Underground Cable Fault Report

UNDERGROUND CABLE FAULT DETECTION
ABSTRACT
In this paper, the analysis of underground power cable is performed using timer & counter and op
amp’s with the objective of detecting fault and the average life of the cable. Three types of cables
are used in this project (red, yellow &blue respectively).Various windowing techniques are applied
to the experimental data to eliminate any interface . This analysis reveals differences in the
frequency response of the three different types of cable and eventually can be used as measure for
fault detection.
Preliminary results reveal the differences in the frequency response. Accordingly this
type of method can be effectively used as low cost and variable solutions to identify and detect
the fault in underground cables.
Dept. of Telecommunication ,Dr.AIT Page 1

TABLE OF CONTENTS
Chapter-1……………………………………………………………………
INTRODUCTION…………………………………………………….
1.1 Objective…………………………………………………………
1.2 Aim………………………………………………………………..
1.3 IoT……………………………………………………………………
1.4 Sensors…………………………………………………………..
Chapter-2…………………………………………………………………..
LITERATURE SURVEY…………………………………………………….
Chapter-3………………………………………………………………………..
MOTIVATIONAL BACKGROUND……………………………………………….
Chapter-4……………………………………………………………..
PROPOSED SYSTEM………………………………………………………..
4.1 Block Diagram…………………………………………….
4.2 Flow diagram /flow chart and its description…………………..
4.2.1 Flow Chart…………………………………………
4.2.2 Description………………………………………..
4.3 Circuit Diagram………………………………
Chapter-5
IMPLEMENTATION DETAILS……………………………………………….
5.1 Hardware Description………………………………………………..
5.1.1
5.2 Software Description……………………………………………………
Chapter-6
ADVANTAGES, APPLICATIONS……………………………………………
6.1 Advantages………………………………………………….
6.2 Applications………………………………………………….
Chapter-7
RESULT…………………………………………………………..
Chapter-8
CONCLUSION AND FUTURE SCOPE…………………………
8.1 Conclusions…………………………………………………
8.2 Future scope…………………………………………………
References

Chapter 1
INTRODUCTION
1.1 Objective
Power supply networks are growing continuously and their reliability is getting more important
than ever. The complexity of the whole network comprises numerous components that can fail and
interrupt the power supply for the end user. For most of the worldwide operated low voltage and
medium voltage distribution lines underground cables have been used for many decades. During
the last years, also high voltage lines have been developed to cables. To reduce the sensitivity of
distribution networks to environmental influences underground high voltage cables are used more
and more. They are not influenced by weather conditions, heavy rain, storm, snow and ice as well
as pollution. Even the technology used in cable factories is improving steadily certain influences
may cause cables to fail during operation or test. Cables have been in use for over 80years. The
number of different designs as well as the variety of cable types and accessories used in a cable
network is large. The ability to determine all kind of different faults with widely different fault
characteristics is turning on the suitable measuring equipment as well as on the operator’s skills.
The right combination enables to reduce the expensive time that is running during a cable outage
to a minimum.
1.2 Aim
This project proposes fault location model for underground power cable using microcontroller.The
aim of this project is to determine the distance of underground cable fault from
base station in kilometers. This project uses the simple concept of Ohm’s law. When any
fault like short circuit occurs, voltage drop will vary depending on the length of fault in cable,since the
current varies.

1.3 IoT
The evaluation of IOT in the electrical Power Industry transformed the way things performed in usual
manner. IOT increased the use of wireless technology to connect power industry assets and infrastructure in
order to lower the power consumption and cost. The applications of IOT are not limited to particular fields,
but span a wide range of applications such as energy systems, homes, industries, cities, logistics, heath,
agriculture and so on. Since 1881, the overall power grid system has been built up over more than 13
decades, meeting the ever increasing demand for energy. Power grids are now been considered to be one of
the vital components of infrastructure on which the modern society depends. It is essential to provide
uninterrupted power without outages or losses. It is quiet hard to digest the fact that power generated is not
equal to the power consumed at the end point due to various losses. It is even harder to imagine the after
effects without power for a minute. Power outages occur as result of short circuits. This is a costly event as it
influences the industrial production, commercial activities and consumer lifestyle. Government &
independent power providers are continuously exploring solutions to ensure good power quality, maximize
grid uptime, reduce power consumption, increase the efficiency of grid operations and eradicate outages,
power loss & theft.

Chapter 2
LITERATURE SURVEY
Literature survey earlier to begin a research project is essential in understanding fault in underground cable
lines, as this will supply the researcher with much needed additional information on the methodologies and
technologies available and used by other research complement around the world. Dhivya Dharani.A,
Sowmya.T [1] the paper titles as―Development of a Prototype Underground Cable Fault Detector‖ —Cable
faults are damage to cables which affects the resistance in the cable. If allowed to persist, this can lead to a
voltage breakdown. To locate a fault in the cable, the cable must first be tested for faults.
This prototype uses the simple concept of OHMs law. The current would vary depending upon the length of
fault of the cable. This prototype is assembled with a set of resistors representing cable length in Kilo meters
and fault creation is made by a set of switches at every known Kilo meters (km’s) to cross check the
accuracy of the same. The fault occurring at what distance and which phase is displayed on a 16X2 LCD
interfaced with the microcontroller. The program is burned into ROM of microcontroller. The power supply
consists of a step down transformer 230/12V, which steps down the voltage to 12V AC. This is converted to
DC using a Bridge rectifier. The ripples are removed using a capacitive filter and it is then regulated to +5V
using a voltage regulator 7805 which is required for the operation of the microcontroller and other
components.
Nikhil Kumar Sain, Rajesh Kajla [2] paper titled as ―Underground Cable Fault Distance Conveyed Over
GSM. This paper proposes fault location model for underground power cable using microcontroller. The aim
of this project is to determine the distance of underground cable fault from base station in kilometers. This
project uses the simple concept of ohm’s law. When any fault like short circuit occurs, voltage drop will
vary depending on the length of fault in cable, since the current varies. A set of resistors are therefore used
to represent the cable and a dc voltage is fed at one end and the fault is detected by detecting the change in
voltage using analog to voltage converter and a microcontroller is used to make the necessary calculations so
that the fault distance is displayed on the LCD display.
R.K.Raghul Mansingh, R.Rajesh, S.Ramasubramani, G.Ramkumar [3] titled as ―Underground Cable Fault
Detection using Raspberry Pi and Arduino‖-The aim of this project is to determine the underground cable
fault. This project uses the simple concept of CT Theory. When any fault like short circuit occurs, voltage
drop will vary depending on the length of fault in cable, since the current varies CT is used to calculate the
varying. The signal conditioner manipulates the change in voltage and a microcontroller is used to make the
necessary calculations so that the fault distance is displayed by IOT devices.

Chapter 3
MOTIVATIONAL BACKGROUND

Chapter 4
PROPOSED SYSTEM
4.1 Block diagram

4.2 Flow diagram/ Flow Chart and its Description

4.2.1 Flow chart
4.2.2 Description
The prototype uses resistors to represent the cable length. The resistors RR1 to RR5
represents
R phase of the cable. Similarly RY1 to RY5 and RB1 to RB5 represent Y and B phase of the
cable. RN1 to RN12 are used to represent the neutral lines. To represent the occurrence
of fault
in underground cables switches are used. Each phase is connected with a relay which
in turn
is connected to Port C of Microcontroller. When there is no fault, the LEDs connected
to each
relay glows.


CABLE TYPES
Cable types are basically defined as low-, medium- and high voltage cables. The most
common designs of medium- and high voltage cables are shown below. According to the
cable type, different requirements to cable testing, cable fault location as well as maintenance
strategy are defined. Three-conductor cables have been in use in the lower voltage ranges.
The tendency of the last years show the shifting to single-core systems as they are lower in
price, lower in weight and cheaper in regards to repair costs. Furthermore oil impregnated or
oil filled cables are used less and less, as the environmental sustainability cannot be
guaranteed. Especially in industrialized countries, these cable types have been replaced and
are no more installed. On the other hand a high demand for maintenance of those cables is
given as the installed oil- insulated networks do show up a lifetime of 50 years and more.
Today mainly XLPE insulated cables are used. The improvement of the XLPE insulation
material combined with the modern design of the cable enable to manufacture cables even for
the extra high voltage level.

Single core, XLPE insulated medium voltage cables 6kV up to 36kV
3-core EPR, incl. 3-core XLPE 11kV 1-core XLPE 115kV

Data line, radial type
All kind of low-, medium- and high voltage cables are delivered and stored on cable
drums. The maximum available cable length is mainly specified by the diameter (1-
core ore 3-core cable) and the voltage level of the cable.

Overview of Pulse Velocity v/2 for different cable types: Cable

Type Remark Average Propagation Time Velocity:
CABLE TYPES REMARKS Average Propagation
Time Velocity v/2 [m/μs]
PLIC Impregnated paper 75-85
Dry paper 108-132
XLPE 78-87
PE Approx. 100
PVC 76-87
EPR 68-83
Propagation Velocity V/2 For Different Types Of Cables
Cable Faults:
A cable fault can be defined as any defect, inconsistency, weakness or non-homogeneity that
affects the performance of a cable. All faults in underground cables are different and the
success of a cable fault location depends to a great extent on practical aspects and the
experience of the operator. To accomplish this, it is necessary to have personnel trained to
test the cables successfully and to reduce their malfunctions. The development of refined
techniques in the field of high voltage testing and diagnosis, in addition to the variety of
methods for locating power cable faults, makes it imperative that qualified and experienced
engineers and service operators be employed. In addition, it is important for the trained
personnel to be thoroughly familiar with the fundamentals of power cable design, operation
and the maintenance. The purpose of this document is therefore to be an additional support to
the user manuals of the different equipments concerning all aspects of the fault location in
order to make up a volume of reference which will hopefully be useful for operators and field
engineers. The technology used and the experience that can be shared is based on the BAUR
expertise collected over more than 60 years.

WORKING :
Power is stepped down by a step down transformer and the output is connected with 12v
relay now ac is converted to dc power by full wave rectifier and the dc power is smoothen by
the use of a power filter. Power is filtered and the supply is passed to timer and counter chip
IC. We have used 6 LED’s mainly 3 green and 3 red. These LED’s are connected to op amps,
3 pipe lines are used representing the three cables red yellow and blue and a switch is
connected to trip the supply which symbolize short circuit
When supply is given all the 3 red led glow one by one with the help of counter ic. The 3
green led keeps glowing until the power is interrupted. In case of short circuit in any cable
there is interruption in power in the cable with fault this interruption is read by the op amp as a
result the green led blows off and the led glows for the fault carrying cable and finally we find
which cable is faulty.

EQUIPMENTS USED:
1. Step down transformer

2. Relay
3. Full wave rectifier
4. Timer and Counter
5. Diode & Resistor
6. LED’s & IC’s
7. Plastic pipe for UG cables
8. Power filter
9. SPST switches
Cable Fault Location Procedure:
Cable fault location as such has to be considered as a procedure covering the following steps
and not being only one single step.
 Fault Indication.
 Disconnecting and Earthing.
 Fault Analyses and Insulation Test.
 Cable Fault Pre-location.
 Cable Route Tracing.
 Precise Cable Fault Location (Pinpointing).
 Cable Identification.
 Fault Marking and Repair.
 Cable Testing and Diagnosis.
 Switch on Power.

Cable Fault Types:
1. Fault between core-core and/or core - sheath:
 Low resistive faults (R < 100 - 200 Ω)

o short circuit
 High resistive faults (R > 100 - 200 Ω)
o Intermittent faults (breakdown or flash faults)
o Interruption (cable cuts)
2. Defects on the outer protective shield (PVC, PE):
 Cable sheath faults-
Most of the cable faults occur between cable core and sheath. Furthermore, very frequently
blown up open joint connections or vaporized cable sections can cause the core to be
interrupted. To figure out whether such a fault is present, the loop resistance test shall be
done. By using a simple multi-meter, the continuity in general can be measured. The easiest
way to perform this test is to keep the circuit breaker at the far end grounded. Corrosion of
the cable sheath may increase the line resistance. This is already an indication for possible
part reflections in the TDR result. As a rough guidance, a line resistance of 0.7 Ohm/km can
be considered as normal condition. In dependence of the fault characteristic, the suitable
cable fault pre-location and pinpointing methods need to be selected by the operator.

Cable Fault Pre-location:

Overview:
1. Bridge method
2. Low and Low voltage method
 Impulse Reflection Method TDR for: o Low

resistive faults.
 Determination of the cable length.
 Localization of cable interruptions.
 Detection of joints along the cable.
3. High voltage methods
 Multiple Impulse Method SIM/MIM.

