International Journal of Electrical and Computer Engineering (IJECE) Vol.
No.
April 2013, pp.
ISSN: 2088-8708
Underground Cable Fault Detection using Robot Jery Althaf*.
Muhammad Imthiaz*.
Rejith Raj* *Young India fellowship.
Delhi.
India **Dept of electrical engineering.
College of Engineering.
India ***Self Affiliated.
Kerala.
India
Article Info
ABSTRACT
Article history:
Present trend of laying cables for various purposes is to lay underground.
Companies prefer laying the cables underground because the climatic adversities donAot affect this.
With advantages come challenges.
There are many difficulties in laying the cables and once laid in case of any complaints, it is difficult and costly to fix it.
This paper is about the robot that is designed by us which is capable of finding where the complaint lies, so the engineer can directly get the hole dug at that point and fix the issue.
The basic principle of Electromagnetic Theory is employed to detect the discontinuity in the cable.
Using a signal injector, a low frequency signal is passed through the wire and the induced magnetic field is used to detect the fault.
Received Jan 12, 2013 Revised Mar 15, 2013 Accepted Mar 26, 2013 Keyword:
Cable fault Fault detection Robot Signal detection Underground cable Copyright A 2013 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Jery Althaf.
Young India fellowship.
Delhi.
India Email: jeryalthaf@ie.
INTRODUCTION
Till the last decade the cables where made to lay overhead and currently the scenario is to lay underground cable, which is superior to the earlier method.
This is because the underground cables are not affected by the adverse weather conditions.
Neither the hot sunny day nor the rain is to influence it.
But when the cable breaks due to some reasons itAos very difficult to locate that.
Currently what is done is they find the approximate location and dig the cables out from the location and check it manually to find the exact point of Currently a robot is developed which can be used to locate the break from an external point.
When an underground cable is broken or Short-circuited then our robot will move over it and locate the exact position of Hence it is an advantage for repairing the same.
The other instruments that can be included are odometer, video cam, remote navigation etc.
For most of the worldwide operated low voltage, medium voltage and high voltage distribution lines underground cables have been used for many decades.
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.
The rising demand for electrical energy increases the importance and priorities of uninterrupted service to customer.
Thus, faults in power distribution networks have to be quickly detected, located and repaired.
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 system depends to a great extent on practical aspects and the experience of the operator.
accomplish this, it is necessary to have personnel trained to test the cables successfully and to reduce their An efficient cable fault location service must include, taking full control of electrical safety.
Journal homepage: http://iaesjournal.
com/online/index.
php/IJECE A ISSN: 2088-8708 pinpointing the position of the fault, excavation, repair of the cable, testing of the repaired cable and return to service reinstatement of the ground service.
WORKING PRINCIPLE
The fault detection robot consists of a signal generator part and robotic part.
Short circuit cable is checked for its continuity by passing a 3 KHz low frequency signal.
A signal generator can be used to generate this signal.
The AC signal passing through wire produces a magnetic field around it.
This magnetic field is sensed by the robot using a inductor circuit.
The AC signal sensed by robot is then amplified using a LM386 This amplified signal is then rectified and converted to DC.
DC level is provided to the analog input of Microcontroller converts this analog input to digital signal.
Based on the program programmed in the microcontroller the robots movement is controlled.
Figure 1.
Schematic representation.
When the robot reaches the point where the discontinuity lies, the magnetic field will be zero.
In such case the input signal at the analog input port will be substantially low.
When the input signal strength is less than 10 .
inary readin.
, the PIC is programmed to display, short circuit Detected and is displayed in LCD.
PROBLEM ANALYSIS
The actual implementation of the robot is fields where the cables are laid.
In such scenario the robot is bulky in size.
Hence, for the presentation sake, a model of actual robot is developed and the fault detection is done on a wire that is laid on the floor.
As more priority is for accuracy, it is advised to use simple low speed DC motor drive.
For higher speed movement, a stepper motor can be used.
But the cost of motor and motor drive is costly.
Also, testing of Open loop circuit can be conducted.
But due to time constraint and the requirement of a high amplifier circuit, it is decided to avoid this for the time being.
PROPOSED SYSTEM
The basic principle behind the proposed system is FaradayAos law.
If a current is flowing inside the wire there will be a EMF generated around it.
An inductor circuit is used to generate a voltage using the EMF.
In cases of short circuit, the EMF generated will be zero and there will be negligible voltage Hence, a condition is provided where voltage is less than say 20 .
inary valu.
, the robot will stop and that will be the point of discontinuity.
This voltage is amplified using a LM386 circuit and compared with the reference voltage in PIC and based on the values, the robot is driven forward or to the right or to the left.
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There is a LCD which will w display thee field strength Figuure 2.
Block Diagram
COMPONEN
NTS
The signall generated byy the signal generator can be b detected ussing a field seensing coil.
A LM 386
amplifier amplifies the signal prooduced by signnal generator.
It can be recttified and inpuut to the analog g pin RA1 of miccrocontroller.
After the proocessing the innput for contro olling the direcction of motorr is taken from m RC0 and RC1 respectively a LCD conected to port RB.
The curent through the t motor is am mplified by ULN The microcontrolle er is worked sufficiently byy a 5V regulaated supply.
I microcontrroller a 20 Mh oscillaator is used foor providing frrequency.
Figuure 2 shows th he overall circuuit diagram.
