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This workshop aims to review the study scope and procedures proposed by ERCOT regarding risk criteria, screening studies, detailed studies, and modeling requirements in power system analysis.
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Project No. 43506PUCT Staff Workshop11/19/14 Julia Harvey Kristi Denney Kevin Mathis Jasmin Thevaril
Agenda • Introductions • Workshop goals • Discussion/Q&A by topic • ERCOT proposed approach • Expert perspectives • Stakeholder comments and questions Discussion Topics • Study scope • Risk criteria based on topology review • Screening studies • Detailed studies • Study Process • Modeling requirements • Communication & review process
PUCT Staff Workshop Goals • Facilitate ERCOT/stakeholder review of study scope and procedures • Solicit expert perspectives • Gather enough information to report back to the Commissioners with recommendations • Address ERCOT/stakeholder goals
ERCOT’s Proposed Risk Criteria Based on Outages • How should units be ruled in or out for more detailed study? • Outages based probabilistic analysis? (ERCOT topology test) • Counting outages: double vs. single circuit • If units are ruled in, what is the next step?
Detailed Studies: Sensitivities for Damping Analysis • Switched shunt status • Series capacitor staging/bypass status • Series compensation levels (as appropriate) • For existing series capacitors, consider minor variations (-10%) due to the possibility of capacitor cans failing • For new series capacitors consider adjusting the series compensation levels as mitigation for SSO observed within the ERCOT specified risk criteria • System load levels and load models including plant station loads • Modeling and status of nearby generators • Split bus configurations, relaying schemes, or other area-specific concerns as identified by the affected TSP(s) and ERCOT • Sensitivity of generation dispatch level and number of units online • Whether units within the plant or nearby plants have similar modes • Effect combined cycle configurations • Impact of Power System Stabilizer (PSS)
Sensitivities for IRRs • What parameters should be assessed in IRRs frequency domain analysis? ERCOT suggestions: • Varying dispatch levels, (10% and 100%) • Varying number of units or collector feeders online (including effect of various collector feeder configurations) • Interaction with neighboring units.
Sensitivities for TA Analysis • Should torque amplification in turbine-generators be the subject of detailed studies? • If so, what parameters should be assessed? • ERCOT suggestions: • Simulations of critical faults and reclosing events, both failed and successful if identified by the affected TSP(s) and ERCOT. • Sensitivities of fault inception time and fault location or worst-case condition • How should the age of the generator be considered?
Modeling Requirements: TSPs • What data is required from the TSP? • For TA studies, TSP must provide information regarding series capacitor protection and metal oxide varistor (MOV) circuits. • Station one-lines where not standard breaker-and-a-half, or alternatively, information of split bus configurations, stuck breaker contingencies, and bus faults • Dynamic load models of nearby load centers
Modeling Requirements: Conventional Units • What data is required from turbine-generators? • Protection modeling • Mechanical Data • Number of Masses • Inertia constant for each mass • Associated self-damping of each mass • Spring constant associated with shaft connecting various masses • Mutual damping between masses • Generator electrical and dynamic data • Exciter model and data • Power System Stabilizer (PSS) model and data • Plant load data and load ratios (PQ, motor, etc) • If necessary, shaft fatigue curve
Modeling Requirements: IRRs • What data is required from IRRs? • Number and type of turbines or inverters and associated • Collector system model and one-line • Supplemental reactive equipment, including switchable shunts, STATCOMs, and SVCs • EMTP models of turbines / inverters • EMTP models of supplemental dynamic devices unless if it can be verified to not exacerbate subsynchronous interaction
Study Process Issues • Data sharing: can stakeholders supply necessary data to perform detailed studies? • If not, what is the impact of using conservative assumptions? • Do ongoing and completed studies need to be updated? • Should studies recommend specific protection/mitigation solutions?
NPRR562 • How much detail should be added? • Study parameters • Study process guidelines • Necessity of the “action table”
Related Questions • Operational issues • Necessity of series capacitors • To support exports: West Texas study • Reliability purposes
Next Steps? • Report to the Commission • Early 2015 • NPRR562/Additional workshops?