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Power Monitoring And Control System (PMACS)

Power Monitoring And Control System (PMACS). NEPTUNE Preliminary Design Review 4-5 December 2003 Chen-Ching Liu, Ting Chan, Kevin Schneider. Overview. Compliance matrix PMACS State estimation and topology error identification Load management and emergency control Fault location.

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Power Monitoring And Control System (PMACS)

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  1. Power Monitoring And Control System (PMACS) NEPTUNE Preliminary Design Review 4-5 December 2003 Chen-Ching Liu, Ting Chan, Kevin Schneider

  2. Overview • Compliance matrix • PMACS • State estimation and topology error identification • Load management and emergency control • Fault location

  3. Compliance Matrix

  4. Base 46 node system • 2 shore stations • 46 BU’s • 46 Science nodes • 3000 Km of cables

  5. PMACS

  6. PMACS • PMACS functions are performed at two shore stations, and possibly a third control station • input signals are received from science nodes • command sequences are sent to science nodes

  7. State Estimation and Topology Error Identification

  8. State Estimation • By using a limited number of measurements, the state of the system can be estimated • Allows for the identification of “bad” data • Reduce errors in estimated states

  9. Unobservability Issue backbone branching unit backbone single-conductor spur cable to science node, 2½ water depths sensor long “extension cord” science node sensor up to 100 km Instrument module short “extension cord” sensor up to 1 km sensor

  10. Weighted Least Square (WLS) : Column vector of measured science node voltages and currents :Column vector of estimated BU voltages

  11. Calculated Residual • Helps to identify “bad data” • Gives an estimate of the accuracy of the estimation n:number of measurements

  12. Topology Error Identification • Allows for the possibility of a single back bone breaker being out of position • Method should also work for multiple breakers out of position, but this has not been verified

  13. Method of Topology Error Identification • Voltage at each shore station is varied independently • Variation of residual is then examined

  14. Correct Topology

  15. Incorrect topology

  16. Load Management and Emergency Control

  17. Load Management • Uses values from science nodes, shore stations, and state estimation to determine if the current system load violates any limits • Interfaces with Observatory Control System • Performs traditional security assessment in a limited manner

  18. Power Flow with Zener Diodes Where: PGi=Power injected at node I, source PDi=Power removed at node I, load. Yik=Resistance of the line between node I and k VZ=Voltage drop of zener diodes m=number of BU’s

  19. Emergency Control • If/when the load management module determines that a system limit has been violated, emergency control attempts to correct the problem • Can adjust shore station voltages • Can shed load at science nodes

  20. Adjustment of Shore Station Voltage • The sensitivity coefficients of the node(s) that have violated a limit are calculated • The shore station voltage is then adjusted by the amount calculated

  21. Load Shedding • The science node loads are tentatively categorized into three load classes • High • General • Deferrable

  22. Load Shedding Cont. • The sensitivity coefficients of the node(s) that have violated a limit are calculated • The load is then shed by the amount calculated

  23. Fault Location

  24. Fault Location • Determine the location of backbone cable fault to within 1 km • Use voltage and current measurements at two shore stations • Models include cable resistances and BU voltage drops

  25. Assumptions • Faulted link is known based on result of state estimation • Network topology is known and fixed (all breakers closed onto the fault) • Resistances of cables and BU voltage drops can be calculated using state estimation • BU voltage drops are constant assuming Zener diodes are operating in saturated region

  26. Fault Current Characteristics • Type 1 • If from each end known • Type 2 • If from each end not known • Type 3 • If from one end known

  27. Fault Location Formulation • For a Zero- ground fault, multiple non-linear equations can be set up based on Ohm’s Law and Loop Analysis • VNode = VPrevious Node + ILink * RLink + BU Voltage drop • All breakers closed onto the fault • Negative shore station voltage outputs

  28. Distance Calculation • Cable resistance = 1 /km • BU voltage drop = 15.2V per link (Zener diodes in saturated region) • Measurement errors = 0.01% (voltage and current)

  29. Voltage and Current Requirements • If faulted link is known before taking measurements • Apply predetermined voltage levels at both shore stations • Ensure backbone currents in branches are sufficient without causing over-current violation • If faulted link is not known before taking measurements • Increase current outputs at both shore stations until the total current output reaches limit

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