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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.
Phasor Measurement Units PMUsPhasor Measurement Units PMUs
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Secondary
sides of the
3 P.T. orC.T.
Corresponding
Voltage or
Current phasors
input output
PMU
Phasor Measurement Units PMUsPhasor Measurement Units PMUs
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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
Phasor Measurement Units PMUsPhasor Measurement Units PMUs
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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
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.
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
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
Applications of PMU in power SystemApplications of PMU in power System
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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
Applications of PMU in power SystemApplications of PMU in power System
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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.
52
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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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Conclusions (continued):
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.
Conclusions (continued):
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Conclusions (continued):
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: