Download FAC-010-2 1 System Operating Limits Methodology for the Planning

White Paper
Retirement of WECC Regional Variance
FAC-010-2.1 System Operating Limits Methodology for the
Planning Horizon
Reliability Subcommittee
155 North 400 West, Suite 200
Salt Lake City, Utah 84103-1114
WECC-0113 FAC-010-2.1 Variance Request to Retire
Executive Summary
After examination of WECC Regional Differences (RD) contained in NERC Standard FAC-010-2.1, System
Operating Limits Methodology for the Planning Horizon (FAC), the WECC Reliability Subcommittee (RS) acting in
its role as a subcommittee of the WECC Planning Coordination Committee (PCC) concluded that each of the RDs
contained in FAC-010-2.1 should be retired as they are either outdated or redundant to existing NERC Reliability
Standards.
This white paper forms the foundation for a filing with the North American Electricity Reliability Corporation
(NERC) and the Federal Energy Regulatory Commission (FERC) requesting that the RD section of FAC-010-2.1 be
retired in its entirety.
Both of the NERC Reliability Standards FAC-010-2.1, System Operating Limits Methodology for the Planning
Horizon, and FAC-011-2, System Operating Limits Methodology for the Operations Horizon, contain WECC
Regional Differences. The purpose of this white paper is to provide background and justification for complete
retirement of the FAC-010-2.1 RD. A separate white paper addresses the recommended retirement of all RDs in
FAC-011-2.
Implementation Plan
TEXT
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Table of Contents
Introduction...................................................................................................................................... 1
Section Title ...................................................................................................................................... 1
Subsection Title ..................................................................................................................................... 11
Supporting Topic .................................................................................. Error! Bookmark not defined.
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Introduction
In April 2003, WECC merged its transmission planning standards with that of the North American Electricity
Reliability Corporation (NERC1) creating a single document titled NERC/WECC Planning Standards (PS), approved
on April 10, 2003. Noting that in some circumstances WECC’s criteria were more stringent than that of NERC,
WECC adopted the approach that “the more restrictive reliability criteria and guides must be observed.”2
In April 2005, WECC migrated its transmission planning criteria into the WECC Reliability Criteria, at Part I, as
approved in April 2005.
In November 2006, the NERC Board of Trustees approved FAC-010-1, System Operating Limit Methodology for
the Planning Horizon (FAC) that included a WECC Regional Difference (RD) reflecting WECC’s more stringent
planning criteria in affect at the time specific to the Requirements of the FAC.
In June 2008, the Federal Energy Regulatory Commission (FERC) approved version two of the FAC-010 Standard
(later subject to 2.1 errata) with an Effective Date of July 1, 2008.
In the 12 years following approval of the original planning standards, WECC’s planning criteria have continued to
evolve based on current and best practices;3 however, NERC FAC-010-2.1 still reflects the planning criteria of
2003, rendering that RD over a decade old and without updates. In addition to the outdated nature of the FAC
RDs, FERC has approved a number of NERC Standards that now stand in conflict with the RD, creating: 1)
duplicate Requirements, 2) conflicting Requirements, 3) ambiguities of Requirements, and 4) the impossibility of
implementation of Requirements.
In 2014, the WECC Reliability Subcommittee (RS) reviewed FAC-010-2.1 and concluded that the entirety of the
outdated RD should be retired. An analysis of that decision follows. The language from the affected FAC-0102.1 Requirements and RDs is located in Attachment A of this document.
1
2
In 2005 this was the North American Electricity Reliability Council.
WECC NERC/WECC Planning Standards, Page 4, April 10, 2003.
3
WECC Regional Criteria, TPL-(001 thru 004)-WECC-CR, System Performance Criteria, approved by the WECC Board of
Directors (Board) on April 16, 2008; replaced by TPL-001-WECC-CRT-2 (December 1, 2011, new naming convention) and
TPL-001-WECC-CRT-2.1 (errata, July 29, 2013) refines WECC’s planning criteria; WECC Requirements WR1, WR2, WR4 and
WR5 to be retired coincident with the staged Effective Date of NERC TPL-001-4, Transmission System Planning Performance
Requirements.
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FAC-010-2.1 Analysis for Retirement
The WECC RD associated with FAC-010-2.1 only affects Requirement R2 (Sections 2.5 and 2.6) of the supporting
FAC. Requirement R2 of FAC-010-2.1 requires that each Planning Authority’s System Operating Limit (SOL)
Methodology include a requirement that SOLs provide performance at a specified threshold.
