PHASOR MEASUREMENT UNIT (PMU) AKANKSHA PACHPINDE

Transcription

1 PHASOR MEASUREMENT UNIT (PMU) AKANKSHA PACHPINDE

2 INTRODUCTION

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4 OUTLINE Conventional control centers Introduction to Synchrophasors A generic PMU Applications of PMU Role of GPS Cost profile of PMU with GPS PMU with IEEE 1588

5 TASKS PERFORMED BY CONTROL CENTER

6 Data is acquired from SCADA every 2s or so OPF for transmission- constrained economic State estimation carried out to provide state of dispatch system Historical and forecasted data stored in storage Load forecast carried out every 15mins devices AGC used balance power generation and load Various copies of data coordinated, synchronized demand and merged in databases Contingency analysis carried out Control centers integrate horizontally & vertically

7 INTRODUCTION TO SYNCHROPHASORS

8 An AC waveform can be mathematically represented as: In phasor notation it can be represented as: where: = rms magnitude of waveform = phase angle

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10 A GENERIC PMU

11 - Provides 1 PPS signal - Time- tagging Current/voltage signal from Instrument Transformer Communication links to higher level Restricts bandwidth to satisfy Nyquist criterion Calculates positivesequence estimates Analog-to-digital converter

12 An architecture involving the following must exist in order to realize the full benefit of the technology PMUs Communication links Data concentrators

13 MEASUREMENT ACCURACY REQUIRED BY SYNCHROPHASOR STANDARD

14 The value of Total Vector Error (TVE) < 1% Possible sources of error- magnitude, angle and timing Only magnitude error < 1% Only phase error < 0.573º Only time error < 31.8µs for 50 Hz system and 26.5µs for 60Hz system

15 APPLICATIONS OF PMU

16 Real-time operations applications Wide-area situational awareness Frequency stability monitoring and trending Power oscillation monitoring Voltage monitoring and trending Event detection and avoidance Resource integration State estimation Dynamic line ratings and congestion management Outage restoration Planning and off-line applications Baselining power system performance Event analysis Power plant model validation Load characterization Special protection schemes and islanding

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18 ROLE OF GPS

19 PULSE PER SECOND (PPS) SIGNAL This pulse as received by any receiver on earth is coincident with all other received pulses to within 1 microsecond PPS signal is used for sampling the analog data TIME STAMP The GPS time does not take into account the earth s rotation Corrections to the GPS time are made in the GPS receivers so that they provide UTC clock time

20 COST PROFILE OF PMU WITH GPS

21 Total installed cost of the technology includes cost of device, design and engineering, labor and material, any needed construction Cost of the device one-quarter of the total cost Upgrades cost considerably less than installing new PMUs Projects installing a greater number of PMUs or PDCs did not have lower average costs per device.

22 REASONS FOR HIGH COST GPS requirement Data storage needs Communication infrastructure requirement Changes required in substation like new busbars, additional CTs and PTs Downtime, labor cost, commissioning costs Limited experience Projects more about research, testing and demonstration

23 REASONS FOR HIGH COST GPS requirement Data storage needs Communication infrastructure requirement Changes required in substation like new busbars, additional CTs and PTs Downtime, labor cost, commissioning costs Limited experience Projects more about research, testing and demonstration

24 PMU WITH IEEE 1588

25 Precision Time Protocol (PTP) was first defined in IEEE and upgraded in 2008 It is designed for local systems requiring accuracies beyond those attainable using Network Time Protocol Designed for applications that Cannot bear the cost of a GPS receiver at each node OR For which GPS signals are inaccessible

26 IEEE 1588 has three types of clocks: Master clock- A clock which is controlled ideally by a radio clock or a GPS receiver Boundary/ Transparent clock- A clock in a transmission component like an Ethernet Switch Ordinary clock- A clock in an end device

27 Assuming that the master-to-slave and slave-to-master propagation times are equal, the offset and propagation time can be computed as follows: Synchronization accuracies better than 1 sub-microsecond can be achieved PTP is supported by Ethernet and TCP/ IP

28 Reallocation of time signals is done to bring the samples in their correct position The number of samples N coming between two successive PPS edges is evaluated and the new sampling interval is calculated as inverse of N After reallocation, samples are passed to the DFT block

29 Does not require GPS at every node Communication costs lowered as based on Ethernet Eliminates the extra cabling requirements of 1PPS to propagate highly accurate timing signals Non-recurring engineering costs firmware development Cost of goods sold negligible as only requires modification in Ethernet physical layer to support IEEE 1588 High grade oscillators required which are expensive Lack of testing equipment supporting IEEE 1588 v2 protocol

30 QUESTIONS?

31 THANK YOU