government of india ministry of railways handbook on … on cable fault... · railways and the...

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GOVERNMENT OF INDIA MINISTRY OF RAILWAYS

Handbook on

Cable Fault Localization

CAMTECH/S/PROJ/2020-21/SP1/1.0 April 2020

INDIAN RAILWAYS

Centre for Advanced Maintenance Technology Maharajpur, Gwalior (M.P.) Pin Code – 474 005

End user: SSE, JE & Maintainer of S&T deptt.

ii

Handbook on Cable Fault Localization

CAMTECH/S/PROJ/2020-21/SP1/1.0 April 2020

iv

Foreword

The long distance underground cables are the nerves of a Railway Signalling or Telecom system. If the cables connected with the system are healthy and free from any defect, it will run smoothly and efficiently. Any fault in the cable may affect the connected circuit or equipment and paralyze the train operation. Locating the cable fault by conventional methods and repairing thereafter are time consuming and require substantial manpower. The repercussions for these failures may be in the form of punctuality losses and high maintenance cost to the Railways. To save time, manpower and at the same time reduce cost and downtime, Railways need to adopt innovative techniques in cable fault localization. With the advent of advanced Electronics and Communication technology, equipments have been developed over the years which can accurately locate faults in underground cables.

CAMTECH has prepared this handbook for S&T Supervisors and Technicians to get them acquainted with modern techniques in cable fault localization. I hope that this handbook shall guide them in the process of locating cable fault with the help of equipments designed for this purpose.

CAMTECH Gwalior Jitendra Singh Date: 30.04.2020 Principal Executive Director

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Preface

Underground cables play an important role in keeping the S&T system operational by carrying different circuits through them. Although every safety precaution is taken for the safety of cable while laying it underground, unpredictable faults in a cable due to various reasons are not ruled out. The type of fault for example earth, open, short or low insulation fault in underground cables can be detected easily with the help of a megger. But finding the exact location of the cable fault needs special techniques. CAMTECH has prepared this handbook to introduce S&T personnel with the modern techniques of cable fault localization in less time and minimum manpower. The handbook covers procedure for locating fault in underground cables with the help of equipments using TDR and other techniques. We are sincerely thankful to M/s Andig Systems, Bangalore and M/s Aishwarya Technogies & Telecom Ltd., Hyderabad who helped us in preparing this handbook. If some addition/modification is needed in this handbook please mail us on [email protected] or write to us at Indian Railways Centre for Advanced Maintenance Technology, In front of Adityaz Hotel, Airport Road, Maharajpur, Gwalior (M.P.) 474005. CAMTECH Gwalior Dinesh Kumar Kalame Date:30.04.2020 Joint Director (S&T)

mailto:[email protected]

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Contents Foreword………………………………………iv Preface………………………………………...vi Contents………………………………………viii Correction Slip………………………………… x Disclaimer & Our Objective.…........................xi CAMTECH publications………………….......xii

Cable Fault Localization ...................................................... 1 1.1 Introduction ....................................................................... 1

1.2 Type of Cables carrying S&T circuits ................................ 1

1.3 Major causes of cable fault ................................................ 2

1.4 Types of cable faults .......................................................... 2

1.5 Need for cable fault localization ........................................ 4

1.6 Advantages of cable fault localization ................................ 6

1.7 Techniques used for cable fault localization ........................12

1.8 Time Domain Reflectometer (TDR) ....................................12

1.9 General Precautions for Underground S&T cables ..................15

ANDIG Model 5289M Digital Cable Fault Locator................................................ 17

2.1 Introduction ..........................................................................17

2.2 Technical specifications .........................................................18

2.3 Front Panel Description .........................................................19

2.4 Powering On .........................................................................20

2.5 Operating Instructions ............................................................21

ix

2.5.1 To Locate Open/Short circuit faults ................................21

2.5.2 To Locate Low Insulation faults ......................................25

2.5.3 To measure Insulation Resistance ....................................29

2.5.4 To measure Foreign potential..........................................31

2.6 Menu Flowchart .....................................................................32

2.7 Instrument charging procedure ..............................................33

2.8 Calibration .............................................................................33

Aishwarya Technology & Telecom Model FM111 Cable Fault Locator ................................... 34

3.1 Introduction ..........................................................................34

3.2 Specifications ........................................................................35

3.4 To choose Testing Mode .....................................................37

3.5 Pulse Reflection Testing ......................................................38

3.5.1 Intelligent Testing ...........................................................39

3.5.2 Manual Testing ...............................................................39

3.6 Intelligent Bridge Testing ....................................................41

3.6.1Testing set up Intelligent Bridge Testing ...........................42

3.6.2 Megameter and Ohmmeter ..............................................44

3.7 Charging .............................................................................46

3.8 Precautions..........................................................................46

x

ISSUE OF CORRECTION SLIPS

The correction slips to be issued in future for this report will be numbered as follows:

CAMTECH/S/PROJ/2020-21/SP1/1.0# XX date .......

Where “XX” is the serial number of the concerned correction slip (starting from 01 onwards).

CORRECTION SLIPS ISSUED

Sr. No. of Correction

Slip

Date of issue

Page no. and Item No. modified

Remarks

xi

DISCLAIMER It is clarified that the information given in this handbook does not supersede any existing provisions laid down in the Signal Engineering Manual, Telecom Engineering Manual, Railway Board and RDSO publications. This document is not statuary and instructions given are for the purpose of guidance only. If at any point contradiction is observed, then Signal Engineering Manual, Telecom Engineering Manual Railway Board/RDSO guidelines may be referred or prevalent Zonal Railways instructions may be followed.