SSignal Injectorr Signal injeector is used to t generate low w frequency voltage .
rounnd 3 KH.
usiing a 555 mullti vibrator How the siggnal is generatted is explaineed in detail bellow.
Two capaacitors are aded in series to t the power supply.
Hencce at the centter of the capacitor, the voltagge will be Vc/2.
Also a cappacitor circuitt is preferred over a resistorr circuit to get the voltage as it blocks DC annd transmits only o AC.
The cable is connected between the Pin P 3 and the capacitor midd-point.
The 5555 circuit oscillates and togglees the voltagee at Pin 3 beetween Vcc annd Ground.
When Pin 3 iss grounded, thhe voltage at center of capacitor is higher than the Pin 3 and hence thhe current wil flow inside the t IC.
When the Pin 3 has Vcc, then the vooltage at the center point is less than the Pin 3 and the current flowss outside.
Hennce the currentt flow will be bi--directional annd hence this will w generate an a alternate cu Such an alternating curent through the wire wil produce an electromagnet tic field.
Thiss magnetic field will w produce a voltage insidde the inductivve sensor.
Cable Sensor The low frequency AC voltage signaal from a signaal generator iss amplified using a LM386 circuit.
normaal case the inpput voltage is 20mV to 100m The amplifier circuit am mplifies this arround 50 to 20 00 times.
This ampllified signal iss passed throuugh a diode and a is used too charge a cappacitor.
This voltage is passedd to RA0 pin of o PIC microccontroller.
Undergroun nd Cable Faullt Detection ussing Robot (Jeery Altha.
A ISSN: 2088-8708 Figure Signaal injector.
Figure 4.
4 Signal senso or circuit diagrram When the inductor circuuit moves awaay from the wire, the field strength decreases and when n it moves near the t wire field strength incrreases.
The chhange in field d strength is passed on to P PIC, which co ontrols the directtion of movem ment of robot.
Microcontrolle er Circuit Microconttroller is the core unit of thhe circuit.
Thee program wrritten on it conntrols the mov vement of motorrs and the mesage display based on the cable signal strrength which is i provided as input.
When cable fault is deteected, this wil trigger the alarm.
We use an a audio annoouncement as an a alarm.
Figurre 5.
Microcon ntroller circuitt E Vol.
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Navigation Cirrcuit Relays aree used for trigering the mootor circuit.
H-bridge can also be used foor navigation circuit but the lim mitation it hass is that tempeerature rises at a a steep rate thereby damaaging the mottor and hence cannot be used for f long duratiion.
Figure 6.
Naavigation and switching circcuit Transmitter annd Receiver Transmitteer and Receiveer Circuit cann be used for manual operatiion of the robot.
This can be b used for appliccations such as path findingg in addition too cable fault detection.
HT112D/E can be used as transmitter and receivver module whhose circuit diaagram and pinn-out details iss same as those shown in Figure 7.
Figure 7.
7 Transmitter Receiver Circcuit Motor Controll Circuit The outpuut from the micro controler is passed through the ULN relay driver circuit which is conneected to left annd right motorr.
The signal strength whicch is provided at the RA0 ppin of microco ontroller is prograammed to conntrol the moveement of the motor.
Also theree is an externnal input navigator using which can bee used to conntrol the robo ot from an externnal point so as a to place thhe robot at a specified po By usingg this externaal navigation, the relay disconects from thhe microcontrooller unit and connects to reemote system.
Undergroun nd Cable Faullt Detection ussing Robot (Jeery Altha.
A ISSN: 2088-8708 Figure 8.
Overrall Circuit
WORKING
The core aim a of the robbot is designeed for short circuit detectioon which is very useful to detect the underrground cabless breaks.
As the t cables aree laid for a larrger area, the continuity caan be checked d using the meter first.
Onnce the stretchh of wire wheere the disconttinuity exists is i detected, thhe robot can be b used for detectting the exact location.
A wire is connected to the t signal gennerator unit an nd then the robbot is placed oon to the cablee using the externnal remote navvigator circuitt.
The robot iss placed in su uch a way thatt the discontinnuity lies in th he forward Then thee 3 KHz signaal is passed thhrough the wirre and also prrovides the poower to the rob botic unit.
Once the current starts moving, as per the Faradays law there will bee an Electro M Magnetic Fielld will be generaated which wiill generate a voltage whichh is provided to Micro conttroller RA0 piin and there by b controls the movement of thhe robot.
FLOWCHA
ART
Figure 9.
Flowchart of fault location E Vol.
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When the robot reaches the point of discontinuity, there will no EMF and hence this will trigger the alarm circuit .
ere use an Audio Announce.
The HALL sensor unit can be provided to measure the exact distance the robot has moved which will be displayed in the LCD module.
As one get to know the exact location, he/she can get dig at that point and get the issue fixed easily.
MERITS AND DEMERITS
Merits Used for short circuit detection in underground cables from an external point.
Reduce manual labour.
Cost effective.
Can be used for applications other than cable fault detection.
Demerits Not Self reliable Difficult to replace a component in the robot if it fails.
CONCLUSION
Current scenario of digging along the cable laid and then pulling the cable out and checking whether the fault exists in the cables is a tedious work.
This is not only is wastage of manpower and money for the companies, but this also causes a lot of inconvenience to the normal public.
We believe that our cable fault detection robot will solve this issue to a great extent and will be really helpful for such application.
The robot that we have designed is very much user-friendly and can be easily controlled.
Also, the robot is cost effective.
References