WECC-0113 FAC-010-2.1 Variance Request to Retire
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
Western Electricity Coordinating Council
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Committee (PCC) concluded that each of the RDs contained in the FAC-010-2.1 should be retired as they are either outdated or redundant to existing NERC Reliability Standards.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 the 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
Table of Contents
Introduction 1
Section Title 1
Subsection Title 11
Supporting Topic Error! Bookmark not defined.
Western Electricity Coordinating Council
WECC-0113 FAC-010-2.1 Variance Request to Retire
Introduction
In April 2003, WECC merged its transmission planning standards with that of the North American Electricity Reliability Corporation (NERC[1]) 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 criteriastandards 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, the 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 the 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-010-2.1 Requirements and RDs is located in Attachment A of this document.
FAC-010-2.1 Analysis for Retirement
The WECC RD associated with the FAC-010-2.1 only affects Requirement R2 (Sections 2.5 and 2.6) of the supporting FAC. Requirement R2 of the 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)-003-2b, System Performance Following Loss of Two or More Bulk Electric System Elements (Category C) (TPL), currently listed by NERC as an inactive reliability standard[4].
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. TPL-001-4 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 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 the 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
Much like the language in 1.1.1, tThis 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
Thise requirement is address in the NERC Standard TPL-001-4, Table 1, Category P7 contingency.
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-012-0[5], 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, TPL-002-0, 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.”
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 the associated definition of Adjacent Transmission Circuits[8] 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 connectedconfigured 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.
Table A /Western Interconnection Average Data
2008-2012 / Circuits on Common Structure / Circuits on Common Right-of-Way Separate Structures / Circuits not on Common ROW or Structure /
Transmission Miles / 8,822 / 14,782 / 51,649
Number of Events / 24 / 22 / 103
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 athe common mode outage of two generating units connected to the same switchyard demonstratemeet the performance requirement of transient, dynamic, and voltage stability. There will be is now duplication upon of Requirement E.1.1.6 with the adoption of TPL-001-4 Requirements 3.5 and 4.5 incorporating Table 1 – Steady State & Stability Performance Extreme Events as follows:
· 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
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.