OUR OBJECTIVE

To upgrade Maintenance Technologies and Methodologies and achieve improvement in Productivity and Performance of all Railway assets and manpower which inter-alia would cover Reliability, Availability and Utilisation. If you have any suggestion & any specific comments, please write to us: Contact person :Jt. Director (Signal & Telecommunication) Postal Address : Centre for Advanced Maintenance

Technology, Maharajpur, Gwalior (M.P.) Pin Code – 474 005

Phone : 0751 - 2470185 Fax : 0751 – 2470841 Email : [email protected]

mailto:[email protected]

xii

CAMTECH Publications CAMTECH is continuing its efforts in the documentation and up-gradation of information on maintenance practices of Signalling & Telecom assets. Over the years a large number of publications on Signalling & Telecom subjects have been prepared in the form of handbooks, pocket books, pamphlets and video films. These publications have been uploaded on the internet as well as railnet. For downloading these publications On Internet: Visit www.rdso.indianrailways.gov.in Go to Directorates → CAMTECH Gwalior → Other Important links → Publications for download - S&T Engineering On Railnet: Visit RDSO website at 10.100.2.19 Go to Directorates → CAMTECH → Publications → S&T Engineering A limited number of publications in hard copy are also available in CAMTECH library which can be got issued by deputing staff with official letter from controllong officer. The letter should be addressed to Director (S&T), CAMTECH, Gwalior. For any further information regarding publications please contact:

Director (S&T) – 0751-2470185 (O)(BSNL) SSE/Signal - 7024141046 (CUG) Or Email at [email protected] Or FAX to 0751-2470841 (BSNL) Or Write at Director (S&T) Indian Railways Centre for Advanced Maintenance Technology, In front of Hotel Adityaz, Airport Road, Maharajpur, Gwalior (M.P.) 474005

http://www.rdso.indianrailways.gov.inmailto:[email protected]

CAMTECH/S/PROJ/2020-21/SP1 1

Cable Fault Localization April 2020

Cable Fault Localization

1.1 Introduction There are hundreds of trains which run daily on Indian Railways and the various systems which are involved in the operation of trains are Track, Rolling stock, Loco, Electrical Traction, Signalling and Telecom and traffic control systems. Railway Signalling and Telecom circuits run on hundreds of kilometers of underground cables. Although adequate precautions are taken in lying of cables beneath the ground and underground cables are not affected by any adverse weather condition like pollution, heavy rainfall, snow and storm etc. there are other factors which may cause faults in the cables.

1.2 Type of Cables carrying S&T circuits (i) Signalling cables

PVC insulated PVC sheathed and armoured signalling cables. Generally, used copper conductor core sizes are 1.5 sq.mm. and 2.5sq.mm. Most commonly used cores are 2C, 4C, 6C, 8C, 9C, 12C, 19C, 20C, 24C & 30C.

(ii) Telecom cables Polyethylene Insulated Jelly Filled (PIJF) cables 4 or 6 Quad cables (Core size 0.9 mm) Co-Axial Cables



1.3 Major causes of cable fault Some of the causes of cable faults are as given below: Ageing. Corrosion of sheath. Moisture in the insulation. Heating of cable. Fire and lightning surges. Electrical puncture Damage during laying. Damage while in use due to excavation works.

1.4 Types of cable faults The common faults which develop in the conductors of

multi-core cables are:

Earth fault When any of the conductors of the cable comes in contact with the earth, it is called an earth fault. This type of fault allows the current, carried by the conductor to leak to the earth directly or indirectly instead of going to the apparatus to which the conductor is connected. This usually occurs when the outer sheath is damaged due to chemical reactions with soil or due to vibrations and mechanical crystallization.

Fig.1: Earth fault

Damage to outer sheath Outer sheath

Conductor Insulation



Short circuit fault When two or more conductors of a multi-core cable come in contact with each other, then this is called a short circuit fault. A short-circuit fault occurs when the individual insulation of the conductor core is damaged.

Fig.2: Short Circuit fault

Open circuit fault As the name suggests, this fault involves an open circuit in the conductors. When one or more cable conductors (cores) break, it leads to discontinuity. This discontinuity also occurs when the cable comes out of its joint due to mechanical stress. This is known as Open circuit fault..

Fig.3: Open Circuit fault

Low insulation fault Sometimes when the cable core insulation material is deteriorated by ageing, moisture, excessive heating or dirt the insulation resistance is dropped to very low value (several hundred to several kilo ohms) it is called as low insulation fault. But if the insulation resistance is of the order of mega ohms and less than 2 Mega Ohms it is

1

2

Short

1

2

1

2

Break

1

2



termed as high resistance fault or bad insulation. In both the cases, the quality of communication or flow of current through the cable is badly affected and the cable needs replacement.

1.5 Need for cable fault localization Whenever a fault occurs in one or more conductors of underground cable, be it an earth fault, open/short circuit fault or low insulation fault, the circuit completing through the conductor or conductors is interrupted which in turn affects the functioning of connected equipments. In a railway signalling system the operation of signals or its associated equipments is badly affected due to cable fault. Similarly if a cable fault occurs in a telecom cable, the circuits associated with Block working, Control or other communication systems may not work. Unless the fault is identified and rectified, the train movement is badly disrupted.

(i) Detection of type of fault The type of cable faults mentioned in section 1.4 cannot be detected visually as these are buried underground. However all the above type of faults can be detected with the help of a Megger. Usually 500 V megger is used for testing insulation resistance of Signalling cables whereas 100 V megger is used for Telecom cables



Fig.4: Analog Megger Fig.5: Digital Megger

An open circuit fault is characterized by infinite resistance. Hence when the resistance between conductor which is break at some point and the earth is measured using a megger it will read infinite resistance.

A short-circuit is characterized by zero resistance. If the resistance between any two conductors which are shorting each other at some point is measured using a megger it will read zero resistance. If the resistance between any two conductors is low, the megger may show reading between several hundred ohms to less than 2 Mega Ohms. An earth fault is somewhat similar to a short circuit fault as the current again takes the least resistive path and flows through the earth. The megger is connected between the faulty conductor and the ground. If an earth fault is present, the megger will show nearly zero reading.



