APPLICATIONS OF GPS IN POWER ENGINEERING

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APPLICATIONS OF GPS IN POWER ENGINEERING
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What is GPS?

• GPS or Global Positioning Systems is a highly
  sophisticated navigation system developed by the
  United States Department of Defense. This system
  utilizes satellite technology with receivers and
  high accuracy clocks to determine the position of
  an object.

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The Global Positioning System

• A constellation of 24 high-altitude satellites

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GPS is

• A constellation of satellites, which orbit the
  earth twice a day, transmitting precise time and
  position (Latitude, Longitude and Altitude)
  Information.
• A complete system of 21 satellites and 3 spares.

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GPS at Work

• Navigation - Where do I want to go?
• Location - Where am I?
• 3. Tracking - Monitoring something as it moves
• 4. Mapping - Where is everything else?
• 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) Applications in
Power Systems
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Power companies and utilities have fundamental
requirements for time and frequency to enable
efficient power transmission and
distribution. Repeated power blackouts have
demonstrated to power companies the need for
improved time synchronization throughout the
power grid. Analyses of blackouts have led
many companies to place GPS-based time
synchronization devices in power plants and
substations
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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 0.021 for a 60 Hz
system and 0.018 for a 50 Hz system and is
certainly more accurate than any other
application
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GPS time synchronization

• By synchronizing the sampling processes for
  different signals which may be hundreds of
  kilometers apart it is possible to put their
  phasors in the same phasor diagram

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GPS time synchronization
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Absolute Time Reference Across the Power System
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Phasor Measurement Units PMUs
Synchronized phasor measurements (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.
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Phasor Measurement Units (PMU) or SYNCHROPHASORS
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DAWN OF THE GRID SYNCHRONIZATION
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Phasor Measurement Units PMUs
Phasor Measurement Units )PMU)
They are devices which use synchronization
signals from the global positioning system (GPS)
satellites and provide the phasor voltages and
currents measured at a given substation.
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Phasor Measurement Units PMUs
PMU
input
output
Corresponding Voltage or Current phasors
Secondary sides of the 3F P.T. or C.T.
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Phasor Monitoring Unit (PMU) Hardware Block
Diagram
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Sampling at Fixed Time Intervals Using an
Absolute Time 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 per second for sampling
of the analog signals. In most systems being used
at present, this is 12 times per cycle of the
fundamental frequency. The analog signals 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.

ABB
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• Now

RES 521
SEL-421
ABB
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Phasor Measurement Units
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Phasor Measurement Units PMUs
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• Data Concentrator (Central Data Collection)

ABB
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Different applications of PMUs in power system
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Applications of PMU in power System

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

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Applications of PMU in power System
1-Adaptive relaying
Adaptive relaying is a protection philosophy
which permits and seeks to make adjustments in
various protection functions in order to make
them more tuned to prevailing power system
conditions
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Applications of PMU in power System
2-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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Applications of PMU in power System
3-State estimation
The state estimator uses various measurements
received from different substations, and, through
an iterative nonlinear estimation procedure,
calculates the power system state.
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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Applications of PMU in power System
4-Improved control
Power system control elements use local
feedback to achieve the control objective.

• 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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Applications of PMU in power System
5-Fault Recording
They can capture and display actual 60/50 Hz
wave form and magnitude data on individual
channels during power system fault conditions.
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Applications of PMU in power System
6-Disturbance Recording
Loss of generation, loss of load, or loss of
major transmission lines may lead to a power
system disturbance, possibly affecting customers
and power system operations.
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Applications of PMU in power System
Disturbance Recording
These figures are examples of long-term data used
to analyze the effects of power system
disturbances on critical transmission system
buses.
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Applications of PMU in power System
7-Transmission and Generation Modeling
Verification
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.
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
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Applications of PMU in power System
7-Transmission and Generation Modeling
Verification
The shown figure compares a remote substation
500 kV bus voltage captured by the PMU to the
stability program results
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8-Wide Area protection
Applications of PMU in power System

• The introduction of the Phasor Measurement Unit
  (PMU) has greatly improved the observability of
  the power system dynamics. Based on PMUs,
  different kinds of wide area protection,
  emergency control and optimization systems can be
  designed

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Applications of PMU in power System
9-Fault Location
A fault location algorithm based on synchronized
sampling. 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.
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Applications of PMU in power System
Fault Location
The Phasor measurement units are installed at
both ends of the transmission line. The three
phase voltages and three phase currents are
measured by PMUs located at both ends of line
simultaneously
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SPM-based applications in power systems

• off-line studies
• real-time monitoring and visualization
• real-time control, protection and emergency
  control

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SOME RESEARCH PROGECTS (I participated in)
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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. Mansour Dr.
Said Fouad Mekhemer
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CONCLUSIONS

• The conclusions extracted form the present work
  can be summarized as follows
• A technique for estimating the fault location
  based on synchronized data for an interconnected
  network is developed and implemented using a
  modal transform
• One-bus deployment strategy is more useful than
  tree search for fault location detection as it
  gives more system observability

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Conclusions

• 3- The average value of mode 1 and 2 of
  Karrenbauer transformation is used for 3-phase
  and line-to-line faults, while the average value
  of the 3 modes is used for line-to-line-ground
  and line-to-ground faults
• 4- The results obtained from applying the
  developed technique applied to a system depicted
  from the Egyptian network show acceptable
  accuracy in detecting the fault and locations of
  different faults types.

