18112008 Mansour GPS in Power Systems

7/31/2019 18112008 Mansour GPS in Power Systems

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APPLICATIONS

OF GPS IN

POWER

ENGINEERING


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What is GPS?

GPS or Global Positioning Systems isa highly sophisticated navigationsystem developed by the UnitedStates Department of Defense. Thissystem utilizes satellite technology

with receivers and high accuracy

clocks to determine the position ofan object.


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The Global Positioning

System A

constellati

on of 24high-altitudesatellites


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GPS is

A constellation of satellites, whichorbit the earth twice a day,transmitting precise time andposition (Latitude, Longitude andAltitude) Information.

A complete system of 21 satellites

and 3 spares.


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GPS at Work

1.Navigation - Where do I want to go?

2.Location- Where am I?

3. Tracking - Monitoringsomething as it moves

4. Mapping - Where is everythingelse?

5. Timing - When will it happen?


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Why do we need GPS?

Safe Travel

Traffic Control

Resource Management Defense Mapping

Utility Management

Property Location Construction Layout


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4 birds (as we say) for 3-D fix


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Global Positioning Systems (GPS) Applicationsin Power Systems


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Power companies and utilities havefundamental requirements for time and

frequency to enable efficient powertransmission and distribution.Repeated power blackouts have

demonstrated to power companies the needfor improved time synchronization throughouthe power grid. Analyses of blackoutshave led many companies to placeGPS-based time synchronizationdevices in power plants andsubstations


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Why GPS For power Eng

It furnishes a common-access timing pulse

which is accurate to within 1 microsecond at any

location on earth.

A 1-microsecond error translates into 0.021for a 60 Hz system and 0.018 for a 50 Hzsystem and is certainly more accurate thanany other application


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GPS time synchronization

By synchronizing the samplingprocesses for different signals

which may be hundreds ofkilometers apart it is possibleto put their phasors in the same

phasor diagram


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V

V

V1

V2

Substation 1

Substation 2t1 t2 t3 t4 t5 t6 t7

GPS time synchronized

pulses

V1

V2

FFT or any other

technique gives:

Magnitude

Phase angle

With respect to GPS

GPS time synchronizationGPS time synchronization


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Absolute Time ReferenceAcross the Power System


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Synchronized phasormeasurements (SPM) have

become a practical proposition.As such, their potential use in

power system applications has

not yet been fully realized by

many of power system engineers.

Phasor Measurement Units PMUsPhasor Measurement Units PMUs


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Phasor Measurement UnitsPhasor Measurement Units

(PMU)(PMU)[or SYNCHROPHASORS][or SYNCHROPHASORS]


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Phasor Measurement UnitsPhasor Measurement Units

))PMU)PMU)

They are devices which use

synchronization signals from theglobal positioning system (GPS)

satellites and provide the phasor

voltages and currents measured at agiven substation.



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Secondary

sides of the

3 P.T. orC.T.

Corresponding

Voltage or

Current phasors

input output

PMU



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Phasor Monitoring Unit (PMU) Hardware BlockDiagram:

GPS

receiver

Phase-locked

oscillator

16-bit

A/D

converter

Phasor

micro-

processor

Modems

Anti-aliasing

filters

Analog

Inputs


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Sampling at Fixed TimeIntervals Using an AbsoluteTime Reference


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The GPS receiver provides the 1 pulse-per-second

(pps) signal, and a time tag, which consists of the year,

day, hour, minute, and second. The time could be the

local time, or the UTC (Universal Time Coordinated).

The l-pps signal is usually divided by a phase-locked

oscillator into the required number of pulses persecond for sampling of the analog signals. In most

systems being used at present, this is 12 times per

cycle of the fundamental frequency. The analogsignals are derived from the voltage and current

transformer secondary's.


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The Birth of the PMUs Computer Relaying developments in 1960-70s.Computer Relaying developments in 1960-70s.


