Design & Simulation of 3 Phase Line Fault
Detector Using WiFi/IoT
By
Muhammad Saeed
CIIT/FA18-REE-001
BS Thesis
In
Electrical Engineering
COMSATS UNIVERSITY
Islamabad - Pakistan
Spring, 20
COMSATS UNIVERSITY, ISLAMABAD
Design & Simulation of 3 Phase Line Fault Detector
Using WiFi/IoT
A Thesis Presented to
COMSATS UNIVERSITY, Islamabad
Abbottabad Campus
In partial fulfillment
of the requirement for the degree of
MS (Electrical Engineering)
By
Muhammad Saeed
CIIT/FA18-REE-001
Spring, 2021
ii
Design & Simulation of 3 Phase Line Fault Detector
Using WiFi/IoT
An Under Graduate Thesis submitted to Department of Electrical Engineering as
partial fulfillment of the requirement for the award of Degree of B.S (Electrical
Engineering).
Name
Registration Number
Muhammad Saeed
CIIT/FA18-REE-001
Muhammad Dawood
CIIT/FA18-REE-001
Fahad
CIIT/FA18-REE-001
Supervisor
Dr. Gul Khan
Professor Department of Electrical Engineering
Abbottabad Campus
COMSATS UNIVERSITY (CU)
Islamabad
May, 2021
iii
Final Approval
This thesis titled
Design & Simulation of 3 Phase Line Fault Detector
Using WiFi/IoT
By
Muhammad Saeed
CIIT/FA18-REE-001
Has been approved
For the COMSATS UNIVERSITY, Islamabad
External Examiner: ___________________________________________
Dr. .………………..
Supervisor: _________________________________________________
Dr. Gul Khan
Department of Electrical Engineering, Abbottabad
Head of Department: _________________________________________
Dr. Shah Fazal
Department of Electrical Engineering, Abbottabad
iv
Declaration
I, Muhammad Saeed, CIIT/SP16-REE-005/ISB
hereby declare that we have produced the work presented in this thesis during the scheduled
period of study. We also declare that we have not taken any material from any source except
referred to wherever due that amount of plagiarism is within acceptable range. If a violation
of HEC rules on research has occurred in this thesis, we shall be liable to punishable action
under the plagiarism rules of the HEC.
Date: ______________
Signature of Student:
____________________
Name.
Roll No.
v
Certificate
It is certified that NAMES Students,
have
carried out all the work related to this thesis under my supervision at the Department of
Electrical Engineering, COMSATS UNIVERSITY, Islamabad and the work fulfills the
requirement for award of BS degree.
Date: ______________
Supervisor:
_________________________
Dr. Gul Khan
Professor
Head of Department:
_____________________________
Professor. Dr. abc
Department of Electrical Engineering
vi
DEDICATION
We dedicate our work to our family and friends.
vii
ACKNOWLEDGEMENT
First and foremost, our utmost gratitude to the Almighty Allah for giving us the strength and
courage to complete this task despite of all the problems and difficulties that we faced during
this research work. we have taken efforts in this thesis; however, it would not have been
possible without the kind support and help of many individuals and organizations. We would
like to extend our sincere thanks to all of them.
We are highly indebted to our Supervisor Prof. Dr.Gul Khan who has been a constant source
of encouragement and enthusiasm during this research work.
We would like to express our gratitude towards our parents & members of COMSATS
UNIVERSITY, Abbottabad Campus for their kind co-operation and encouragement which
means a lot to us. We would like to express our special gratitude and thanks to our seniors
also for giving us such attention and time.
Our thanks and appreciations also go to the people who have willingly helped us out with
their abilities.
M Saeed
M Dowood
Abc
viii
ABSTRACT
Design & Simulation of 3 Phase Line Fault Detector
Using WiFi/IoT
Electrical short circuit and or fault events on overhead or underground cables due to bad
weather storm, snow fall and rain cause voltage sags or swell at the end user location can
damage the equipment’s.
Line faults are the major issues facing the utility and distribution power system. Line fault
clearing in distribution network is not an easy job it requires some automatic techniques to
identify the exact location of the fault to avoid the manual patrolling of the entire line.
Automatic fault location system use data from power quality monitoring system and circuit
by calculating impedance. A timely and accurate identification of a faulted segment on the
transmission network is very critical to reduce circuit interruption time during a fault. In this
research work we have presented a method which will be very useful to identify the exact
distance of fault of underground cable/distribution lines from base station named Ohm’s law,
according to this law of fault inspection when a fault arises the variation in voltage drop is
directly related to variation in current along the length of fault in the cable/distribution lines.
To validate the performance of the designed scheme simulation has been conducted in
MATLAB-Simulink after that it is implemented in hardware as well which also give accurate
results as performed in simulation. The cable/distribution lines faults as well as transformer
faults are monitoring via internet of thing (IoT) using Arduino and WiFi module ESP32,
results of MATLAB/Simulink simulation and hardware are shown in chapter 6 and 7.