The above tests are performed on the portion of cable between two junctions where the fault is suspected. If it is not certain that in which patch of cable route the cable is faulty then the cable is disconnected at each junction and tested to find the faulty patch.

By above testing one can detect only the type of fault and the portion of cable between two junctions in which the fault exists. To restore the circuit either the circuit is transferred in spare conductors if available or a new cable has to be laid between the junctions containing faulty part of cable.

(ii) Detection of location of fault Finding the type of a fault in underground cables using a megger may not be a difficult task. But it is very difficult to locate and repair the fault. For detecting the exact location of cable fault special techniques are required.

1.6 Advantages of cable fault localization Detecting the cable faults and pinpointing the fault location makes task faster and easier for the site engineers through modern Cable Fault Localization techniques. Fast and precise fault location plays a significant role in speeding up system renovation, diminishing great financial loss and operating cost thereby minimizing down time and most importantly ensuring system availability and performance.



(i) Reduction in cost

There is a huge saving in cost if we use cable fault localization techniques instead of conventional methods. We can take the example of Signalling cable which is used to carry circuits for Signal lamp and control, points operation and detection, track repeater relay circuits etc. In reference to RVNL Standard bill of quantities for S&T Works March 2018, the approximate cost of a signalling cable including laying is summarized below: Description of item/work Unit Rate/Km Approximate cost of Jelly Filled 0.9 mm dia 6 Quad Cable

Kms Rs 350000.00

Approximate cost of excavation of trenches at a depth of 1.2 Mtr. deep and 300 mm wide and back filling the trench after laying of cable along with supply and fixing of Cable route marker.

Kms Rs 100000.00

Total approximate cost for 1 Km cable laying

Rs 450000.00

Total approximate cost for 1 Mtr cable laying

Rs 450.00

Suppose a 6 Quad cable becomes faulty between two junctions which are 600 mtrs. apart. If we don't know the location of fault, the whole 600 mtr. cable is to be laid which shall cost 600 X 450 = Rs.270000.00 approx.



Whereas, in a working cable even if approximate location of fault is detected, the whole cable need not be replaced or circuit transferred to spare conductors. Only a cable piece of few meters is to be laid which will be less costlier including the junctions to be provided. For new works also, before laying of cable if a fault is located, the part containing the fault can be cut and the remaining good portion of cable can be used by jointing it or as separate pieces as per the requirement

(ii) Saving of manpower To detect a fault in an underground cable by disconnecting at each junction/joint manually and testing from both ends is time consuming and requires manpower. We can take the example of quad cable in block sections which run continuously from one station to other with a number of joints buried underground. Communication with Level Crossing Gate if situated in the section may be of some help; otherwise it is difficult to predict the location of fault. When exact location of fault is not known, each underground cable joint is required to be opened and joined one by one, which require at least 5 to 6 persons at site and minimum 2 persons at the station end. The task becomes more difficult when cable markers are not available along the route. Similarly in case of fault in a signalling cable in station yard, termination in each location box or junction box coming in the route has to be disconnected and tested with megger.



If cable is tested with equipment like Cable Fault Locator the joints need not be disconnected. Suppose the total length of a 6 Quad cable between two stations A and B is 8 Kms. The cable is first disconnected at Station A and tested with all joints/junctions intact upto station B. The distance of fault from station A is located, say at 4880 mtr. The cable is then tested from station B in a similar manner. Now the distance to fault from station B comes out to be say 3125 mtr. By comparing both the results it is confirmed that the fault is within 4875 to 4880 mtr from station A or within 3120 to 3125 mtr from station B. Thus exact location of fault can be arrived at in just two rounds testing with minimum staff and in this case only a specified 5 mtr portion of cable has to be replaced. Fig.6: Locating fault distance between two points

(iii) Reduction in breakdown time When there is a fault in underground cable carrying signalling or block circuits, the equipments connected to it do not respond and as a result a part or whole signalling system becomes inoperative. Trains are piloted and despatched on paper authority until cable fault is identified and restored. Suppose a cable is cut by miscreants in a block section of 8 km length, then in the absence of any fault locator the only means to locate the fault/damage is foot by foot inspection. This means that

Station A

Station B

Fault distance 4880 Mtr.

Fault distance 3125 Mtr.

6 Quad Cable



the downtime will be more. In such cases sometimes it takes one or more days to identify and restore the fault. Examples of two cable cut/theft cases are given below (Ref.: Railway Board Failure data):

Sr. No.

Train Nos (Det. Min.) & Total Trains

detained

Station, Sec., Div. &

Rly.

Time, Date &

Duration in Min.

Remarks

1 22419 (30) 13258 (55) 14617 (35) 14227 (17) 22355 (10) 12317 (55) Total - 6

Pakhrauli-Sultanpur,

SLN - ZBD, LKO, NR

20.58-10.40

29/30.5.19,

725

UP SSDAC with SLN Failed after 13237UP .B/Instt with (Dn Line) FaileI. SE/E/SLN-21.05,SSE/SLN-21.10,T/R at 21.15,6 quad cable burnt by outsider at km no. 911/27-29, new 6 quad cable about 15 metres provided, jointed & put right by SSE/T/SLN

2 11014 (151) 11312 (49) 12627 (118) 12786 (100) 12684 (28) 16232 (112) 16520 (95) 16521 (18) 16522 (58) 16526 (63) Total -10

Kadlimatti KJM,

SBC-JTJ, SBC, SWR

18.10-20.40,

01.05.19,

260

Point No.71 failed for normal, Slot failed bet KJM-CSDR & KJM-BPHI, due to 19C cable cut & theft by unknown person. New 19C cable laid and restored to normal. Failed after cable restoration since newly laid cable conductor No.10 defective. Conductor changed over to spare conductor No.11 and restored.

In the first case the breakdown time is about 12 hrs. in which 6 trains detained. The downtime in second case is less (4 hrs) but total 10 trains are detained for longer periods. The breakdown time can be reduced drastically



if Cable Fault Locator is used for detecting the fault as explained in para (ii) above.

