Transmission Reliability Margin Implementation Document (TRMID) Revised 6/8/2012 Ver 2.0

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1 Transmission Reliability Margin Implementation Document (TRMID) Revised 6/8/2012 Ver 2.0

2 Table of Contents Process Details... 3 Purpose... 3 User Requirements... 3 Process... 3 Process Overview... 3 Calculation Process... 5 Step-by-step Procedure to Generate TRM Data Files... 5 Exceptions to the Calculation Process... 6

3 Process Details Purpose This document describes the terms and methodologies used in the calculation of Transmission Reliability Margin (TRM) as required by MOD and SPP Criteria 4 Process User Requirements Users should be familiar with the use of PSSE, IPLAN, and MUST. Access to the latest set of SPP seasonal planning models is required. Definition Transmission Reliability Margin (TRM) on a flowgate is described in SPP Criteria 4 as the capacity required to withstand the impact of the most critical generation loss to that facility. This capacity is set-aside by reducing available capacity by the amount of the TRM. Roles and Responsibilities The SPP Operations Engineering Analysis and Support ( Operations ) team performs the TRM calculations for each flowgate and maintains the official list of permanent flowgates. SPP is required to recalculate TRM values annually for each season (spring, summer, fall, winter). The highest seasonal TRM is recommended. In addition to the yearly calculations, TRM calculations will be provided upon request. These requests can come from the TWG, SPP Planning, SPP Operations AFC Support, or could be initiated by a change in the SPP Tariff. Process Overview SPP Planning reviews Operation s permanent flowgate list once a year. They suggest removals and additions and make these recommendations to Operations for their review. After that the list is sent to the TWG for review and approval. Part of the TWG review includes the updated TRM values for both existing and newly added flowgates. Once the TWG has approved the updated flowgate list and TRM calculations, including any exceptions noted in this document, the Permanent Flowgate Process is initiated and the new TRM values are updated in the Real-Time Response Factor Calculator ( RTRFCALC ). TRM Calculation results, input files, and seasonal models are archived for (six) years in addition to the current year. Methodology Determination of the most critical generation loss to a facility or flowgate includes the distribution factor impact that reserve sharing schedules would create on the flowgate,

4 combined with the size of those schedules. Reserve sharing is the primary component used for calculations and the only one of the components of uncertainty referenced in MOD-008-1, R1.1 that SPP uses for establishing TRM. For example, a simple transmission system: Figure 1 To speed calculation times, the megawatt (MW) impact calculation was divided into two steps. The first step determines the Transfer Distribution Factor ( TDF ) impact of providing reserve assistance for the loss of each generator. The result of this calculation is a percentage impact on the flowgate for a transaction from the Balancing Authorities (BAs) in the Reserve Sharing Group to the generator being studied. The transaction from the BAs is provided based on a pro-rata share of the total transaction amount via participation factors, based on the amount of reserves carried by each BA as a percentage of the total. In Example 1, a transaction of 1 MW is made to generator A, with MW from BA 1, MW from BA 2, MW from BA 3, etc. The resulting flow on the flowgate increased by 0.34 MW. To provide reserves to the system point represented by generator A, 34% of the reserves provided would flow across flowgate, FloGatEnoTrel. This calculation is made using Siemens PTI s MUST software and is calculated for each seasonal model, resulting in a set of TDF s for each generator and flowgate pair. There are approximately 450 unique generator locations and 200 unique flowgates for study. This results in approximately 90,000 calculations to evaluate. The list of flowgate and generator pairs is reduced by removing from the evaluation those generators that would provide a negative or zero TDF (relieving or neutral flow change) if they were lost in a contingency. This substantially reduces the evaluation list. The second step of the evaluation translates TDF percentages into a MW impact. The maximum MW capability of the generator is multiplied by the TDF percentage. The resulting