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STATE ESTIMATION AND OBSERVABILITY OF LARGE
POWER SYSTEM USING PHASOR MEASUREMENT UNITS
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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 estimation utilizing the optimal allocation
of PMUs based on Global Positioning Systems
(GPS). 3- Power system voltage stability
monitoring based on the allocated PMUs readings.
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Wide Area Protection System for Maximizing Power
System Stability

• Prepared By
• Fahd Mohamed Adly Hashiesh
• Under Supervision of
• Prof. Dr. M. M. Mansour
• Dr. Hossam Eldin M. Atia
• Dr. Abdel-Rahman A. Khatib
• Cairo Egypt
• 2006

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Research Objective

• Propose a protection system (strategy) to
  counteract wide area disturbance (instability),
  through employing adaptive protection relays, and
  fast broadband communication through wide area
  measurement.
• Configure and adapt the proposed system to be
  applied on Egypt wide power system network.

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A Master Student is Trying to Implement a PMU Lab
Prototype in Ain-Shams Univ.
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CONCLUSIONS AND FUTURE WORKS

• thanks to their multiple advantages, nowadays,
  the technologies based on synchronized phasor
  measurements have proliferated in many countries
  worldwide (USA, Canada, Europe, Brazil, China,
  Egypt !,..).
• up to now most applications based on synchronized
  phasor measurements have concerned mainly
  off-line studies, on-line monitoring and
  visualization, and to a less extent the real-time
  control, Protection, and the emergency control.
• the toughest challenge today is to pass from Wide
  Area Measurements Systems (WAMS) to Wide Area
  Control Systems (WACS) and WAP.

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Thank You
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Off-line SPM-based applications

• software simulation validation
• SPM-based technologies can be very useful to help
  the validation of (dynamic) simulation software
• system parameter/model identification (e.g. for
  loads, lines, generators, etc.)
• the identification of accurate model/parameter is
  a very important and tough task for the power
  system analysis and control.
• difficulty large number of power system
  components having 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 the recorded data if
  required.
• the use of SPM allows more flexibility and
  effectiveness.

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Real-time monitoring SPM-based applications

• fault location monitoring
• accurate fault location allows the time reduction
  of maintenance of the transmission lines under
  fault and help evaluating protection
  performance.
• 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 to significant
  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 Remote Terminal 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, dynamic voltage magnitude evolution,
  real-time frequency and its rate of change, etc.

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Real-time (emergency) control SPM-based
applications

• automatic (secondary and tertiary) voltage
  control
• aim optimize the var distribution among
  generators, controllable ratio transformers and
  shunt elements while keeping all bus voltage
  within limits.
• in the context of WAMS application, the solution
  of this optimization problem can be used to
  update settings of those reactive power
  controllers, every few seconds.
• damping of low frequency inter-area oscillations
  (small-signal angle 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 and
  loadability.
• In Europe, in particular, many research studies
  have been performed to reveal such oscillations
  as well as provide best remedial actions to damp
  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 identified in off-line studies
  while being less effective against unforeseen
  disturbances.

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Real-time (emergency) control SPM-based
applications (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 (switching on/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- Discrete Particle Swarm Optimization
Technique

• A new modified DPSO technique is developed to
  determine the optimal number and locations for
  PMUs in power system network for different depths
  of unobservability. It gives the optimal PMUs'
  allocation for different depths of
  unobservability comparable to other techniques
• The developed DPSO is tested on both 14-bus and
  57-bus IEEE standard systems.
• For small power systems, DPSO gives either
  equivalent or better results. However for large
  power systems, it gives almost better locations
  and sometimes less number of PMUs for large power
  systems.
• DPSO determines the optimal PMUs' allocation for
  complete observability of the large system
  depicted from the Egyptian unified electrical
  power network.

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Conclusions (continued)
B- Hybrid State Estimation Technique

• The phasors readings of PMUs are taken into
  consideration in a new hybrid state estimation
  analysis to achieve a higher degree 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 state estimation is also studied with
  a new methodology.
• The hybrid state estimation technique is tested
  on both 14-bus and 57-bus IEEE standard systems.
  It is also applied to a large system depicted
  from the Egyptian unified electrical power
  network.
• PMUs' outputs affect the state estimation
  analysis in a precious way. It improves the
  response and the output of the traditional state
  estimation.

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Conclusions (continued)

• The locations of PMUs according to state
  estimation improvement do not need to be similar
  to those locations according to observability
  depth.
• The system parameters, system layout and power
  flow affect the PMUs' positioning for optimal
  state estimation.
• For each system there is a certain number of PMUs
  with certain connections that reduces the
  estimation error significantly. As the number of
  PMUs' increases over the optimal solution, the
  estimation analysis begins to magnify the
  measurements error of the other devices.

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Conclusions (continued)
C- On-line Voltage Instability Alarming
Predictor

• The readings of the allocated PMUs are to be
  utilized using a newly developed technique for
  on-line voltage instability alarming predictor.
• The predictor gives two types of alarms, one for
  voltage limit violation (10 voltage decrease)
  and the other for voltage collapse prediction
  according to the maximum permissible angle
  difference between bus voltages for certain bus
  loading angle.
• The time taken by the alarming predictor is
  small, and is determined by the speed of PMUs and
  the used computational system.
• The voltage instability alarming predictor
  concept is tested on both 14-bus IEEE standard
  system. It gives effective results.
• The alarming predictor is applied to the large
  system depicted from the Egyptian unified
  electrical power network, with the aid of the
  voltage instability limits calculation of the
  system.