Dated
reports, spreadsheets, or other documentation are acceptable as evidence.
M.E.A.18 If the Generator Operator uses outside control loops to manage MVar loading, the
Generator Operator shall have and provide upon request, evidence that it met the
control loop specifications in sub-parts E.A.18.1 through E.A.18.2. Design
specifications with identified agreed-upon control loops, system reports, or other
dated documentation are acceptable as evidence.
1

The number for each measure corresponds with the number for each requirement, i.e. M.E.A.13 means the measure for Requirement E.A.13.

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Application Guidelines
Violation Severity Levels
E#

Lower VSL

Moderate VSL

High VSL

Severe VSL

E.A.13

For the specified
period, the
Transmission
Operator did not
issue one of the
voltage schedules
listed in E.A.13 to
at least one
generation
resource but less
than or equal to 5%
of the generation
resources that are
on-line and part of
the BES in the
Transmission
Operator Area.

For the specified
period, the
Transmission
Operator did not
issue one of the
voltage schedules
listed in E.A.13 to
more than 5% but
less than or equal to
10% of the
generation
resources that are
on-line and part of
the BES in the
Transmission
Operator Area.

For the specified
period, the
Transmission
Operator did not
issue one of the
voltage schedules
listed in E.A.13 to
more than 10%
but less than or
equal to 15% of
the generation
resources that are
on-line and part of
the BES in the
Transmission
Operator Area.

For the specified
period, the
Transmission Operator
did not issue one of the
voltage schedules listed
in E.A.13 to more than
15% of the generation
resources that are online and part of the BES
in the Transmission
Operator Area.

E.A.14

The Transmission
Operator did not
provide a voltage
schedule reference
point for at least
one but less than or
equal to 5% of the
generation
resources in the
Transmission
Operator area.

The Transmission
Operator did not
provide a voltage
schedule reference
point for more than
5% but less than or
equal to 10% of the
generation
resources in the
Transmission
Operator Area.

The Transmission
Operator did not a
voltage schedule
reference point
for more than 10%
but less than or
equal to 15% of
the generation
resources in the
Transmission
Operator Area.

The Transmission
Operator did not
provide a voltage
schedule reference
point for more than
15% of the generation
resources in the
Transmission Operator
Area.

E.A.15

The Generator
Operator failed to
convert at least one
voltage schedule in
Requirement
E.A.13 into the
voltage set point
for the AVR for less

The Generator
Operator failed to
convert the voltage
schedules in
Requirement E.A.13
into the voltage set
point for the AVR
for 25% or more but

The Generator
Operator failed to
convert the
voltage schedules
in Requirement
E.A.13 into the
voltage set point
for the AVR for
50% or more but
less than 75% of

The Generator
Operator failed to
convert the voltage
schedules in
Requirement E.A.13
into the voltage set
point for the AVR for
75% or more of the
voltage schedules.

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Application Guidelines

E#

Lower VSL

Moderate VSL

High VSL

Severe VSL

than 25% of the
voltage schedules.

less than 50% of the
voltage schedules.

the voltage
schedules.

E.A.16

The Generator
Operator provided
its voltage set
point conversion
methodology
greater than 30
days but less than
or equal to 60
days of a request
by the
Transmission
Operator.

The Generator
Operator provided
its voltage set
point conversion
methodology
greater than 60
days but less than
or equal to 90
days of a request
by the
Transmission
Operator.

The Generator
Operator
provided its
voltage set point
conversion
methodology
greater than 90
days but less
than or equal to
120 days of a
request by the
Transmission
Operator.

The Generator
Operator did not
provide its voltage
set point conversion
methodology within
120 days of a request
by the Transmission
Operator.

E.A.17

The Transmission
Operator provided
its data to
support
development of
the voltage set
point conversion
methodology
than 30 days but
less than or equal
to 60 days of a
request by the
Generator
Operator.

The Transmission
Operator provided
its data to support
development of
the voltage set
point conversion
methodology
greater than 60
days but less than
or equal to 90
days of a request
by the Generator.
Operator.

The Transmission
Operator
provided its data
to support
development of
the voltage set
point conversion
methodology
greater than 90
days but less
than or equal to
120 days of a
request by the
Generator.
Operator.

The Transmission
Operator did not
provide its data to
support development
of the voltage set
point conversion
methodology within
120 days of a request
by the Generator
Operator.

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Application Guidelines

E#

Lower VSL

E.A.18

N/A

Moderate VSL
The Generator
Operator did not
meet the control
loop specifications
in EA18.2 when the
Generator Operator
uses control loop
external to the AVR
to manage Mvar
loading.

High VSL
The Generator
Operator did not
meet the control
loop specifications
in EA18.1 when
the Generator
Operator uses
control loop
external to the
AVR to manage
Mvar loading.

Severe VSL
The Generator
Operator did not meet
the control loop
specifications in EA18.1
through EA18.2 when
the Generator
Operator uses control
loop external to the
AVR to manage Mvar
loading.

