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SETTING OF DISTANCE RELAY ON POWER TRANSMISSION LINE
USING PSCAD
SHAKIRA AZEEHAN BINTI AZLI
A report submitted in partial fulfilment of the
requirements for award of degree of
Bachelor of Engineering (Electrical)
Faculty of Electrical Engineering
University Teknologi Malaysia
APRIL 2010
ii
iii
Dedicated to my beloved father
PM Dr Azli Bin Sulaiman
Mother
Noor Sharidah Binti Alias
Siblings
Hizaz Shahiela
Izzat Fahmi
Adib Fikri
Amelia Adrina
and
My Entire friend in SEE programme
For their encouragement
iv
ACKNOWLEDGEMENT
“Praise is to Allah S.W.T, the Most Merciful and the Most Compassionate.
Peace is upon him, Muhammad, the messenger of God”.
I wish to express my sincere appreciation to my project supervisor, Dr
Ahmad Safawi Bin Mokhtar for all his guidance, encouragement and support in
completing the final year project.
I would also like to express my gratitude to all the lectures who have taught
me throughout the years of studying in UTM, thank you for all the knowledge that
has been provided.
My gratitude is also extending to my fellow colleagues for sharing their ideas
and discussions. Last but not least, I would like to thanks my family for their
motivation and moral support.
v
ABSTRACT
The role of protective relays in a power system is to detect systems
abnormalities and to execute appropriates commands to isolate swiftly only at the
faulty component from healthy system. One of the protective relays is the distance
relay. High current flows through the network when fault occur. So, the distance
relay will detect the over current by measuring the impedance on the transmission
line and send the tripping signal to the circuit breaker to break the power line. This
project focuses on determining the optimum setting of distance relay and also the
performance of the distance relay when single line-to-ground fault occur in the
system. In this project, the setting can be determined by using PSCAD software.
The system consist of two source, five faults and two 100Km transmission line
which are protected by distance relays. The modelling and analysis of the test
system with corresponding relay circuits are done solely using PSCAD. From the
simulation, it can be observed that the fault voltage and current characteristics are
consistent with those from the theoretical concept. The optimum setting is also
obtained from the analysis.
vi
ABSTRAK
Peranan geganti perlindungan dalam system kuasa adalah untuk mengesan
ketidakseimbangan sistem dan melaksanakan arahan yang sewajarnya untuk
mengasingkan bahagian rosak sahaja daripada sistem yang normal. Salah satu
daripada komponen sistem perlindungan ialah geganti jarak. Apabila kerosakan
berlaku, arus yang tinggi akan mengalir melalui rangkaian. Oleh itu geganti jarak
akan mengesan lebihan arus dengan mengukur galangan pada talian penghantaran
dan akan menghantar isyarat putus kepada pemutus litar untuk memutuskan talian
kuasa. Projek ini difokuskan untuk menentukan pengesatan optimum geganti jarak
dan analisis penilaian prestasi geganti jarak beroperasi pada kerosakan satu talian ke
bumi. Dalam projek ini, pengesatan optimum geganti jarak dapat ditentukan dengan
menggunakan perisian PSCAD. Sistem ini mempunyai dua penjana, lima kerosakan
dan dua talian penghantaran 100Km panjang yang dilindungi dengan geganti jarak.