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NowNow

RESES52121SEL-421EL-421


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Phasor Measurement Units

Ph M t U it PMUPh M t U it PMU


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central data

collection



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Data Concentrator (Central DataCollection)


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Different applications ofDifferent applications of

PMUs inPMUs in

power systempower system

A li ti f PMU iA li ti f PMU i


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1. Adaptive relaying

2. Instability prediction

3. State estimation

4. Improved control

5. Fault recording

6. Disturbance recording

7. Transmission and generation modeling verification

8. Wide area Protection

9.Fault location

Applications of PMU in powerApplications of PMU in power

SystemSystem

A li ti f PMU i S tApplications of PMU in power System


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1-Adaptive relaying1-Adaptive relaying

Adaptive relaying is a protection

philosophy which permits andseeks to make adjustments in

various protection functions in

order to make them more tuned toprevailing power system conditions

Applications of PMU in power SystemApplications of PMU in power System



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2-Instability prediction2-Instability prediction

The instability prediction can be used

to adapt load shedding and/or out of

step relays.

We can actually monitor the progress of

the transient in real time, thanks to the

technique of synchronized phasor

measurements.




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The state estimator uses various measurements

received from different substations, and, through an

iterative nonlinear estimation procedure, calculates the

power system state.

3-State estimation3-State estimation

By maintaining a continuous stream of phasor data

from the substations to the control center, a state

vector that can follow the system dynamics can be

constructed. For the first time in history, synchronized phasor

measurements have made possible the direct

observation of system oscillations following system

disturbances




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Power system control elements use local feedback to

achieve the control objective.

4-Improved control4-Improved control

The PMU was necessary to capture data during the

staged testing and accurately display this data and

provide comparisons to the system model.

The shown figure

shows a typical

example of one of

the output plots

from the PMU

data




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They can capture and display actual 60/50 Hz waveform and magnitude data on individual channels during

power system fault conditions.

5-Fault Recording5-Fault Recording




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Loss of generation, loss of load,

or loss of major transmission

lines may lead to a power systemdisturbance, possibly affecting

customers and power systemoperations.

6-Disturbance Recording6-Disturbance Recording




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These figures areexamples of long-term

data used to analyze

the effects of power

system disturbances oncritical transmission

system buses.

Disturbance RecordingDisturbance Recording




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Computerized power system modeling and studies are

now the normal and accepted ways of ensuring that

power system parameters have been reviewed before

large capital expenditures on major system changes.

7-Transmission and Generation7-Transmission and Generation

Modeling VerificationModeling Verification

In years past, actual verification of computer models

via field tests would have been either impractical or even

impossible

The PMU class of monitoring equipment can now

provide the field verification required


7-Transmission and7-Transmission andApplications of PMU in power SystemApplications of PMU in power System


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The shown figure compares a remote substation 500

kV bus voltage captured by the PMU to the stability

program results

7-Transmission and7-Transmission and

Generation ModelingGeneration Modeling

VerificationVerification

Applications of PMU in power Systempp p y



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The introduction of the Phasor

Measurement Unit (PMU) has greatly

improved the observability of thepower system dynamics. Based on

PMUs, different kinds of wide area

protection, emergency control andoptimization systems can be designed

8-Wide Area protection

pp cat o s o U powe Systepp p y



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A fault location algorithm based on synchronizedsampling. A time domain model of a transmission line

is used as a basis for the algorithm development.

Samples of voltages and currents at the ends of a

transmission line are taken simultaneously(synchronized) and used to calculate fault location.

