WECC-0111 TOP-007-WECC-1a, System Operating Limits

Drafting Team

MEMO

Date:{TBA}

To:WECC Ballot Pool for Retirement

TOP-007-WECC-1a (TOP), System Operating Limits

Subject:Supporting Evidence for Retirement of the TOP

Recommendation

The WECC-0111 TOP Drafting Team (DT) is recommending retirement of the TOP as the substance of the TOP is redundant to peripheral NERC Standards.

Background

On April 21, 2011, in Order 752 FERC approved the TOP as a permanent replacement for TOP-SDT-007-0, the TOP’s “Version Zero” predecessor. The Effective Date of the TOP was set as July 1, 2011.

The Purpose of the TOP is to ensure that if actual flows on specified WECC paths are exceeded, the associated schedules and flows do not exceed a specified duration. Specific paths are those identified in the “Major WECC Transfer Paths in the Bulk Electric System” (Table), an attachment to the TOP. The Table is incorporated by reference into the TOP.

To meet this goal, the TOP consists of two Requirements, both of which are applicable to the Transmission Operator of those paths specified in the Table. Requirement R1 requires the TOP to take immediate action to reduce the actual power flow across the path such that at no time shall the power flow for the path exceed the System Operating Limit (SOL) for more than 30 minutes. Requirement R2 states that the TOP shall not have the Net Scheduled Interchange for power flow over an interconnection or specified path above the path’s SOL during specified conditions.

After reviewing existing NERC Standards, the DT concluded that the above two Requirements duplicate requirements contained in other NERC Standards, supported by Reliability Coordinator procedures. As such, the DT is recommending full retirement of the TOP. The following crosswalk illustrates the duplication.