ix
TABLE OF CONTENTS
Chapter 1
Introduction ................................................................................................. 1
1.1
Introduction .......................................................................................................... 2
1.2
Causes of Cable/Distribution Faults..................................................................... 2
1.3
Types of Faults ..................................................................................................... 3
1.3.1
Open Circuit Fault ........................................................................................ 3
1.3.2
Short Circuit Fault ........................................................................................ 3
1.3.3
Network Sequence ........................................................................................ 4
1.4
Ohms Law Method ............................................................................................... 5
1.5
Impedance-Based Methods .................................................................................. 6
1.6
Statement of Problem ........................................................................................... 6
1.7
Research Methodology......................................................................................... 6
1.8
Literature Review ................................................................................................. 7
Chapter 2
2.1
Distributed Parameters of Transmission Lines ..................................... 10
Distributed Parameters of Transmission Lines .................................................. 10
2.1.1
Resistance ................................................................................................... 11
2.1.2
Inductance ................................................................................................... 11
2.1.3
Capacitance ................................................................................................. 12
2.1.4
Admittance .................................................................................................. 12
2.1.5
Capacity and Charging Current .................................................................. 13
2.2
Types of Conductors .......................................................................................... 14
2.2.1
AAC – All Aluminium Conductor.............................................................. 14
2.2.2
AAAC – All Aluminium Alloy Conductors ............................................... 14
2.2.3
AACSR – All Aluminium Alloy Conductors Steel Reinforced ................. 14
2.2.4
ACAR – Aluminium Conductors Alloy Reinforced................................... 14
2.2.5
ACSR – Aluminium Conductors Steel Reinforced .................................... 14
2.3
Underground Power Cables ............................................................................... 14
2.3.1
Types of Underground Cables .................................................................... 15
2.3.2
Belted Cables .............................................................................................. 15
2.3.3
Screened power cable ................................................................................. 16
x
2.3.4
High Pressures Power Cables ..................................................................... 16
2.3.5
Conductors .................................................................................................. 16
2.4
XLPE Cables ...................................................................................................... 17
Chapter 3
3.1
Testing of Transmission Lines/Cables and Fault Location ................... 19
Basic Diagnostic Testing Used for Underground Power Cables ....................... 20
3.1.1
Time Domain Reflectometry ...................................................................... 20
3.1.2
Dissipation Factor Measurement ................................................................ 20
3.1.3
Electric Stress of power cable ..................................................................... 21
3.2
Fault Location Schemes ..................................................................................... 22
3.2.1
Impedance-Based Methods ......................................................................... 22
3.2.2
Traveling Wave-Based Methods ................................................................ 22
3.2.3
Detection and Location Using Magnetic Field Sensors.............................. 22
Chapter 4
Design and Simulation for Transmission Fault Location ..................... 23
4.1
3-Phase transmission/distribution line fault location ......................................... 24
4.1.1
3-Phase transmission line equivalent circuit ............................................... 25
4.1.2
Open Circuit Fault Calculation ................................................................... 27
4.2
Hardware main circuit and components ............................................................. 28
4.2.1
Hardware Specification............................................................................... 29
4.2.2
Measurement Circuit................................................................................... 29
Chapter 5
Simulation Results and Discussion .......................................................... 32
5.1
Simulation Results ............................................................................................. 33
5.1.1
5.2
Transmission lines faults and fault codes ................................................... 35
Transformer Protection ...................................................................................... 36
5.2.1
Differential Protection of a Transformer .................................................... 36
5.2.2
Transformer faults and alarm binary descriptions ...................................... 37
5.3
Internet of thing (IoT) based line faults monitoring........................................... 38
5.3.1
Features of Cayenne IoT Cloud Platform ................................................... 38
Chapter 6
Conclusion & Future Work ..................................................................... 41
6.1
Conclusion.......................................................................................................... 42
6.2
Future work ........................................................................................................ 42
xi
LIST OF FIGURES
Figure 1.1 Sequence Network (i) Positive (ii) Negative (iii) Zero sequence voltage ......... 4
Figure 2.1 HV transmission lines or power cable equivalent circuit ................................ 10
Figure 2.2 Conductor arrangement in 3 Phase Lines (a) Trefoil (b) Flat ....................... 11
Figure 2.3 3 Core XLP cable view [22] ........................................................................... 17
Figure 2.4 1 Core XLP cable side view 230 kV XLPE cable[22] ................................... 17
Figure 3.1 Calculating dissipation factor, equivalent circuit and vector diagram [23] .... 21
Figure 4.1 Three phase transmission line equivalent circuit for a distance up to 10 km .. 24
Figure 4.2 Three phase transmission line equivalent circuit for 1km distance, the cable
resistance, Inductance and Capacitance are modeled per phase per km distance. ............ 25
Figure 4.3 Simulation of transmission line fault location calculation in Simulink .......... 25
Figure 4.4 Three phase input current, output voltage and distance calculation blocks .... 26
Figure 4.5 Open circuit fault in transmission line at 8 km ............................................... 28
Figure 4.6 Open circuit fault and short circuit fault locations are displayed .................... 28
Figure 4.7 Current measuring circuit and wave form, AC Current ................................. 30
Figure 4.8 Hardware three phase line circuit diagram ...................................................... 30
Figure 4.9 Hardware measurement circuit diagram of 3 phase line fault detector .......... 30
Figure 4.10 Voltage & current signals, Arduino UNO and interfacing of WiFi module . 31
Figure 4.11 Hardware for WiFi based line fault detector and location finder .................. 31
Figure 5.1 Single Line to Ground Fault (L1G) is generated at distance of 7 km ............. 33
Figure 5.2 Single Line to Ground Fault (L1G) and location is shown in display ............ 33
Figure 5.3 Single Line to Ground Fault (L3G) is occurred at distance of 2 km ............... 34
Figure 5.4 Single Line to Ground Fault (L3G) and location is shown in display ............ 34
Figure 5.5 Three Lines Fault (L1L2L3) is generated at distance of 4 km ........................ 34
Figure 5.6 Three Lines Fault (L1L2L3) and location is shown in display ....................... 35
Figure 5.7 Transformer protection monitoring and control system .................................. 36
Figure 5.8 Single Line Fault is generated at transformer and the result is displaying ..... 37
Figure 5.9 A three-phase load is theft from transmission/distribution line ...................... 38
Figure 5.10 The results of line theft is calculated and shown in the display .................... 38
Figure 5.11 IoT based single line to ground (L1G) fault detection and display .............. 39
Figure 5.12 IoT based two line to line and ground (L1L2G) fault detection ................. 39
Figure 5.13 IoT based three line to line and ground (L1L2L3G) fault detection ........... 40
Figure 5.14 IoT based Transformer fault detection and display ...................................... 40
Figure 5.15 IoT based Open circuit fault detection and display ...................................... 40
xii
LIST OF TABLES
Table 3.1 Cable insulation materials, di-electric strength (kV/mm) and tangent loss ..... 21
Table 3.2 Types of Cable and electric stress Emax (kV/mm) [23]................................... 21
Table 5.1 Transmission lines faults and fault codes ......................................................... 35
Table 5.2 Transformer faults and alarm binary descriptions ............................................ 37
xiii
LIST OF ABBREVIATION
A
Ampere
B
Susceptance (Siemens)
C
Capacitance
f
Frequency (Hz)
L
Inductance (Hennery), Length of cable (km)
R
Radius of the conductor
D
Distance (km), Diameter of Cable (mm)
DOC
Open circuit fault distance (km)
DSC
Short circuit current fault distance (km)
d
GMD (Geometric mean radius)
G
Conductance (Siemens)
I
Current (A)
IC
Charging Current (A)
If
Fault Current (A)
IoT
Internet of Thing
ISC
Short circuit current (A)
R
Resistance (Ohm), Conductor Radius (mm)
Rc
Conductor radius (mm)
Rg
Ground Resistance (Ohms)
S
Distance between conductors (mm)
V
Voltage (Volt)
VOC
Open circuit voltage (Volt)
VS
Sending end voltage
VR
Receiving end voltage
XLPE Cross-linked poly ethylene
X
Reactance (Ohms)
Y
Admittance (Siemens)
Z
Impedance (Ohms)
xiv
LIST OF SYMBOLS
α
Operator  1200
j
Operator

Resistivity of earth in (Ωm)
o
Free space permittivity 8.85x10-12 F/m

Relative permittivity

Angular frequency (2.π.f)

Delta
Π
constant (3.142)
Ω
Ohms
r
Relative Permeability
0
Permeability of free space 4 x 10-7 (H)
tan( ) Dissipation Factor
xv
Chapter 1
Introduction
1
1.1
Introduction
Transmission lines are used to transfer electrical energy from generating station to
distribution system and load center. A healthy transmission/distribution line is one which
delivered energy without any interruption. However, due to human mistakes and bad weather
conditions 30 % faults are occurs on transmission and 30 % faults are occurs on distribution
lines [1]. Since the last decade most of the distribution networks have been replaced by
underground distribution networks. These networks are generally preferred in populated
areas and places such as hospitals, colleges and large metropolitan centers to avoid hazards
because these cables are not affected by bad weather conditions like storms, snow falls and
heavy rains. Underground cables are less vulnerable to bad weather conditions and hence
reduced number of faults occur on them as compared to overhead lines. In comparison to
overhead distribution networks underground cables are more expensive and require complex
mechanisms for installation and maintenance. Identification and clearance of faults in
underground networks are also very difficult to monitor. For efficient operation it is very
essential to identify the exact location of the fault in the cable. Various aspects of design,
analysis and special considerations are required due to their underground construction [2].