Rekaan dan ujian analisa pada sistem dengan litar geganti dijalankan sepenuhnya
dengan PSCAD. Daripada keputusan, ia boleh dilihat bahawa sifat kerosakan voltan
dan arus mematuhi sifat-sifat dalam teori. Pengesatan optimum juga diperolehi
daripada analisis ini.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLE xi
LIST OF FIGURES xii
LIST OF SYMBOLS AND ABBREVIATION xiv
1 INTRODUCTION
1.1 Background 1
1.2 Problem of Statement 2
1.3 Objectives 2
1.4 Scope of the Project 3
viii
1.5 Thesis Outline 3
2 LITERATURE REVIEW
2.1 Faults on Power System 4
2.2 Single Line-to-Ground Fault 5
2.3 Principles of Distance Relay 9
2.4 Distance Protection Scheme 9
3 METHODOLOGY
3.1 PSCAD Software 11
3.2 Process of Analysis 12
3.3 Circuit Construction 12
3.4 Components 14
3.4.1 Source 14
3.4.1.1 Configuration 15
3.4.1.2 Parameters 15
3.4.2 Multimeter 16
3.4.3 Transmission Line 17
3.4.3.1 Parameters 17
3.4.4 Circuit Breaker 18
3.4.5 Fault Component 19
3.4.6 Online Frequency Scanner 20
3.4.7 Sequence Filter 20
ix
3.4.8 Line to Ground Impedance Component 21
3.4.9 Parameters 21
3.4.9.1 Main Data 22
3.4.9.2 Initializing 23
3.4.10 MHO Circle 23
3.4.10.1 Parameters 24
3.5 Run Simulation 24
4 RESULTS AND DISCUSSION
4.1 Introduction 25
4.2 No Fault Condition 26
4.3 Fault at Location 1 28
4.4 Fault at Location 2 31
4.5 Fault at Location 3 35
5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 38
5.2 Recommendation 39
x
REFERENCES 40
APPENDIX A 41
APPENDIX B 43
APPENDIX C 45
APPENDIX D 46
xi
LIST OF TABLES
NO. TABLE TITLE PAGE
3.1 Configuration of Voltage Source 17
xii
LIST OF FIGURES
NO. FIGURE TITLE
PAGE
2.1 The Condition of Each Types of Faults 5
2.2 Single Line-to-Ground Fault 6
2.3 Connection of Sequence Network for L-G fault 8
2.4 3-Zone Distance Protection Scheme 10
3.1 Project Flow 12
3.2 Main Circuit 13
3.3 Relay Circuit 13
3.4 Three Phase Voltage Source 14
3.5 Multimeter 16
3.6 Transmission Line 17
3.7 Parameters of Bergeron Model 18
3.8 Circuit Breaker 18
3.9 Three Phase Fault 19
3.10 Online Fast Fourier Transform 20
3.11 Sequence Filter 20
3.12 Line to Ground Impedance 21
3.13 MHO Circle Component 23
4.1 Waveform at No Fault Condition 27
xiii
4.2 Fault at Location 1 28
4.3 Waveform of Breaker 1 when Fault at Location 1 29
4.4 Waveform of Breaker 2 when Fault at Location 1 30
4.5 Fault at Location 2 31
4.6 Waveform of Breaker 1 when Fault at Location 2 33
4.7 Waveform of Breaker 2 when Fault at Location 2 34
4.8 Fault at Location 3 35
4.9 Waveform of Breaker 1 when Fault at Location 3 36
4.10 Waveform of Breaker 2 when Fault at Location 2 37
A1 Main Circuit Connection 41
A2 Output Channel Connections 42
B1 Relay Circuit Connection 43
B2 Sequence Module for Current 44
B3 Sequence Module for Voltage 44
C1 Breaker Control Circuit 45
D1 Waveform of fault at Location 4 for Relay 1 46
D2 Waveform of fault at Location 4 for Relay 2 47
D3 Waveform of fault at Location 5 for Relay 1 48
D4 Waveform of fault at Location 5 for Relay 2 49
xiv
LIST OF LIST OF ABBREAVIATIONS AND SYMBOLS
Ea - Voltage Source
Ia - Current phase a
Ib - Current phase b
Ic - Current phase c
If - Fault current
I0 - Zero sequence current
I1 - Positive sequence current
I2 - Negative sequence current
Va - Voltage phase a
Vb - Voltage phase b
Vc - Voltage phase c
V0 - Zero sequence voltage
V1 - Positive sequence voltage
V2 - Negative sequence voltage
CHAPTER 1
INTRODUCTION
1.1 Background
Electrical energy is the most popular form of energy because it can be
transported easily at high efficiency and reasonable cost [1]. Modern power
engineering consists of three main subsystems, which is the generation, transmission
and distribution. In order to provide electrical energy to consumers in usable form, a
transmission and distribution system must satisfy some basic requirements. Thus,
the system must [2]:
1. Provide, at all times, the power that consumers need.
2. Maintain a stable, nominal voltage that does not vary by more than +10%.
3. Maintain a stable frequency that does not vary by more than +0.1 Hz.
4. Supply energy at an acceptable price.
5. Meet standards of safety.
6. Respect environmental standards
The electrical power is distributed to a multiplicity of consumers for different
applications. In the process of distributing or transmitting the power, faults
2
sometimes occur due to the physical accidents or insulation breakdowns [3]. Power
system protection deals with the protection from faults through the isolation of
faulted parts from the rest of the electrical network. The objective of a protection
scheme is to keep the power system stable by isolating only the components that are
under faults, whilst leaving as much of the network as possible in operation.
Protective relay system detects abnormal condition such as fault in electric
circuit and the circuit breakers will operates automatically to isolate the fault that
occurs in the system as fast as possible. Distance relays are generally used for phase-
fault primary and back-up protection on transmission lines. Distance relay meet the
requirements of reliability and speed needed to protect the circuit.
1.1 Problem Statement
All faults that occur on a power system circuit must be cleared quickly
otherwise it may result in disconnection of customers, loss of stability in the system
and damage to the equipment. Therefore, in order to minimize the damage, suitable
and reliable protection system should be installed on all of the circuit and
equipments. In this project, distance relay is used to detect the fault that occurs.
1.2 Objective
i. To study the principle and application of Distance Relay in Power
System.
ii. To optimize the performance and the effect of Distance Protection
System.
iii. To obtain the optimum settings of the Distance Relay in a transmission
system.
3
1.3 Scope of the Project
The scopes of the project are as the following:
i. The study on the characteristic, operation and performances of Distance
Relay.
ii. The modeling and simulation of Distance Protection System using
PSCAD.
iii. The use of Single Line-to-Ground fault on the system.
1.4 Thesis Outline
This thesis is divided into five chapters. For the first chapter, the introduction
of the project study is covered, followed by the literature review in the second
chapter. The third chapter is the methodology of the study that covers the software
used for the simulation and its related library tools. The result and discussion is in the
fourth chapter. Last but not least, the last chapter provides the conclusion of the
study and the recommendation for future analysis.
CHAPTER 2
LITERATURE REVIEW
2.1 Faults on Power System
Power system fault is a condition or abnormality of a system which involves
the electrical failure of the equipment such as generator, transformer, busbar,
overhead line and cable. The type of fault can be categorized into two types which is
symmetrical fault and asymmetrical fault. Fault occur as single line to ground faults,
line to line faults, double line to ground faults or three phase fault. Each fault has its
own characteristic and condition that make the fault happen. Since any
unsymmetrical fault causes unbalance currents flow in the system, the method of
symmetrical component is very useful in an analysis to determine the currents and
voltages in all parts of the system after the occurrence of the fault [3]. Figure 2.1
shows the network condition when the faults occur.
5
Figure 2.1: The condition of each types of fault
There are many factors that cause the fault to occur in the transmission line.
For instance, the single line-to-earth fault often occurs because of the physical
contact due to lightning. Line-to-line fault will occur by ionization of air or when
line comes into physical contact due to broken insulator. Others examples of
condition that will make the fault occur at the transmission line are [1]:-
a) Lightning strikes on bus bar
b) Collapse of transmission line
c) Accidental short circuit by snake, kite and bird
d) Tree or bamboo touching line
e) Human mistakes.
2.2 Single Line-to-Ground Fault
The single line to ground fault can occur in any of the three phases.
However, it is sufficient to analyze only one of the cases. Looking at the symmetry
6
of the symmetrical component matrix, it is seen that the simplest way to analyze
would be the phase a which is the single line-to-ground fault as shown in Figure 2.2.
