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

1. Facilitate ERCOT/stakeholder review of study scope and procedures

2. Solicit expert perspectives

3. Gather enough information to report back to the Commissioners with recommendations

4. 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?

ERCOT’s Proposed Approach to Screening Studies

Screening Studies: IGE

Screening Studies: Torque Amplification

Screening Studies: SSTI

ERCOT’s Proposed Approach to Detailed Studies

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

Potential Risk Action(a) 3 or fewer concurrent

Transmission OutagesProtection and Structural Mitigation

(b) 4 or fewer concurrent Transmission Outages

Protection

(c) 4, 5, 6 concurrent Transmission Outages

Procedural Mitigation

• 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?