Requirement R2.5 requires performance with all Facilities in service and following any of the multiple
Contingencies identified in Reliability Standards TPL-003-0(i), System Performance Following Loss of Two or
More Bulk Electric System Elements (Category C) (TPL), currently listed by NERC as an inactive reliability
standard4.
Requirement R2.6 requires that when determining acceptable response to any of the TPL Contingencies, the
following conditions are allowed: 1) planned or controlled interruption of electric supply to customers, 2) the
planned removal from service if certain generators, and/or 3) the curtailment of contracted Firm electric power
Transfers.
Sub Section 1.1
In Section E. Regional Differences, Subsection 1.1, the WECC RD adds an additional seven criteria to those
established in the underlying NERC Requirement R2.
Text
WECC RD 1.1.1 states:
“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 for only station entrance and exist purposes, and if that do not exceed five towers at each station,
then this condition is an acceptable risk and therefore can be excluded.”
Analysis
At the threshold, the language included at 1.1.1 requiring a mandate to address multiple circuit towers is
redundant to requirements in other NERC standards, and there is no technical justification for the variance.
The underlying Requirement R2 incorporates by reference TPL-003 (an inactive standard) that is due to be
replaced by TPL-001-4, Transmission System Planning Performance Requirements, on December 31, 2015. TPL001-4 requires that the Transmission Planner and Planning Coordinator maintain planning models that contain
certain specifications, many of which are included in Table 1 of that document. Among the modeling criteria
4
Will be replaced by TPL-001-4 (R2 through R6 and R8). The inactive date for TPL-003-0b is 12/31/2015.Please see the
details link for TPL-001-4 for more information. Will be replaced by TPL-001-4 (R2 through R6 and R8). The inactive date for
TPL-003-0b is 12/31/2015. North American Electric Reliability Corporation, Docket RD13-8-000
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specified in Table 1 is Category P7, Multiple Contingency, addressing “the loss of: 1) Any two adjacent (vertically
or horizontally) circuits on common structure, 2) Loss of a bipolar DC line.” Because the RD is addressed in other
NERC standards, it should be deleted from FAC-010-2.1 as it adds no additional reliability margin but does create
the potential for double jeopardy.
In addition to this redundancy, the common stability programs in use today are based upon positive sequence
modeling and do not have the ability to simulate a simultaneous ground fault on different phases of two
different circuits. Further, no reliability benefit is obtained by simulating a single phase-to-ground fault on two
different phases of two transmission circuits nor was the RS able to find where any technical study on the
matter was ever performed. As such, the legacy language is arbitrary and should be retired.
Recommendation
Whereas the language of 1.1.1 is redundant to other NERC standards, creates the potential for double jeopardy,
and is not based on any technical study, the entirety of the language should be retired. Retirement should be
effective as of when?
Text
WECC RD 1.1.2 states:
“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”
Analysis
This requirement is addressed in NERC Standard TPL-001-4, Table 1, Category P4 and P5 contingencies.
Recommendation
Whereas the language of 1.1.2 is redundant to other NERC standards and creates the potential for double
jeopardy, the entirety of the language should be retired.
Text
WECC RD 1.1.3 states:
“1.1.3 Simultaneous permanent loss of both poles of a direct current bipolar Facility without an
alternating current Fault.”
Analysis
This requirement is address in the NERC Standard TPL-001-4, Table 1, Category P7 contingency.
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Recommendation
Whereas the language of 1.1.3 is redundant to other NERC standards and creates the potential for double
jeopardy, the entirety of the language should be retired.
Text
WECC RD 1.1.4 states:
“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.”
Analysis
This requirement is addressed in NERC Reliability Standard PRC-012-05, Special Protection System Review
Procedure, at Requirement R1.3.:
“R1.3. Requirements to demonstrate that the RAS shall be designed so that a single RAS component
failure, when the RAS was intended to operate, does not prevent the interconnected transmission
system from meeting the performance requirements defined in Reliability Standards TPL-001-0, TPL002-0, and TPL-003-0.”
The PRC-012-0 Requirement requires that failure of a single component does not prevent the interconnected
system from meeting required performance in the TPL-related standards. This reliability concern is also address
in NERC Standard TPL-001-4, Table 1, Category P4 and P5 contingencies, which specifies system performance
requirements for stuck breaker and protection system failure.