Figure 2.2: Single Line-to-Ground Fault
Assuming the generator is initially on no load, the boundary condition at the
fault point is:
V Z I I I 0 1.1
By substituting for Ib = Ic =0, the symmetrical components of the currents is
given as:
III
13
1 1 11 a a1 a a
I00
1.2
The observation from the equation (1.2) is:
I I I I (1.3)
7
The symmetrical voltage components of voltage are given as:
VVV
0E0
Z 0 00 Z 00 0 Z
III
1.4
The phase a voltage is:
V V V V E Z Z Z I (1.5)
The fault current, If can be found by substituting the equations (1.1), (1.3)
and (1.5) as follows:
3Z I E Z Z Z I (1.6)
I I 3I3E
Z Z Z 3Z
The equation can be obtained from the equivalent circuit as shown in Figure
2.3 which shows the connection of sequence network for a single-line-to ground
fault.
8
Figure 2.3: Connection of Sequence Networks for L-G fault
2.3 Principles of distance relays
Distance relay is used on power system network because the relay meets the
requirement of reliability and speed needed to protect the circuit. Distance relays are
preferred to overcurrent relays because they are not nearly so much affected by
changes in short-circuit-current magnitude as overcurrent relays are and hence, they
are much less affected by changes in generating capacity and in system
configuration. This is because distance relays achieve selectivity on the basis of
impedance rather than current.
Distance relay respond to a ratio of the voltage and current at the relay
location. The ratio has the dimensions of impedance between the relay location and
the fault point is proportional to the distance of the fault [3]. Such a relay is
described as a distance relay and is designed to operate only faults occurring between
the relay location and the selected point, thus giving discrimination for faults that
may occur between different line sections.
9
2.4 Distance protection scheme
One of the most critical issues in power system protection is the speed with
which a fault can be cleared quickly to prevent from abnormalities of a system.
Distance relays are classified according to polar characteristics, the number of inputs
and the method by which the comparison is made.
The common types compare two input quantities are compared are essentially
either amplitude or phase comparators. Modern static distance relays, based on
single-phase measurement, use phase comparators to produce the required relay
characteristic.
Due to uncertainty in impedance measurements, when protecting a
transmission line with non-pilot distance protection schemes, it is necessary to rely
on stepped zones of protection. This technique protects any given section of
transmission line with multiple zones.
The usual practice in applying distance protection is to install three sets of
distance relays at each relaying point, creating the 3-zone distance protection scheme
as shown in Figure 2.4. The zone 1 relays have the shortest reach and the fastest
operating speed, while zone 2 and zone 3 relays have successively longer reaches
and slower speeds. Zone 2 acts as a back-up for zone 1 and zone 3 acts as a back-up
for zone 1 and 2.
A common arrangement is to make zone 1 and 2 polarised mho and zone 3
offset mho [3]. The first zone tripping which is instantaneous is normally set to 80%
of the protected line detected by zone 1 unit should be cleared immediately without
the need to wait for other device to operate. The zone 2 will cover the remaining
20% portion of the protected section.
10
Figure 2.4: 3-Zone distance protection scheme
CHAPTER 3
METHODOLOGY
3.1 PSCAD SOFTWARE
Power System CAD which is known as PSCAD is a powerful and flexible
graphical user interface to the world-renowned, EMTDC solution engine. PSCAD
enables user to schematically construct a circuit, run a simulation, analyze the results
and manage the data in a completely integrated graphical environment. Online
plotting functions, controls and meters are also included so that user can alter system
parameters during a simulation run and view the results directly.
PSCAD comes with a library of pre-programmed and tested models,
ranging from simple passive elements and control functions to more complex
models, such as electric machines, FACTS devices, transmission lines and
cables. If a particular model does not exist, PSCAD provides the flexibility of
building custom models, either by assembling them graphically using existing
models or by utilising an intuitively designed Design Editor.
