Download A Novel Back Up Wide Area Protection Technique for Power

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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010
A Novel Back Up Wide Area Protection Technique
for Power Transmission Grids Using Phasor
Measurement Unit
M. M. Eissa, Senior Member, IEEE, M. Elshahat Masoud, and M. Magdy Mohamed Elanwar
Abstract—Current differential protection relays are widely applied to the protection of electrical plant due to their simplicity,
sensitivity and stability for internal and external faults. The proposed idea has the feature of unit protection relays to protect large
power transmission grids based on phasor measurement units. The
principle of the protection scheme depends on comparing positive sequence voltage magnitudes at each bus during fault conditions inside a system protection center to detect the nearest bus to
the fault. Then the absolute differences of positive sequence current angles are compared for all lines connecting to this bus to
detect the faulted line. The new technique depends on synchronized phasor measuring technology with high speed communication system and time transfer GPS system. The simulation of the interconnecting system is applied on 500 kV Egyptian network using
Matlab Simulink. The new technique can successfully distinguish
between internal and external faults for interconnected lines. The
new protection scheme works as unit protection system for long
transmission lines. The time of fault detection is estimated by 5
msec for all fault conditions and the relay is evaluated as a back
up relay based on the communication speed for data transferring.
Index Terms—Digital protection, discreet Fourier transform,
(GPS) system, synchronized phasor measurement, time synchronization.
I. INTRODUCTION
S
YSTEM-WIDE disturbances in power systems are a challenging problem for the utility industry because of the large
scale and the complexity of the power system. When a major
power system disturbance occurs the protection and control actions are required to stop the power system degradation, restore
the system to a normal state, and minimize the impact of the
disturbance [1]. The present control actions are not designed
for a fast developing disturbance and may be too slow. Further, dynamic simulation software is applicable only for off-line
analysis.
The recent enlargement and increased complexity of power
system configurations has led to adjacent arrangements of short
and long distance power transmission lines, both connected to
Manuscript received May 20, 2009. First published December 11, 2009; current version published December 23, 2009. Paper no. TPWRD-00055-2009.
M. M. Eissa was with the Faculty of Engineering, Electrical Engineering Department, Helwan University, Cairo 11795, Egypt. He is now with King AbdulAziz University, Jeddah 21415, Saudi Arabia (e-mail: [email protected]).
M. E. Masoud and M. M. M. Elanwar are with the Faculty of Engineering,
Power Department, Helwan University at Helwan, Cairo 11795, Egypt.
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TPWRD.2009.2035394
the same busbar in a substation [2]. This causes difficult situations when relay engineers coordinate reach or operate time
among distance relays. To cope with this, current differential
protection which utilizes wide-area current data would be effective for wide-area backup protection although such protection
needs system-wide timing synchronism for the simultaneous
current sampling at all remote terminals and data exchanges
among them.
In this area, an adaptive Phasor Measurement Unit (PMU)
based protection scheme for both transposed and un-transposed
parallel transmission lines is given [3]. The development of the
scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of
eigenvalue/eigenvector theory to decouple the mutual coupling
effects between parallel lines, the fault detection and location
indexes are derived.
A fault detection/location technique with consideration of
arcing fault discrimination based on phasor measurement units
for extremely high voltage/ultra-high voltage transmission lines
is presented in [4]. The proposed arcing fault discriminator
can discriminate between arcing and permanent faults within
four cycles after fault inception. Some techniques presented
fault location algorithm based on phasor measurement units for
series compensated lines [5].
A new wide area differential protection (WADP) system is
proposed to suit the need of the shipboard application [6]. The
close proximity of all the components in a shipboard power
system makes communication less of an issue than in a landbased system. With an overall view of the protected system and
by use of a differential search algorithm, a minimum fault isolation area is decided.
A very few papers are published for applications of wide area
on transmission lines protection. Most of the published papers
are used for determining the fault location on the transmission
lines. The suggested paper provides a new technique for wide
area protection using PMU. This paper introduces protection
scheme depending on comparing positive sequence voltage
magnitudes for specified areas and positive sequence current
phase difference angles for each interconnected line between
two areas on the network. The paper will cover all fault events.
