SSR Monitoring in EMS Bill Blevins Manager, Operations Planning

12/6/ Agenda Purpose SSR Displays Discussion

12/6/ Stations with Series Capacitors Actual and Planned

12/6/ SSR concerns For the modes in which the generator participates, the generator’s rotational speed will oscillate around the normal operating speed. If fm is the frequency of the oscillatory component of the machine speed and if f0 is the system frequency associated with the normal operating speed, then the generator oscillation will result in electrical currents being injected into the system at complementary sideband frequencies of f0, specifically f0-fm and f0+fm. These currents result in a pulsating torque on the generator rotor that is passed into the turbine-generator mechanical system through the shaft connecting the different masses of the mechanical system. If the frequency of this torque is near one of the torsional mode frequencies, the group of masses participating in the mode will oscillate against each other across the shaft connecting the masses. This causes additional stresses in the shaft. A “worst case” for series capacitor SSR is depicted by the IEEE First Benchmark System shown in Figure This is a highly compensated radial transmission system that exhibits classical SSR characteristics. The IEEE First Benchmark System is based on the Navajo plant (a plant with quite complex SSR potential) and comprises a single MVA dynamic machine model connected to an infinite bus via a 75% series compensated 500 kV transmission line. In this Benchmark System both positive sequence (R1, X1) and zero sequence (R0, X0) system impedances are specified when appropriate. The level of series compensation in the line was chosen to cause undamped torsional oscillations on the generator shaft in the absence of any mitigating measures as shown

12/6/ EMS SSR Alarm System Features SSR risk increases when certain combinations of specific lines or transformers are out of service. The system detects complex outage conditions that may place a generator at elevated risk for sub- synchronous resonance (SSR). Subsynchronous Resonance (SSR) Alarms developed to aid in real-time and study applications when the series capacitors should be bypassed.

12/6/ EMS SSR Alarm System Features This project provides SSR Alarm displays for the use of current business users (System Operators/Shift Engineers). Alarm system similar to the RAS editor where SSR Alarms setup in an application similar to the RAS. Display details of SSR’s to the control room. Archive SSR Alarms messages info which is saved and replicated to the data warehouse. SSR generated Alarms available for real time and study.

12/6/ SSR DISPLAYS

12/6/ Network Online Sequence Display

12/6/ Contingency Violation Display

12/6/ TCM Display

12/6/ SSR Summary Display EXAMPLE ONLY

12/6/ SSR Trigger Details Display

12/6/ SSR Summary Display

12/6/ RAS Editor

12/6/ RAS Editor

12/6/ SSR Summary Display

12/6/ Business Process For SSR Develop Criteria for NPRR Develop Criteria for Operations Departments Monitoring. Training the Operators / Engineers(April 15 th ) New Departmental Procedures(TBD) Update Control Room Operating Procedures(TBD) Possible GTL to create for handling when Series Capacitors need to be bypassed.

12/6/ Discussion/Questions?