In underground cables the value of capacitance is larger than inductance whereas in overhead
lines it is the opposite. In addition to all this their operational analysis also becomes more
complicated when different types of cables are used [3].
1.2
Causes of Cable/Distribution Faults
There are various reasons due to which underground fault occur. Mainly they occur due to
mechanical damage when cable is not sufficiently protected during installation or poor cable
jointing. Secondly, overloading increases insulation temperature or it may also rise due to
surrounding temperature of nearby factory or steam pipes. Thirdly, chemical action of
different materials in the soil causes corrosion and rusting in the cable. Last but not the least
is oil leakage from cable boxes.
 Natural Causes: different types of natural disasters that could lead to a fault in the
EPG, such as hurricanes, storms, flooding, earthquakes, tornados, heat waves or solar
flares;
 Errors: causes related to human faults or equipment technical malfunction;
2
 Attacks: cyber-attacks such as denial of service (most common), or human attacks
1.3
Types of Faults
1) Open Circuit Fault
2) Short Circuit Fault
1.3.1
Open Circuit Fault
Open circuit faults are usually caused by breakdown in the conducting path of the current i.e
when two or more conductors get broken or are disconnected. Open circuit faults are less
harmful as compared to short circuit faults as almost zero current flows when open circuit
occurs and load side of the network gets isolated from the generation side eventually saving
the equipment from any major damage. Here the meter also indicates infinite resistance.
1.3.2 Short Circuit Fault
In this type of fault when two or more phase conductors come in contact with each other the
value of current increases manifolds and causes damage at the point of intersection. This
type of fault is considered very harmful for the system as increased value of the current can
affect equipment at the load side. The meter will indicate zero resistance in this case. Short
circuit faults are further divide into two categories
1.3.2.1 Symmetrical Faults
The symmetrical faults are
Three phase line to line fault (3L)
Three phase to ground fault (3LG)
Short circuit current in all phases is the same. These faults are more severe but occur less
(10%) as compared to single line to ground faults. Short circuit KVA capacity at fault point
can be given by
KVASCC  3VLL I F
Where I F 
VLG
(A)
ZF
3
(1.1)
1.3.2.2 Unsymmetrical Faults
In a three phase system when all three phases come in contact with each other, a short
circuit fault occurs which is known as symmetrical fault. In unsymmetrical cases faults
occur due to single line to ground or two line to ground intersections. In this case phase
angles in each phase shift and the current also varies. Fault current in all phases is different
and voltage in all phases also is unbalanced. Probability of their occurrence can be given
as follows
1 Phase fault: line to ground (1LG)
65-70%
2 Phase fault: line to line (LL or 2L)
20-25%
2 Phase to ground; line to line and ground (LLG or 2LG)
10-20%
1.3.3 Network Sequence
The positive sequence sets have three phase currents/voltages with equal magnitude, with
phase b lagging phase a by 120°, and phase c lagging phase b by 120°. [4-6]
I a1  I a100  I a1
I b1  I a12400  a 2 I a1
(1.2)
I c1  I a11200  aI a1
where α = -0.5+j0:866,
α2 = -0.5-j0:866,
α3 = 1+j0
(1.3)
The negative sequence sets have three phase currents/voltages with equal magnitudes,
where phase b leads phase a by 120°, and phase c leads phase b by 120°. Negative sequence
sets are similar to positive sequence, except the phase order is reversed [5].
Figure 1.1 Sequence Network (i) Positive (ii) Negative (iii) Zero sequence voltage
4
I a2  I a2 00  I a2
I b2  I a2 1200  aI a2
(1.4)
I c2  I a2 2400  a 2 I a2
In zero sequence components all the currents are the same and there is no phase
difference among them I a  I b  I c
0
 I a  1 1
 I   1 a 2
 b 
 I c  1 a
0
0
0
1   Ia 
 
a   I a1 
a 2   I a2 
 
1 1
A  1 a 2
1 a
(1.5)
1
a 
a 2 
(1.6)
To find out the magnitude of fault current during positive, negative and zero sequences
equation 2.7 is used.
I abc  AI a012 ,
1
A
1 1
1
 1 a 2
3
1 a
I a012  A1 I abc
(1.7)
1
a 
a 2 
(1.8)
Equation 2.9 can be used to find out the magnitude of voltage during fault, in positive,
negative and zero sequences. [5]
Vabc  AVa012 ,
1.4
Va012  A1Vabc
(1.9)
Ohms Law Method
This method is simply based on ohms law. In this method a DC voltage is applied at the
end of a feeder through a series resistor voltage drop across this resistor is used for
identification of fault location. During AC or DC voltage the fault current in cable is
inversely proportional to the fault resistance. The transmission line has impedance which
5
increases along with the length of the cable from one end to the other end. Thus fault at
shorter distance will have low impedance and high current, and vice versa.
1.5
Impedance-Based Methods
The impedance-based fault location methods use the voltages and currents at one or both
ends of a transmission line to determine where a fault has occurred. The impedance of the
transmission line per unit length is usually required in these calculations. One of the major
problems with basic one-terminal impedance-based fault location methods – those that only
use measurements from one end of the transmission three lines – is that the fault impedance
must be near-zero for the result to be accurate, since the fault impedance affects the
impedance seen at the end of the transmission line [3].
1.6
Statement of Problem
Detection of cable fault in underground cables is not an easy job and poses a serious
challenge to the quality and reliability of underground transmission cables network. To
identify the exact location of the fault on the line accurately and timely is very critical for
determining the circuit interruption time during a fault. Different techniques are used to
identify fault locations in which Murray loop method and Ohm’s law method are the most
common and cost effective. They can be used to identify the exact location of fault in
underground cables but most of them have been tested on no-load condition. In this
research work it is intended to implement a prototype design using conventional
underground distribution system and determine the exact location of fault on running onload system and also present a in-depth analysis of its performance.