9-Fault Location9-Fault Location

pp p ypp p y

Fault LocationFault LocationApplications of PMU in power SystemApplications of PMU in power System


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The Phasor

measurement units are

installed at both ends

of the transmission

line. The three phase

voltages and threephase currents are

measured by PMUs

located at both ends of

line simultaneously

Fault LocationFault Locationpp p ypp p y

PMU A

Synchronize

d phasor

Modal Transform of

synchronized

samples

PMU B

Synchronize

d phasor


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SPM-based applications inpower systems

off-line studies

real-time monitoring and visualization

real-time control, protection andemergency control

42


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SOME RESEARCH

PROGECTS (I

participatedin)


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Global Positioning System (GPS)-

Based Synchronized Phasor

Measurement

By

Eng. Marwa M. Abo El-Nasr

Supervised by

Prof. Dr. Mohamed M. MansourDr. Said Fouad Mekhemer


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CONCLUSIONS

The conclusions extracted form the present work can be

summarized as follows:

1. A technique for estimating the fault location based on

synchronized data for an interconnected network is

developed and implemented using a modal transform

2. One-bus deployment strategy is more useful than tree

search for fault location detection as it gives moresystem observability

ConclusionsConclusions


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3- The average value of mode 1 and 2 ofKarrenbauer transformation is used for 3-phase

and line-to-line faults, while the average value ofthe 3 modes is used for line-to-line-ground andline-to-ground faults

4- The results obtained from applying thedeveloped technique applied to a systemdepicted from the Egyptian network showacceptable accuracy in detecting the fault and

locations of different faults types.


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Essence:

This thesis is to address three issues:

1- Optimal allocation of Phasor Measurement Units(PMUs) using Discrete Particle Swarm

Optimization (DPSO) technique.

2- Large scale power system state estimationutilizing the optimal allocation of PMUs basedon Global Positioning Systems (GPS).

3- Power system voltage stability monitoring basedon the allocated PMUs readings.


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49

Prepared By

Fahd Mohamed Adly Hashiesh

Under Supervision of

Prof. Dr. M. M. MansourDr. Hossam Eldin M. Atia

Dr. Abdel-Rahman A. Khatib

Cairo Egypt2006


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Research Objective

Propose a protection system (strategy) to

counteract wide area disturbance(instability), through employing adaptive

protection relays, and fast broadbandcommunication through wide areameasurement.

Configure and adapt the proposed system tobe applied on Egypt wide power systemnetwork.

50


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A Master Student

is Trying toImplement a PMU

Lab Prototype inAin-Shams Univ.

CONCLUSIONS AND FUTURE WORKS


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CONCLUSIONS AND FUTURE WORKS

thanks to their multiple advantages,

nowadays, the technologies based onsynchronized phasor measurements haveproliferated in many countries worldwide(USA, Canada, Europe, Brazil, China,Egypt !,..).

up to now most applications based onsynchronized phasor measurements haveconcerned mainly off-line studies, on-linemonitoring and visualization, and to a less

extent the real-time control, Protection, andthe emergency control.

the toughest challenge today is to pass fromWide Area Measurements Systems (WAMS) toWide Area Control Systems (WACS) and WAP.

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Off-line SPM-based


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Off line SPM basedapplications

software simulation validation

SPM-based technologies can be very useful to help thevalidation of (dynamic) simulation software

system parameter/model identification (e.g. for loads,lines, generators, etc.)

the identification of accurate model/parameter is a veryimportant and tough task for the power system analysisand control.

difficulty: large number of power system componentshaving time-varying characteristics.

synchronized disturbances record and replay this task is like that of a digital fault recorder, which can

memorize triggered disturbances and replay therecorded data if required.

the use of SPM allows more flexibility and effectiveness.54


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Real-time monitoring SPM-basedapplications

fault location monitoring

accurate fault location allows the time reduction of maintenance of thetransmission lines under fault and help evaluating protectionperformance.

power system frequency and its rate of change monitoring the accurate dynamic wide-area measured frequency is highly

desirable especially in the context of disturbances, which may lead tosignificant frequency variation in time and space.

generators operation status monitoring this function allows the drawing of generator (P-Q) capability curve.

Thus, the generator MVAr reserve, can be supervised.

transmission line temperature monitoring the thermal limit of a line is generally set in very conservative criteria,

which ignores the actual cooling possibilities. The use of SPM allows the

higher loading of a line at very low risk. on-line "hybrid" state estimation

the SPM can be considered, in addition to those from the RemoteTerminal Units (RTU) of the traditional SCADA system, in an on-line"hybrid" state estimation.