 Impulse Current Method ICM.
 Decay Method.
 High resistive faults.
 Breakdown / intermittent faults.
 high resistive cable faults.

 Low and high resistive cable sheath faults.
 Core to core faults in unshielded cables.
 faults in pilot cables and signal lines
 faults in unshielded cores to ground

Cable Route Tracing:

Cable route tracing is applied to determine the exact route of the underground cable.
Depending on the availability of cable laying maps, route tracing is of very high importance
as prior step to cable fault pin-pointing. Route tracing can be performed either active or
passive. At live cables the harmonics of the mains frequency can be heard as ‘mains hum’.
However, all grounded conductors, water pipes and parallel running cables which are
connected to the 50Hz mains system also have this ‘mains hum’. To avoid confusion, it is
recommendable to disconnect the conductor and feed the cable with an audio frequency to
perform an active cable route tracing.
Signal detection:
Above the ground, the electromagnetic signal transmitted via the audio frequency generator
can be measured along the cable trace. Depending on the pick- up coil direction, the signal
can be coupled differently.
1. Maximum method
The detecting coil is horizontal to path of line. Maximum audio signal is directly above the
line. The maximum method is used for cable routing as well for terrain examination.
2. Minimum method
The detecting coil is vertical to the path of the line. The minimum audio frequency signal is
directly above line. The minimum method is used for depth determination measurement as
well for exact cable tracing and pinpointing.

Depth Measurement according to the Minimum

Method
For the depth determination with a simple surge coil, the characteristic of an isosceles
triangle
- first determine the exact position of the cable.
- subsequently, the coil has to be rotated to 45°
- The minimum audio-frequency signal is heard at the depth “d” at a corresponding distance
from the path of the cable. Instruments designed specifically for route tracing are operated
with two integrated antenna covering the functions of minimum and maximum method as
well as depth determination.

Terrain examination
Another application where the cable locating set can be applied is the
so called terrain examination. The signal is injected into the soil via two earth spikes. In case
there is any metallic conductor, the signal will return along the conductor. The
electromagnetic signal along the conductor can be detected and the conductor can be found.
To examine a particular area for existing cable/pipes system, the follow procedure is
recommended:
- dividing the area into squares of approx. 25x25 m
- the audio frequency generator has to be set up in the centre of the cable run
- the ground rods need to be set into the ground to the left and right of the generator at
approx. 12 to 15m
- the output power of the generator is kept low
If there is a metallic conductor within the set out area, it will propagate a magnetic field in its
vicinity. The magnetic field has in most cases the shape of a single sided maximum; e.g. with
a steep edge to the audio frequency waveform.
Selection of Audio Frequency:

Every audio frequency generator is offering the possibility to select different signal output
frequencies.
- The higher the frequency, the higher the inductive coupling effect
Basically the frequency has to be selected as following:
Low frequency e.g. 2kHz:

- for galvanic signal coupling
- the signal induction to other cables and pipes can be minimized
High frequency e.g. 10kHz:

- for inductive signal coupling with current clamp or

frame antenna
- high inductive coupling effect is required to couple the signal into the cable
Cable Fault Pin-Pointing:
 Acoustic Fault Location
1. Acoustic Fault Location in direct buried cables
For pin-pointing of high resistive and intermittent faults in buried cables the acoustic method
is used to pin-point the exact fault location. As signal source, a surge generator is used in
repetitive pulsing mode. High energy pulses which are released by a surge generator (SSG)
force a voltage pulse to travel along the cable. At the fault the flashover happens. This causes
a high acoustic signal that is locally audible. Depending on the pulse energy, the intensity
of the acoustic signal varies. These noises are detected on the ground surface by means of a
ground microphone, receiver and headphone. The closer the distance from the fault to the
microphone, the higher is the amplitude of flashover noise. At the fault position the highest
level of flashover noise can be detected.
The acoustic fault location set comprising the receiver UL30 and the
ground microphone BM 30 offers the special feature of digital propagation time – distance
measurement.

Firstly, the ground microphone is measuring the electromagnetic signal that can be recorded
all along the cable where the HV impulse is travelling before finally flashing over at the
faulty position. As this signal is available all along the cable trace towards the fault, it can
further be used to make sure that the “cable trace” is followed. The maximum signal
confirms to be directly above the cable.
Secondly the ground microphone will receive the flashover noise next to
the fault on the ground surface as soon as the very close area around the fault is reached.

Schematic Connection And Shape Of

Acoustic Signal – Acoustic Fault Location
Cable Fault,1-Core 11kv XLPE Cable
Therefore, every flashover activates two trigger situations. –magnetic trigger and acoustic
trigger The two signals are of different propagation velocity. Further the distance to the
fault influences the difference in trigger of acoustic trigger compared to the trigger of the
electromagnetic signal. As soon as the magnetic trigger is reacting on the bypassing HV
impulse in the cable underneath, a timer is started. When the ground microphone receives the
delayed acoustic signal, the measuring cycle is stopped.

The receiver UL automatically indicate the measured time distance (propagation time) to
the fault via a digital meter indication. According to the meter indication, the faulty position,
where the distance indication is lowest, can be found. By means of the audible acoustic signal
the final exact location of the cable fault can be determined. This special feature increases the
performance compared to convenient acoustic pick-up sets, as the magnetic indication offers
an integrated tracing feature.
2. Pin-Pointing Of Cable Faults In

Pipe Arrangements
When cables are laid in pipes the acoustic signal is no more audible right above the cable
fault. The acoustic signal in that case is travelling through the air in the pipe and therefore
only audible at both ends of the pipe or on the manhole covers.
By means of the previously carried out cable fault pre-location, the section
of pipe can be determined. Up to today, the final step to determine the exact fault position in
the pipe was very difficult or by most pick-up sets impossible. The latest model of pick-up set
UL/BM therefore uses a special feature to determine the exact fault position also in
manhole arrangements.

Manhole Arrangement, Cable Laid
In PVC Pipe, Acoustic Signal Only Audible
On Manhole Cover
Acoustic Fault Location at Manholes
For this method, no additional instrument is requested. Every latest UL

receiver offers the mode of pinpointing in manhole arrangement.
In a first step, the ground microphone is placed on the first manhole cover,
where the acoustic signal and the magnetic signal are shown up in a certain propagation time
value. By confirming the signal, this value is stored in the receiver.
In a second step, the ground microphone is placed on the second manhole
cover. Also at this location, the ground microphone can pick-up an acoustic signal and the
magnetic signal that is showing up in a second propagation time value. By entering the
distance between the manholes, via the propagation time ratio over the distance, the direct
distance to the fault in the pipe is indicated.
UL30 Display, Manhole Mode,

Display Of Two Propagation Time Values Used For
Distance Calculation

3. Fault pin-pointing of low resistive cable

faults
Cable faults that are showing up in a solid grounded condition do not enable to create a
flashover at the faulty point by means of a surge generator. Therefore also no acoustic signal
is audible and the cable fault pinpointing according to the acoustic fault location is not
possible. This condition is mainly resulting from a completely burnt cable fault that is
furthermore also low resistive to the surrounding soil. These kinds of cable faults can be
pinpointed by means of the step voltage method explained below. Faults in low voltage
cables as well as pilot cables (signal lines) are often difficult to be pin-pointed, because the
maximum voltage that may be applied to these cables does not enable to force sufficient
surge energy to create a strong flashover that can be pinpointed by means of the acoustic
method. As these cables are mainly unshielded, the fault in most cases also appears towards
the surrounding soil. Also here, the step voltage method is the suitable pin-pointing method.
Another difficult fault condition to pin-point in low voltage cables is if the fault is not related
to ground and therefore only showing up between two cores. For these conditions, the Twist
Method enables successful pointing out the fault. The 3rd fault type showing similar
conditions is the cable sheath fault. A fault in the outer protective PVC insulation of a XLPE
cable cannot be located via the acoustic method, as no defined potential point, where the
flashover can take place, is given. Here, also the step voltage method enables the localization.
This method also enables to locate several sheath fault locations along a cable.
 Step voltage method Pinpointing of:
- Any earth contacting low resistive faults