(iv) Reduction in maintenance Although every precaution is observed while laying of the cable and periodical meggering is done as per the annual programme, unpredictable faults in an underground cable due to various reasons are not ruled out. Sometimes the cable sheath is damaged due to excavation works and gone unnoticed. In RE area due to traction currents there is spark in the armour under damaged sheath which results in deterioration of conductors coming in contact with it. Over a period of time the other conductors also come in contact and the cable becomes faulty. In other cases, sometimes the moisture enters the damaged sheath and the low insulation fault is developed in the cable. All these types of faults can be prevented if a quick test is performed with Cable Fault Locator within specified periods. Thus, cable fault localization with special techniques avoid wastage of cable which in turn cuts cost, ease of operation requires less manpower, quick fault localization reduces downtime and can be better utilized for preventive maintenance. In view of the above, apart from detection of fault type, cable fault localization is needed before laying of cable or at the time of cable fault. Note: Apart from Signal & Telecom cables, cable fault localization techniques can be utilized for electrical cables also



1.7 Techniques used for cable fault localization There are different technique for locating faults in underground cables namely: (i) Murray loop test (ii) Varley loop test (iii) Cable Thumping (iv) Time Domain Reflectometer (TDR) (v) High Voltage Radar method (vi) Intelligent Bridge Testing

All the above techniques have some advantages and disadvantages. There is no single method or combination of methods which can be considered as best. However employing a technique which can efficiently locate fault without causing damage or degradation of cable is the key to safety of the system. The most popular technique among the above is TDR which is explained below.

1.8 Time Domain Reflectometer (TDR) A Time Domain Reflectometer (TDR) sends a short-duration low energy signal (of about 50 V) at a high repetition rate into the cable. This signal reflects back from the point of change in impedance in the cable (such as a fault). TDR works on the similar principle as that of a RADAR. A TDR measures the time taken by the signal to reflect back from the point of change in impedance (or the point of fault). The TDR uses Velocity of propagation (VOP) to calculate cable length.



Velocity of propagation (VOP) Velocity of propagation is a cable specification indicating the speed at which a signal travels down the cable. A VOP of 66 means the signal travels at 66% of the speed of light. The tester uses VOP to calculate cable length. Different cables have different VOP settings. Using the VOP specified for a cable ensures the most accuracy in fault location and length measurement.

Suppose the Velocity of propagation (VOP) of pulse transmission in a cable is V, the time taken by the signal to travel and reflect back from the point of fault is T and the distance of fault is L then

2L = VT L = VT/2

Thus if VOP and total time of to and fro travel of pulse transmission is known, the distance to the fault can be found. The reflections are traced on a graphical display with amplitude on y-axis and the elapsed time on x-axis. The elapsed time is directly related to the distance to the fault location. If the injected signal encounters an open circuit (high impedance), it results in high amplitude upward deflection on the trace. While in case of a short-circuit fault, the trace will show a high amplitude negative deflection.



Fig.7: Graphical representation of pulse transmission

and reflection in open and short circuit faults Advantages and disadvantages of TDR As a TDR sends a low energy signal into the cable, it causes no degradation of the cable insulation. This is a major advantage of using TDR to find the location of a fault in an underground cable. A TDR works well for open-circuit faults as well as conductor to conductor shorts. A weakness of TDR is that it cannot pinpoint the exact location of faults. It gives an approximate distance to the location of fault. Sometimes, this information alone is sufficient and other times it is required to be used in conjunction with other technique. In the following sections details of Cable Fault locating equipments using TDR are given.

Cable pair open

Cable pair shorted



1.9 General Precautions for Underground S&T cables Insulation resistance for a new cable should not be

less than 200 Mega Ohms/Km at 20°C. First measurement of insulation resistance of cable

should be carried out after laying of cable and after first monsoon for all the conductors.

Thereafter the periodical testing of insulation should be carried out once in 12 months for main cables and once in months for tail cables. Circuits of low insulation conductors should be transferred to healthy conductors in time.

If during periodical testing, the insulation resistance of cable is found between 5 and 1 Mega Ohms/Km at buried temperature, the subject cable should be programmed for replacement.

All defective tail cables should be replaced before monsoon. All tail cables at entry of junction boxes, location boxes, signal posts should be checked for breakage of insulation. All earth faults should be removed beforehand.

Insulation of cables should be monitored with the help of Earth Leakage Detector where provided. For effective monitoring, ELD data may be linked to Data Logger.

Minimum 5% healthy spare conductors are to be made available in each location/goomty/relay room and to be kept labelled /marked for easy identification during emergency.

All supervisors shall familiarize themselves with the position of spare conductors in their respective sections.



Protective works provided for the cables at places like track crossings, culverts, bridges etc. shall be inspected periodically especially before and after monsoon.

Earthing of armour of all cables and continuity of cable armour be ensured.

Quad cable meant for Block should be tested or their insulation resistance, cross talk, loop resistance, db losses. Position of cable joints should be known accurately and joints to be repaired if required before onset of rains.

It is a good practice to provide Cable route markers along the route of cable. Alternatively distance of cable route from OHE mast to be recorded n cable route plan during cable laying.



ANDIG Model 5289M Digital Cable Fault Locator

2.1 Introduction

ANDIG Model 5289M Digital Cable Fault Locator is manufactured and supplied by of M/s Andig Systems, Bangalore. It is basically a combination of Pulse Echo Meter (TDR) and High Resistance Fault locator. It can locate break, short (loop) and low insulation faults in underground copper cable. The distance to fault is displayed directly in metres and there are no calculations involved.