12
3.2 PROCESS OF ANALYSIS
In order to do the research, several steps have to be taken to obtain the
result of the simulation. The process of the research is shown in Figure 3.1
below.
Figure 3.1: Project Flow
3.3 CIRCUIT CONSTRUCTION
In order to do the simulation, the major step that has to be done is the circuit
construction. This is the process where circuit is designed and build up by using the
PSCAD software. By using the PSCAD software, components are selected from the
master library.
13
The master library consists of different types of components such as the
sources, input and output devices, transmission lines and cables. Each component
has the editing feature that enables user to alter the input depends on the appropriate
parameter of the component. Figure 3.2 and Figure 3.3 shows the two circuits that
were constructed in this project, which is the main circuit and relay circuit.
Figure 3.2: Main Circuit
Figure 3.3: Relay Circuit
14
The relay circuit shown in Figure 3.3 is constructed by using line-to-ground
impedance, MHO circle component, comparator and gates. Each of the components
is connected together and connects to the circuit breaker in the main circuit. The
relay circuit is used to detect the fault that occurs in the system. Thus, the relay
circuit will give a signal to the breaker so that the breaker will trip the system.
3.4 COMPONENTS
Components are either network components such as resistors, inductors,
capacitors, switches, ac machines, transformers or power electronic devices and it
can also be measurement, control, monitoring functions, signal processing and
outputs. A component is essentially a graphical representation of a device model,
and is the basic building block of circuits created in PSCAD. Component is usually
designed to perform a specific function, and can exist as either electrical, control,
documentary or simply decorative in type.
3.4 1 SOURCE
Figure 3.4: Three Phase Voltage Source
15
The three phase voltage source models which is shown in Figure 3.4 is a 3-
phase AC voltage source, where users may specify the positive sequence and zero
sequence source impedances or select an ideal source.
3.4.1.1 CONFIGURATION
The parameters of the voltage source which consist of voltage, base MVA,
frequency and voltage input time constant that is used in this simulation is shown
in Table 3.1.
Table 3.1: Configuration of Voltage Source
PARAMETERS VALUE
Base Voltage (L-L) 230 KV
Base MVA ( 3-PHASE ) 100 MVA
Base Frequency 50 Hz
Voltage Input Time Constant 0.01 Second
3.4.1.2 PARAMETERS
The positive sequence impedance is calculated based on the equation shown
and the parameters used are as stated in Table 3.1. The positive sequence
impedance is important in the setting of the distance protection relay because it is
used to set the radius of the circle.
16
Based on the calculation, the value of the positive sequence impedance used in
this project is 53.16 ⎳ 84.3º Ω.
3.4.2 MULTIMETER
Figure 3.5: Multimeter
The Multimeter performs virtually all possible system quantity
measurements, all contained within a single, compact component. The Multimeter
which is shown in Figure 3.5 is inserted in series within the circuit either 3-phase,
single-line or 1-phase.
17
3.4.3 TRANSMISSION LINE
Figure 3.6: Transmission Line
As shown in Figure 3.6, the transmission line that is used in this project is the
Bergeron Model, where the impedance or admittance data can be entered directly to
define the transmission corridor. The Bergeron model represents the L and C
elements of a PI section in a distributed manner.
It is accurate on at the specified frequency and is suitable for studies where
the specified frequency load-flow is most important such as in the relay studies. In
this project, the transmission line is set to a distance of 100 Km for both of the
transmission line.
3.4.3.1 PARAMETERS
The parameters that is used in the Bergeron Model is shown in Figure 3.7
where it is copied to the transmission line format in PSCAD system.
18
Figure 3.7: Parameters of Bergeron Model
3.4.4 CIRCUIT BREAKER
Figure 3.8: Circuit Breaker
19
The component shown in Figure 3.8 simulates of single-phase circuit breaker
operation. The ON (closed) and OFF (open) resistance of the breaker is specified
along with its initial state. This component is controlled through a named input
signal where the breaker logic is:
• 0 = ON (closed)
• 1 = OFF (open)
3.4.5 FAULT COMPONENT
Figure 3.9: Three Phase Fault
The fault component is used for generating the fault condition. The three
phase fault component which is shown in Figure 3.9 puts a combination of phase to
phase and phase to ground faults to allow any combination of faults to be selected,
even during multiple runs.
