Reliability Standards-FAC-011-2

Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

A. Introduction
1.

Title:

System Operating Limits Methodology for the Operations Horizon

2.

Number:

FAC-011-2

3.

Purpose:
To ensure that System Operating Limits (SOLs) used in the reliable operation of
the Bulk Electric System (BES) are determined based on an established methodology or
methodologies.

4.

Applicability
4.1. Reliability Coordinator

5.

Effective Date:

April 29, 2009

B. Requirements
R1. The Reliability Coordinator shall have a documented methodology for use in developing SOLs
(SOL Methodology) within its Reliability Coordinator Area. This SOL Methodology shall:

R2.

R1.1.

Be applicable for developing SOLs used in the operations horizon.

R1.2.

State that SOLs shall not exceed associated Facility Ratings.

R1.3.

Include a description of how to identify the subset of SOLs that qualify as IROLs.

The Reliability Coordinator’s SOL Methodology shall include a requirement that SOLs
provide BES performance consistent with the following:
R2.1.

In the pre-contingency state, the BES shall demonstrate transient, dynamic and
voltage stability; all Facilities shall be within their Facility Ratings and within their
thermal, voltage and stability limits. In the determination of SOLs, the BES condition
used shall reflect current or expected system conditions and shall reflect changes to
system topology such as Facility outages.

R2.2.

Following the single Contingencies 1 identified in Requirement 2.2.1 through
Requirement 2.2.3, the system shall demonstrate transient, dynamic and voltage
stability; all Facilities shall be operating within their Facility Ratings and within their
thermal, voltage and stability limits; and Cascading or uncontrolled separation shall
not occur.
R2.2.1. Single line to ground or 3-phase Fault (whichever is more severe), with
Normal Clearing, on any Faulted generator, line, transformer, or shunt
device.
R2.2.2. Loss of any generator, line, transformer, or shunt device without a Fault.
R2.2.3. Single pole block, with Normal Clearing, in a monopolar or bipolar high
voltage direct current system.

R2.3.

In determining the system’s response to a single Contingency, the following shall be
acceptable:
R2.3.1. Planned or controlled interruption of electric supply to radial customers or
some local network customers connected to or supplied by the Faulted
Facility or by the affected area.

1

The Contingencies identified in FAC-011 R2.2.1 through R2.2.3 are the minimum contingencies that must be
studied but are not necessarily the only Contingencies that should be studied.

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

R2.3.2. Interruption of other network customers, (a) only if the system has already
been adjusted, or is being adjusted, following at least one prior outage, or
(b) if the real-time operating conditions are more adverse than anticipated in
the corresponding studies
R2.3.3. System reconfiguration through manual or automatic control or protection
actions.
R2.4.

R3.

To prepare for the next Contingency, system adjustments may be made, including
changes to generation, uses of the transmission system, and the transmission system
topology.

The Reliability Coordinator’s methodology for determining SOLs, shall include, as a
minimum, a description of the following, along with any reliability margins applied for each:
R3.1.

Study model (must include at least the entire Reliability Coordinator Area as well as
the critical modeling details from other Reliability Coordinator Areas that would
impact the Facility or Facilities under study.)

R3.2.

Selection of applicable Contingencies

R3.3.

A process for determining which of the stability limits associated with the list of
multiple contingencies (provided by the Planning Authority in accordance with FAC014 Requirement 6) are applicable for use in the operating horizon given the actual or
expected system conditions.
R3.3.1. This process shall address the need to modify these limits, to modify the list
of limits, and to modify the list of associated multiple contingencies.

R4.

R5.

R3.4.

Level of detail of system models used to determine SOLs.

R3.5.

Allowed uses of Special Protection Systems or Remedial Action Plans.

R3.6.

Anticipated transmission system configuration, generation dispatch and Load level

R3.7.

Criteria for determining when violating a SOL qualifies as an Interconnection
Reliability Operating Limit (IROL) and criteria for developing any associated IROL
Tv.

The Reliability Coordinator shall issue its SOL Methodology and any changes to that
methodology, prior to the effectiveness of the Methodology or of a change to the Methodology,
to all of the following:
R4.1.

Each adjacent Reliability Coordinator and each Reliability Coordinator that indicated
it has a reliability-related need for the methodology.