Fig.7:Andig Model 528M Digital Cable fault Locator



2.2 Technical specifications Physical Dimension Width : 265 mm Height : 195 mm Depth : 140 mm Weight : 3 Kgs (Approx.)

Power Battery : Internal Rechargable Li-Ion Battery Charging source : External 16 V DC, 1A Adapter Operating time : 8 hours continuous without Back light

Environment Operating temperature : 0 to 50° C

Display 240 X 128 dot-matrix Graphic, Liquid Crystal Display (LCD) with Back light

Pulse Echo mode Max range : 10 Kms (0.9 to 1.5 mm) Accuracy : Better than 1% of reading V.O.P.: Fixed for Standard cable or User Programmable Waveform Storage : Upto 20 Waveform Low Insulation Faults Mode Max. range : For open & Short Circuit faults - 5 Kms. For Low insulation faults - 15 Kms Accuracy : +/- 0.5% of reading Output Connectors : 4 Front Panel Banana sockets Serial I/O Ports : RS-232 Testable Low insulation Resistance : 2 Mega Ohms Accessories Standard: Battery Adaptor, Operation Manual, connectors,

carry bag



2.3 Front Panel Description The front panel of Digital Cable Fault Locator is given

below:

Fig.8: Front panel of Digital Cable fault Locator

Function of different keys SELECT : When Pressed selects highlighted menu on

display screen MENU : When Pressed Main Menu is displayed

: Moves Up & Down the highlighted Menu : Moves Left or Right the selected cursor or

increments/ decrements function selected in multifunction box.



RANGE : Display range status (RANGE 1 upto 1km, RANGE 2 upto 2km, RANGE 3 upto 3.5km, & RANGE 4 upto 5km) Select range using Left & Right arrow keys.

ZOOM : It displays current zoom status from zoom1-zoom5. At zoom 6 it displays maximum expanded waveform. (Select Zoom level Using Left & Right arrow keys)

CUR : Selects Cursor 1 or Cursor 2 BACK : Not Used GAIN : Selects Gain level (Default sets to Gain 1) &

displays status in multifunction box. START : When pressed starts testing the Cable Pair

under test (Display Scanning) PRINT : Not Used B/L : Switches ON Back Light LINE 1 : Socket pair for connecting faulty pair under

test LINE 2 : Socket pair for connecting good reference pair

RS 232 : Connector for PC Interface PRINTER : not used DC Socket : Socket for Ext DC & for battery charging (12 To 15 VDC)

Note: Following keys are used only in Pulse Reflection mode When pulse (Waveform) is displayed on LCD.

a) RANGE, b) ZOOM, c) GAIN, d) CURSOR.

2.4 Powering On On powering on the instrument performs self check and on completion will display Main Menu.



Fig.9: Main Menu

Use UP & DOWN arrow keys to select one from following:

1.Pulse Echo Reflection : for Open & Short Faults 2. Low Insulation Faults : for Low Insulation Faults 3. Insulation Resistance : for measuring Insulation Resistance 4. Foreign Potential : for measuring Foreign Voltage on Cables

2.5 Operating Instructions In this section the operating instructions for detection and localization of different types of faults in underground cables through digital fault locator are given.

2.5.1 To Locate Open/Short circuit faults Select Pulse Echo Reflection, it displays

PULSE ECHO REFLECTION 1. Normal Scan (L1 Scan) 2. L2-L20 Scan 3. L1 & L2-L20 Scan 4. Differential Scan 5. Settings

Software Version....................................

1. Pulse Echo Reflection 2. Low Insulation Faults 3.Insulation Resistance 4.Foreign Potential Press Select key to enter Battery Level



Go to Settings and press Select. It displays

By default instrument sets to 0.5mm gauge and cable type jelly filled. To change gauge & type of the cable go to settings and do changes as given below: Go to Cable Type and press Select. It displays

Go to required cable type and press Select Press Menu key to exit.

Go to Guage and press Select. It displays

TDR SETTINGS 1. Cable Type 2. Gauge

CABLE TYPE 1. Jelly 2. Paper 3. Co-Axial 4. Others 5. PVC

GAUGE SELECTION 1. 0.4 mm 2. 0.5 mm 3. 0.63 mm 4. 0.9 mm 5. 1.5 mm



Go to required gauge and press Select Press Menu key to exit.

Connect pair under test to LINE1 Terminals on the top right corner of front panel.

There is no need to disconnect the pair at the other end.

An electrical pulse of 30V amplitude is sent along the cable , which will be reflected back from the point of fault. The signal propagation time is calculated and the distance arrived at based on the velocity of propagation based on the medium involved. Go to Normal Scan (L1 Scan) and press Select. Both Incident and reflected pulse appear on the LCD screen. For open circuit fault the incident and reflected waveform will be

Fig.10: Incident and reflected waveform for open

circuit fault



For short circuit fault the incident and reflected waveform will be

Fig.11: Incident and reflected waveform for short

circuit fault. If the fault is at less than 1 km distance, use Zoom 4, Zoom 3 to check whether reflected pulse appears within the screen along with incident pulse. If reflected pulse is not displayed clearly in zoom 5, zoom 4, zoom 3 then Press Range - Using Left & Right Arrow Keys Select range depending on the distance to fault. Range 1 upto 1 Km, Range 2 upto 2km, Range 3 upto 3 km, & Range 4 upto 5km. Press Start : Both incident & reflected Pulse appears on screen. If reflected pulse is not seen press range & select next range Press Gain : Select Gain 1, Gain 2, for amplifying reflected pulse & Press Start Press Cur : Displays Cursor 1 or Cursor 2 in the multifunction box. Using Left & Right Arrow keys adjust Cursor 1 to the starting point of incident pulse (The Point from Where



incident pulse starts rising) & Cursor 2 to starting point of reflected pulse. After aligning cursors to the incident and reflected pulse distance to fault is displayed in distance box.

Note: F For better accuracy at different fault distances select Range, Zoom & Gain positions. For faster cursor movements you can use zoom facilities.

2.5.2 To Locate Low Insulation faults (i) To locate Low Insulation faults using Good pair Basic requirement to conduct this test.

A Good (Reference) pair preferably in the same cable in which faulty pair exists is to be tested.

