Transcript applications of gps in power engineering

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 highaltitude
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
3. Tracking
4. Mapping
- Where am I?
- Monitoring something as it moves
- 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 ‘birds’ (as we say) for 3-D
fix
Global Positioning Systems (GPS) Applications
in Power Systems
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
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
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
GPS time synchronization
V1
V
V1
Ψ
Substation 1
V2
FFT or any other
technique gives:
•Magnitude
•Phase angle
With respect to GPS
V
Substation 2
t1 t2 t3 t4
t5 t6 t7
GPS time synchronized
pulses
V2
Absolute Time Reference
Across the Power System
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.
Phasor Measurement Units
(PMU)
[or SYNCHROPHASORS]
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.
Phasor Measurement Units PMUs
input
Secondary
sides of the
3Φ P.T. or
C.T.
PMU
output
Corresponding
Voltage or
Current phasors
Phasor Monitoring Unit (PMU) Hardware Block
Diagram:
GPS
receiver
Analog
Inputs
Anti-aliasing
filters
Phase-locked
oscillator
16-bit
A/D
converter
Modems
Phasor
microprocessor
Sampling at Fixed Time Intervals
Using an Absolute Time Reference
v
LPF
A/D
¦s
Time
Synch
GPS
Clock
Synchronized
Phasor
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.
The Birth of the PMUs

Computer Relaying developments in 1960-70s.
ABB

Now
SEL-421
RES 521
ABB
Phasor Measurement Unit’s
Phasor Measurement Units PMUs
central data
collection
 Data Concentrator (Central Data Collection)
ABB
Different applications of
PMUs in
power system
Applications of PMU in power
1. Adaptive relaying System
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 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
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.
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
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
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.
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.
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.
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
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
Applications of PMU in power System
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
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.
Applications of PMU in power System
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
Fault Location
PMU A
Synchroniz
ed phasor
Modal Transform of
synchronized
samples
PMU B
Synchroniz
ed phasor
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)
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
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
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.
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.
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.
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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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 timevarying 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
(cont’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.
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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.
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.
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.
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.