Transmission Reliability Margin Implementation Document (TRMID)

Transcription

1 Page 1 of 10 TRANS Standard Validation Date Review Frequency 1 year Validated By Marshalia Green Effective Date 03/31/2017 Level of Use: Responsible Execu. Approved by:

2 Page 2 of 10 Revision Log Revision or Change Number Effective Date Affected Page Numbers Description of Revision/Change /31/2014 All Initial issue. Supersedes ED-SPP Organization names and titles changed /31/2015 All SPP Validation. Annual Review. Organization names and titles changed. No intent changes made /31/2016 All Page 4, /31/2017 All Various Page 5 SPP Validation. Annual Review. Added references for GOES. SPP Validation. Annual Review. Updated standard references from MOD-008 to MOD Wrote out SS&C to Stakeholder Services & Contracts. F

3 Page 3 of 10 Table of Contents 1.0 PURPOSE SCOPE PROCESS Roles and Responsibilities Executive Owner Functional Lead Reliability Analysis Transmission Engineering Stakeholder Services & Contracts (SS&C) Program Elements Total TRM Transmission System Uncertainty Calculation Aggregate Load Forecast Parallel Path (loop flow) Impacts Transmission System Uncertainty Component Values [MOD R1.2, R1.3] Reserve Sharing Component Values Converting the Reserve Sharing Component of TRM to a Flowgate TRM Amount [MOD R1.2] Converting the TRM Set Aside on a Flowgate to an Amount Set Aside on a Path Applying TRM in the Transfer Capability Calculation Process [MOD R1.2] Availability of TRM to the Market on a Non-Firm Basis Documentation TRMID and Underlying Documentation Availability RECORDS QA Records Non-QA Records DEFINITIONS... 9 Source Notes: Source Notes... 10

4 1.0 PURPOSE Page 4 of 10 (TRM) is comprised of two uncertainty components. One component is based upon the uncertainty in the transmission system and the second component is based upon the requirements of the generation Contingency Reserve Sharing Group (CRSG) agreement. The inherent uncertainty in the assumed system conditions used to compute Available Transfer Capability (ATC) can result in unreliable transmission system operations. To ensure reliable operation of the transmission system under a broad range of system conditions, a portion of the computed ATC will be set aside as TRM. This capability will provide the operating flexibility required to ensure reliable operations and will minimize the need to curtail transmission service. TRM will also be used to deliver the power obligations as identified in the CRSG agreement. 2.0 SCOPE This document satisfies the MOD requirement for a TRM Implementation Document and describes the methodology by which the TRM values are determined [MOD R1]. Applies to Reliability Analysis, Transmission Engineering, and Stakeholder Service & Contracts in the Transmission & Power Supply Organization. Review Cadence: This procedure will be reviewed annually with the review documented in the Revision Log. 3.0 PROCESS 3.1 Roles and Responsibilities Executive Owner The Senior Vice President of Transmission & Power Supply is the owner and approval authority for this procedure. Approval of this SPP is indicated by the Executive Owner s signature on the cover page. The Senior VP is responsible for governance of this procedure Functional Lead The Senior Manager, Reliability Authority and Regional Operations has the overall responsibility for all aspects of implementation of this procedure. The Senior Manager is responsible for oversight of this procedure Reliability Analysis A. Reliability Analysis is responsible for execution of this procedure. B. Reliability Analysis is responsible for evaluating and determining the quantity of the TRM uncertainty components. Reliability Analysis will recalculate TRM values as changing conditions warrant and will review the values annually [MOD R4]. C. Reliability Analysis is responsible for applying the TRM values to the Flowgates in the TVA Transmission Service Provider area for short-term firm transmission service system impact studies.