Insulation Resistance (Megger Value) between Limb A & B and between each Limb to Earth should be more than 5 Mega Ohms.

Faulty pair should have less than 2 Mega Ohms Insulation Resistance.

Distance of fault

Curser 1 Curser 2

Fig.12: Display showing distance to fault



Testing setup Measure the Good pair insulation resistance and Faulty pair insulation resistance as per procedure given in section 2.5.3. Loop the Good pair and extend it to one limb of Faulty pair. (refer Fig.13). Connect the Faulty pair to Line 1. The extended limb of faulty pair must be connected to Black terminal of Line 1 in the instrument and the other limb to Red terminal. Connect Good pair to Line 2 Ensure that the connections are perfect. Check the resistance between limb to limb of good pair using multi meter to ensure it is properly looped at the far end (say it reads 500 Ohms). Check the resistance between any one limb of good pair to faulty pair limb, it should read the same resistance as good pair. If fault is between Limb to Earth, connect Red terminal of Line 1 to Earth

Fig.13: Setup to locate Low Insulation faults using Good pair



Using Up & Down arrow keys, Go to Low Insulation Faults. Press Select. It displays:

Using Up & Down arrow keys highlight Setting and Press Select Key. Select the ambient Temperature and Gauge of cable under test. By default instrument sets to temp 27 Degree Centigrade and gauge 0.5 mm. Press Menu key, the Main Menu is displayed. Using Up & Down arrow keys, again Go to Low Insulation Faults. Press Select, the LOW INSULATION FAULTS menu is displayed as above. Go to Double Limb Scan and Press Select.

LOW INSULATION FAULTS 1. Double Limb Scan 2. Mixed Gauge Scan 3. Settings 4. Mixed Gauge Settings 5. Single Limb Scan

Temperature Gauge

LOW INSULATION FAULTS 1. Double Limb Scan 2. Mixed Gauge Scan 3. Settings 4. Mixed Gauge Settings 5. Single Limb Scan



After 30 seconds the result will be displayed as shown below: All the distances are in Metre.

(ii) To locate Low Insulation faults using only one good Limb

Verify good Limb for more than 5M ohms insulation resistance.

Short Red & Black terminal of Line 2 & connect to good Limb.

Loop good Limb to faulty limb at the far end. Connect Black terminal of Line 1 to faulty Limb, which

is looped to good Limb. Connect Red terminal of Line 1 to 2nd Limb of faulty

pair if the fault is between Limb to Limb. Connect Red terminal of Line 1 to Earth if the fault is

between Limb to Earth.

Fig.14: Setup to locate Low Insulation faults using only one

Good limb

Distance to Loop : 540 Mts. Distance to Fault : 210 Mts.



Select Low Insulation Fault & then Select Single Limb Scan from Menu. (Available in Software version 1.1/171103)

If the Menu for Single Limb Scan is not available then the fault distance displayed should be multiplied by 2 for actual distance to fault.

2.5.3 To measure Insulation Resistance Test for Good pair

In the Main Menu, using Up & Down arrow keys, Go to Insulation Resistance.

Press Select. It displays Connect Limb A & Limb B to Line 1 Go to Scan & press Select After few seconds it display resistance value in K ohms: --- Connect Limb A & Ground to Line 1 & Press Start After few seconds it display resistance value in K ohms: ---

1. Pulse Echo Reflection 2. Low Insulation Faults 3.Insulation Resistance 4.Foreign Potential

RESISTANCE MODE Scan



Connect Limb B & Ground to Line 1 & Press Start After few seconds it display resistance value in K ohms: --- In all the above cases Insulation resistance should be more than 5000 K ohms for a good pair. Test for Faulty pair Similar to the test procedure for Good pair.

Connect Limb A & Limb B to Line 1 Go to Scan & press Select

After few seconds it display resistance value in K ohms, less than 2 M ohms for fault between limbs.

Connect Limb A & Ground to Line 1 & Press Start After few seconds it display resistance value in K ohms,

less than 2 M ohms for fault between limb A to Earth.

Connect Limb B & Ground to Line 1 & Press Start After few seconds it display resistance value in K ohms, less than 2 M ohms for fault between limb B to Earth. If Insulation resistance is less than 2000 K ohms, the distance to the fault can be located in the pair as per procedure given in section 2.5.2.

Insulation Resistance is 1500 K Ohms



2.5.4 To measure Foreign potential Connect pair under test to Line1 terminals In the Main Menu, using Up & Down arrow keys, Go to Foreign Potential

Press Select, it will display

Go to Scan & press Select. After a few seconds a display similar to that shown below:

1. Pulse Echo Reflection 2. Low Insulation Faults 3.Insulation Resistance 4.Foreign Potential

POTENTIAL MODE Scan

Foreign Potential is 5 Volts



2.6 Menu Flowchart



2.7 Instrument charging procedure Connect external supply (15VDC) and switch ON the

instrument. Observe for charging enabled on the screen after few

seconds. Please do not charge the instrument more than 14 hours.

2.8 Calibration Andig Model 5289M is pre calibrated for various types of cables. No need to calibrate in the field. However for unknown type of cable option to calibrate is in menu driver.



Aishwarya Technology & Telecom Model FM111 Cable Fault Locator

3.1 Introduction Model FM 111 cable fault locator is a product of M/s Aishwarya Technologies & Telecom Ltd., Hyderabad. It combines both Time Domain Reflectometer (TDR, pulse reflection testing) and intelligent bridge testing (Bridge) for measuring the exact fault location such as the broken line, cross faults, earthing, poor insulation and poor contact of the lead covered cables as well as plastic cables.

Fig.15: Cable Fault Locator Model FM 111



Features Large colour LCD Display (480 x 280 dot); humanized

operation interface; six function keys for simple operation.

Combination of pulse reflection testing (TDR) and intelligent bridge testing (Bridge) techniques.

Manual testing function is preserved. Megameter and ohmmeter, to test insulation resistance

and loop resistance. USB Port, to upload testing data to computer Rechargeable lithium battery, intelligent charging

without duty. Small dimension, light weight and portable design.