- Cable Sheath Fault
As a signal source, a high voltage impulse sequence or impulse block sequence is sent into
the cable under test. The HV pulse is discharged via the resistive fault to the surrounding
soil without a flashover. The voltage drop into the soil at the fault location results in a
voltage funnel, which can be measured by means of the step voltage method. By using two
earth probes, the voltage distribution field is indicated. The multifunctional receiver UL

indicates the positive or negative voltage (left or right side from the fault location) via a bar
graph as well as an acoustic tone. As soon as the earth sticks are placed
symmetrical above the fault, the resulting voltage is zero and the fault position is
determined.
Useable HV signal sources:
- SSG / STG surge generators function
Useable receivers:
- UL of latest version in combination with cable sheath fault location accessories

- KMF 1 in combination with cable sheath fault location accessories In case of multiple
sheath faults, e.g. 3 faults, all faults can be located as explained above during one passage
over the cable route. This requires appropriate practice and one should know that the step
voltage shows several passing through zero position that might irritate (5 passing through
zero).
 Twist method
The twist method can be applied for pin-pointing of low resistive faults in twisted cables.
In this method, the effect that the cores are longitudinally turned-in is used. The basic signal
used is a high frequency audio signal causing equivalent signals like used for cable route
tracing. Differing to route tracing, where the signal is sent through a healthy core, for this
method the signal is forced over the fault. Therefore the application is depending on the
fault resistance. Higher resistive faults request a very powerful audio frequency generator.
The audio frequency signal is passing back and forth in the same cable up to the fault where
the signal faces the return point. Due to the twist, what means the steadily change of
geometrical position of the cores in the cable, the maxima and minima of signal resulting can
be followed on the surface. The twist length in the cable is depending on the type of cable but
is roughly 1meter. According to this, the point where the signal ends can be determined as
the cable fault.

Cable identification:
Cable identification is the most critical and safety related sequence during all the procedure of
cable fault location. The correct identification of a cable out of a bundle of cables, where most
of them can be cables in service, has to be carried out not only carefully, but also by means of
an instrument widely eliminating the possibility of human error or misinterpretation.
Additionally, it is highly recommended to use cable cutters according to EN 50340 and / or a
cable shooting devices. The local safety and accident precaution instructions are always
applicable, and mandatory. The BAUR cable identification system KSG 100 was designed
to fulfil these most important safety aspects.
Principle of operation of the KSG 100

The transmitter of the KSG contains a capacitor that is charged and then discharged into the
target cable. During this process the test sample must be connected in such a way that current
can flow through it. The flexible coupler is used to couple the current pulse at the target
cable. The direction of flow of the current pulse and its amplitude are indicated on the
display of the receiver. The amplitude of the current pulse is dependent on the loop
resistance. To be able to clearly determine the direction of current flow, the positive output is
colour-coded red and the flexible coupler marked with an arrow. The current difference that
is calibrated can be measured very accurately. As there are no relevant losses, the displayed
current is nearly equivalent to the calibration signal.
Pulse Signal Flow Scheme

Field Application Of Cable Identification

Depending on the cable arrangement, the signal loop is changing. The application of cable
identification can be carried out on any cable arrangement. Before the actual process of cable
identification begins, the instrument is performing a self calibration whereby the target cable is
analyzed. During this sequence the receiver analyses the test sample for interference and the
amplitude of the pulse. As the signal amplitude is dependent on the loop resistance, the receiver
automatically sets the internal amplifier to 100% output amplitude. In this way it is ensured that not
only the direction in which the current pulse flows, but also the amplitude is used for the evaluation.
In the final calibration step, the transmitter is synchronized to the receiver using a defined cycle time.
This synchronization is performed because during the subsequent cable identification the receiver
will only evaluate the pulses during a period of 100 ms(Phase). This impulse is not affected by any
magnetic field, as a high current impulse is used. Finally there is only one single core fulfilling all the
calibrated values with positive direction on site, independent how many cables are faced in the tray or
manhole. These relevant signal characteristics mentioned above can be mentioned shortly as
ATP - signal acquisition:

A … Amplitude and direction of signal;
T … Time interval of released signals synchronized with transmitter;
P … Phase: same signal direction in the correct cable, all neighbouring cables are used as
return wire or do not carry any signal.

The BAUR KSG 100 is the only instrument available providing such high safety certainty.
The fully automatic setting adjustment and calibration minimizes the risk of operating error.
The signal coupling can be done on either dead cables as well as on live cables: On dead
cables, the direct coupling can be performed to the core of the cable. In such arrangements,
where the core is used as the conductor, there is no limitation in regards to voltage rating or
diameter of the cable. The flexible Rogowski coil can loop a diameter of 200mm and
therefore is applicable even on high voltage cables.
Full cable not accessible, application of Expert mode enables the safe cable
identification.