SPM-based visualization tools used in control centers

display: dynamic power flow, dynamic phase angle separation, dynamicvoltage magnitude evolution, real-time frequency and its rate of55

Real-time (emergency) control SPM-based


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( g y)applications

automatic (secondary and tertiary) voltage control

aim: optimize the var distribution among generators, controllable ratiotransformers and shunt elements while keeping all bus voltage withinlimits.

in the context of WAMS application, the solution of this optimizationproblem can be used to update settings of those reactive powercontrollers, every few seconds.

damping of low frequency inter-area oscillations (small-signalangle instability) low frequency inter-area oscillations (in the range of 0.2 1 Hz) are a

serious concern in power systems with increasing their size andloadability.

In Europe, in particular, many research studies have been performed toreveal such oscillations as well as provide best remedial actions todamp them out.

transient angle instability since such instability form develops very quickly, nowadays, Special

Protection Systems (SPS), also known as Remedial Action Schemes(RAS), are designed to act against predefined contingencies identified56

Real-time (emergency) control SPM-based


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g yapplications (contd)

short- or long-term voltage instability a responde-based (feedback) Wide-Area stability and voltage Control

System (WACS) is presently in use by BPA.

this control system uses powerful discontinuous actions (switchingon/off of shunt elements) for power system stabilization.

frequency instability the underfrequency load shedding has its thresholds set for worst

events and may lead to excessive load shedding.

new predictive SPM-based approaches are proposed aiming to avoid the

drawbacks of the conventional protection.

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Conclusions:

A new modified DPSO technique is developed to determine theoptimal number and locations for PMUs in power systemnetwork for different depths of unobservability. It gives theoptimal PMUs' allocation for different depths of unobservabilitycomparable to other techniques

The developed DPSO is tested on both 14-bus and 57-busIEEE standard systems.

For small power systems, DPSO gives either equivalent orbetter results. However for large power systems, it gives

almost better locations and sometimes less number of PMUsfor large power systems.

DPSO determines the optimal PMUs' allocation for completeobservability of the large system depicted from the Egyptianunified electrical power network.

A- Discrete Particle Swarm Optimization Technique:


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Conclusions (continued):

The phasors readings of PMUs are taken into consideration ina new hybrid state estimation analysis to achieve a higherdegree of accuracy of the solution.

The effect of changing the locations and numbers of PMUs

through the buses of the power network on the system stateestimation is also studied with a new methodology.

The hybrid state estimation technique is tested on both 14-busand 57-bus IEEE standard systems. It is also applied to a large

system depicted from the Egyptian unified electrical powernetwork.

PMUs' outputs affect the state estimation analysis in a preciousway. It improves the response and the output of thetraditional state estimation.

B- Hybrid State Estimation Technique:


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The locations of PMUs according to state estimationimprovement do not need to be similar to those locationsaccording to observability depth.

The system parameters, system layout and power flow affectthe PMUs' positioning for optimal state estimation.

For each system there is a certain number of PMUs withcertain connections that reduces the estimation errorsignificantly. As the number of PMUs' increases over the

optimal solution, the estimation analysis begins to magnify themeasurements error of the other devices.



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The readings of the allocated PMUs are to be utilized using anewly developed technique for on-line voltage instability

alarming predictor.

The predictor gives two types of alarms, one for voltage limitviolation (10% voltage decrease) and the other for voltagecollapse prediction according to the maximum permissible

angle difference between bus voltages for certain bus loadingangle.

The time taken by the alarming predictor is small, and isdetermined by the speed of PMUs and the used computationalsystem.

The voltage instability alarming predictor concept is tested onboth 14-bus IEEE standard system. It gives effective results.

The alarming predictor is applied to the large system depictedfrom the Egyptian unified electrical power network with the

C- On-line Voltage Instability Alarming Predictor:

Documents

18112008 Mansour GPS in Power Systems