5 Page 5 of Reliability Analysis (continued) D. Reliability Analysis is responsible for providing revised TRM values to Stakeholder Services & Contracts in a document suitable for posting on OASIS. E. Reliability Analysis is responsible for providing a revised TRMID to Stakeholder Services & Contracts prior to the implementation date for posting to OASIS Transmission Engineering A. Transmission Engineering is responsible for support and execution of this procedure. B. Transmission Engineering is responsible for applying the TRM values to facilities in the TVA TSP area for long-term firm transmission service system impact studies Stakeholder Services & Contracts (SS&C) A. SS&C is responsible for support of this procedure. B. SS&C shall post the TRMID on OASIS before the effective date when the document changes. C. SS&C shall make available the underlying documentation used to determine TRM to any of the following entities who make a written request to the address TransmissionSpecialist@tva.gov. If requested documentation is not readily available to SS&C, Reliability Analysis will provide the documentation. Documentation will be provided within 30 calendar days after receiving the request. 1. Transmission Service Providers 2. Reliability Coordinators 3. Planning Coordinators 4. Transmission Planners 5. Transmission Operators D. SS&C shall provide the TRM values to the Transmission Service Provider and Transmission Planners, including Nashville Electric Service (NES), Memphis Light Gas & Water (MLGW) and Smoky Mountain Transmission (SMT) no more than seven calendar days after a TRM value is initially established or subsequently changed. Posting the TRM values on the OASIS website will be considered providing the values [MOD R5]. 3.2 Program Elements Total TRM TRM is the sum of TRM transmission system uncertainty plus TRM CRSG requirements. Total TRM does not include any of the components of Capacity Benefit Margin (CBM) [MOD R2].

6 Page 6 of Transmission System Uncertainty Calculation The transmission system uncertainty component of TRM is applied against the facility ratings of network components and is measured as a percentage or MW reduction of those ratings. The TRM calculation will use at least one of the following components of transmission system uncertainty [MOD R1.1, R2]: Aggregate load forecast Parallel path (loop flow) impacts An assessment of the impacts that the transmission system uncertainty components have on the transmission system was made in order to determine the amount of TRM that is sufficient to maintain reliable system operations Aggregate Load Forecast The inability to precisely predict a future load level and the subsequent loadings experienced on transmission system elements requires a reasonable quantity of transfer capability to remain uncommitted in the form of TRM. The existing load forecast error can be separated into time horizons. The further the horizon from present day, the more error in the load forecast. The load forecast Mean Annual Percent Error (MAPE) values were used to establish these assumptions. 1 year: 2.3% 5 year: 3.1% 10 year: 6.2% The load forecast error horizons don't match up with the transfer capability calculation horizons. The short-term horizon is from next day to 18 months. The load forecast uncertainty for the short-term horizon would be somewhere between 2.3% to 3.1%. Therefore in order to capture the possible uncertainty seen in the short-term horizon, 3.0% will be used. The long-term horizon is any yearly request from one year to ten years in the future. The uncertainly used in the long-term horizon can be calculated using a weighted average: (1 * * * 6.2)/10 = 4.5 => 5% In the long-term horizon, on average a 5% uncertainty from load forecast error will be seen Parallel Path (loop flow) Impacts The uncertainty caused by parallel path loop flow impacts does not affect each facility the same and tends to change from day to day. On occasion, when loop flow impacts on a facility exceeds the aggregate load forecast error uncertainty amount, TVA will study the impact on the facilities. If they are greater than the current TRM uncertainty amount, TVA will increase the TRM uncertainty to reflect the conditions on the Flowgates.