Recommendation
Whereas the language of 1.1.4 is redundant to other NERC standards and creates the potential for double
jeopardy, the entirety of the language should be retired.
Text
WECC RD 1.1.5 states:
“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.”
5
Although this is a Version Zero document its successor Version 1 is pending regulatory filing and Requirement R1.3 is
virtually unchanged with the exception of a definition change from Special Protection System to Remedial Action Scheme.
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Analysis
Requirement E1.1.5 extends the requirement of NERC Reliability Standard TPL-001-4, Table 1, Category P5
contingency to “two adjacent circuits” on separate structures. This language will be redundant to TPL-001-4
upon adoption of TPL-001-4 Requirements 3.5 and 4.5 incorporating Table 1 – Steady State & Stability
Performance Extreme Events:
 Steady state item 2.b
2. Local area events affecting the Transmission System such as:
a. Loss of a tower line with three or more circuits.
b. Loss of all Transmission lines on a common Right-of-Way.
c. Loss of a switching station or substation (loss of one voltage level plus transformers).
d. Loss of all generating units at a generating station.
e. Loss of a large Load or major Load center.
 Stability item 1
1. With an initial condition of a single generator, Transmission circuit, single pole of a DC line, shunt
device, or transformer forced out of service, apply a 3Ø fault on another single generator,
Transmission circuit, single pole of a different DC line, shunt device, or transformer prior to System
adjustments.
When the RD in FAC-010 was written (2003) there was no action required in the NERC standards for multiple
contingencies in the same rights-of-way. Transmission Planners are now required to conduct simulations of
multiple circuit outages in the same rights-of-way and take action to mitigate if there is Cascading caused by the
occurrence of extreme events. An evaluation of possible actions designed to reduce the likelihood or mitigate
the consequences is required. Therefore, there is duplication of the study efforts contained in FAC-010-2.1
Requirement E.1.1.5.
In addition, Requirement E1.1.5 uses the term “adjacent circuits” but the term is not defined in the NERC
Glossary of Terms Used in Reliability Standards (NERC Glossary). This lack of definition in the NERC Glossary
creates ambiguity in the implementation of the RD.6 Although WECC has made efforts to clarify the ambiguity
through approval of a WECC Regional Criterion TPL-001-WECC-CRT-2, System Performance Criterion (CRT) 7 and
6
WECC recently defined this term in relation to its application for this requirement. WECC’s intention is to apply the
Adjacent Transmission Circuits definition consistently to all standards and criteria when ‘adjacent circuits’ or ‘Adjacent
Transmission Circuits’ are referenced.
7
“Regional Criteria” means reliability requirements developed by a Regional Entity that are necessary to implement, to
augment, or to comply with Reliability Standards, but which are not Reliability Standards. Such Regional Criteria may be
necessary to account for physical differences in the Bulk Power System but are not inconsistent with Reliability Standards
nor do they result in lesser reliability. Such Regional Criteria are not enforceable pursuant to NERC-delegated authorities,
but may be enforced through other available mechanisms. Regional Criteria may include specific acceptable operating or
planning parameters, guides, agreements, protocols or other documents.” NERC Rules of Procedure, Definitions.
There are conflicts and ambiguities between FAC-010-2.1 and the WECC Regional Criterion TPL-001-WECC-CRT-2.1.
Regional Difference Requirement E.1.1.5 of the current standard FAC-010-2.1 only applies to adjacent circuits that are Bulk
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the associated definition of Adjacent Transmission Circuits8 because the CRT only augments the standard, the
CRT is not the definitive authority on how the standard must be implemented. As such the ambiguity would be
eliminated if the language was deleted.9
Finally, at the time the RD was developed, it was believed that the rate of common mode outages of adjacent
circuits on separate structures was similar to that of any two circuits of a multiple circuit tower line (covered by
Category P7). As such, it made sense to apply the same performance criteria to both classes of contingencies.
However, actual performance data for 230kV and above transmission lines in the Western Interconnection
indicate that the average outage rate per 100 miles of line is actually less than one-half the rate for circuits on
common structures as shown in the table below.
The actual outage rate for circuits on common rights-of-way but on separate structures is also less than that for
any two circuits not on a common right-of-way. The reason for these statistical differences is the configuration
of the substation. Adjacent circuits are typically connected into separate bays of a substation, which reduces the
common mode outages of breaker or protection system failures. Therefore, Requirement E1.1.5 can be deleted
without adversely impacting the reliability of the Bulk Electric System.