Respectfully,

Mr. Vic Howell

Chair, WECC-0111 TOP DT

Crosswalk of Duplicated Requirements

TOP-007-WECC-1 Requirement / Covered Elsewhere
R1. When the actual power flow exceeds an SOL for a Transmission path, the Transmission Operators shall take immediate action to reduce the actual power flow across the path such that at no time shall the power flow for the Transmission path exceed the SOL for more than 30 minutes. [Violation Risk Factor: High] [Time Horizon: Real-time Operations] / FAC-014-2
Establish and Communicate System Operating Limits
R2. The Transmission Operator shall establish SOLs (as directed by its Reliability Coordinator) for its portion of the Reliability Coordinator Area that are consistent with its Reliability Coordinator’s SOL Methodology.
R5.2. The Transmission Operator shall provide any SOLs it developed to its Reliability Coordinator and to the Transmission Service Providers that share its portion of the Reliability Coordinator Area.
Peak Reliability Coordinator System Operating Limit (SOL) Methodology Version 7.0
  • Item #2, page 6 – “If any of the acceptable pre- or post-contingency system performance criteria stipulated in this Methodology are not being met, an SOL is being exceeded.”
  • Item #3, page 6 – Pre-Contingency : Acceptable system performance for the pre-contingency state in the Operations Horizon is characterized by the following [NERC Standard FAC-011-2 R2.1]:
  1. The BES shall demonstrate transient, dynamic and voltage stability.
  2. All Facilities shall be within their continuous Facility Ratings and thermal limits (Refer to illustration in Appendix II).
  3. All Facilities shall be within their pre-contingency voltage limits.
  4. All Facilities shall be within their stability limits.
  • Item #4, page 7 – Post-Contingency [SCs]: Acceptable system performance for the post-contingency state for Single Contingencies (SC) in the Operations Horizon is characterized by the following (NERC Standard FAC-011-2 R2.2):
  1. The BES shall demonstrate transient, dynamic and voltage stability.
  2. All Facilities shall be within their applicable short-term Facility Ratings and thermal limits. (Refer to illustration in Appendix II).
  3. All Facilities shall be within their post-contingency voltage limits.
  4. All Facilities shall be within their stability limits.
  5. Cascading or uncontrolled separation shall not occur.
  • Item #8, page 8 – Conditions that expose the system to unacceptable BES performance cannot be allowed to continue indefinitely. As such, when the system is experiencing unacceptable pre- or post-contingency performance, the system must be adjusted as soon as practicable to prepare for the next Contingency.
  • Item #9, page 9 – When system studies conducted throughout the Operations Horizon (including Real-time Assessments) indicate that any of the acceptable post-contingency system performance criteria are not being met, the TOP shall take pre-contingency actions to achieve acceptable performance. These actions may include, at a minimum, the following: [NERC Standard FAC-011-2 R2.4]
  1. Commit and re-dispatch generation.
  2. Make adjustments to the uses of the transmission system (e.g., schedule curtailments/adjustments).
  3. Make changes to system topology.
  • Item #47, page 18 – TOPs and the RC shall identify the subset of SOLs that qualify as IROLs consistent with this SOL Methodology. When a TOP identifies an SOL that qualifies as an IROL, the TOP shall communicate the results of its analysis with impacted TOPs and the Peak RC. The Peak RC shall make the final determination whether the identified SOL shall be declared an actual IROL.
  • Item #48. Page 18 – SOLs qualify as IROLs when impact containment cannot be demonstrated as described in the ‘Impact Containment and IROL Load Impact’ section below or when studies indicate that instability, Cascading, or uncontrolled separation may occur resulting in uncontrolled interruption of load equal to or greater than 1000 MW.
IROL-009-1, Reliability Coordinator Actions to Operate Within IROLs
R3. When an assessment of actual or expected system conditions predicts that an IROL in its Reliability Coordinator Area will be exceeded, the Reliability Coordinator shall implement one or more Operating Processes, Procedures or Plans (not limited to the Operating Processes, Procedures, or Plans developed for Requirements R1) to prevent exceeding that IROL. (Violation Risk Factor: High) (Time Horizon: Real-time Operations)
R4. When actual system conditions show that there is an instance of exceeding an IROL in its Reliability Coordinator Area, the Reliability Coordinator shall, without delay, act or direct others to act to mitigate the magnitude and duration of the instance of exceeding that IROL within the IROL’s Tv. (Violation Risk Factor: High ) (Time Horizon: Realtime Operations)
PRC-004-WECC-1, Protection System and Remedial Action Scheme Misoperation
R2.3. If the Protection System or RAS has a Security-Based or Dependability-Based
Misoperation and a FEPS and FERAS is not in service to ensure BES reliability, Transmission Owners or Generator Owners shall repair and place back in service within 22 hours the Protection System or RAS that misoperated. If this cannot be done, then Transmission Owners and Generator Owners shall perform the following. [Violation Risk Factor: High] [Time Horizon: Same-day Operations]
R2.3.1. When a FEPS is not available, the Transmission Owners shall remove the associated Element from service.
R2.3.2. When FERAS is not available, then:
2.3.2.1. The Generator Owners shall adjust generation to a reliable operating level, or
2.3.2.2. Transmission Operators shall adjust the SOL and operate the facilities within established limits.
TOP-004-2
Transmission Operations
R1. Each Transmission Operator shall operate within the Interconnection Reliability Operating Limits (IROLs) and System Operating Limits (SOLs).
R4. If a Transmission Operator enters an unknown operating state (i.e. any state for which valid operating limits have not been determined), it will be considered to be in an emergency and shall restore operations to respect proven reliable power system limits within 30 minutes.
R5. Each Transmission Operator shall make every effort to remain connected to the Interconnection. If the Transmission Operator determines that by remaining interconnected, it is in imminent danger of violating an IROL or SOL, the Transmission Operator may take such actions, as it deems necessary, to protect its area.
R6. Transmission Operators, individually and jointly with other Transmission Operators, shall develop, maintain, and implement formal policies and procedures to provide for transmission reliability. These policies and procedures shall address the execution and coordination of activities that impact inter- and intra-Regional reliability, including:
R6.1. Monitoring and controlling voltage levels and real and reactive power flows.
R6.2. Switching transmission elements.
R6.3. Planned outages of transmission elements.
R6.4. Responding to IROL and SOL violations.
TOP-007-0
Reporting System Operating Limit (SOL) and Interconnection reliability Operating Limit (IROL) Violations
R1. A Transmission Operator shall inform its Reliability Coordinator when an IROL or SOL has been exceeded and the actions being taken to return the system to within limits.
R2. Following a Contingency or other event that results in an IROL violation, the Transmission Operator shall return its transmission system to within IROL as soon as possible, but not longer than 30 minutes.
R3. A Transmission Operator shall take all appropriate actions up to and including shedding firm load, or directing the shedding of firm load, in order to comply with Requirement R2.
R4. The Reliability Coordinator shall evaluate actions taken to address an IROL or SOL violation and, if the actions taken are not appropriate or sufficient, direct actions required to return the system to within limits.
TOP-008-1
Response to Transmission Limit Violations
R1. The Transmission Operator experiencing or contributing to an IROL or SOL violation shall take immediate steps to relieve the condition, which may include shedding firm load.
R2. Each Transmission Operator shall operate to prevent the likelihood that a disturbance, action, or inaction will result in an IROL or SOL violation in its area or another area of the Interconnection. In instances where there is a difference in derived operating limits, the Transmission Operator shall always operate the Bulk Electric System to the most limiting Parameter.
VAR-001-2b
Generator Operation for Maintaining Network Voltage Schedules
R10.Each Transmission Operator shall correct IROL or SOL violations resulting from reactive resource deficiencies (IROL violations must be corrected within 30 minutes) and complete the required IROL or SOL violation reporting.
R2. The Transmission Operator shall not have the Net Scheduled Interchange for power flow over an interconnection or Transmission path above the path’s SOL when the Transmission Operator implements its real-time schedules for the next hour. For paths internal to a
Transmission Operator Area that are not scheduled, this requirement does not apply. [Violation Risk Factor: Medium] [Time Horizon: Real-time Operations]
R2.1. If the path SOL decreases within 20 minutes before the start of the hour, the Transmission Operator shall adjust the Net Scheduled Interchange within 30 minutes to the new SOL value. Net Scheduled Interchange exceeding the new SOL during this 30-minute period will not be a violation of R2. / At the threshold, if retained the Applicable entitiy assigned to Requirement R2 of the TOP must be reassigned as the assigned tasks do not match those assigned to the Transmission Operator under the NERC Functional Model (Model). The TOP, Requirement R2 assigns to the Transmission Operator responsibility for Net Scheduled Interchange (NSI) of power flow. (NSI is the algebraic sum of all Interchange Schedules with each Adjacent balancing Authority.) Under the Model, interchange is the purview of multiple entities but not the Transmission Operator.
That said, the DT maintains that the Requirement should be retired in its entirety.
INT-006-4 (Enforcement Date: October 1, 2014)
Evaluation of Interchange Transactions
[TEXT – USE THE VERSION 4 TO ARGUE THE CASE.]
Must counter:
  • No NSI above the SOL when TOP implements real-time schedule for next hour
  • R2.1

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