R4.2.

Each Planning Authority and Transmission Planner that models any portion of the
Reliability Coordinator’s Reliability Coordinator Area.

R4.3.

Each Transmission Operator that operates in the Reliability Coordinator Area.

If a recipient of the SOL Methodology provides documented technical comments on the
methodology, the Reliability Coordinator shall provide a documented response to that recipient
within 45 calendar days of receipt of those comments. The response shall indicate whether a
change will be made to the SOL Methodology and, if no change will be made to that SOL
Methodology, the reason why. (Retirement approved by FERC effective January 21, 2014.)

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

C. Measures
M1. The Reliability Coordinator’s SOL Methodology shall address all of the items listed in
Requirement 1 through Requirement 3.
M2. The Reliability Coordinator shall have evidence it issued its SOL Methodology, and any
changes to that methodology, including the date they were issued, in accordance with
Requirement 4.
M3. If the recipient of the SOL Methodology provides documented comments on its technical
review of that SOL methodology, the Reliability Coordinator that distributed that SOL
Methodology shall have evidence that it provided a written response to that commenter within
45 calendar days of receipt of those comments in accordance with Requirement 5. (Retirement
approved by FERC effective January 21, 2014.)
D. Compliance
1.

Compliance Monitoring Process
1.1. Compliance Monitoring Responsibility
Regional Reliability Organization
1.2. Compliance Monitoring Period and Reset Time Frame
Each Reliability Coordinator shall self-certify its compliance to the Compliance Monitor
at least once every three years. New Reliability Authorities shall demonstrate
compliance through an on-site audit conducted by the Compliance Monitor within the
first year that it commences operation. The Compliance Monitor shall also conduct an onsite audit once every nine years and an investigation upon complaint to assess
performance.
The Performance-Reset Period shall be twelve months from the last non-compliance.
1.3. Data Retention
The Reliability Coordinator shall keep all superseded portions to its SOL Methodology
for 12 months beyond the date of the change in that methodology and shall keep all
documented comments on its SOL Methodology and associated responses for three years.
In addition, entities found non-compliant shall keep information related to the noncompliance until found compliant. (Deleted text retired-Retirement approved by FERC
effective January 21, 2014.)
The Compliance Monitor shall keep the last audit and all subsequent compliance records.
1.4. Additional Compliance Information
The Reliability Coordinator shall make the following available for inspection during an
on-site audit by the Compliance Monitor or within 15 business days of a request as part
of an investigation upon complaint:
1.4.1

SOL Methodology.

1.4.2

Documented comments provided by a recipient of the SOL Methodology on its
technical review of a SOL Methodology, and the associated responses.
(Retirement approved by FERC effective January 21, 2014.)

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

2.

1.4.3

Superseded portions of its SOL Methodology that had been made within the past
12 months.

1.4.4

Evidence that the SOL Methodology and any changes to the methodology that
occurred within the past 12 months were issued to all required entities.

Levels of Non-Compliance for Western Interconnection: (To be replaced with VSLs once
developed and approved by WECC)
2.1. Level 1:
There shall be a level one non-compliance if either of the following
conditions exists:
2.1.1

The SOL Methodology did not include a statement indicating that Facility
Ratings shall not be exceeded.

2.1.2

No evidence of responses to a recipient’s comments on the SOL Methodology
(Retirement approved by FERC effective January 21, 2014.)

2.2. Level 2:
The SOL Methodology did not include a requirement to address all of the
elements in R3.1, R3.2, R3.4 through R3.7 and E1.
2.3. Level 3:
There shall be a level three non-compliance if any of the following
conditions exists:
2.3.1

The SOL Methodology did not include a statement indicating that Facility
Ratings shall not be exceeded and the methodology did not include evaluation of
system response to one of the three types of single Contingencies identified in
R2.2.

2.3.2

The SOL Methodology did not include a statement indicating that Facility
Ratings shall not be exceeded and the methodology did not include evaluation of
system response to two of the seven types of multiple Contingencies identified in
E1.1.

2.3.3

The System Operating Limits Methodology did not include a statement
indicating that Facility Ratings shall not be exceeded and the methodology did
not address two of the six required topics in R3.1, R3.2, R3.4 through R3.7.