The technique uses the time synchronized phasor measurements. This provides a dynamic view of the power system.
The measurements are processed in a system protection central
(SPC). This capability is used to set up a wide area control,
protection and optimizing the platform by means of new fast
communication system and (GPS).
0885-8977/$26.00 © 2009 IEEE
EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT
Fig. 1. Three zones of operation for each stand alone relay.
II. CONVENTIONAL PROBLEMS
The distance relays which are widely applied in the protection today and involve the determination of impedance achieve
operating times of the order of a period of the power system
frequency. A distance relay is designed to only operate for
faults occurring between the relay location and the selected
reach point, and remains stable for all faults outside this
region or zone [7]. The resistance of the fault arc takes the
fault impedance outside the relay’s tripping characteristic and,
hence, it does not detect this condition. Alternatively, it is only
picked up either by zone 2 or zone 3 in which case tripping will
be unacceptably delayed [8]. The distance relays are based on
stand alone decision, while each relay operates independently
according to three different zone of operation, see Fig. 1.
The mal-operation or fail-to trip of protection is determined
as one of the origins to raise and propagate major power system
disturbances [9]. A vast majority of relay mal-operations is unwanted trips and have been shown to propagate major disturbances. Backup protections in fault clearance system have the
task to operate only when the primary protection fails to operate
or when the primary protection is temporarily out of service. The
recent complexity and enlargement of power systems makes
it difficult to coordinate operation times and reaches among
relays.
In the areas of power system automation and substation automation, there are two different trends: centralization and decentralization. More and more dynamic functions are moving
from local and regional control centers toward central or national control centers. At the same time we also observe more
“intelligence” and “decision power” moving closer towards the
actual power system substations. Greater functional integration
is being enclosed in substation hardware.
In view of global security of power systems, the action algorithms of conventional backup protections possibly are not best
choices because the operations of individual relays are hardly
coordinated each other. Therefore, the principle of the protection design needs innovation to overcome the above problem.
Modern protection devices have sufficient computing and communications capabilities to allow the implementation of many
novel sophisticated protection principles.
Therefore, a novel wide-area backup protection system is reported in this paper. This system is capable of acting as the
substitution of conventional distributed backup protections in
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Fig. 2. The new protected zones of the proposed relay.
substation. To ensure the fast responsibility of such a system to
the emergent events, the communication requirements are discussed as well. Conclusively, the proposed system is designed
by two ways. First, in substation, concentrate some conventional backup protection functions to an intelligent processing
system; second, concentrate the coordinated and optimized processing and controlling arithmetic of all backup protection in a
region into a regional processing unit. The communication of
data among them is carried via optic-fiber networks.
The relay decision is based on collected and shared data
through communication network. The suggested technique satisfies high degree of reliability and stability while it is based on
shared decision rather than stand alone decision. The suggested
technique can see all the power system area and can deal with
the transmission lines as unit protection, see Fig. 2. The primary
purpose of these systems is to improve disturbance monitoring
and system event analysis. These measurements have been sited
to monitor large generating sites, major transmission paths, and
significant control points. Synchronized phasor measurements
provide all significant state measurements including voltage
magnitude, voltage phase angle, and frequency.
III. COMPONENTS OF PHASOR MEASUREMENT UNIT
The technology of synchronized phasor measurements is
well established. It provides an ideal measurement system
with which to protect, monitor and control a power system, in
particular during conditions of stress. The essential feature of
the technique is to measure positive sequence (negative and
zero sequence quantities if needed) voltages and currents of a
power system in a real time with precise time synchronization.
This allows accurate comparison of measurements over widely
separated locations as well as potential real-time measurement
based control actions. Very fast recursive discrete Fourier
transform (DFT) calculations are normally used in phasor
calculations. In the suggested technique, a positive sequence
voltage and phase angle of the positive sequence current is
used.
The DFT technique is a short-time variation of the Fourier
analysis. While the Fourier transform is applied to signals in
the continuous time domain, the DFT is applied to time-domain
signals represented by sequences of numbers. The basic phasor
measurement process is that of estimating a positive-sequence,
fundamental frequency phasor representation from voltage or
current waveforms.