3.2 Specifications Pulse reflection testing(TDR)

Max range: 8 km Dead Zone: 0 m Testing Accuracy: 1m Pulse width: 40 ns-10 μs with automatic adjustment Automatic impedance balance adjustment Automatic and manual gain adjustment

Intelligent bridge testing(Bridge)

Max poor insulation resistance: 100 MΩ. Testing accuracy: ±1%×cable length The max length of testing cable: 15 Km Charging time: 3 hours Continued operating time: 8 hours Dimension: 220×160×90 (mm3) Weight: 1Kg



3.3 Front Panel Description

Fig.16:Front Panel of Model FM111 Cable fault Locator

: Power Supply On/OFF switch

ADJ : Adjust testing parameters

◄► : To move the cursor - Under Pulse Reflection testing To adjust relevant parameters - Under Electric Bridge testing. Users can also complete the operations with Menu prompt.

PULSE :To process Manual pulse testing - Under Pulse

Reflection testing.



To enter the Pulse Reflection testing interface automatically - Under Electric Bridge testing.

Users can also complete the operations with Menu prompt. AUTO : To perform the testing automatically. TEST : To insert and connect the testing lead lines. USB : To communicate with hot computer CHARGE : Socket for charging the instrument

Testing line There are three clips at the end of testing lead line -Red, Yellow & Black. Under Pulse Reflection testing - Only red & yellow clips to be used. Under Intelligent Bridge testing - All the three clips red, yellow & black to be used. Testing socket

Fig.17: Testing lead line

3.4 To choose Testing Mode When the cable lines have faults, first use testing board, megameter (or megger) or multimeter to find the character and degree of fault, so as to choose most suitable testing mode. When the fault resistance is smaller than several hundred to several kilo ohms, we call it low insulation fault otherwise it is called high resistance (or bad insulation) fault.

Clips Red Yellow Black

Testing Lead



The Pulse Reflection Testing is suitable for testing open circuit (break) faults and low insulation faults. This testing is simple and direct-viewing, requiring no co-ordination at other end. The Bridge testing method is suitable for high resistance faults of the order of 2 Mega ohms or slightly less. It requires a good line (reference line) and co-ordination from other end. The test preparatory work is also tedious. Sometimes the high resistance faults can also be detected using Pulse Reflection Testing. Hence Bridge Testing method should be resorted to only after confirming that Pulse Reflection Testing cannot detect the fault. Switching between Pulse Reflection Testing and Bridge Testing Press On/Off key to turn on the instrument, the testing mode will be selected as Pulse Reflection Testing by default. Press Adjust until "Press◄ or ►to enter into Bridge mode" appears in reverse colour. Press ◄ or ► to enter Electric Bridge Testing. Under Electric Bridge Testing press Pulse to switch over to Pulse Reflection Testing.

3.5 Pulse Reflection Testing

Under Pulse Reflection testing, analog signal is sent to locate the fault in a cable which after reflection is converted to digital pulse for distance measurement.

Preparatory steps

Before commencing the process, disconnect the faulty cable at both ends. Make sure the cable to be tested is free from any supply voltage.



First the instrument should be used to perform Intelligent testing. If the fault cannot be detected with the above process, then it can be changed to Manual testing.

3.5.1 Intelligent Testing Intelligent Testing means Pulse Reflection Testing

(Finding Open or short circuit fault) in AUTO mode. First Power On the instrument.

Connect the cable pair under test to red and yellow test lead lines. Press AUTO and the instrument will show the result. Note: The default setting of wave velocity of propagation (VOP) is 200 m/µs. Before performing Intelligent testing, user shall check whether it is required to adjust the velocity. (Refer "Adjust Velocity" in next section).

3.5.2 Manual Testing The relevant setting and parameters to be adjusted are displayed below the display screen. Press Adjust to adjust the following settings and parameters:

(i) Gain Press Adjust until Gain XX shows reverse colour display. Then press ◄ or ► to adjust the amplitude (adjustable 1-99). Press Pulse the screen will display the wave after gain adjustment.

(ii) Range During manual testing the range value shall be chosen longer than the actual length of cable to be tested. To adjust the range repeatedly press Range until Range XX



shows reverse colour display. Then press ◄ or ► to adjust the range.

(iii) VOP The wave velocity shall be calibrated according to the cable character to improve the precision of testing result. Press Adjust until VOP XX shows reverse colour display. Then press ◄ or ► to adjust the wave velocity. Adjust Range and Velocity according to the character and estimated length of cable. Appropriately adjust the wave amplitude to make waveforms on the display screen to be observed easily. Move the cursor to the inflection (point of rising) of the reflected waveform. The fault distance will be displayed at the bottom of display screen.

(iv) Zoom in & Zoom out Users can Zoom in or Zoom out when zoom value is not "1". Continuously press Adjust till Zoom is selected. The prompt box will display "press ◄ or ► to zoom the wave". Zoom to the proper size and press Pulse. Users can move the cursor to fix position. Press Pulse to return to original state.

(v) Save waveform to RAM The waveform should be saved to RAM when comparing

the fault line and good line under manual testing. Continuously press Adjust till Save is selected. The prompt box will display "press ◄ or ► to save wave". Users can save the current waveform by pressing ◄ or ►.



(vi) Compare Current Wave with stored Wave in RAM Users can compare the current waveform with the already stored waveform in RAM. Continuously press Adjust till Both is selected. The prompt box will display "press ◄ or ► to both display".

(vii) Save file Press Adjust until "press ◄ or ► to do file management" appears. Now press◄ or ► to enter into save file mode. One can not only save and test the current file but check and analyze previous wave files. Saving file to U disk: When "Current Test" is chosen, press Auto to test the current cable. Press Adjust to save the current file. A display showing "Press ◄ to quit file mode, press ► to save current wave" will appear. Press ◄ to quit file mode or press ► to save current file to U disk.

