MOD-008-1: TRM Calculation Methodology

To promote the consistent and reliable calculation, verification, preservation, and use of Transmission Reliability Margin (TRM) to support analysis and system operations.

Transmission Operators that maintain TRM.

Proposed Effective Date
First day of the first calendar quarter that is twelve months beyond the date this standard is approved by applicable regulatory authorities, or in those jurisdictions where regulatory approval is not required, the standard becomes effective on the first day of the first calendar quarter that is twelvemonths beyond the date this standard is approved by the NERC Board of Trustees.

R1. Each Transmission Operator shall prepare and keep current a TRM Implementation Document (TRMID) that includes, as a minimum, the following information: [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

R1.1. Identification of (on each ofits respective ATC Paths or Flowgates) each of the following components of uncertainty if used in establishing TRM, and a description of how that component isused to establish a TRM value:

    • Aggregate Load forecast.
    • Load distribution uncertainty.
    • Forecast uncertainty in Transmission system topology (including, but not limited to, forced or unplanned outages and maintenance outages).
    • Allowances for parallel path (loop flow) impacts.
    • Allowances for simultaneous path interactions.
    • Variations in generation dispatch (including, but not limited to, forced or unplanned outages, maintenance outages and location of future generation).
    • Short-term System Operator response (Operating Reserve actions ).
    • Reserve sharing requirements.
    • Inertial response and frequency bias.

R1.2. The description of the method used toallocate TRM across ATC Paths or Flowgates.

R1.3. The identification of the TRM calculation used for the following time periods:

R1.3.1. Same day and real-time.

R1.3.2. Day-ahead and pre-schedule.

R1.3.3. Beyond day-ahead and pre-schedule, up to thirteen months ahead.

R2. Each Transmission Operator shall only use the components of uncertainty from R1.1 to establish TRM, and shall not include any of the components of Capacity Benefit Margin (CBM). Transmission capacity set aside for reserve sharing agreements can be included in TRM. [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

R3. Each Transmission Operator shall make available its TRMID, and if requested, underlying documentation (if any) used to determine TRM, in the format used by the Transmission Operator, to any of the following who make a written request no more than 30 calendar days after receiving the request. [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

  • Reliability Coordinators
  • Planning Coordinators

R4. Each Transmission Operator that maintains TRM shall establish TRM values in accordance with the TRMID at least once every 13 months. [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

R5. The Transmission Operator that maintains TRM shall provide the TRM values to its Transmission Service Provider(s) and Transmission Planner(s) no more than seven calendar days after a TRM value is initiallyestablished or subsequently changed. [Violation Risk Factor: Lower] [Time Horizon: Operations Planning]

M1. Each Transmission Operator shall produce its TRMID evidencing inclusion of all
specified information in R1. (R1)

M2. Each Transmission Operator shall provide evidence including its TRMID, TRM values, CBM values, or other evidence, (such aswritten documentation, study reports, documentation of its CBM process, and supporting information) to demonstrate that its TRM values did not include any elements of uncertainty beyond those defined in R1.1 and to show that it did not include any of the components of CBM. (R2)

M3. Each Transmission Operator shall provide a dated copy of any request from an entity described in R3. The Transmission Operatorshall also provide evidence (such as copies of emails or postal receipts that showthe recipient, date and contents) that the requested documentation (such as work papersand load flow cases) was made available within the specified timeframe to the requestor. (R3)

M4. Each Transmission Operator shall provide evidence (such as logs, study report, review notes, or data) that it established TRM values at least once every thirteen months for each of the TRM time periods. (R4)

M5. Each Transmission Operator shall provide evidence (such as logs, email, website postings) that it provided their Transmission Service Provider(s) and Transmission Planner(s) with the updated TRM value as described in R5. (R5)