Table A: Outage Comparison of Circuits on Common ROW and/or Structures when 2 or more circuits
went out of service.
Electric System (BES) elements, is not restricted by voltage levels, and does not exclude circuits that share a common rightof-way. Whereas, TPL-001-WECC-CRT-2.1 Regional Criterion excludes circuits on common right-of-way for less than 3 miles
and circuits less than 300 kV.
8
“Adjacent Transmission Circuits are two transmission circuits with separation between their center lines less
than 250 feet at the point of separation with no Bulk Electric System circuit between them.
Transmission circuits that cross, but are otherwise separated by 250 feet or more between their centerlines, are
not Adjacent Transmission Circuits.” WECC Glossary for Terms Developed Using the WECC Reliability Standards
Development Procedures
9
In WECC Regional Criterion TPL-001-WECC-CRT-2, System Performance Criterion (CRT), the adjacent circuit application is
limited to the following:
 Applies to circuits 300 kV and higher.
 Does not apply to Adjacent Transmission Circuits that share a common right-of-way for a total of three miles or
less, including – but not limited to – substation entrances, pinch points, and river crossings.
 Applies only to effects on facilities external to a Transmission Planner area.
Thus, FAC-010 regional differences create confusion and ambiguity.
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Table A
Circuits on
Circuits on Common
Common RightStructure
of-Way Separate
Structures
8,822
14,782
22
24
Western
Interconnection
Average Data
2008-2012
Transmission Miles
Circuits not on Common ROW or
Structure
51,649
103
Number of Events
No. of Outages/ 100
miles of line
0.271
0.147
0.207
The above table is based upon most recent six years of historical data collected by WECC. WECC began collecting
right-of-way outage data in 2008.
Recommendation
Whereas the language of 1.1.5 is redundant to other NERC standards, creates the potential for double jeopardy,
creates ambiguity in the implementation of the standard, and is not needed for reliability, the entirety of the
language should be retired.
Text
WECC RD 1.1.6 states:
“1.1.6 A common mode outage of two generating units connected to the same switchyard, not
otherwise addressed by FAC-010.”
Analysis
Requirement E1.1.6 requires that a common mode outage of two generating units connected to the same
switchyard demonstrate transient, dynamic, and voltage stability. There will be duplication upon adoption of
TPL-001-4 Requirements 3.5 and 4.5 incorporating Table 1 – Steady State & Stability Performance Extreme
Events:
 Steady-state Item 1
1. Loss of a single generator, Transmission Circuit, single pole of a DC Line, shunt device, or
transformer forced out of service followed by another single generator, Transmission Circuit, single
pole of a different DC Line, shunt device, or transformer forced out of service prior to System
adjustments.
 Steady-state Item 2.d
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2. Local area events affecting the Transmission System such as:
a. Loss of a tower line with three or more circuits.
b. Loss of all Transmission lines on a common Right-of-Way.
c. Loss of a switching station or substation (loss of one voltage level plus transformers).
d. Loss of all generating units at a generating station.
e. Loss of a large Load or major Load center.
 Stability Item 1
1. With an initial condition of a single generator, Transmission circuit, single pole of a DC line, shunt
device, or transformer forced out of service, apply a 3Ø fault on another single generator,
Transmission circuit, single pole of a different DC line, shunt device, or transformer prior to System
adjustments.
When the WECC RD in FAC-010 was written (2003) there was no action required in the NERC transmission
planning standards for loss of two generating units at a generating station resulting from contingencies beyond
those specified in Table 1. Transmission Planners are now required to conduct simulations of loss of multiple
generators at a generating station and take action to mitigate if there is Cascading caused by the occurrence of
this event. An evaluation of possible actions designed to reduce the likelihood or mitigate the consequences is
required. Therefore, there is duplication of the study efforts contained in FAC-010-2.1 Requirement E.1.1.6.
Therefore, Requirement E1.1.6 can be deleted without adversely impacting the reliability of the Bulk Electric
System.
Recommendation
Whereas the language of 1.1.6 is redundant to other NERC standards and creates the potential for double
jeopardy, the entirety of the language should be retired.
Text
WECC RD 1.1.7 states:
“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.”
Analysis
This requirement is addressed in NERC Reliability Standard TPL-001-4, Table 1, Categories P4 and P5
contingencies. Having a regional difference duplicating the TPL-001-4 Reliability Standard is redundant and
unnecessary.
