11 PMU simulation and application for power system stability monitoring Harmeet Kang Areva Technology Centre – Stafford, UK Sept MOSCOW

22 Historical Perspective  Impossible to compare data from geographically different locations  No context to the measurements  Slow RTU data  Technology cost prohibitive

33 Why Synchrophasors  Difficult to do post analysis if measurements cannot be aligned  Very difficult to develop a pre-emptive strategy if the phase angles between various points in a system cannot be determined  GPS and Ethernet have made it possible to have time aligned measurements from geographically different locations  Systems are operating closer to the limit than they were before  Better State Estimation

44 Comparison with traditional SCADA Parameter/AttributeSCADASynchronised Phasor Resolution2-4 measurements/sec Maximum 50/60 meas./sec ObservabilitystaticStatic/dynamic Phase AngleNoYes

55 What is a Phasor IEEE C specifies that the angle  is 0 degrees when the maximum of the signal to be measured coincides with the GPS pulse and -90 degrees if the positive zero crossing coincides with the GPS pulse.

66 Measurement

77 Phase Angle Not constant if Frequency is constant 2π(f–f0)T0, where f0 = 1/T0 =2π(49.93–50)0.02= degrees/measurement = 25.2 degrees between two GPS pulses 50 Hz Hz

88 PMU device basics GPS Receiver Microprocessors Oscillator A/D Analog Digital IEEE C37.118Data Electrical signal Digitised Samples Data Frame over Serial or Ethernet (TCP/UDP) P847PMU Anti Aliasing

99 PMU device basics GPS Receiver Microprocessors Oscillator A/D Analog Digital IEEE C37.118Data Electrical signal Digitised Samples Data Frame over Serial or Ethernet (TCP/UDP) P847PMU Anti Aliasing Phase delays /Variable CT/VT Mag/Angle Errors Fixed delay in gathering data Small error

10 GPS input Time  Output Site 1 Light ON Light OFF Time  Output Site 2 Light ON Light OFF 200ms +/- 1ms <100 ns Leading edge is timing point

11 MiCOM P594  MiCOM P594 is the universal time synchronising unit for the substation  Accurate for PMU applications  Accurate for GPS line differential  Accurate for NCIT merging units  Accurate for all other purposes  Modulated IRIG-B  Un-modulated IRIG-B  4 x 1 PPS fibre outputs to synchronise P54x relays  P594 Status, Static Output Relays  Visual time reference on LCD One Device Synchronises All – One Single Investment

12 Acceptable Total Vector Error (TVE) Where X r (n) and X i (n) are the measured real and imaginary components and Xr and Xi are the reference values. This measurement accuracy varies with the magnitude and frequency of the input signal. 1% TVE ~ 0.5 degrees ~ 26 

13 Measurement Window Filter Coefficients are chosen to provide A zero degrees phase shift if the middle of the window corresponds to the peak of the signal

14 Filter Length  Programmable  1 – 7 Cycles  Default - 5 Cycles

15 Impact of Filter Length Particularly important to have good noise rejection as inter area and local oscillations are around Hz

16 MiCOM P847 Main Functionality Multifunctional Disturbance /Transient Recorder Phasor Measurement Function Breaker Fail Re-trip & Backtrip Fault Location, Events, Recording Communications Programmable Logic, I/O Marshalling Local/Remote Control & Monitoring Voltage, Current & Freq. Protection

17 PMU’s in a System PMU1 PMU2 PMU3 PMU4 PDC E-terra

18 Phasor Data Transfer

19 IEEE C Protocol  Configuration => To PDC  Header =>To PDC  Data => To PDC  Command <= From PDC

20 PMU Protocol Settings

21 PMU Data & Config

22 Communication/Data Architecture PMU SsPDC Ethernet or serial To Control Centre Super PDC Small Signal Stability Visualization Archiving To Regional Control Centre/EMS Substations/DG Archiving

23 Why Substation PDC 1) Can create a virtual PMU for a complete substation out of many PMU's, hence lowering network congestion 2) Provides a reliable and persistent data storing environment when the communication link is down 3) Can be used to make the Control Centre ‘catch up’ data to a certain extent if the communication link is intermittent 4) Creates a set up for the future where direct control actions (substation based logic or Wide Area Control) can be taken based on PMU data.

24 Communication Issues  Communication bandwidth can be reduced by combining data from multiple PMU’s in one channel  Communication bandwidth can be reduced by choosing integer data transfer (16 bit) over floating point(32 bit)  Must be considered carefully – depends on what applications are using phasor data  The same channel should be capable of configuring a substation PDC or PMU without loss of data

25 Embarking on a PMU based WMS system

26 PMU / WAMPAC roadmap Short Term 1-3 years Medium Term 3-5 years Long Term > 5 years Situational Awareness – Angle/Frequency Monitoring Situational Awareness – Advanced Visualisation Tools State Measurement (Linear) Post Mortem AnalysisModel Benchmarking; Parameter Estimation (Dynamic) Real-Time Control State Estimation (Improve)State Estimation (hybrid system) Adaptive Protection Model Benchmarking; Parameter Estimation Stabilization (PSS) Power System RestorationPlanned Power-System Separation – Special Protection Systems Voltage Stability Monitoring Advanced Stability monitoring applications Envisaged User Requirements

27 PMU Locations and Number of » Which feeders are key to the interconnection between grid regions » Which nodes exhibit large shifts in power angle based on a loss of generation, load and change in topology. » Which areas are of interest from a load modelling perspective » Which areas of the grid are known to contain dynamic stability issues » Which areas can form frequency Islands » Which areas of the grid are prone to voltage collapse » Which nodes will be most beneficial for the current state estimator improvement and a future linear state estimator

28 PMU Locations and Number of Phenomena Power Angle Load Dynamics Stability monitoring Frequency Islands Voltage Collapse State Estimation

29 System Study and Virtual PMU’s

30 Application of PMU’s in Power System Stability

31 Small Signal Stability Ability of a power system to maintain synchronism When subjected to small disturbances. In today’s practical power systems, the small signal Stability problem is usually of insufficient damping of system oscillations Ref: Power System Stability and Control Prabha Kundur

32 Small Signal Stability

33 System Oscillations Ref: UNDERSTANDING POWER SYSTEM STABILITY Michael J. Basler and Richard C. Schaefer

34 Oscillations

35 Anatomy of an Oscillation

36 Power Transfer Between Two Systems after a disturbance

37

38 PMU Data

39 Modal Analysis Oscillatory Modes and associated damping factors for two buses in a system after a small disturbance

40 Frequency ModeAmplitudeDamping FactorPhase

41 Significance of Negative Damping

42 Effect of Data Transmission rate of application Every PMU measurement Every second PMU measurement Every tenth PMU measurement Every second

43 Operator View of PMU data

44 Conclusions  Technology enablers have made PMU’s a logical choice for Wide Area Applications  PMU’s can be used for variety of monitoring and stability applications  The common angle reference provides context to the measurements  Adaptive filter length and data rate can be used to match measurement to application  PSS tuning can be done to improve system response to disturbances  PMU Simulation can help in planning –location, number, characteristics

45 Conclusions Applications  Real-time measurement of the power system state  Real time monitoring of angular stability  Real time monitoring of damping issues  Post event analysis  Post-Disturbance Analysis and Compliance Reporting  System Operations and Planning

46 Thank You