1.7
Research Methodology
In this research work underground faults will be detected by using Ohm’s law method by
measuring current at the source side and voltage at the load side at different faults by
measuring these two values at different types of faults like short circuit ground faults for
single line two line and three line to grounds. By constantly monitoring input current and
6
output voltage we will calculate the fault impedance when the voltage at output is minimum
and current at the input side is maximum it means that some fault has occurred. In order to
know the exact location of the fault we will test different fault conditions and accordingly
we will implement and formulate the strategy on the basis of which we will be able to find
the location of the fault. All this research work will be implemented in MATLAB
SIMULINK software.
1.8
Literature Review
An electrical power grid (EPG) is a dynamical system based on four main operations:
generation, transport, distribution and control [1]. Technological development over the last
decade, in particular with the increased use of information and communication
technologies (ICTs), has exposed EPGs to an all-new set of threats [2]. Like any system,
an EPG is not fully fault-proof. A fault can occur at any point of the grid, whether due to
natural causes, operational errors, cyber-attacks or physical attacks, among others causes
[3,4]. Whenever there is a fault at any part of the EPG, different levels of consequences
will be generated for the grid as a whole. Faults affecting only a small part of the EPG, and
with easy and fast resolution, do not imply a redirection of the energy flow through other
transmission lines. However, catastrophic events may imply the isolation or overloading
of other sections of the EPG, due to load redistribution, which can lead to a cascade failure.
As an example, extreme weather conditions can affect the EPG at different levels: at system
level, where loading on feeders and lines can be affected, or at component level, affecting
their rate of failure. The EPG is undoubtably one of the most critical infrastructures in any
country. Therefore, it is crucial to prevent catastrophic events that can break it down as
well as to improve its capability to recover after any abnormal event. This last feature is
known as system resilience [6-7].
Power system fault location and identification of different faults on distribution lines/
underground power cable system for quick & reliable operation of protection scheme is of
utmost importance. Fault location estimation is a critical issue in power system functioning
in order to clear faults quickly [7].
Different methods commonly used for distribution line’s fault detection and relevant work
is summarized below:
7
A novel method for detection of multi-cycle fault in distribution line is discussed in [8].
The fault is of self-clearing nature and occurs for a very short time, the amount of
disturbance in the voltage magnitude during fault is used for detection that an incipient
fault has occurred. After successful detection of the fault the difference between the
waveforms is used to find the fault location in the cable. Incipient fault angle and power
loss characteristics also aid in improvement of the amount of accuracy required in the
whole process.
Artificial Neural Network (ANN) technique based on three steps by creating a distribution
system model in MATLAB/Simulink and simulating a fault condition hence after. In order
to detect the fault, voltages and currents obtained from Simulink model during fault are
analyzed through Fourier and then fed into “Artificial Neural Network” in the second step.
In the last step the fault distance from either end of the cable is determined using software
“Or Cad” which works on the principle of domain reflectometry [9].
In [10] the possibility to apply an approach based on combining complex wavelets and
continuous wavelet transform is discussed to determine impedance using the value of
current and voltage signals in the wavelet domain. An in-depth analysis is carried out to
examine impedance magnitude and its phase distribution under various fault conditions.
The results obtained through this analysis show that this technique is very promising in
fault detection of underground cables.
Discusses an approach to detect fault in an underground cable by carefully monitoring
current in the cable sheath. MATLAB/Simulink is used to analyze the data and results
obtained using this technique show that this method effectively detects cable insulation
breakdown and hence proves valuable for online monitoring of underground cables [11].
In [12] Kamlan filter is used to detect an incipient fault via an innovation signal which is
calculated from fault current fed into Kamlan filter. Variation in magnitude is detected
through innovation signal and further processed to check for likelihood of occurrence of
incipient faults under similar operating conditions.
[13] Underground cables of medium voltage levels could exhibit incipient as well as faults
of self-clearing nature before failing permanently. These incipient and other cable
deteriorating events last for usually one-half cycle and subside at first zero crossing of the
current cycle. The magnitude of these events depends on the fault location on the feeder
8
as well as point on the voltage waveform for starting of the fault.
[14] The initial current is analyzed in the model domain and theoretical part shows the
sum of currents in sheath that can be used to find the initial faults. Both the wavelet
transforms current and the single sheath current at end user are used to find the initial fault.
When the incipient fault is detected then the faulty phase is selected by using root squares
of all the three phases. All the simulation work is carried out in PSCAD.
[15] A novel method for underground distribution automated rapid fault detection
(UDAS) is discussed. UDAS reduce outage time and maintenance cost significantly as
compared to the method previously done manually by the field crew.
[16] Signal processing technique by using voltage and current signals applying the
complex wavelet technique is used to detect the fault location. In this method complex
wavelets is combine with continuous wavelet and calculate the impedance from current
and voltage in wavelet domain and then phase distribution and magnitude are examined
under different conditions.
[17] Fourier analysis is used in this paper for detecting fault and life of a cable. Three
types of cables are used in this experiment first one is normal cable second one a shorted
cable and last one with holes. In each case impedance is calculated and after that Fourier
transformation is applied so that all the parameters like impedance magnitude and
impedance phase can be determined in frequency domain. Different windowing
techniques are used to the data to remove interference. After this Fourier is applied to the
impedance data which is calculated from both sending end voltage and differential
voltage. This experiment gives different frequency response of the three different types of
cables and also can be used for fault detection.
[18] In this paper underground faults detection is done by using wavelet analysis with two
different algorithms to detect the incipient faults. One algorithm is suitable by detecting
single line to ground (SLG) initial fault. The other one is based on transients induced
during fault and therefore point out the incipient faults.
9
Chapter 2
Distributed Parameters of
Transmission Lines
10
2.1
Distributed Parameters of Transmission Lines
In Power system transmission line and power cables are represented by its distributed
elements, i.e. R, L and C, Resistance, Inductance and capacitance. High voltage transmission
lines for short distance less than 50km are represented as series circuit of resistor and inductor,
the capacitance of the line can be ignored. A medium transmission line which has distance
more than 50km up to 240km, are represented as Pi and T circuit. In Pi circuit the capacitance
of the line can be divided into two sections having single resistor and inductor. In T circuit the
resistor and inductor of the line can be divided into sections having single capacitor in the
center. Transmission line longer than 240km can be model as many sections serially connected
of T or Pi circuits. Transmission lines are characterized by a series resistance, inductance, and
shunt capacitance per unit length. These values determine the power-carrying capacity of the
transmission line and the voltage drop across it at full load [19-20].
Figure 2.1 HV transmission lines or power cable equivalent circuit
 Shield and Ground wire – used primarily for protection from lightning strikes and
corresponding surges
 Insulators – used to contain, separate, or support electrical conductors
 Conductors – metal cables used for carrying electric current
 Structures – support structures to hold up the conductors
 Foundation – system which transfers to the ground the various dead and live loads of
the tower and conductors.