For the application on live cables, it is independent whether the load rating is high or low or
whether the line voltage is low voltage or even high voltage. As the coupling in that case is
done via a current clamp, the restriction is given by the diameter of the clamp only. KSG 100
Expert Mode Certain substation arrangements in combination with 3-core cables do not
allow an access to the full diameter of the cable in the substation. The calibration as
explained above can not be done similar. The Rogowski coil has to be connected around the
core without the sheath involved. Therefore the calibration signal is not equal to the signal
that is measured on the whole cable diameter on site. For these arrangements the KSG 100 is
equipped with an Expert mode that enables to adjust the gain of the received signal. The
indication of direction as well as the phase synchronization is still corresponding to the
calibration performed in the substation. Therefore, it is enabled to perform the safe cable
identification even on very difficult arrangement. The application of cable identification in
PILC cables may be influenced by the characteristic that the outer protective layer is
conductive and therefore the cable sheath is also conductive to soil. If the signal return path is
defined via the cable sheath, a certain amount of signal may be leaking and travelling via
surrounding conductors. These so called vagabonding currents are then no more routed along
a defined path. This effect is the reason, why on such arrangement not the full signal value
may be available on site.
By using the KSG 100 in the Expert mode, also the effect of
vagabonding currents can be considered. As long as possible, the forward and return path of
the signal should be defined via the cable cores. Like this, the effect of vagabonding currents
in PILC cables can be eliminated.

Cable Fault location in High Voltage cables e.g. 115kV:

High voltage cables such as e.g. 115kV cables, 230kV cables or similar are mainly operated
at high load. In case of a cable fault the flash over energy is very high.
XLPE cables:
In XLPE cables most often a big explosion is happening and the cable parts around the fault
are burnt and/or vaporized completely. Also the other cores as well as neighbouring cables
are very often damaged beside. Due to this reason cable fault location can be carried out
easily with basic cable fault location equipment used for medium voltage cables. A fault
location system based on a surge generator up to 32kV is mostly fully sufficient to pre-locate
these cable faults. The comparison of TDR graphs of a healthy core in comparison with the
faulty phase leads to precise cable fault pre-location graphs in low resistive fault conditions.
Depending on the current load of the cable at the moment of flash over the conditions may
also remain high resistive or intermittent. In general the 32kV surge generator combined with
the SIM/MIM or ICM method can cover these fault conditions. If the fault condition shows
solid grounded conditions the pin pointing may not be possible by means of the acoustic
fault location method as no flash over can take place at a short circuit fault. In such a case the
step voltage method is the only method to perform the cable fault pin pointing in 1- core
cables.

Vaporized Core After Cable Fault, 132kv XLPE
In 3-core cables, which are used rarely, also the Twist Method can be used for pin pointing.
PILC cables: High voltage PILC cables are more resistant to the flash over. In these cables
the remaining fault condition may be an intermittent fault with a certain breakdown voltage
possibly higher than 32kV. To pre- locate such faults the Decay method based on a HV DC
or VLF instrument that is covering the breakdown voltage is required. Basically all these
available HV instruments enable to be used in burn mode. Most of the fault conditions can be
changed by application of the burn mode over a certain time.
During this fault burning the paper insulation is carbonizing and the break down voltage of
the fault can be reduced.

Cable Fault In A 132kv PILC Cable
Finally for pin pointing a surge generator with a maximum output

voltage of 32kV can be applied. Only very seldom it is required to use a surge generator with
higher output voltage.

Chapter-6
APPLICATIONS AND ADVANTAGES

6.1 Applications
 Industrial Applications
 Ground Cable Fault Detection Applications
 Electrical Cable Fault Detection Applications
 Highway street lighting
6.2 Advantages
 Less maintainance
 Higher efficiency
 Easy Fault Location Detection
6.3 Disadvantages
 Cost, must consider life time costs not just initial

 Cost differential decreasing with time
 Fault location instantaneous, can have longer repair time

Chapter-7
RESULT
Thus the underground cable fault using AT Mega 16 Microcontroller was identified in the underground
cable from feeder end in a km. To measure the particular distance and location an individual resister is
connected between zones. Solid State relay is a sensing device it will work in a particular location of
cable and intimate the fault to microcontroller and distance of fault is displayed in the LCD display.