20
3.4.6 ONLINE FREQUENCY SCANNER
Figure 3.10: Online Fast Fourier Transform (FFT)
Figure 3.10 shows an online Fast Fourier Transform (FFT), which determines
the harmonic magnitude and phase of the input signal as a function of time. The
input signals first sampled before it is decomposed into harmonic constituents.
Options are provided to use one, two or three inputs. In the case of three inputs, the
component provides output in the form of sequence components.
3.4.7 SEQUENCE FILTER
Figure 3.11: Sequence Filter
21
The component shown in Figure 3.11 is a sequence filter which calculates the
magnitudes and phase angles of sequence components when the magnitudes and
phase angles of the phase quantities are given by the FFT component.
3.4.8 LINE TO GROUND IMPEDANCE COMPONENT
Figure 3.12: Line to Ground Impedance Component
The component shown in Figure 3.12 computes the line-to-ground impedance
as seen by a ground impedance relay and the output impedance is in rectangular
format (R and X).
3.4.9 PARAMETERS
The line-to-ground impedance consist of several parameters that needs to be
calculated. The important parameter that is used in this component is the constant for
ground impedance, K.
22
3.4.9.1 MAIN DATA
When the distance of the transmission line is set to 100Km, the constant for
ground impedance is calculated as below:
Z1 = (0.36294X10-4
+ J0.5031X10-3
)(100km)
= 50.44 ∟ 85.87º Ω
Z0 = (0.37958X10-3
+J0.13277X10-2
)(100km)
= 138.089 ∟ 74.05º Ω
Therefore:
K =( Z0 - Z1 ) / Z1
= 1.771 ∟ -18.48º
The constant for ground impedance is used in the setting of the line to
ground impedance component to prevent from overreach and underreach.
Without the constant, the relay will cause underreach or overreach in the
system. Thus, the optimum setting of the relay could not be obtained.
23
3.4.9.2 INITIALIZING
• Initializing Time = 0.02 Second
• Output R during initialization = 1 x 106Ω
• Output X during initialization = 1 x 106Ω
3.4.10 MHO CIRCLE
Figure 3.13: MHO Circle Component
The Mho Circle component is classified as an ‘Impedance Zone Element’,
which checks whether or not a point described by inputs R and X, lies inside a
specified region on the impedance plane. R and X represent the resistive and reactive
parts of the monitored impedance. The component produces an output '1' if the point
defined by R and X is inside the specified region, otherwise the output will be '0'.
24
3.4.10.1 PARAMETER
• Radius of the circle = 50 Ω
• Z coordinate of the centre = 25
• Theta coordinate of the centre = 1.49766[rad]
The Z coordinate of the centre is calculated based on the equation below:
Z = Z1 / 2 = 50 / 2 = 25
3.5 RUN SIMULATION
To run the project, simply click on the Run button in the Main Toolbar.
When this button is pressed, PSCAD will go through several stages of processing the
circuit before starting the simulation. The simulation will run if no error occur in the
circuit that was constructed. If an error occur, the warning will appear and correction
has to be done. The output of the simulation can be seen based on the graphs and also
the measurement of current, voltage and power.
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Introduction
The final accomplishments and results of the project shall be explained in this
chapter. This chapter discusses on the result, analysis and problems that are
encountered throughout the completion of the project. After the development and
completion of the simulation, it will then be evaluated in order to ensure whether it
had met the outlined objectives successfully. By the methodology as discussed in the
previous chapter, this project has made remarkable result and achievement.