10
2.1.1 Resistance
The AC Resistance of the transmission line is based its DC resistance, suppose the current is
uniformly distributed
R DC =
ρl
Ω
A
(2.1)
 m
R E =π 2f.10-7 Ω
Where
Positive and negative sequence
(2.2)
RE =49.3
RE
m
m
for f=50Hz
is cancel out each other and then
R1  Ra
Ra = conductor internal resistance /meter
R1 = conductor 1 Resistance,
Zero sequence Resistance
R o =R a +3R E
(2.3)
Figure 2.2 Conductor arrangement in 3 Phase Lines (a) Trefoil (top) (b) Flat (Bottom)[20]
2.1.2 Inductance
The mutual and self-inductance of the conductors per unit length is given by [19-21
Lij 
 
o DE H
ln
m
2 dij
DE  659
Where
(2.4)

f
 = Resistivity of earth in (Ωm)
11

1
dii  e 4 R  0.778R Self GMD of cylindrical conductor
d ij = mutual GMD of conductor i and j
In single core power cable
Lij  0.05  0.2ln

K .s mH
km
rc

S = distance between conductor (mm),
Rc= conductor radius (mm)
K=1, trefoil formation,
K=1.26 flat formation
2.1.3
(2.5)
Capacitance
Capacitance per phase to neutral is
C
C
2 o F
m
D
ln
R
 
(2.6)
0.0556
  f km 
D
ln
R
(2.7)
ε o = 8.85x10-12 F/m, R = Radius of the conductor, D= Distance between the conductors
In single core power cable
C

d
18.ln( 0 )
di
[  F / km]
(2.8)
ε = relative permittivity of cable insulation
d0
= external diameter of insulation (mm)
di
= diameter of conductor and screen (mm)
For XLPE power cable  = 2.5
[IEC-60287]
2.1.4 Admittance
Impedance
Z  R  jX
(2.9)
Admittance
12
Y 
Y
1
Z
(2.10)
1
1

Z R  jX
(2.11)
By taking conjugate
Y
1
R - jX
.
R  jX R - jX
(2.12)
Y
R - jX
R - ( jX ) 2
(2.13)
Y
R - jX
R2  X 2
(2.14)
Y
R
- jX
 2
2
R X
R  X2
(2.15)
2
2
Y  G - jB
(2.16)
2.1.5 Capacity and Charging Current
The capacitive charging current is flowing due to cable capacitance during no load. The capacitive
charging current is as
Ic  V0 ..ca  A / km
V0 =
(2.17)
Operating voltage (kV)
 = Angular frequency
ca =
Operating capacity [19-21]
13
2.2
Types of Conductors
Transmission and distribution line conductors are responsible for carrying power from
generating station to receiving stations.
2.2.1 AAC – All Aluminium Conductor
AAC contains one or more aluminum alloy strands. AAC is preferred for short spans (usually
in urban areas). AAC has the highest conductivity to weight but has a poor strength to weight
ratio.
2.2.2 AAAC – All Aluminium Alloy Conductors
AAAC is an alloy conductor that is made of aluminum, silicon, and magnesium. Its ampacity
is equivalent to AAC and possesses excellent tension characteristics. AAAC provides
excellent resistance against corrosion and is used in coastal areas. AAACs are becoming more
popular than ACSR for the last two decades. They are stronger, lighter and more conductive
than ACSR. However, they are more expensive than ACSR.
2.2.3 AACSR – All Aluminium Alloy Conductors Steel Reinforced
They are less common than AAACs.
2.2.4 ACAR – Aluminium Conductors Alloy Reinforced
ACAR involves a combination of aluminum strands that are helically wrapped around
aluminum alloy wires. The combination increases the mechanical strength of conductors.
2.2.5 ACSR – Aluminium Conductors Steel Reinforced
ACSR involves the Aluminium conductor reinforced with steel core. The central steel core is
surrounded by a number of aluminum strands. Steel strands are used for increasing the strength
of conductor. Usually, steel is coated with zinc. At present ACSR conductors are most popular
for longer transmission lines.
2.3
Underground Power Cables
The underground power cables are used for power transmission and distribution where it is
difficult, or dangerous to use the overhead lines. The underground power cables are in densely
populated areas, in industries, and to supply power from the overhead lines to the load centers.
The underground cables have several advantages over the overhead lines;
14
a- low voltage drops
b- less chances of faults
c- low maintenance cost
The underground cables have also disadvantages over the overhead lines;
a- Expensive to manufacture
b- Cost increases as voltage rating increases
c- Fault rectification
d- High installation cost
2.3.1
Types of Underground Cables
The underground cables are classified in following two categories
According to voltage ratting
Low-tension cables
(Voltage ratting below than 1000 V)
a) High-tension cables
(Voltage ratting up to 11 KV)
b) Super-tension cables
(Voltage ratting 22 KV - 33 KV)
c) Extra high-tension cables
(Voltage ratting 33 KV - 66 KV)
d) Extra super voltage cables
(Voltage ratting above 132)
According to Insulation and manufacturing design
There are some types of underground electric power cables which are categorized on the basis
of insulation materials, these are [22]
EPR: Ethylene propylene rubber
LDPE: Low density polyethylene
HDPE: High density polyethylene
XLPE: Cross linked polyethylene
a- Belted cables
b- Screen cables
c- Pressure cables
2.3.2 Belted Cables
The cores in the belted underground power cables are insulated by impregnated paper. In the three
phase power cable, the three cores are combined together and then belted with the insulation paper
belt. The gaps between the cable cores and the paper insulation are filled with fibrous materials.
15
A lead sheath is used to cover the paper belt hence to protect it from moisture and provide
mechanical strength. The lead sheath is then covered with a single or multiple
2.3.3 Screened power cable
In a typical three phase 3-core power cable, each of the three cores is insulated by impregnated
paper and covered by Aluminium foil or other metallic screen. The arrangement of the cores is
designed to allow each of the three metallic screens to make contact with each other. The three
cores are then wrapped around using a conduction belt made of copper woven fabric tape.
2.3.4 High Pressures Power Cables
These are high power cables used for voltages above 66KV. The cable construction is
different from the above two and majority uses a cooling gas or oil.
2.3.5 Conductors
The conductors in underground power cable are generally made of copper or aluminum material.
Conductors used in underground power cable should have the following properties
i- High electrical conductivity
ii- high tensile strength in order to withstand mechanical stresses
iii- low cost and low specific gravity
Commonly used conductor materials in HV Transmission are
i-
Copper
ii- Aluminum,
The Copper conductors have high electrical conductivity, greater tensile strength, cheap and light
weight. As compared to copper the aluminum conductors have smaller conductivity and tensile
strength. Conductivity of aluminum is approximately 60% that of the copper conductor.For the
same resistance: the diameter of aluminum conductor is about 1·26 times the diameter of copper
conductor. The specific gravity of aluminum conductor is 2·71 gm/cc which is lower than the
copper’s specific gravity (8·9 gm/cc). Aluminum conductor has almost one-half the weight of
equivalent copper.
