20-04-2010, 01:36 PM
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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
APPLICATIONS OF GPS IN POWER ENGINEERING
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.
The Global Positioning System
A constellation of 24 high-altitude satellites
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.
GPS at Work
1. Navigation - Where do I want to go
2. Location - Where am I
3. Tracking - Monitoring something as it moves
4. Mapping - Where is everything else
5. Timing - When will it happen
Why do we need GPS
Safe Travel
Traffic Control
Resource Management
Defense Mapping
Utility Management
Property Location
Construction Layout
4 Ëœbirdsâ„¢ (as we say) for 3-D fix
Why GPS For power Eng
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
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.
Phasor Measurement Units
(PMU)
[or SYNCHROPHASORS]
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.
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.
Different applications of PMUs 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
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
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.
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
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
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.
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.
Disturbance Recording
These figures are examples of long-term data used to analyze the effects of power system disturbances on critical transmission system buses.
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
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
8-Wide “ Area protection
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
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.
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
SPM-based applications in power systems off-line studies
real-time monitoring and visualization
real-time control, protection and emergency control
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 more system observability
3. 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. 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.
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 PMUsâ„¢ readings.
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.
A Master Student is Trying to Implement a PMU Lab Prototype in Ain-Shams Univ.
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.
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.
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.
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.
Real-time (emergency) control SPM-based applications (contâ„¢d)
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.