2.4. Level 4:
with R4.

The SOL Methodology was not issued to all required entities in accordance

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

3.

Violation Severity Levels:

Requirement

Lower

Moderate

High

Severe

R1

Not applicable.

The Reliability Coordinator has a
documented SOL Methodology
for use in developing SOLs
within its Reliability Coordinator
Area, but it does not address
R1.2

The Reliability Coordinator has a
documented SOL Methodology
for use in developing SOLs
within its Reliability Coordinator
Area, but it does not address
R1.3.

The Reliability Coordinator has a
documented SOL Methodology
for use in developing SOLs
within its Reliability Coordinator
Area, but it does not address
R1.1.
OR
The Reliability Coordinator has
no documented SOL
Methodology for use in
developing SOLs within its
Reliability Coordinator Area.

R2

The Reliability Coordinator‘s
SOL Methodology requires that
SOLs are set to meet BES
performance following single
contingencies, but does not
require that SOLs are set to
meet BES performance in the
pre-contingency state. (R2.1)

Not applicable.

The Reliability Coordinator‘s
SOL Methodology requires that
SOLs are set to meet BES
performance in the precontingency state, but does not
require that SOLs are set to
meet BES performance following
single contingencies. (R2.2 –
R2.4)

The Reliability Coordinator’s
SOL Methodology does not
require that SOLs are set to
meet BES performance in the
pre-contingency state and does
not require that SOLs are set to
meet BES performance following
single contingencies. (R2.1
through R2.4)

R3

The Reliability Coordinator’s
SOL Methodology includes a
description for all but one of the
following: R3.1 through R3.7.

The Reliability Coordinator’s
SOL Methodology includes a
description for all but two of the
following: R3.1 through R3.7.

The Reliability Coordinator’s
SOL Methodology includes a
description for all but three of the
following: R3.1 through R3.7.

The Reliability Coordinator’s
SOL Methodology is missing a
description of four or more of the
following: R3.1 through R3.7.

R3.6

N/A

N/A

N/A

N/A

R4

The Reliability Coordinator failed
to issue its SOL Methodology
and/or one or more changes to
that methodology to one of the
required entities specified in
R4.1, R4.2, and R4.3.

The Reliability Coordinator failed
to issue its SOL Methodology
and/or one or more changes to
that methodology to two of the
required entities specified in
R4.1, R4.2, and R4.3.

The Reliability Coordinator failed
to issue its SOL Methodology
and/or one or more changes to
that methodology to three of the
required entities specified in
R4.1, R4.2, and R4.3.

The Reliability Coordinator failed
to issue its SOL Methodology
and/or one or more changes to
that methodology to four or more
of the required entities specified
in R4.1, R4.2, and R4.3

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

Requirement

R5
(Retirement
approved by FERC
effective January
21, 2014.)

Lower

Moderate

High

Severe

OR
For a change in methodology,
the changed methodology was
provided to one or more of the
required entities before the
effectiveness of the change, but
was provided to all the required
entities no more than 10
calendar days after the
effectiveness of the change.

OR
For a change in methodology,
the changed methodology was
provided to one or more of the
required entities more than 10
calendar days after the
effectiveness of the change, but
less than or equal to 20 days
after the effectiveness of the
change.

OR
For a change in methodology,
the changed methodology was
provided to one or more of
required entities more than 20
calendar days after the
effectiveness of the change, but
less than or equal to30 days
after the effectiveness of the
change.

OR
For a change in methodology,
the changed methodology was
provided to one or more of the
required entities more than30
calendar days after the
effectiveness of the change.

The Reliability Coordinator
received documented technical
comments on its SOL
Methodology and provided a
complete response in a time
period that was longer than 45
calendar days but less than 60
calendar days.

The Reliability Coordinator
received documented technical
comments on its SOL
Methodology and provided a
complete response in a time
period that was 60 calendar days
or longer but less than 75
calendar days.

The Reliability Coordinator
received documented technical
comments on its SOL
Methodology and provided a
complete response in a time
period that was 75 calendar days
or longer but less than 90
calendar days.
OR
The Reliability Coordinator’s
response to documented
technical comments on its SOL
Methodology indicated that a
change will not be made, but did
not include an explanation of
why the change will not be
made.