16
2.4
XLPE Cables
XLPE cables were first designed in 1960’s which improved significantly giving reliable duty
used by utility industry. In present, XLPE power cable are operating up to 500kv with short circuit
length of 40km. XLPE cables pass different types of tests like long duration test as one of the
first test was taken of Brugg cables on 400kv according to the international standard ICE 62067
in 2001 this test takes one year by monitoring temperature of all cables at joints and terminators.
It was test it CESI laboratory Milan, Italy 2004.
Figure 2.3 3 Core XLP cable view [22]
Figure 2.4 1 Core XLP cable side view 230 kV XLPE cable[22]
17
Modern XLPE cables are composed of core, sheath which is metallic and outer insulation
covering. The core is consists of conductor, wrapped (semiconductor), inner semiconducting
layer, the main solid insulation the outer layer which is semiconducting. The high voltage cable
can be made of aluminum or copper in order to minimize the current losses.
Figure 2.2 Field Distribution of XLPE cable
High voltage XLPE cables can be regarded as homogenous cylindrical form. The voltage gradient
at point X can be calculated as [22]
Vx 
V0
 kV / mm 
 ra 
rx .ln  
 ri 
V0 =
Operating voltage (kV)
(2.18)
rx = Radius at position X (mm)
ra =
ri =
External radius above the insulation (mm)
Radius of the internal field diameter (mm)
Electrical field strength is at highest at the inner semiconductor and lowest at above the
insulation and below the external semiconductor rx
18
 ra
Chapter 3
Testing of Transmission Lines/Cables
and Fault Location
19
3.1
Basic Diagnostic Testing Used for Underground Power Cables
The following tests are carried out during, manufacturing, installation, and fault diagnosing in
underground power cables [22-24]
a- TDR- Time Domain Reflectometry
b- PD- Partial Discharge test at very low frequency
c- DC current leakage Test
d- Polarization and de-polarization current test
e- Dissipation factor tan( ) measurement or Di-electric spectroscopy at very low
frequency
f- Withstand Voltage test
g- Sequence Impedance
h- Insulation Resistance Test
3.1.1 Time Domain Reflectometry
A TDR-Time Domain Reflectometry measures the reflections of signals which can be sent from
one end to the other end a conductor of a power cable. If the cable conductor is of equal and
uniform impedance, and is in healthy condition, then there will be no signals reflection. Instead,
if some of the transmitted signal reflected back to the source then there are impedance variations
in the power cable.
3.1.2 Dissipation Factor Measurement
Dissipation Factor: Cable power factor (P.F), Capacitance and dissipation factor (tan delta, tan( )
) are important measurements to make ensure the cables insulation is good or weak. The tests are
very useful in detecting of moisture or other contaminants and deterioration of cable insulation.
A voltage source at power frequency is provided to the cable, at no load condition, there will be
no inductance effect, the cable will be purely capacitive and the angle between voltage and current
be about 90 degrees as shown in figure below. If there is any low resistance or leakage found then
the flowing current will be leading the voltage below the 90 degree. [23]
Wd 
V2
.2 fC.tan( )[ watt / km]
3
(3.1)
F = frequency (Hz),
C= Cable capacitance [  F / km]
V = Rated voltage (kV),
tan( ) = loss
angle
20
Figure 3.1 Calculating dissipation factor, equivalent circuit and vector diagram [23]
3.1.3 Electric Stress of power cable
The high voltage electric stress can be calculated as
Ei 
V
r
ri ln( 0 )
ri
[kV / mm]
(3.2)
V = Rated voltage across cable Insulation
ri =
radius of the conductor screen (mm)
r0
= radius of XLPE Cable Insulation (mm)
Table 3.1 Cable insulation materials, di-electric strength (kV/mm) and tangent loss (tanδ) [23]
Type of Insulation Di-electric strength Tangent Loss
Tangent Loss
(tanδ) at 250 C
(tanδ) at 1000 C
10.5
2.2 x 10-3
3.48 x 10-3
Impregnated Paper
57
2.5 x 10-3
8.45 x 10-3
Impregnated Oil
25
0.8 x 10-3
3.32 x 10-3
Materials
ACV [kV/mm]
Dry paper
Table 3.2 Types of Cable and electric stress Emax (kV/mm) [23]
Type of Cable
Medium Voltage
High Voltage
Extra High Voltage
XLPE
11
6
3
EPR
8.2
5
3
Fluid filled
18
14.5
10
21
3.2
Fault Location Schemes
A variety of fault location schemes have been developed over the years. Common systems
include impedance-based locators [1,2], or those which measure the impedance seen by one
or both ends of the transmission line, and traveling wave-based locators [8- 10], or those which
rely on the timing of fault detections. In addition to categorizing these fault location methods
by the way in which they locate faults, they can also be classified into one-terminal and twoterminal based on whether they require information from one end or both ends of the
transmission line, respectively.
3.2.1 Impedance-Based Methods
Traditional impedance-based fault location methods use the voltages and currents at one or
both ends of a transmission line to determine where a fault has occurred. The impedance of
the transmission line per unit length is usually required in these calculations. One of the major
problems with basic one-terminal impedance-based fault location methods – those that only
use measurements from one end of the transmission 6 line – is that the fault impedance must
be near-zero for the result to be accurate, since the fault impedance affects the impedance seen
at the end of the transmission line [3].
3.2.2 Traveling Wave-Based Methods
Traveling wave-based fault location methods, like impedance-based methods, can be divided
into one-terminal and two-terminal methods. With traveling wave analysis, however, the entire
method of location rather than simply the equations change between the one- and two-terminal
methods. One-terminal methods rely on the timing between reflections of voltage or current
at impedance discontinuities – in this case, the fault – to find the distance between the sensor
and the fault while two-terminal methods work based on the time delay between arrivals of
information at the ends of the transmission line.
3.2.3 Detection and Location Using Magnetic Field Sensors
Due to the simple relationship between current and magnetic field intensity, it is
understandable that magnetic field sensors have previously been used in fault detection and
location schemes. These schemes often use magnetic field sensors in place of current
transformers since magnetic field sensors can be installed independently from a substation or
switching station with a minimum amount of additional equipment [11,12].
