1. Phase Angle Alarming in ROSE for Steady-State Stability Analysis Marianna Vaiman V&R Energy JSIS Meeting Salt Lake City, UT March 5, 2015 1 Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

2. V&R’s Approaches to Phase Angle Limit Computation Phase angle limit should be determined in real time, and not based on historical data Phase angle limit is a physical limit: – Depends on system topology and conditions; – Depends on how the system is stressed; – The limit changes with system conditions. Voltage and thermal limits are operating limits: – Depend on the equipment/hardware. Three types of different phase angle limits: – 1. Based on user-defined scenario-based stressing; – 2. Based on optimal scenario-based stressing; – 3. Based on “natural” direction of system stressing. Phase angle limit can be computed using different data sets: – State Estimator data; combination of State Estimator and PMU data; PMU data 2 Phase angle limit should be determined in real time, and not based on historical data Phase angle limit is a physical limit: – Depends on system topology and conditions; – Depends on how the system is stressed; – The limit changes with system conditions. Voltage and thermal limits are operating limits: – Depend on the equipment/hardware. Three types of different phase angle limits: – 1. Based on user-defined scenario-based stressing; – 2. Based on optimal scenario-based stressing; – 3. Based on “natural” direction of system stressing. Phase angle limit can be computed using different data sets: – State Estimator data; combination of State Estimator and PMU data; PMU data Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

3. Approach 1. User-Defined Scenario-based Stressing 3 Approach 1. User-defined sources/sinks: – “Traditional”, but not optimal (maximum stressing) Maximum transfer capability may be reached due to exhausting resources before reaching voltage/thermal/stead-state stability violation. POM computes the most critical (sensitive) phase angle differences to each stressing: – Both in real-time and off-line. In addition, can monitor user-defined phase angle differences. Phase angle limit is computed based on State Estimator (SE) data. Alarming is done based on both SE and PMU data. Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

4. Computing Limits and Alarming in ROSE The key computation in ROSE: – ROSE computes both the limit and the current state, and can issue an alarm based on these two parameters; – Since the limits are computed in real-time, these limits are “dynamic” (changing). There are two types of alarms in ROSE: – SE-based (model-based) alarming; – PMU-based alarming. Both types of alarms may be expressed in terms of MW on the interfaces or phase angles. 4 Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

5. 5 SE-Based Alarming Two types of alarming are available: – Flow on the interface in MW; – Phase angle difference between two PMU locations in Degrees: PMU locations are user-defined as an input. Limit is computed both in MW and degrees. If the difference between the limit in MW and base case MW flow is less than MW alarming threshold, a MW alarm is issued. If the difference between the limit in degrees and base case phase angle difference in degrees is less than Phase Angle alarming threshold, a Phase Angle alarm is issued. Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

6. 6 PMU-Based Alarming Two types of alarming are available: – Flow on the interface in MW; – Phase angle difference between two PMU locations in Degrees: PMU locations are user-defined as an input Limit is computed both in MW and degrees. If the difference between the limit in MW and the current MW flow obtained from PMU data is less than MW alarming threshold, a MW alarm is issued. If the difference between the limit in degrees and current phase angle difference obtained from the PMU stream in degrees is less than Phase Angle alarming threshold, a Phase Angle alarm is issued. Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

7. 7 Both 1-D or 2-D ROSE boundaries are computed; – Each point on the boundary corresponds to thermal overload, flowgate constraint, voltage violation, or voltage collapse. Alarms are issued for 1-D scenarios: – Visualization includes trending of results in Real Time and Historical Trend. ROSE Analysis Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

8. 8 ROSE Client at ISO NE Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

9. 9 2-D Limits in MW and Degrees Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

10. Approach 2. Optimal Scenario-based Stressing Approach 2. Optimal sources/sinks determine by the software: – Such that interface/path flow is maximized; – Can be a pre-selected list of potential source/sink locations (such as several control areas); – This is maximum phase angle limit for the given interface/path. POM computes the most critical (sensitive) phase angle differences to each path/interface: – Both in real-time and off-line. – In addition, can monitor user-defined phase angle differences. Phase angle limit is computed based on State Estimator (SE) data. Alarming is done based on both SE and PMU data. V&R has a planning tool to determine maximum interface flow and phase angle limit. 10 Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

11. Approach 3. “Natural” Direction of Stressing PMU data is used to determine the “natural” direction of stressing. Phase angle limit is computed based on both SE and PMU data: – PMU data is used to determine the change in system conditions, and thus direction in which the system is stressed; – SE data is used to determine the limit for the “natural” stressing direction; – Stressing in the traditional sense is not performed. – This is not a commercial tool yet: Technology/algorithms have been developed. 11 Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

12. Only PMU-Based Analysis Phase angle limit is computed based on PMU data. PMU data is used to: – Create a measurement-based real-time case; – Determine phase angle limit using stressing. Two ways to use measurement-based real-time case: – Run the analysis when State Estimator (SE) case is not available or the system approaches stability limits between the two SE cases. – Run the analysis continuously without interruption all the time: Case is created and computations are performed with approx. the sampling PMU rate; Stressing can be performed using any of the three approaches described in the previous slides. – This is not a commercial tool yet: Technology/algorithms have been developed. 12 Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.

13. 13 V&R has developed different approaches to compute phase angle limits. Different types of phase angle limit computation are discussed. Computations are based on SE and PMU data. Conclusion Copyright © 1997-2015 V&R Energy Systems Research, Inc. All rights reserved.