Based on the project that had been done, the results are obtained when Single
Line- to-Ground fault occurs at five different locations in the transmission line
circuit. The performance of the distance relay can be seen when the circuit breaker
trips during fault condition. This section will discuss on the performance of the
distance relay at no fault condition and when the Single Line-to-Ground fault occur
at different locations. The discussion will only focus on the phase a fault which is
the blue line in the output waveform that can be seen in Figure 4.1 which indicates
the Single Line-to-Ground fault.
26
4.2: No Fault Condition
At no fault condition, there are no faults that occur in the circuit. Since there
is no fault in the system, the shape of the voltage and current waveform remains
stable for Relay 1 and Relay 2. From Figure 4.1(a), it can be seen that no voltage
drop occur and the value remains the same as the supply voltage which is 230KV.
Similar to the voltage, the current waveform is also stable and constant.
Since the unit measurement for the current is in kilo ampere (kA), the value of the
current is too small until it seems like there is no current at the transmission line
which is shown in figure 4.1(b).
The distance relay does not detect any fault in the transmission line, so the
circuit breaker behaves in a normal condition where it is in a CLOSE condition.
Since there is no detection of fault in the transmission line, no tripping signals were
sent to the breaker and it has been proved by the relay output signal in Figure 4.1(c)
where the outputs are in’0’ condition at all time.
27
(a)
(b)
(c)
Figure 4.1: Waveform at No Fault Condition
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
28
4.3: Fault at location 1
Figure 4.2: Fault at Location 1
As shown in Figure 4.3(c) and Figure 4.4(c), when single line-to-ground fault
is applied at location 1 at t = 0.2 s and duration of 0.1 s, both of the circuit breaker is
not affected. It can be seen that the breaker does not trip and the signal is still in ‘0’
condition.
Since the fault occurred at 0.2 second, the voltage of phase a at breaker 1
which is equal to zero because the fault that occurs is bolted fault. The voltage which
is at phase b and phase c has also been affected, where both of the voltage
magnitudes decrease a little bit.
From the waveform of the fault current in figure 4.3(b) and Figure 4.4(b), the
existing current at the transmission line is only the phase a current. The other phase
b and phase c current are equal to zero when the fault occur. By comparing with the
theoretical, when single line-to-ground fault occur, the value of Ib=Ic=0.
Fault Point
29
(a)
(b)
(c)
Figure 4.3: Waveform of Breaker 1 When Fault at Location 1
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
30
(a)
(b)
(c)
Figure 4.4: Waveform of Breaker 2 When Fault at Location 1
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
31
4.4 Fault at Location 2
Figure 4.5: Fault at Location 2
When single line-to-ground fault occur at location 2, the distance relay will
send a tripping signal to circuit breaker 1. The breaker breaks the circuit at 0.22s
after fault occur at 0.2s, so the voltage at transmission line becomes zero. But, when
the fault clears, the breaker will reclose back at 0.3s and transient voltage occur in
few microseconds.
From the voltage waveform shown in Figure 4.6(a), voltage at phase b and
phase c is not stable. It is cleared and goes back to the normal condition at 0.35s.
This is known as the post-fault. For phase a, voltage becomes zero which means that
there is no voltage at phase a when single line-to-ground fault occur.
Figure 4.6(b) shows current waveform when single line-to-ground fault
occurs at location 2. The existing current at the transmission line is only the phase a
current and the other phases current are equal to zero when the fault occur.
Figure 4.7(c) shows the signal of the circuit breaker for relay 2. The signal is
in ‘0’ condition even though fault occurs at location 2. This is due to the voltage and
current value that flows through the circuit when fault occurs. The fault current that
Fault Point
32
flows from source 2 is lower than the fault current that flows from source 1. The
fault voltages at source 2 are higher than the fault voltage at source 1. The values are
difference because of the total impedance of the transmission line between the fault
location and sources. So, the mho circle characteristic does not detect any fault
because of the total value of impedance is higher than inside the specified region.
33
(a)
(b)
(c)
Figure 4.6: Waveform of Breaker 1 When Fault at Location 2
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
34
(a)
(b)
(c)
Figure 4.7: Waveform of Breaker 2 When Fault at Location 2
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
35
4.5 Fault at Location 3
Figure 4.8: Fault at Location 3
When fault occurs at location 3, relay 1 and relay 2 does not detect the fault.