3.6 Intelligent Bridge Testing When the insulation resistance of a faulty cable pair is very high (above several thousand ohms) and is much larger than characteristic impedance of cable. In this case the pulse reflection is weak hence it is not easy to detect the fault by Pulse Reflection Testing. At this time Bridge Testing has to be carried out. Testing principle Suppose the resistance of the entire core is R. The resistance of core from one end (test point) to the fault is Ra



The core length is L, and The fault distance is La , then La = (Ra/R)L The instrument adopts Intelligent Electric Bridge technique, so the user has to connect lines, input some data such as length and diameter of the core and the fault distance is calculated.

3.6.1Testing set up Intelligent Bridge Testing First confirm that the type of fault for example core to earth resistance is low (in thousand ohms) or bad insulation fault between same pair cable (self-crossed) or two conductors of different pairs (other-crossed). The testing setup for locating the distance of fault, requires two conductors - one consisting earth fault and the other one with good insulation with earth. One end is designated as testing end and the other as co-ordination end. Disconnect both the conductors at either ends from the circuit. If core to earth resistance is low (in thousand ohms) Loop the faulty and good line at the co-ordination end. At testing end, connect the black clip of testing lead line to earth, the yellow clip to good line and red clip to faulty line as shown in Fig.18

Fig.18: Localization of earth fault



If there is poor insulation between conductors of same pair (self-crossed) Loop one conductor of the faulty pair with one conductor of good pair at the co-ordination end. Connect the same faulty and good conductors to red and yellow clips of testing lead line respectively at testing end. Connect second conductor of faulty pair to black clip at testing end as shown in Fig.19. Remaining ends are left free.

Fig.19: Localization of fault in self - crossed lines

If there is poor insulation between conductors of different pairs (other-crossed) Here we require two good conductors besides faulty pair. Loop the faulty core of first cable and first good line at the co-ordination end. At testing end, connect the red clip of testing lead line to faulty core of first cable which is looped with first good line at co-ordination end (the first good line is left free at testing end), yellow clip to second good line which is left free at co-ordination end, and black clip to faulty core of second cable which is left free at other end as shown in Fig.20.



Fig.20: Localization of fault in other- crossed lines

Testing procedure Check the connections and ensure that they are correct and intact. When everything is ready Press Auto, the instrument will give ratio of Fault resistance and Resistance of entire cable span. Next input cable span (Length) to get fault distance. Note: The cable length here refers to the cable length in testing fault sector i.e. length from testing end to co-ordination end. To input the known cable length, press Adjust the "line span = 0000m" starts blinking. Depending upon the value of known cable length using ◄ or ► keys increment or decrement the digits. The instrument will automatically calculate the fault distance during inputting data.

3.6.2 Megameter and Ohmmeter The instrument consists Megameter and Ohmmeter under Electric Bridge Test method to test line insulation electric resistance and loop electric resistance.



Function of Megameter To test insulation resistance of a conductor with respect to ground, connect the black clip with ground and red clip to the conductor under test. Press Adjust, the test result will be shown at the top of the screen. For example if the insulation resistance is 3.6 MΩ it will show "red & black 3.6 MΩ, yellow & black ∞ no loop".

Fig.21: Testing of insulation resistance of conductor

w.r.t. ground with Megameter Function of Ohmmeter

To test Loop resistance of a cable pair, the loop the far end of cable pair. Connect the red and yellow clips to the two conductors at testing end. Press Auto key, the loop resistance is displayed after a few seconds. For example, if the loop resistance is 1360 Ω, then it will show " Insulation ∞ loop resistance =1360 Ω".



Fig.22: Testing of loop resistance of a pair with

Ohmmeter

3.7 Charging Current battery power is displayed at the top right corner on the screen. If battery power is inadequate, instrument charger should be used for charging. The indication light of the charge adapter will be red when charging, and it will turn green after the instrument is fully charged. The charge time should not be more than 4 hours.

3.8 Precautions Keep display screen away from direct sunlight. The

contrast ratio of LCD will drop when temperature higher than 60°C and it will return to normal when temperature is lower than 60°C.

Before testing it is better to measure voltage in faulty cable to be tested, in order to avoid test errors or damage to the instrument.

Avoid damage to LCD screen.

गुणव ता नी त “आर .डी .एस .ओ. ” लखनऊ म हम सतत सधुार और ाहक मू याकंन

ा त करने हेतु गणुव ता बधं णा लय को आव धक समी ा के मा यम से रेल म या ी एव ंमाल यातायात क बढ़ती आव यकताओं, मांग और अपे ाओं को परूा करने के लए गणुव ता बधं णाल क यावहा रक आव यकताओं और अनवरत सधुार को परूा करने के समपण, गणुव ता उ े य को नधा रत करके अनसुधंान, अ भक प और मानक म उ कृ टता के मा यम से वधैा नक और नयामक अपे ाओं का अनपुालन करते हु ए सुर त, आधु नक और कफ़ायती रेल ौधो गक वक सत करने हेतु सेवाओं को बनाए रखने और अ यतन पारदश मानक हेत ु तब ह । इसे संगठन के अदंर ससंू चत एव ं लाग ू कया गया ह तथा सभी संबि धत इ छुक प कार को भी उपल ध कराया गया ह ।"

Quality Policy “We at RDSO Lucknow are committed to maintain and update transparent standards of services to develop safe, modern and cost effective railway technology complying with statutory and regulatory requirements, through excellence in research, designs and standards by setting quality objectives, commitment to satisfy applicable requirements and continual improvements of the quality management system to cater to growing needs, demand and expectations of passenger and freight traffic on the railways through periodic review of quality management systems to achieve continual improvement and customer appreciation. It is communicated and applied within the organization and making it available to all the relevant interested parties.”

INDIAN RAILWAYS

Centre for Advanced Maintenance Technology Maharajpur, Gwalior (M.P.) Pin Code – 474 005

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