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Fig. 3. Synchronized phasor measurement block diagram.
Fig. 3 shows the analog power signal that converted into
digital data by the analog to digital converter. For example, if
the voltage is needed to be measured, the samples are taken
for each cycle of the waveform and then the fundamental
frequency component is calculated using (DFT). The figure
also shows a simple block diagram explaining the procedure
of measured voltage or current analog signal. The sampled
data are converted to a complex number which represents the
phasor of the sampled waveform. Phasors of the three phases
are combined to produce the positive sequence measurement.
The figure includes a hardware low-pass filter (Hardware LPF)
for antialiasing and an analog-to-digital (A/D) converter for
analog-to-digital conversion.
The system of supervision permits capturing records of the
same event at different points in the power system with a unique
time reference, the phasor measurement units at present are located strategically, with the purpose of capturing information on
the impact of contingencies at the local or system level. Fig. 4
shows the electric system with the location of the PMUs. The
phasor measuring unit is represented by a discrete phase sequence analyzer block which convert 3 phase signals (Vabc or
Iabc) to a positive, negative and zero sequence component magnitudes and angle. Each phase signal (Va, Vb and Vc) is converted to real and imaginary component using Discrete Fourier
Transform. The positive sequence component is calculated in
sequences analyzer by the following equation:
where
, the overall process to calculate positive,
negative or zero sequence component using Matlab simulink.
IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010
Fig. 4. The PMUs arrangement with phasor data concentration and system protection center.
IV. COMMUNICATION ISSUES AND BACK UP RELAYS
The application of the wide area in the protection is not
straight forward from the communication point of view. In such
case the communication issues related to time delay is discussed
here. Standard communication systems are adequate for most
phasor data transmission. The issue for data communications
includes speed, latency and reliability. Communication speed
(data rate) depends on the amount of phasor data being sent.
A. Communication Options Available
Communication links used by WAPS include both wired
(telephone lines, fiber-optics, power lines) and wireless (satellites) options. Delays associated with the link act as a crucial
indicator to the amount of time-lag that takes place before action is initiated. The delays are an important aspect and should
be incorporated into any power system design or analysis, as
excess delays could ruin any control procedures adopted to
stabilize the power grid.
B. Communication Delay Causes
Although more and more control systems are being implemented in a distributed fashion with networked communication, the unavoidable time delays in such systems impact the
achievable performance. Delays due to the use of PMUs and the
communication link involved are due primarily to the following
reasons.
Transducer Delays: Voltage transducers (VT) and current
transducers (CT) are used to measure the RMS voltages and currents respectively, at the instant of sampling.
Window Size of the DFT: Window size of the DFT is the
number of samples required to compute the phasors using DFT.
EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT
Processing Time: The processing time required in converting
the transducer data into phasor information with the help of
DFT.
Data Size of the PMU Output: Data size of the PMU message
is the size of the information bits contained in the data frame,
header frame and the configuration frame.
Multiplexing and Transitions: Transitions between the communication link and the data processing equipment leads to delays that are caused at the instances when data is retrieved or
emitted by the communication link.
Communication Link Involved: The type of communication
link and the physical distance involved in transmitting the PMU
output to the central processing unit can add to the delay.
Data Concentrators: Data concentrators are primarily data
collecting centers located at the central processing unit and are
responsible for collecting all the PMU data that is transmitted
over the communication link.