5 MW number is the calculated TRM for that flowgate, based on the loss of the corresponding unit. Continuing with Example 1, see the impacts as calculated: Figure 2 Generator B is the most impacting contingency for flowgate, FloGatEnoTrel, even though the higher TDF impact is found on Generator A. Generator A has a TDF impact almost four times as high as that for Generator B. However, considering the fact that Generator B could have up to 1,200 MW of reserves, the resulting MW impact is higher than that of Generator A. Therefore, the TRM calculated for flowgate, FloGatEnoTrel is 114 MW. Calculation Process TDF calculations use the study transfer capabilities of PTI s MUST software. MUST provides results for large numbers of transfers and impacts for many combinations of systems. It depends on a set of input files that define the systems between which transfers are studied, the facilities to be monitored during transfers, and the set of transfers to make. SPP staff created an IPLAN software program that generates the files necessary to put into MUST to perform TDF analysis. A second IPLAN program extracts and filters the large amount of data into a useable format. The steps below need to be performed for each season. Step-by-step Procedure to Generate TRM Data Files 1. The name of the first program is TRM_CREATE_FILES.IPL. This program should be placed into a directory on the user s computer, which should also include the power flow model representing the season being studied. The power flow model is obtained through SPP s Engineering department and should include the most up-to-date information, including projects and projected status of facilities.

6 2. Also necessary is a file named BASIC.MON, which is a MUST input file listing the definitions of the flowgates for which TRM s are to be calculated. 3. Rename the model file TRM_CASE.sav. 4. Execute the IPLAN (TRM_CREATE_FILES.IPL). It should only take a few seconds to complete. Generated files: a. Subsystem.sub - Input file to MUST detailing the Reserve Sharing Group s generators and BAs. b. Study.asc - Response file for MUST command line. Instructions for MUST to perform the analysis. c. RunStudy.bat - Batch file that opens MUST and executes study instructions in Study.asc. d. Units.txt - List of all units in the Reserve Sharing Group. e. Units_temp.txt - Data file with filtered results out of Units.txt used in the next IPLAN program. 5. Run the file just created RunStudy.bat. This will execute MUST and generate 2 files: a. Mustlog.txt Log file from the MUST program. Review Mustlog.txt for any errors that would render the impact calculations on a flowgate incorrect. b. StudyOutput.txt Several megabyte output file from MUST with the TDF impact for every generator on every flowgate. 6. After MUST command line closes, execute the second IPLAN program, EXTRACT_DATA.IPL. Files that are created: a. A text file for each flowgate is named xxxx.txt, where xxxx stands for the flowgate number assigned in the BASIC.MON file. This file contains the: i. Sorted results (highest TRM MW first) of generator bus number ii. Generator bus name iii. TDF iv. Generator max MW, TRM (TDF * max MW) for each generator with a + TDF value. NOTE: Generators whose loss would relieve the flowgate are ignored in TRM calculation. 7. TRM_SUMMARY.txt Summary file listing each flowgate and the most impacting generator contingency (largest TRM MW). Exceptions to the Calculation Process Flowgate ID # 6006 (GGS Stability) The GGS flowgate is allowed a special condition for TRM due to the stability based flowgate definition. The special condition allows an incremental 150 MW of TRM to be reserved as firm to address the Sidney DC Tie RAS actions integral to the GGS stability flowgate. The 150 MW of incremental TRM should be added to the calculated TRM value through the Calculation Process above. Flowgate ID # 6009 (COOPER_S) The COOPER_S flowgate is allowed a special condition for TRM due to the FERC accepted Facilities Modification and Construction Agreement for Cooper South Flowgate Upgrades. The special condition allows an incremental 14 MW of

7 TRM to be reserved as firm effective June 1, 2009 and beyond. The 14 MW of incremental TRM should be added to the calculated TRM value through the Calculation Process above. Flowgate ID # 5247 (SPPSPSTIES), # 5352 (SPPSPSTIEJ07), # 5392 (SPPSPSTIESWE) The SPPSPSTIES flowgate and derivative flowgates mentioned here, used during prior outage situations, are allowed a special condition for TRM due to the stability based flowgate definition. The special condition results in a calculated TRM value of 540 MW, which represents the most impacting reserve sharing event. However, due to the stability limitation, the TRM value is set aside in the form of transmission capacity, and not sold as non-firm. Therefore, the calculated TRM of SPPSPSTIES and the derivative flowgates are overridden in the AFC process and replaced with 0 (zero) MW to prevent the sale of non-firm energy.

Transmission Reliability Margin Implementation Document (TRMID)

Transmission Reliability Margin Implementation Document (TRMID) Page 1 of 10 TRANS Standard Validation Date 03-10-2017 Review Frequency 1 year Validated By Marshalia Green Effective Date 03/31/2017 Level of Use: Responsible Execu. Approved by: Page 2 of 10 Revision