This is because the fault that occurs is out of the protection zone. As discussed
earlier in Chapter 2, distance relay protects the system if fault occurs at about 85% of
the distance of the transmission line. Since the fault occur at 100Km of the
transmission line, both of the relay cannot detect the fault and the breaker signal is in
‘0’ condition.
The voltage waveform for both of the relay is the same. The output can be
seen from the waveform in Figure 4.9 and Figure 4.10. The voltage for phase a
decrease more then voltage of phase b and phase c at 0.2s, which is during the fault
that occur in the transmission line. The current at breaker 2 increase really high
compared to the current at breaker 1, this is due to the fault that occur is near the
breaker 2.
Fault Point
36
(a)
(b)
(c)
Figure 4.9: Waveform of Breaker 1 When Fault Occur at Location 3
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
37
(a)
(b)
(c)
Figure 4.10: Waveform of Breaker 2 when Fault occur at Location 3
(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal
CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 Conclusion
This project involved the usage of PSCAD simulation. To understand the
theories for this project, it is important to understand the concept of distance relay type
mho characteristic and the output waveform. PSCAD software is very useful in terms of
obtaining the waveform of the current and voltage fault. It gives similar result with the
theoretical concept. By referring to the waveform are enough to determine the type of
fault without doing the calculation. It makes the user can know the fault in very short
time.
The optimum setting of the distance relay is when the relay does not overreach or
underreach and the relay only operates in its protection zone as required. The
automatically tripping of circuit breaker by using relay system will protect the generator,
transformer and other electrical equipments that is connected to the network.
39
5.2 Recommendation
For further analysis, simulation can be done by considering:
i. Other types of faults that can occur in transmission line such as the double line-
to-ground fault, line-to-line fault and three-phase fault.
ii. Other types of distance relay such as the Apple Characteristic and Lens
Characteristic.
iii. Other types of system such as the parallel transmission line circuit.
40
REFERENCES
1. Hadi Saadat “Power System Analysis” Mc Graw Hill, 2004.
2. Theodore Wildi “Electrical Machines, Drives, And Power Systems” Pearson
Prentice Hall, 2006.
3. Abdullah Asuhaimi Mohd Zin, Md Shah Majid & Faridah Mohd Taha “
Power System Engineering” Fakulti Kejuruteraan Elektrik, 2009.
4. M.Sanaye-Pasand and H. Seyedi “Simulation, Analysis and Setting of
Distance Relays on Double Circuit Transmission Line” Faculty of
Engineering, University of Tehran, Iran.
5. G.E Alexander and J.G Andrichak “Ground Distance Relaying: Problems and
Principles” General Electric Company Malvern, PA, 1991.
6. G.E Alexander and J.G Andrichak “Ground Distance Fundamentals” General
Electric Company Malvern, PA, 1991.
7. M.I. Gilany, O.P. Malik and G.S. Hope “A Digital Protection Technique For
Parallel Transmission Lines Using A Single Relay at Each End”, Transaction
On Power Delivery, Vol 7 No1, January 1992.
APPENDIX A
MAIN CIRCUIT
Figure A1: Main Circuit Connection
OUTPUT CHANNELS
Figure A2: Output Channel Connections
43
APPENDIX B
REALY CIRCUIT
Figure B1: Realy Circuit Connection
44
Figure B2: Sequence module for current
Figure B3: Sequence module for voltage
45
APPENDIX C
BREAKER CONTROL
Figure C1: Breaker Control Circuit
46
APPENDIX D
1. Fault at location 4
Figure D1: Waveform of fault at location 4 for relay 1
47
Figure D2: Waveform of fault at location 4 for relay 2
48
2. Fault at location 5
Figure D3: Waveform of fault at location 5 for relay 1
49
Figure D4: Waveform of fault at location 5 for relay 2
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