C. Delay Calculations
Delay calculations form an important aspect of WAMS;
these delays indicate the viability of a particular communication medium, since large communication delays amount to
slower controller actions that can correct power grid instabilities and oscillations. Communication delay given in [10], [11]
can be expressed as
where is the total link delay,
is the fixed delay associated
with transducers used, DFT processing, data concentration and
is the link propagation delay, L is the amount
multiplexing,
of data transmitted, R is the data rate of the link, and is the
associated random delay jitter. Delay calculations can be made
on the assumptions that there are 10–12 phasor measurements,
each 4 bytes in length, 10 input status channels, each 2 bytes in
length, and the combined delay caused by processing, concentrators, multiplexing and transducers is estimated to be around
75 msec. This is the fixed delay and is independent of the communication medium used. The propagation delay is dependent
on the medium and thus is a function of both the medium and
the physical distance separating the individual components of
WAMS. We have assumed that media like fiber-optic cables,
power lines, and telephone lines, on an average, have a propagation delay of around 25 ms. Considering the total length of the
PMU packet, the delay caused due to the amount of data transmitted and the data rate can then be estimated to be around 125
ms, considering a telephone line channel with an average capacity of 33.6 kbps. In the case of substations, where isolation
circuits are required, the telephone line channel capacity could
drop to as low as 9.6 kbps, creating a bottleneck, and thereby
increasing the delay to more than 200 ms. Even though power
lines can reach speeds of up to 4 Mbps.
Standard communication systems are adequate for most
phasor data transmission. The issues for data communications
include speed, latency, and reliability. Communication speed
(data rate) depends on the amount of phasor data being sent
and the number of messages. A PMU sending 10 phasors at 30
messages has an actual data rate of about 17 kbps. Reliability in
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TABLE I
THE INTERCONNECTED AREAS
this application includes both error rate and component failures.
Such protection scheme suggested here needs to a very high
media of communication system, the available data transfer can
reach speed up to 2 Mpbs [10], [11].
From above the proposed relay is evaluated as a backup relays
from the point of view data handling through the communication
channels, in spite of the fast detection time estimated by 5 msec
for all fault cases.
V. THE TECHNIQUE COMPONENTS BASED ON WIDE AREA
MEASUREMENT SYSTEM
The primary purpose of these systems is to improve
disturbance monitoring and system event analysis. These
measurements have been sited to monitor large generating
sites, major transmission paths, and significant control points.
Synchronized phasor measurements provide all significant state
measurements including voltage magnitude, voltage phase
angle, and frequency.
Most of these phasor measurement systems have been implemented as real-time systems. With these systems, phasor measurement units (PMUs) installed at substations send data in real
time over dedicated communications channels to a data concentrator at a utility control center. This approach allows the data
to be used in System Protection Center (SPC) as well as being
recorded for system analysis and monitored via SCADA system
as shown in Fig. 4.
PMUs measure the bus voltage(s) and all the significant line
currents. These measurements are sent to a Phasor Data Concentrator (PDC) at the control center. The PDC correlates the
data by time tag to create a system-wide measurement. The PDC
exports these measurements as a data stream as soon as they
have been received and correlated. System protection center
(SPC) receive Data stream and make a wide area protection depending on wide area view. This principal of operation is used
in this paper. WAPS schemes are designed to detect abnormal
system conditions, take pre-planned corrective actions intended
to minimize the risk of wide-area disruptions and isolate the
faulted segment from the over all power system. WAPS depend
on WAMs to take hieratical action depending on wide area monitor of the over all network.
VI. THE STUDIED NETWORK
Part of the 500/220 kV Egyptian interconnected electrical
network is used for the study; five main buses that represent
five different areas with 500 kV are selected to verify the suggested technique. The selected five different areas with buses
are given in Table I. Fig. 5 shows the selected five areas from
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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010
Fig. 5. Single line diagram of the studied network.
VII. THE PROPOSED TECHNIQUE
Fig. 6. Positive sequance current angles.
TABLE II
THE LENGTHS AND ANGLES
the overall network. In the single line diagram, each bus represents the selected area in the simulation that can connect the 500
kV network with 220 kV network through three single phase
500/220 kV power transformers. A sampling frequency of 20
kHz for a system operating at a frequency of 50 Hz is used in
this study.
Table II defines each transmission line that connecting two
neighboring areas. The lengths of the transmission lines are
is defined as the absolute difference begiven in km.
tween positive sequence current angles measured at transmission line terminals. Fig. 6 shows the positive sequence current
measured at transmission line terminals, from its
angles
area to the other connected area.
The proposed technique is based mainly on two components
to identify the faults on the transmission lines. The first component is the voltage reduction due to fault occurrence. The second
component is the power flow direction after fault occurrence.