Recommendation
Whereas the language of 1.1.7 is redundant to other NERC standards and creates the potential for double
jeopardy, the entirety of the language should be retired.
Sub Section 1.2
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In Section E. Regional Differences, Subsection 1.2, the WECC RD requires that SOLs 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 seven specific performance requirements.
Recommendation
Each of the seven specific requirements within WECC RD 1.2 are duplicated in the FAC-010-2.1 Requirements
R2.5 and R2.6. As such the entire section should be retired because it is redundant to FAC Requirements R2.5
and R2.6.
FAC / WECC RD Cross-reference Table
FAC Requirement
Requirement 2.5
R2.5 Starting with all Facilities in service and
following any of the multiple Contingencies
identified in Reliability Standard TPL-003 the
system shall demonstrate:
R2.5 Transient, dynamic and voltage stability
voltage and stability limits
R2.5 All Facilities shall be operating within their
Facility Ratings and within their thermal,
voltage and stability limits
R2.5 Cascading or uncontrolled separation shall
not occur.
WECC RD
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:
1.2.4 The system demonstrates transient, dynamic
and voltage stability.
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.
Requirement R2.6
R2.6.1. In determining the system’s
response…the following shall be acceptable:
1.2.5
Depending on system design and expected
system impacts [the following may be
necessary and are acceptable]
R2.6.1. Planned or controlled interruption of
electric supply to customers (load shedding)
1.2.5
The controlled interruption of electric supply
to customers (load shedding)
R2.6.1. The planned removal from service of
certain generators,
1.2.5
The planned removal from service of certain
generators
R2.6.1 The curtailment of contracted Firm
(non-recallable reserved) electric power
1.2.5 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
R2.3.2. System reconfiguration through manual
or automatic control or protection actions.
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R2.4. 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.
reconfiguration is permitted through manual
or automatic control or protection actions.
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
Text
WECC RD E1.3 states:
“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.”
Analysis
Please refer to the FAC / WECC RD Cross-reference Table that illustrates redundancy of requirements.
Recommendation
This requirement is addressed in Requirements R2.5 and R2.6 of NERC Reliability Standard FAC-010-2.1. Having
this regional difference duplicates the same system conditions as portions of FAC-010-2.1. Therefore, it is
redundant and unnecessary.
Text
WECC RD E1.4 states:
“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.”
Analysis
The WECC RD applies to “the Western Interconnection” and is not applicable to any specific entity identified in
the NERC Reliability Functional Model. Further, it does not add any system performance requirement in addition
to the existing requirements in NERC Reliability Standards TPL-001-4.
Recommendation
Because the WECC RD Section 1.4 does not apply to a specified entity in the NERC Functional Model it cannot be
enforced and should be retired.
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Attachment A NERC FAC-010-2.1 Affected Requirements and Regional Differences
The FAC-010-2.1 Standard has five Requirements. The associated WECC variance only applies to Requirement 2,
specifically Requirement R2.5 and R2.6. This section contains the complete text of Requirement R2, Sections 5
and 6 and the associated RD that is recommended for retirement.
Requirement R2, Sections R5 and R6
R2.
The Planning Authority’s SOL Methodology shall include a requirement that SOLs provide BES
performance consistent with the following:
R2.5.
Starting with all Facilities in service and following any of the multiple Contingencies identified in
Reliability Standard TPL-003 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.
R2.6.
In determining the system’s response to any of the multiple Contingencies, identified in
Reliability Standard TPL-003, in addition to the actions identified in R2.3.1 and R2.3.2, the
following shall be acceptable:
R2.6.1. Planned or controlled interruption of electric supply to customers (load shedding), the
planned removal from service of certain generators, and/or the curtailment of
contracted Firm (non-recallable reserved) electric power Transfers.
Regional Differences (The entirety of this section is proposed for retirement.)
E. Regional Differences
1. The following Interconnection-wide Regional Difference shall be applicable in the Western
Interconnection:
1.1
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As governed by the requirements of R2.5 and R2.6, 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 for only station entrance and exist purposes, and if that
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 bustie breakers addressed in E1.1.7
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1.2.
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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-010.
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.
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.
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.
E S T E R N
E
L E C T R I C I T Y
C
O O R D I N A T I N G
C
O U N C I L
WECC-0113 FAC-010-2.1 Variance Request to Retire
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
1.4.
W
Cascading does not occur.
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.
E S T E R N
E
L E C T R I C I T Y
C
O O R D I N A T I N G
C
O U N C I L