Motion for the WECC-0135 Standard Drafting Team Option #2 21 Sept 2018 PRESENTATION TO WECC-0135 SDT DJORDJE Atanackovic, Ph.D.

Motion: That the WECC-0135 SDT select “Option #2 – Allow Flexibility in Modelling” as the basis for developing a WECC Regional Variance to NERC IRO-002-5, Reliability Coordination-Monitoring and Analysis.

Discussion: Fundmental Benefit/Risk Question: Benefits of RCs modelling remote, insensitive BES elements are non-existent. Major Risks to Reliability of RCs modelling, remote, insensitive BES elements include: Performance is impacted by size of mode: A 20,000 x 20,000 bus matrix takes much longer to solve than a 15,000 x 15,000 or 10,000 x 10,000 matrix, and this will be a significant negative consequence, especially if the RC wants to calculate SOLs /IROLs using real-time transient stability analysis. Robustness will suffer as the risk of State Estimator not solving will increase : Circuits that are not observable, because of failed telemetry, can prevent the State Estimator from converging on a solution for the entire network model Quality will suffer and the risk that real reliability issues may be masked will increase: Inaccurate and untuned telemetry will lower the quality of the State Estimator solution and could shift the study result to incorrect operating points

Option 3: Require a single Interconnection-wide model Main Concerns: RC modelling of remote, insensitive BES elements has no obvious reliability benefit; Impacts to performance, robustness and quality of State Estimator solutions and Advanced Applications are very real risks.

Option 4: Geographic-specific variance Major Concerns: Standards should be based on technical facts and physics as the WECC operates as one interconnected grid, therefore the proposed Regional Variance should apply to all members of WECC; If the US RCs are obligated to include remote, insensitive BES elements in their Network Model this may weaken their performance and as a result impact the entire Western Interconnection; A geographic exemption won’t fully protect BC, Alberta or Mexico from the related problems that arise for US RCs.

Option 1: Rely on Existing NERC Standards Main Concerns: The “No Change” option may not address concerns expressed relative to Network Models used by RCs in the Western Interconnection; Will not require RCs to document their methodologies for developing reliable and efficient Network Models.

Option 2: Allow Flexibility in Modelling Rationale for Option 2: Will require RCs to be clear and transparent about their Network Modelling methodologies; Will naturally foster collaboration and sharing of best practices; Does not add an unreasonable burden to the RCs who will be VERY busy managing Network Modelling and SOL/IROL calculation issues in the next 12 – 16 months.