Till last decades cables were made to lay overhead& currently it is lay to underground cable
which is superior to earlier method. Because the underground cable are not affected by any
adverse weather condition such as storm,snow,heavy rainfall as well as pollution.But when any
fault occur in cable,then it is difficult to locate fault.So we will move to find the exact location of
fault.
Now the world is become digitalized so the project is intended to detect the location of fault in
digital way. The underground cable system is more common practice followed in many urban
areas. While fault occurs for some reason,at that time the repairing process related to that
particular cable is difficult due to not knowing the exact location of cable fault.
Fault in cable is represented as:
• Any defect,
• Inconsistency,
• Weakness or non-homogeneity that affect performance of cable .
• Current is diverted from the intended path .
• Caused by breaking of conductor& failure of insulation
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Fault in cable can be classified in two groups:
1)Open circuit fault:
Open circuit faults are better than short circuit fault,because when these fault occurs current
flows through cable becomes zero.This type of fault is caused by break in conducting path.Such
faults occur when one or more phase conductors break.
2)Short circuit fault: Further short circuit fault can be categorized in two types:
a)symmetrical fault:Three-phase fault is called symmetrical fault.In this all three phases are
short circuited.
b)unsymmetrical fault:In this fault magnitude of current is not equal¬ displaced by 120
degree.
FAULT LOCATION METHODS
Fault location methods can be classified as:
1)Online method:This method utilize&process the sampled voltages& current to determine the
fault points.Online method for underground cable are less than overhead lines.
2)Offline method:In this method special instrument is used to test out service of cable in the
field.There are two offline methods as following
1)Tracer method:In this method fault point is detected by walking on the cable lines.Fault point
is indicated from audible signal or electromagnetic signal.It is used to pinpoint fault location
very accurately.
Example:1) Tracing current method
2) Sheath coil method
2)Terminal method: It is a technique used to detect fault location of cable from one or both
ends without tracing.This method use to locate general area of fault,to expedite tracing on buried
cable.
Example:1) Murray loop method
2)Impulse current method
BLOCK DIAGRAM:
The project uses the simple concept of OHMs law where a low DC voltage is applied at the
feeder end through a series resistor. The current would vary depending upon the length of fault
of the cable in case there is a short circuit of LL or 3L or LG etc. The series resistor voltage drop
changes accordingly which is then fed to an ADC to develop precise digital data which the
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programmed microcontroller would display the same in Kilo meters.The project is assembled
with a set of resistors representing cable length in KMs and fault creation is made by a set of
switches at every known KM to cross check the accuracy of the same.
This is proposed model of underground cable fault distance locator using microcontroller. It is
classified in four parts –DC power supply part ,cable part,controlling part, display part.
DC power supply part consist of ac supply of 230v is stepdown using transformer, bridge
rectifier converts ac signal to dc & regulator is used to produce constant dc voltage.
The cable part is denoted by set of resistors along with switches.Current sensing part of cable
represented as set of resistors &switches are used as fault creators to indicate the fault at each
location.This part senses the change in current by sensing the voltage drop.
Next is controlling part which consist of analog to digital convertor which receives input from
the current sensing circuit, converts this voltage into digital signal and feeds the microcontroller
with the signal. The microcontroller also forms part of the controlling unit and makes necessary
calculations regarding the distance of the fault. The microcontroller also drives a relay driver
which in turn controls the switching of a set of relays for proper connection of the cable at each
phase.
The display part consists of the LCD display interfaced to the microcontroller which shows the
status of the cable of each phase and the distance of the cable at the particular phase, in case of
any fault.
ALGORITHM & FLOWCHART
Algorithm:
Step1: Initialize the ports, declare timer, ADC, LCD functions.
Step2: Begin an infinite loop; turn on relay 1 by making pin 0.0 high.
Step3: Display “R:” at the starting of first line in LCD.
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Step4: Call ADC Function, depending upon ADC output, displays the fault position.
Step5: Call delay.
Step6: Repeat steps 3 to 5 for other two phases.
Flowchart
POWER SUPPLY
The power supply circuit consists of step down transformer which is 230v step down to 12v.In
this circuit 4diodes are used to form bridge rectifier which delivers pulsating dc voltage & then
fed to capacitor filter the output voltage from rectifier is fed to filter to eliminate any a.c.
components present even after rectification. The filtered DC voltage is given to regulator to
produce 12v constant DC voltage.
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diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite
ends of the bridge. The load resistance is connected between the other two ends of the bridge.
LCD
Liquid crystal display are interfacing to microcontroller 8051.Most commonly LCD used are
16*2 &20*2 display.In 16*2 display means 16 represents column & 2 represents rows.
Voltage Regulator:
A voltage regulator is an electrical regulator designed to automatically maintain a constant
voltage level. In this project, power supply of 5V and 12V are required. In order to obtain these
voltage levels, 7805 and 7812 voltage regulators are to be used. The first number 78 represents
positive supply and the numbers 05, 12 represent the required output voltage levels. The L78xx
series of three-terminal positive regulators is available
RELAY
Relay is sensing device which senses the fault &send a trip signal to circuit breaker to isolate the
faulty section. A relay is automatic device by means of which an electrical circuit is indirectly
controlled &is governed by change in the same or another electrical circuit.There are various
types of relay: Numerical relay, Static relay & electromagnetic relay.Relay are housed in panel
in the control room.
ADVANTAGES
1) Less maintainance
2) It has higher efficiency
3) Less fault occur in underground cable
4)Underground cable fault location model are applicable to all types of cable ranging from 1kv
to 500kv&other types of cable fault such as-Short circuit fault, cable cuts, Resistive fault,Sheath
faults, Water trees, Partial discharges.
5) Improved public safety.
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CONCLUSION
In this paper we detect the exact location of short circuit fault in the underground cable from
feeder end in km by using microcontroller8051.For this we use simple concept of OHM’s law so
fault can be easily detected and repaired.
FUTURE SCOPE
In this project we detect only the location of short circuit fault in underground cable line, but we
also detect the location of open circuit fault, to detect the open circuit fault capacitor is used in ac
circuit which measure the change in impedance & calculate the distance of fault.
REFERENCES
[1] Qinghai Shi, Troeltzsch U, Kanoun O. Detection and localization of cable faults by time and
frequency domain measurements. Conf. Systems and Signals and Devices, 7th International
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[2] B. Clegg, Underground Cable Fault Location. New York: McGraw- Hill, 1993.
[3] M.-S. Choi, D.-S. Lee, and X. Yang, “A line to ground fault location algorithm for
underground cable system,” KIEE Trans. Power Eng., pp. 267–273, Jun. 2005.
[4] E. C. Bascom, “Computerized underground cable faultlocation expertise, ”in Proc. IEEE
Power Eng. Soc.General Meeting, Apr. 10–15,1994, pp. 376–382.J. Clerk Maxwell, A Treatise
on Electricity and Magnetism, 3rded., vol. 2. Oxford: Clarendon, 1892, pp.68–73.
[5] 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.
[6] J. Densley, “Ageing mechanisms and diagnostics for power cables—an overview,” IEEE
Electr. Insul. Mag., vol. 17, no. 1, pp. 14–22, Jan./Feb. 2001.
[7] 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.
[8] Tarlochan S. Sidhu, Zhihan Xu, “Detection of Incipient Faults in Distribution Underground
Cables”, IEEE Transactions on Power Delivery, Vol. 25, NO. 3, JULY 2010.
[9] Md. Fakhrul Islam, Amanullah M T Oo, Salahuddin. A. Azad1 , “Locating Underground
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[10]
http://scribd.com
[11] http://ecmwebcontent/locating-underground-cable-fault .