The phase angle is used to determine the direction of fault current with respect to a reference quantity. The ability to differentiate between a fault in one direction or another is obtained by
comparing the phase angle of the operating voltage and current.
The voltage is usually used as the reference polarizing quantity. The fault current phasor lies within two distinct forward
and backward regions with respect to the reference phasor, depending on the power system and fault conditions [12]–[14].
The normal power flow in a given direction will result in the
phase angle between the voltage and the current varying around
. When power flows in the opposite
its power factor angle
direction, this angle will become
. For a fault in the
reverse direction, the phase angle of the current with respect to
[14].
the voltage will be
The main idea of the proposed technique is to identify the
faulted area. This can be achieved by comparing the measured
values of the positive sequence voltage magnitudes at the main
bus for each area. This can result in the minimum voltage value
that indicates the nearest area to the fault. In addition to that, the
absolute differences of the positive sequence current angles are
calculated for all lines connected with the faulted area. These
absolute angles are compared to each other. The maximum absolute angle difference value is selected to identify the faulted
line. The above two keys of operation can be mathematically
described as follows:
(1)
is the positive sequence voltage magnitude meawhere
sured by PMU and located at area “1”, “2”, “3”
“m”, to “n”.
For a fault occurred on the grid, the output from (1) is the
minimum positive sequence voltage magnitude which indicates
the nearest area to the fault. Suppose that the nearest area to the
EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT
275
Fig. 7. The logic implementation of the technique.
Fig. 8. Matlab simulink block daigram.
fault is indicated by number “m”. The next step is to compare
the absolute differences of positive sequence current angles for
all lines connecting area “m” with all other neighboring areas
and then selecting the max one. This can be explained as
(2)
is the absolute difference of positive sequence
where
current angle for a transmission line connecting area “m” with
area “n”. This can be described by the following equation:
(3)
The above process can be implemented logically in Fig. 7.
The output of the logic action is the faulted line. The following
sub-sections will explain the stages of the proposed technique.
VIII. OVERALL STAGES OF THE PROPOSED TECHNIQUE
The studied configuration system is classified into 5 different
areas, the following section explain the main components of the
proposed technique. Fig. 8 shows more details about the elements used in the protection technique.
A. Data Preparation (Bay Level)
Each area contains one PMU which receives analog signals
from (CTs) and (VTs) in bay level.
• Voltage transformers (VTs) on the main bus for each area
receive 3 phase voltage (Vabc) to the PMU.
• Current transformers (CTs) on each line terminal receive
3 phase current (Iabc) to the PMU.
• PMU converts the analog voltage and current signals to
digital samples synchronized in time of measuring, the Discrete Fourier Transform method inside PMU calculates the
positive sequence voltage and current phasors.
B. Output From PMU
The output signal from the PMU is the positive sequence
&
voltage and the positive sequence currents
nm
nm respectively, where
Positive sequence voltage magnitude for area # n.
: Positive sequence voltage angles for area # n.
Positive sequence current magnitude for interconnected line between area # n and area # m.
Positive sequence current angle for interconnected line between area # n and area # m.
For the proposed technique, only positive sequence voltage
and positive sequence current angles
magnitudes
nm
are selected.
C. Phasor Data Concentrator PDC
The PDC is considered as a computer database that contains
data from five phasor measurement units (PMUs). Each PMU
sends measuring data through fast communication system to
PDC which correlates the data by time tag to create a systemwide measurement.
D. System Protection Center SPC
In WAMs, the PMUs are strategically placed throughout a
wide coverage area. The PMUs form part of local devices called
system protection terminals (SPT). SPTs are able to run complete or parts of distributed control algorithms and can communicate directly with other SPTs, substation equipment and
system protection centers (SPC) which is responsible for protection, monitoring and control of the power grid.
E. Data Manipulation in SPC
SPC receives data stream from PDC and provides a wide area
protection depending on wide area view. In the SPC unit, the
measuring values of positive sequence voltage magnitudes are
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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010
Fig. 10. Three phase current signals for all lines connected to the faulted area
(area “2”).
Fig. 9. Three phase voltage signals at each area.
compared, the minimum voltage magnitude is selected, and the
nearest area to the fault is detected.