Chapter-8
CONCLUSION AND FUTURE SCOPE
8.1 CONCLUSION
Further this project can be enhanced by using capacitorinal AC Circuits to measure impedance which
can even locate the open circuited cable, unlike the short circuited fault only using resistor in AC circuit
as followed in the above proposed project.
8.2 FUTURE SCOPE
The proposed system in this paper detect only the location of Short Circuit fault in underground cable
line, and also detect the location of open circuit fault, to detect the open circuit fault capacitor is used
in circuit which measure the change in resistance & calculate the distance of fault. For future research,
the system would proceed with similar neural networks structure for different types fault section and
fault location estimation.

REFERENCES :
[1] K.K. Kuan, Prof. K. Warwick, “Real-time expert system for fault location on high voltage
underground distribution cables”, IEEE PROCEEDINGS-C, Vol. 139, No. 3, MAY 1992.
[2] T. S. Sidhu and Z. Xu, “Detection of incipient faults in distribution underground cables”, IEEE
Trans. Power Del., vol. 25, no. 3, pp. 1363–1371, Jul. 2010.
[3] Raghu Raja Kalia, Preeti Abrol, ’Design and implementation of wireless live wire fault detector
and protection in remote areas’,IEEE,(2014),vol. 97,No.17
[4] Touaibia.I, Azzag.E, Narjes.O,’Presentation of HVA faults in SONELGAZ underground network

and methods of faults diagnostic and faults location’, IEEE,(2014).
[5] D.S. Gastaldello*, A.N. Souza*, C.C.O. Ramos**, P. da Costa Junior* and M.G. Zago “Fault
Location in Underground
[6] Systems Using Artificial Neural Networks and PSCAD/EMTDC” Intelligent Engineering Systems
(INES), 2012 IEEE 16th International Conference. DOI:10.1109/INES.2012.6249871
[7] Shunmugam .R, Divya, Janani.T. G, Megaladevi.P, Mownisha.P “Arduino Based Underground
Cable Fault Detector”

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What is the aim of the paper?

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What techniques are used for fault detection?

What techniques are used for fault detection?

UNDERGROUND CABLE FAULT DETECTION

Dept. of Telecommunication ,Dr.AIT Page 1

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4.1 Block diagram

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4.2 Flow diagram/ Flow Chart and its Description

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Single core, XLPE insulated medium voltage cables 6kV up to 36kV

3-core EPR, incl. 3-core XLPE 11kV 1-core XLPE 115kV

Dept. of Telecommunication ,Dr.AIT Page 12

Overview of Pulse Velocity v/2 for different cable types: Cable

Dept. of Telecommunication ,Dr.AIT Page 13

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1. Step down transformer

Cable Fault Location Procedure:

Dept. of Telecommunication ,Dr.AIT Page 15

Cable Fault Types:

1. Fault between core-core and/or core - sheath:

 Low resistive faults (R < 100 - 200 Ω)

2. Defects on the outer protective shield (PVC, PE):

 Cable sheath faults-

Dept. of Telecommunication ,Dr.AIT Page 16

Cable Fault Pre-location:

2. Low and Low voltage method

 Impulse Reflection Method TDR for: o Low

3. High voltage methods

 Multiple Impulse Method SIM/MIM.

 Breakdown / intermittent faults.

 high resistive cable faults.

Dept. of Telecommunication ,Dr.AIT Page 17

Cable Route Tracing:

well for exact cable tracing and pinpointing.

Dept. of Telecommunication ,Dr.AIT Page 18

Depth Measurement according to the Minimum

Dept. of Telecommunication ,Dr.AIT Page 19

Selection of Audio Frequency:

Low frequency e.g. 2kHz:

High frequency e.g. 10kHz:

Dept. of Telecommunication ,Dr.AIT Page 20

Cable Fault Pin-Pointing:

 Acoustic Fault Location

1. Acoustic Fault Location in direct buried cables

Dept. of Telecommunication ,Dr.AIT Page 21

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Schematic Connection And Shape Of

Cable Fault,1-Core 11kv XLPE Cable

Dept. of Telecommunication ,Dr.AIT Page 23

2. Pin-Pointing Of Cable Faults In