The Reliability Coordinator
received documented technical
comments on its SOL
Methodology and provided a
complete response in a time
period that was 90 calendar days
or longer.
OR
The Reliability Coordinator’s
response to documented
technical comments on its SOL
Methodology did not indicate
whether a change will be made
to the SOL Methodology.

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

Regional Differences
1.

The following Interconnection-wide Regional Difference shall be applicable in the Western
Interconnection:
1.1. As governed by the requirements of R3.3, starting with all Facilities in service, shall
require the evaluation of the following multiple Facility Contingencies when establishing
SOLs:
1.1.1

Simultaneous permanent phase to ground Faults on different phases of each of
two adjacent transmission circuits on a multiple circuit tower, with Normal
Clearing. If multiple circuit towers are used only for station entrance and exit
purposes, and if they do not exceed five towers at each station, then this
condition is an acceptable risk and therefore can be excluded.

1.1.2

A permanent phase to ground Fault on any generator, transmission circuit,
transformer, or bus section with Delayed Fault Clearing except for bus
sectionalizing breakers or bus-tie breakers addressed in E1.1.7

1.1.3

Simultaneous permanent loss of both poles of a direct current bipolar Facility
without an alternating current Fault.

1.1.4

The failure of a circuit breaker associated with a Special Protection System to
operate when required following: the loss of any element without a Fault; or a
permanent phase to ground Fault, with Normal Clearing, on any transmission
circuit, transformer or bus section.

1.1.5

A non-three phase Fault with Normal Clearing on common mode Contingency of
two adjacent circuits on separate towers unless the event frequency is determined
to be less than one in thirty years.

1.1.6

A common mode outage of two generating units connected to the same
switchyard, not otherwise addressed by FAC-011.

1.1.7

The loss of multiple bus sections as a result of failure or delayed clearing of a bus
tie or bus sectionalizing breaker to clear a permanent Phase to Ground Fault.

1.2. SOLs shall be established such that for multiple Facility Contingencies in E1.1.1 through
E1.1.5 operation within the SOL shall provide system performance consistent with the
following:
1.2.1

All Facilities are operating within their applicable Post-Contingency thermal,
frequency and voltage limits.

1.2.2

Cascading does not occur.

1.2.3

Uncontrolled separation of the system does not occur.

1.2.4

The system demonstrates transient, dynamic and voltage stability.

1.2.5

Depending on system design and expected system impacts, the controlled
interruption of electric supply to customers (load shedding), the planned removal
from service of certain generators, and/or the curtailment of contracted firm (nonrecallable reserved) electric power transfers may be necessary to maintain the
overall security of the interconnected transmission systems.

1.2.6

Interruption of firm transfer, Load or system reconfiguration is permitted through
manual or automatic control or protection actions.

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Standard FAC-011-2 — System Operating Limits Methodology for the Operations Horizon

1.2.7

To prepare for the next Contingency, system adjustments are permitted, including
changes to generation, Load and the transmission system topology when
determining limits.

1.3. SOLs shall be established such that for multiple Facility Contingencies in E1.1.6 through
E1.1.7 operation within the SOL shall provide system performance consistent with the
following with respect to impacts on other systems:
1.3.1

Cascading does not occur.

1.4. The Western Interconnection may make changes (performance category adjustments) to
the Contingencies required to be studied and/or the required responses to Contingencies
for specific facilities based on actual system performance and robust design. Such
changes will apply in determining SOLs.
Version History
Version
1

Date

Action

Change Tracking

November 1,
2006

Adopted by Board of Trustees

New

Changed the effective date to October 1,
2008
Changed “Cascading Outage” to
“Cascading”
Replaced Levels of Non-compliance with
Violation Severity Levels
Corrected footnote 1 to reference FAC-011
rather than FAC-010

Revised

2

2

June 24, 2008

Adopted by Board of Trustees: FERC Order
705

Revised

2

January 22,
2010

Updated effective date and footer to April
29, 2009 based on the March 20, 2009
FERC Order

Update

2

February 7,
2013

R5 and associated elements approved by
NERC Board of Trustees for retirement as
part of the Paragraph 81 project (Project
2013-02) pending applicable regulatory
approval.

2

November 21,
2013

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

2

February 24,
2014

Updated VSLs based on June 24, 2013
approval.

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