IX. THRESHOLD BOUNDARY
The final performance of the technique is identified by satisfying two criteria. The first criterion concerns the comparison
of the positive sequence voltage magnitudes at the bus and then
selecting the minimum voltage value that indicates the faulted
area. The voltage magnitude should go lower than setting value
amounted by 0.95 of the operating voltage. The second criterion is used to compare of the absolute difference of the positive
sequence current angles and selecting the maximum one. This
value should go higher than some positive threshold boundary
amounted by 100 . A trip output is produced when the above
two conditions are met. The final trip logic combines the decisions using the AND gate logic shown in Fig. 7.
Fig. 11. Positive sequence voltage magnitudes.
X. CASE STUDY
An extensive series of study is examined on the power system
given in Fig. 8. All fault events are studied and a sample of the
results is given here. More details about the different cases of
faults can be given in [15]. As mentioned above, the studied
network is classified into 5 neighboring areas. The 5 areas are
connected with each others by six lines. Three phases to ground
fault are located on line 1 which connecting area “1” with area
“2”, see Fig. 8.
Fault location is placed away from area “1” and area “2” by
100 and 45 km respectively. The three phase voltage signals at
each area are recorded and displayed in Fig. 9. The three phase
current signals for all lines connected to the faulted area are
recorded and displayed in Fig. 10 as:
• line 1 connecting area 2 with area 1;
• line 3 connecting area 2 with area 3;
• Line 5 connecting area 2 with area 4.
Fig. 11 shows the output from the five PMUs, the graph
shows the five positive sequence voltage magnitudes (PSVM)
for five different areas during fault. The minimum value is
selected which indicates the nearest area to the fault (area “2”).
The next step is used to identify the faulted line. Fig. 12 shows
the absolute diffrences of positive sequance current angles
(PSCA) for all lines connecting the faulted area (area “2”) with
all other neighboring areas (areas “1”, “3”, “4”). The graph
shows the maximum absolute difference of positive sequence
currrent angle (about 175 ) that refers to line 1. The time taken
to reach the threshold voltage is about 4 ms. While the time
taken to reach the threshold angle is 3 ms, then the fault can
be detected in about 4 ms. A single phase to ground fault is
located on transmission line TL3, see Fig. 8, which connecting
area “2” (Kurimat) with area “3” (Cairo 500). The distance
between fault location on the transmission line and the nearest
EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT
Fig. 12. Positive sequance current angle absolute differences for all lines connected to the faulted area (area “2”).
277
Fig. 14. Positive sequence current angles (absolute difference) for all lines connected to area “2”.
Fig. 15. Positive sequence voltage magnitudes measured from five places on
the network.
Fig. 13. Positive sequence voltage magnitudes measured from five places on
the network.
Kurimat bus is 20 km. The 3-phase voltage signals measured
from Kurimat bus are recorded. The 3-phase current signals for
all transmission lines connected to Kurimat are also recorded.
Fig. 13 shows the five PSVM (Positive Sequence Voltage
Magnitudes). The minimum value is selected to indicate that
the nearest area to the fault is area “2”. Fig. 14 shows the absolute differences of PSCA (Positive Sequence Current Angles)
for all lines connecting the faulted area “2” with all other neighboring areas “1”, “3” and “4”. The angles difference of TL3 is
the maximum value given by 160 . This means that the current
is reversed from one terminal only. It is clear that the fault is
internal and this transmission line must be isolated. The figures
also show the threshold boundary.
A double-phase to ground fault is located on transmission
line TL1, see Fig. 8. The distance between the fault point on the
transmission line and the nearest bus “Samalout” is 45 km. The
3-phase voltage signals measured from area “1” are recorded.
The 3-phase current signals for all transmission lines connected
with “Samalout” are also recorded. Fig. 15 shows the five
PSVM for five different areas during the fault. The minimum
Fig. 16. Positive sequence current angles (absolute difference) for all lines connected to area “1”.
value is selected to identify the nearest area to the fault as area
“1”. Fig. 16 shows the absolute differences of PSCAs for all
lines connecting area “1” with all other neighboring areas (area
“2” and area “3”). The angles difference measured at the transmission line terminals (TL1) recorded maximum difference by
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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010
170 . This means that the current is reversed from one terminal
only. It is clear that the fault is internal and the transmission
line must be isolated. Figs. 15 and 16 show also the threshold
boundary with time estimated by 3 msec.