E. Interpretations
None.
F. Associated Documents
None.

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Application Guidelines
Guidelines and Technical Basis
For technical basis for each requirement, please review the rationale provided for each
requirement.
Rationale:

During development of this standard, text boxes were embedded within the standard to explain
the rationale for various parts of the standard. Upon BOT approval, the text from the rationale
text boxes was moved to this section.
Rationale for R1:
Paragraph 1868 of Order No. 693 requires NERC to add more "detailed and definitive
requirements on “established limits” and “sufficient reactive resources”, and identify
acceptable margins (i.e. voltage and/or reactive power margins)." Since Order No. 693 was
issued, however, several FAC and TOP standards have become enforceable to add more
requirements around voltage limits. More specifically, FAC-011 and FAC-014 require that
System Operating Limits (SOLs) and reliability margins are established. The NERC Glossary
definition of SOLs includes both: 1) Voltage Stability Ratings (Applicable pre- and postContingency Voltage Stability) and 2) System Voltage Limits (Applicable pre- and postContingency Voltage Limits). Therefore, for reliability reasons Requirement R1 now requires a
Transmission Operator (TOP) to set voltage or Reactive Power schedules with associated
tolerance bands. Further, since neighboring areas can affect each other greatly, each TOP must
also provide a copy of these schedules to its Reliability Coordinator (RC) and adjacent TOP upon
request.
Rationale for R2:
Paragraph 1875 from Order No. 693 directed NERC to include requirements to run voltage
stability analysis periodically, using online techniques where commercially available and offline
tools when online tools are not available. This standard does not explicitly require the periodic
voltage stability analysis because such analysis would be performed pursuant to the SOL
methodology developed under the FAC standards. TOP standards also require the TOP to
operate within SOLs and Interconnection Reliability Operating Limits (IROL). The VAR standard
drafting team (SDT) and industry participants also concluded that the best models and tools are
the ones that have been proven and the standard should not add a requirement for a
responsible entity to purchase new online simulations tools. Thus, the VAR SDT simplified the
requirements to ensuring sufficient reactive resources are online or scheduled. Controllable
load is specifically included to answer FERC's directive in Order No. 693 at Paragraph 1879.
Rationale for R3:
Similar to Requirement R2, the VAR SDT determined that for reliability purposes, the TOP must
ensure sufficient voltage support is provided in Real-time in order to operate within an SOL.

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Application Guidelines
Rationale for R4:
The VAR SDT received significant feedback on instances when a TOP would need the flexibility
for defining exemptions for generators. These exemptions can be tailored as the TOP deems
necessary for the specific area’s needs. The goal of this requirement is to provide a TOP the
ability to exempt a Generator Operator (GOP) from: 1) a voltage or Reactive Power schedule, 2)
a setting on the AVR, or 3) any VAR-002 notifications based on the TOP’s criteria. Feedback
from the industry detailed many system events that would require these types of exemptions
which included, but are not limited to: 1) maintenance during shoulder months, 2) scenarios
where two units are located within close proximity and both cannot be in voltage control mode,
and 3) large system voltage swings where it would harm reliability if all GOP were to notify their
respective TOP of deviations at one time. Also, in an effort to improve the requirement, the
sub-requirements containing an exemption list were removed from the currently enforceable
standard because this created more compliance issues with regard to how often the list would
be updated and maintained.
Rationale for R5:
The new requirement provides transparency regarding the criteria used by the TOP to establish
the voltage schedule. This requirement also provides a vehicle for the TOP to use appropriate
granularity when setting notification requirements for deviation from the voltage or Reactive
Power schedule. Additionally, this requirement provides clarity regarding a “tolerance band” as
specified in the voltage schedule and the control dead-band in the generator’s excitation
system.
Voltage Schedule tolerances are the bandwidth that accompanies the voltage target in a
voltage schedule, should reflect the anticipated fluctuation in voltage at the Generation
Operator’s facility during normal operations, and be based on the TOP’s assessment of N‐1 and
credible N‐2 system contingencies. The voltage schedule’s bandwidth should not be confused
with the control dead‐band that is programmed into a Generation Operator’s automatic voltage
regulator’s control system, which should be adjusting the AVR prior to reaching either end of
the voltage schedule’s bandwidth.
Rationale for R6:
Although tap settings are first established prior to interconnection, this requirement could not
be deleted because no other standard addresses when a tap setting must be adjusted. If the
tap setting is not properly set, then the amount of VARs produced by a unit can be affected.

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Application Guidelines
Version History
Version

Date

Action

Change Tracking

0

April 1, 2005

Effective Date

New

1

August 2, 2006

BOT Adoption

Revised

1

June 18, 2007

FERC approved Version 1 of the
standard.

Revised

1

July 3, 2007

Added “Generator Owners” and
“Generator Operators” to Applicability
section.

Errata

1

August 23,
2007

Removed “Generator Owners” and
“Generator Operators” to Applicability
section.

Errata

2

August 5, 2010

Adopted by NERC Board of Trustees;
Revised
Modified to address Order No. 693
Directives contained in paragraphs 1858
and 1879.

2

January, 10
2011

FERC issued letter order
approving the addition of LSEs
and Controllable Load to the
standard.

Revised

3

May 9, 2012

Adopted by NERC Board of Trustees;
Modified to add a WECC region
variance

Revised

3

June 20, 2013

FERC issued order approving VAR-001-3

Revised

3

November 21,
2013

R5 and associated elements approved
by FERC for retirement as part of the
Paragraph 81 project (Project 2013-02)

Revised

4

February 6,
2014
August 1, 2014

Adopted by NERC Board of Trustees

Revised

4

FERC issued letter order issued
approving VAR-001-4

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