22
Chapter 4
Design and Simulation for
Transmission Fault Location
23
4.1
3-Phase transmission/distribution line fault location
The location of the fault in the transmission/distribution line will be find out from the input
current and output voltage. When the ground fault occurs in the transmission/distribution line,
the short circuit current from source to fault increases and the voltage at the receiving end
decreases. From this current and voltage, the fault impedance can be also calculated, the fault
impedance and the ground impedance are approximately equal. The fault impedance depends on
ground resistance, fault location, line and load impedance. The fault current increases as fault
location decreases and vice versa.
In this simulation the power transmission/distribution line equivalent circuit is designed, in which
the distributed parameters are modeled and presented. The fault current depends on theses
distributed parameters; these parameters are transmission/distribution line resistance in ohm/km,
line inductance (hennery/km) and transmission/distribution line capacitance in farad/km. The line
inductance and capacitance cancel out each other’s; the transmission/distribution line will be
inductive if the cable inductive reactance is greater than cable capacitive reactance, and vice
versa. Here the cable has more capacitive reactance than cable inductive reactance and that is
why the source side power factor is higher than load power factor.
Figure 4.1 Three phase transmission line equivalent circuit for a distance up to 10 km
24
4.1.1 3-Phase transmission line equivalent circuit
Distributed parameters of a transmission line and its equivalent pi-network is modeled as shown
in figure below. The cable resistance, inductance and capacitance per phase per kilometer are
shown.
Figure 4.2 Three phase transmission line equivalent circuit for 1km distance, the cable resistance,
Inductance and Capacitance are modeled per phase per km distance.
Figure 4.3 Simulation of transmission line fault location calculation in Simulink
25
In this simulation a 3-phase load 200kW is connected to 3 phase power supply sources via cable
equivalent impedance, 3 phase voltage and current monitoring blocks are connected at sending
and the receiving ends of the cable. 3 phase voltage and current monitoring blocks are monitoring
voltage and current of each phase during normal and abnormal condition of the cable. Whenever
a ground fault (low resistance path) occurs the current at the sending end increases as determined
by Ohm’s Law, and the voltage at the receiving end decreases. Short circuit current depends on
line/cable impedance and fault impedance, the fault current increase as cable distance decreases
and vice versa. Similarly, the short circuit current will also increase as ground impedance
decreases.
To find the cable fault location, the following parameters are required
a- Short circuit current at the sending end
b- The receiving end voltage
c- The fault equivalent impedance
(Cable impedance, load impedance and ground impedance)
These parameters are calculated during fault as shown in figure below.
Figure 4.4 Three phase input current, output voltage and distance calculation blocks
When a single line to ground fault occurs the current of that line increases and voltage
decreases, a MinMax block is used to determine which line has min voltage and maximum
current. Also send this minimum voltage and maximum current signal to the distance
calculation block.
26
If V1 or V2 or V3 <9.5 & >7 volt
If V1 or V2 or V3 <7 volt
Dsc 
Dsc 
V 0.93
1.2
V 2.5
25
(4.1)
( km)
(4.2)
(km)
4.1.2 Open Circuit Fault Calculation
When a power cable is connected to the source and the load is removed from the cable at receiving
end, some current will flow in the ampere meter at the sending end due to capacitance of the power
cable. This current depends on cable capacitance per km and cable distance. When this current
flow in the cable produces voltage due to cable inductance which is in phase to the supply source
and thus the receiving end voltage becomes higher than sending, this phenomena s known as
Ferranti Effect, Ferranti was the first scientist who found this phenomenon during testing of 10
kV power cable in 1887.
The open circuit fault can be calculated from the no load current flowing in cable. Remove load
from the receiving end and measure the value of current, this current will be decreased linearly if
open circuit fault distance is decreased and vice versa. The open circuit fault distance can be
calculated from the formulas mentioned below.
The capacitive charging current is flowing due to cable capacitance during no load. The capacitive
charging current is as equation (2.17)
Ic  V0 ..ca  A / km
(4.3)
Maximum charging current per phase of the total cable can be found from equation (4.4).
Icmax =V0 .ω.ca .Dmax  A 
kic 
Dmax =
(4.4)
Dmax
I c max
total length of cable,
(4.5
I c max =
Maximum charging current
kic =
Charging current factor
Open circuit fault distance can be calculated from equation (4.6)
Doc  I c .kic (km)
(4.6)
27
Figure 4.5 Open circuit fault in transmission line at 8 km
Open circuit fault is generated in line 1 at distance of 8 km, the Doc will calculate open circuit
fault distance and Dsc will calculate short circuit and ground fault distance. The simulation results
are displayed in distance calculation block as shown in figure 4.6.
Figure 4.6 Open circuit fault and short circuit fault locations are displayed
4.2
Hardware main circuit and components
In the hardware 220/24 VAC is transformer is used to supply the power to the load through
transmission lines having resistance, capacitance and inductances. The line has total series
resistance of 8.6 Ohms (0.86 Ohm resistance per section), and low inductance of 72uH and 1k
Ohm shunt resistance per section. Leakage current is flowing through these shunt resistances, the
shunt resistances are used instead of shunt capacitances. In shunt capacitors a small value of
current is flowing due to low voltage which is difficult to measure by the CT and controller and
that is why shunt resistor are used in the circuit. In high voltage cable the leakage current is
flowing due to shunt capacitance are also high.
28
In normal healthy condition some voltage will be dropped in transmission line and the load will
get a small voltage. A current limiting resistor (LR) is used to limit the short circuit current during
short circuit fault. Current transformer is used to measure the current flowing in the transmission
line during normal and abnormal condition. The total leakage current of the line is 0.3 ampere.