[7] S. H. Horowitz and A. G. Phake, Power System Relaying. Taunton,
Somerset, U.K.: Research Studies Press, 1992.
[8] M. M. Eissa, “New principle for transmission line protection using
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49–56, 2009.
[9] D.-Q. Wang, S.-H. Miao, X.-N. Lin, P. Liu, Y.-X. Wu, and D. Yang,
“Design of a novel wide-area backup protection system,” in Proc.
IEEE/PES Transm. Distrib. Conf. Exhib.: Asia Pac. Dalian, China,
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[10] B. Naduvathuparambil, M. C. Valenti, and A. Feliachi, Communication
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[11] R. Klump and R. E. Wilson, “Visualizing real-time security threats
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[15] , “Protection of Interconnected Electrical Networks Using Phasor Synchronized Measuring Technique,” Ph.D. dissertation, Helwan University-Faculty of Engineering at Helwan, Cairo, Egypt.
XI. CONCLUSION
The paper presents a new protection technique for transmission grids using phasor synchronized measuring technique in a
wide area system. The protection scheme has successfully identified the faulted line allover the interconnect system. The relay
descried in this paper represents a new state-of-art in the field
of interconnected grid protection for many reasons.
• The relay is based on sharing data from all areas.
• One relay is used instead of many stand alone relays with
different complexity coordination.
• The relay has the feature of unit protection in identifying
the faulted zone.
• One and only one trip decision is issued from the protection
center.
The relay has a very fast detection time estimated by 5 msec
for all fault cases. In the near future and with a very fast communication links the relay can be considered as a main relay on
the interconnected grids.
REFERENCES
[1] Wide Area Protection and Emergency Control, 2002, IEEE Members,
Working Group C-6.
[2] U. Serizawa, M. Myoujin, K. Kitamura, and N. Sugaya, “Wide area
current differential backup protection employing broadband communication and time transfer systems,” IEEE Trans. Power Del., vol. 13,
no. 4, pp. 427–433, Oct. 1998.
[3] C.-S. Chen, C.-W. Liu, and J.-A. Jiang, “A new adaptive PMU based
protection scheme for transposed/untransposed parallel transmission
lines,” IEEE Trans. Power Del., vol. 17, no. 2, pp. 395–404, Apr. 2002.
[4] Y.-H. Lin, C.-W. Liu, and C.-S. Chen, “A new PMU-based fault
detection/location technique for transmission lines with consideration
of arcing fault discrimination—Part I: Theory and algorithms,” IEEE
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[5] C.-S. Yu, C.-W. Liu, S.-L. Yu, and J.-A. Jiang, “A new PMU-based
fault location algorithm for series compensated lines,” IEEE Trans.
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[6] J. Tang and P. G. McLaren, “A wide area differential backup protection
scheme for Shipboard application,” IEEE Trans. Power Del., vol. 21,
no. 3, Jul. 2006.
M. M. Eissa (M’96–SM’01) was born in Helwan, Cairo, Egypt, on May 17,
1963. He received the B.Sc. and M.Sc. degrees in electrical engineering from
Helwan University, Cairo, Egypt, in 1986 and 1992, respectively, and the Ph.D.
degree from the Research Institute for Measurements and Computing Techniques, Hungarian Academy of Science, Budapest, Hungary, in 1997.
He is a Professor at Helwan University. In 1999, he was invited to be a Visiting Research Fellow at the University of Calgary, Calgary, AB, Canada. His
research interests include digital relaying, application of widearea networking
to power systems, power quality and energy management, and wide-area
protection.
Dr. Eissa received the Egyptian State Encouragement Prize in advanced
science in 2002 and the Best Research in advanced engineering science from
Helwan University in 2005.
M. E. Masoud, photograph and biography not available at the time of
publication.
M. M. M. Elanwar, photograph and biography not available at the time of
publication.