7 Page 7 of Transmission System Uncertainty Component Values [MOD R1.2, R1.3] Current TRM Percent Capacity Effect Short-term horizon (next hour to 18 months)* Aggregate load forecast error impact 3.0% TRM Needed 3.0% Long-term (1 year to 10 years) Aggregate load forecast error impact 5.0% TRM Needed 5.0% * Time period includes same day and real-time, day-ahead and pre-schedule, and beyond day-ahead and pre-schedule, up to 18 months. The above values reflect the default TRM values required to account for the uncertainty component of TRM. If it becomes known for a specific Flowgate that a certain component of uncertainty has become greater for a specific time period, the TRM for that Flowgate can be reevaluated. The proper notification and documentation will occur if this is necessary Reserve Sharing Component Values The reserve sharing component values are determined within the CRSG deliverability study. These numbers are based upon system conditions such as load forecast and largest installed generation and therefore can change during the year. The values calculated as the reserve sharing component apply for all time periods including: same day and real-time, day-ahead and pre-schedule, beyond day-ahead and pre-schedule, up to 10 years ahead [MOD R1.3] Converting the Reserve Sharing Component of TRM to a Flowgate TRM Amount [MOD R1.2] The reserve sharing component of the TRM is set as a path-based amount. In order to account for the TRM in our AFC process, the TRM is converted to a Flowgate based number. This conversion will be conducted every time the reserve sharing TRM amounts are recalculated. The reserve sharing component of TRM will also have to be calculated for any Flowgate added to the transfer capability calculation process. The equation to convert a path-based TRM number to a Flowgate TRM number is the following: TRM = TDF TRM flowgate path path where TDF=Transfer Distribution Factor

8 Page 8 of Converting the TRM Set Aside on a Flowgate to an Amount Set Aside on a Path TRM is presently applied against the facility ratings of network components and is measured as a percentage or MW reduction of those ratings. In order to post the amount of TRM on specific paths, the margin must be converted to a path number. This is done using the following equation. TRM TRM path = TDF flowgate path Applying TRM in the Transfer Capability Calculation Process [MOD R1.2] In the short-term horizon (next day to 18 months), TRM is accounted for on each flowgate. Using the AFC calculation equation outlined in the ATCID, TRM is subtracted from the TFC of each Flowgate. In the long-term horizon, TRM is accounted for on each monitored facility as a reduction in the facility rating. Long-term studies utilize a 95% loading cut-off on all facilities, not just those designated as flowgates, to account for load forecast error. Additionally, long-term studies include a contingency reserve sharing component which is applied to all facilities impacted by the CRSG obligations Availability of TRM to the Market on a Non-Firm Basis TVA does not make TRM available on a non-firm basis. This is due to the uncertainty still present in the non-firm transfer capability calculations. 3.3 Documentation TRMID and Underlying Documentation Availability TVA will make the TRMID available by posting the document on OASIS. The underlying documentation used to determine TRM will be made available within 30 days of receiving a request to the following address TransmissionSpecialist@tva.gov with the subject TRM Underlying Documentation Request". At a minimum the TRMID and underlying documentation will be available to any requesting Transmission Service Providers, Reliability Coordinators, Planning Coordinators, Transmission Planners or Transmission Operators [MOD R3]. 4.0 RECORDS 4.1 QA Records None 4.2 Non-QA Records None

9 5.0 DEFINITIONS Page 9 of 10 AFC - Available Flowgate Capability - the flow capability remaining on a Flowgate for further commercial activity over and above already committed uses. ATC - Available Transfer Capability - the measure of the transfer capability remaining in the physical transmission network for further commercial activity above already committed uses. CRSG - Contingency Reserve Sharing Group - A group whose members consist of two or more Balancing Authorities that collectively maintain, allocate, and supply operating reserves required for each Balancing Authority s use in recovering from contingencies within the group. TFC - Total Flowgate Capability - the facility rating of a Flowgate. TDF - Transfer Distribution Factor - the portion of an Interchange Transaction, typically expressed in per unit that flows across a transmission facility (flowgate) TRM - - the amount of transmission transfer capability necessary to provide reasonable assurance that the interconnected transmission network will be secure. TRM accounts for the inherent uncertainty in system conditions and the need for operating flexibility to ensure reliable system operation as conditions change.

10 Source Notes (Page 1 of 1) Page 10 of 10 Requirements Statement Source Document Implementing Statement Scope: This document is to be compliant with applicable standards, specifically MOD MOD