PMU-based Wide Area Protection System Concept and application in a large longitudinal system

Transcription

1 Dr. U. Kerin, Siemens AG PMU-based Wide Area Protection System Concept and application in a large longitudinal system Siemens AG, EM SG PTI, 215 All rights reserved

2 Why is there an increasing demand for information on power system operations? growing demand on electrical energy world wide more and more renewable sources with fluctuating infeed characteristic change of the role of conventional plants part load and flexible operation of conventional plants high flexibility of transmission hybrid system to interconnect new renewable sources with the grid operation closer to the stability and capacity limits of the system new targets : sustainability, environmental friendly sources Page 2

3 Development over time Development of power systems Passive electric systems (transformers, generators transmission lines, mechanical breakers) Complex intelligent systems power electronics, fast digital and protecition systems IGBT based FACTS, MT- HVDC Distributed Generation Smart Grids Electric Vehicles First SCADA systems Development of supervisory systems for power system control PMU SCADA / EMS systems for power systems Stability tools (DSA, TSA, VSA etc) Page 3

4 The role of DSA (dynamic security assessment) and WAPC (wide area protection and control) Task of a modern DSA system: Monitor the actual system state Evaluate how critical a state is Recognize a trend of the system state s development Select credible contingencies Pre-calculate and prepare which counter-measures should be started at what time DSA role is not to act as a fast control and protection system A PMU-based wide area protection and control can take over this role: Automatic counteractions Lower risk of unsafe situations Minimization of outages and blackouts Control of congestion situations Avoiding of part system splitting Prevention of instability Page 4

5 PMU-based wide area monitoring and control - a hybrid solution PMU INDICES ANALYSIS CONTROL Stability - voltage - frequency - generator Monitoring angle voltage Reactive Power Demand SE LS Operator Decision SE: stored energy sources LS: load shedding frequency Trend Analysis RD RD: re-dispatch loading collapse Pattern Analysis RP SR Automated Control RP: reactive power control SR: spinning reserve Dispatch Center SIGUARD DSA / SCADA Page 5

6 Use of WAPC as an intelligent, automatic WALS (wide area load shedding) SCADA, DSA actual load flow situation (slow) PMU fault location identification (fast) load shedding (fast) (where, how much) PMUs: information on fault type and location SCADA + DSA: information on system state, LF situation and pre-calculated counter measures Page 6

7 PMU indices system state as a traffic light Based on local information system state indices help to monitor the system state and automatic counter-action Page 7

8 PMU indices to analyze system dynamic and stability Small signal stability index (SSSI) Angle index (AI) Frequency gradient index (FGI) Maximum Frequency Deviation Index (MFDI) Quasi-Stationary Voltage Index (QSVI) Voltage Drop Index (VDI) Voltage Ride Through Index (VRTI) Line Power Flow Index (LPFI) Transformer Power Flow Index (TPFI) Nodal Loading Index (NLI) Page 8

9 PMU indices Example Voltage Ride Through Index (VRTI) VRTI min 1,max t area j V A area j i area j max adm dt highest value of the three line-to-line grid voltage U/U N 1% limit line 1 limit line 2 lowest value of the voltage band 7% range in which a disconnection is only permissible by the automatic system 45% selective disconnection of generators depending on their condition 15% time in ms time when a fault occurs Page 9

10 PMU indices Example Nodal loading Index (NLI) Information about nodal system ranking margins are available in the LF data! P i, Q i Y im N V m. Ei E Y ik / Y V k 1 k. k 1. V i.. Y ik Y il V k e i 1 2P , P Q / 1 2P 2 Distance to loading limits: P cos sin P Q Y 1 2 sin cos Ei i Q i 4 1 and Q / e 1 i i 1,... N NLI min 1, max 4 Information of neighboring admittances are necessary (SCADA/DSA) Page 1

11 Example of WALS Large 5 kv system with longitudinal structure Nord Case 1 Case 2 South Page 11

12 Blackout May, in Vietnam 22 May 213, 14: - High load situation 19.8 MW - 1 major 5kV line lost - About 9,4 GW, 22 provinces and 8 millions customers lost - 9 hours until system restoration Frequency dependent load shedding too slow Dynamic process irreversable Point of no return reached 1,5 sec Blackout area Page 12

13 Case 1 P [MW] P [MW] P [MW] P [MW] Without LS Active (system power of transmission separation) line Active power of transmission line -5 Active power of transmission line Active power of transmission line Frequency Frequency Nord Frequency 52 Frequency Nord 5 52 South Nord 5 52 South Nord South South Faulted Bus 11 Voltage Faulted Bus 11 Voltage Faulted Bus Voltage.5 1 Faulted Bus Voltage x 14 Load Angle x 14 Load Angle 2 x 14 Load Angle Nord 2 x 14 Load Angle Nord South Nord -2 South Nord South South f [Hz] f [Hz] f [Hz] f [Hz] U [pu] U [pu] U [pu] U [pu] Angle Angle Angle Angle [Degree] -2 n-1 95 criteria 1 violated Activation of 98 MW LS can avoid the black out With LS activated by WALS (stable system behavior) P [MW] f [Hz] -1 Active power of transmission line U [pu] Angle [Degree] Frequency Nord South Faulted Bus Voltage Nord Load Angle 2 South Page 13

14 Case 2 Without LS (no system separation) P [MW] P [MW] Angle [Degree] Angle [Degree] Active power of transmission line 5-5 Active power of transmission line Frequency Nord 5 Frequency 49 South Nord 5 Faulted Bus Voltage 49 South Faulted Bus Voltage Load Angle Nord -2 Load Angle -4 2 South Nord -2-4 South f [Hz] f [Hz] U [pu] U [pu] Critical angle separation -2-4 Stabilization of system frequency by LS of MW LS With LS activated by Active WALS power of (stabilization transmission line of the system) P [MW] P [MW] P [MW] f [Hz] f [Hz] -1 Active power of transmission line Frequency -1 5 Active power of transmission line Nord Frequency South 5 Faulted Bus Voltage Nord Frequency South.5 5 Faulted Bus Voltage Nord Load Angle South -2 Faulted Bus Voltage Nord -4 1 Load Angle South Nord -6 Load Angle South U [pu] f [Hz] Angle [Degree] Angle [Degree] U Angle [pu] [Degree] U [pu] Page 14

15 Conclusion Online tools in combination with WAPC based on PMU-measurement can help to improve system operation increase use of system capacity make better use of system reserve create fast countermeasures in case of critical situations reduce risk of instability and black outs by automatic counteractions The example showed that the reliability of a non safe system can be improved and system splitting and blackout can be prevented Page 15

16 Thank you for your attention Dr. Uros Kerin Consultant Energy Management Smart Grid Division Siemens AG EM SG PTI NC DYS Freyeslebenstraße Erlangen Germany Phone: Fax: uros.kerin@siemens.com Page 16