4.2.1 Hardware Specification
Transformer
= 03 x 220VAC / 12VAC, 3 Amperes
Current Transformer
= 5 Ampere/ 5 mA
Line section
= 08 Nos, each section represent 1 km distance of line
Controller
= Arduino UNO
WiFi Module
= ESP 32
Current limiting Resistor = 3 Ohm
Line Series Resistance
= 0.7 Ohms/section
Shunt resistance
= 1k Ohm/section
Maximum Current
= 3 Ampere continues
Short Current
= 5 Ampere, <5 seconds
Leakage Current
= 0.024 - 0.3 ampere
4.2.2 Measurement Circuit
Current transformer is used to measure the current flowing in the transmission line during normal
and abnormal condition. The output current is converted into AC voltage and then shifted into
dc, an analogue offset value is generated and provided to microcontroller to measure the value of
current, in this current measuring method an accurate value of current can be obtained from 5
milliampere to 5 amperes. Similarly, the voltage divider circuit is used to measure the voltage of
the sending end, however in line fault localization voltage calculation is not required, and the
voltage displaying is also ignored. [29]
29
Figure 4.7 Current measuring circuit and wave form, AC Current shifted into DC Offset
Figure 4.8 Hardware three phase line circuit diagram
Figure 4.9 Hardware measurement circuit diagram of 3 phase line fault detector
30
Figure 4.10 Voltage & Current signals to Arduino UNO and interfacing of WiFi module
Figure 4.11 Hardware for WiFi based line fault detector and location finder
31
Chapter 5
Simulation Results and Discussion
32
5.1
Simulation Results
Different faults on transmission/distribution line are generated at different locations, the
simulation results display the exact location and fault type. Different types of faults are:
 Single line to ground faults: L1G, L2G, L3G
 Line to line faults: L1L2, L2L3, L1L3, L1L2G, L2L3G, L1L3G,
 Three lines faults: L1L2L3, L1L2L3G
 Line theft fault
 Open Circuit (OC) fault
 Transformer faults: Overload, Short circuited at load, internal faults, over
temperature etc
Figure 5.1 Single Line to Ground Fault (L1G) is generated at distance of 7 km
Figure 5.2 Single Line to Ground Fault (L1G) and location is shown in display
33
Figure 5.3 Single Line to Ground Fault (L3G) is occurred at distance of 2 km
Figure 5.4 Single Line to Ground Fault (L3G) and location is shown in display
Figure 5.5 Three Lines Fault (L1L2L3) is generated at distance of 4 km
34
Figure 5.6 Three Lines Fault (L1L2L3) and location is shown in display
5.1.1 Transmission lines faults and fault codes
Table 5.1 Transmission lines faults and fault codes
Sr.No
Fault
L1
L2
L3
G
Binary Description
1
Healthy System
0
0
0
0
0000
2
L1G
1
0
0
1
1001
3
L2G
0
1
0
1
0101
4
L1G
0
0
1
1
0011
5
L1L2
1
1
0
0
1100
6
L1L3
1
0
1
0
1010
7
L2L3
0
1
1
0
0110
8
L1L2G
1
1
0
1
1101
9
L1L3G
1
0
1
1
1011
10
L2L3G
0
1
1
1
0111
11
L1L2L3
1
1
1
0
1110
12
L1L2L3G
1
1
1
1
1111
13
Open Circuit
2
0
0
0
2000
35
5.2
Transformer Protection
In this block of transformer protection; transformer faults internal or at terminals, transformer
overload, transformer short circuit and transformer over temperature are calculated and
displayed. This block also monitoring transmission line theft, if electricity is theft from the
line the protection block will generate theft alarm. Transformer faults and the appropriate
binary description are shown in the table.
5.2.1 Differential Protection of a Transformer
The transformer is one of the major equipment in power system. It is a static device, totally
enclosed and usually oil immersed, and therefore the fault occurs on them are usually rare. But
the effect of even a rare fault may be very serious for a power transformer. Hence the
protection of power transformer against possible fault is very important. The fault occurs on
the transformer is mainly divided into two type external faults and internal fault. External fault
is cleared by the relay system outside the transformer within the shortest possible time in order
to avoid any danger to the transformer due to these faults. The protection for internal fault in
such type of transformer is to be provided by using differential protection system. Differential
protection schemes are mainly used for protection against phase-to-phase fault and phase to
earth faults.
Figure 5.7 Transformer protection monitoring and control system
In this simulation the primary current and secondary current are monitored by using VI block.
The equation is
Ip * k = Is
The load at transformer is 100A (Is=100A), the primary current is (Ip=3.63 A), so the equation
is
3.63 * 27.5 =100 So the difference of the current (Ip * k – Is) is approximately zero. If
36
there is something wrong in transformer then the difference will be more than value one, which
indicates transformer faults.
The line theft monitoring is also based on the differential of the current at sending and
receiving end of the transmission/distribution line.
Sending end current is approximately equal to zero, there are some leakages current due to
capacitance of the line. The theft load current should be greater than line leakage current,
otherwise the difference will be approximately zero.
5.2.2 Transformer faults and alarm binary descriptions
Table 5.2 Transformer faults and alarm binary descriptions
Sr.No
Fault
Fault Number
Binary Description
1
Healthy System
0
0
0
000
2
T/F Fault (internal)
0
1
0
010
3
Transformer Overload
1
0
0
101
4
T/F Short ckt (load)
0
0
1
011
5
Line Theft
1
1
1
111
Figure 5.8 Single Line (L1G) Fault is generated at transformer and the result is displaying
37
Figure 5.9 A three-phase load is theft from transmission/distribution line
Figure 5.10 The results of line theft is calculated and shown in the display
5.3
Internet of thing (IoT) based line faults monitoring
5.3.1 Features of Cayenne IoT Cloud Platform
 Cayenne App is used to remotely control your IoT projects with drag and drop widgets
from an app.
 Cayenne Online Dashboard is used to setup and manage our IoT projects with the help
of the browser.
 Cayenne Cloud store and process the device data.
 Cayenne Agent enables communication with the server, agent and hardware for
implementing incoming and outgoing commands, actions, triggers and alerts.
38
Figure 5.11 IoT based single line to ground (L1G) fault detection and display
Figure 5.12 IoT based two line to line and ground (L1L2G) fault detection and display
39
Figure 5.13 IoT based three line to line and ground (L1L2L3G) fault detection and display
Figure 5.14 IoT based Transformer fault detection and display
Figure 5.15 IoT based Open circuit fault detection and display
40
Chapter 6
Conclusion & Future Work
41
6.1
Conclusion
The simulation work has been carried out in MATLAB/Simulink, to find out fault location in
transmission line/distribution/underground cable. Three phase equivalent circuit is modeled with
distributed parameters.
a)
Fault location can be found by monitoring input current (Isc), voltage sag (Vr) at receiving
end and fault impedance during fault in live cable.
b) Fault location can be found during balanced and unbalanced fault.
c)
Fault location can be found at variable load (  10kW to 200kW).
d) Open circuit fault in 1 line, 2 lines or 3 lines, OC fault location is calculated.
e)
Both open circuit (OC) and short circuit (SC) fault can be analyzed and found at same
time.
f)
Transformer faults and alarms are shown/simulated
g) Line theft has been discussed and shown in simulation
Hardware circuit is designed for three phase line faults and location calculation and the data
are send via WiFi/IoT for monitoring.
In this simulation work, it is studied that newly installed cable distributed parameters can be
determined in the pi-section of the cable model. A fault current can be injected into different
location and fault location can be analyzed.
After final conclusion and test results, the fault location expression can be fed in microcontroller, the phase voltages and currents can be provided to microcontroller though potential
transformers (PTs) and current transformers (CTs) and thus fault location can be calculated
from the same expression determined in Simulink during simulation.
6.2
Future work
In this research work a single WiFi module is used for a single 3 phase line, so multiple WiFi
modules for multiple line can be used and all these WiFi modules should communicate with
master WiFi module. The following information/data can be collected in future work;
 Smart energy monitoring
 Prepaid energy metering/supplying
 Load profile
42
 Faults record and history
 Fault Location
 Line security and protection
 Priority based load management
 Number of faults per year
 Load shedding history
43
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44
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