ST880 Cable Fault Locator User Manual
Contents
1. 21 0 7057777000 21 2 8 Measurement of VOP and Calibration 23 271116 ui Eni R 24 Chapter 3 Bridge Method 26 21 Wy OUR PION wc al n bsa 26 3 2 Bridge test inleriace IMMOCUC MOM sx sssenocnorevesstzssvsoatuaaansstasanonstouseussivsaemsaecsmalecess 27 2 9 Ulu 28 3 4 Connection Method for Bridge 20 23 2 Budge Method Test 3l 3 6 Input the total length to calculate the fault distance 32 Chapter 4 Data Analysis SoftWare i2 cis 35 Chapter 5 Poyver UU 35 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Chapter 6 5 2 3 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au Chapter1 General 1 1 General information ST880 TDR Bridge ST880 Automatic Detection Manual Detection 51880 Cable Fault Locator is the latest test instrument developed by Senter Corporation its working principle is Time Domain Reflectometer TDR and Bridge Methods It is a very convenient intelligent and reliable instrument for precisely locating cable faults like open circuit short circuit cross faults poor insulation and balance test etc We can also2. Tel 03 9023 0189 Fax 03 9700 0583 7 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 1 6 2 Choosing proper detection method If the fault resistance 1s a few hundred to a few thousand Ohm it 1s called Low Resistance Fault if the fault resistance is very high it is called High Resistance Fault But please be noted that there is no clear limit for these two kinds of faults TDR method is suitable to detect Open circuit and Low Resistance Cross fault but for some serious poor isolation faults like water in cable this method can also be applied We should choose this method with priority because it is easy to detect and easy to analyze the waveform simple in operation For BRIDGE method we can use it to detect Poor Isolation faults but since we must have one healthy pair and the far end cooperation is must the preparation work is very complicated the operator can only choose it after you really can not get any helpful result using TDR Method Note when use TDR method the testing cable is different for different method we should press MODE to convert between different modes 1 6 3 Fault distance Detection Use ST880 can detect fault distance precisely we should disconnect the faulty pair of cable from other equipments connected Warning The T CS00 can not withstand voltage over 400V for the safety of operator and equipments we should discharge the cable under tested com
3. 1 201 50 GAIN15 RANG ZOOM Fig 2 18 2 7 7 ZOOM if you want to have a better view for the waveform press IN under ZOOM menu press OUT to revert or ALL to return Tel 03 9023 0189 Fax 03 9700 0583 22 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 7 8 ZERO if there is joint near to the fault position we can use this to determine the fault to joint distance Press ZERO once there will have a solid line appear at the location of dash line and this 1s the zero point of the coordinate If there 1s a joint near the fault location and there will have reflection set the joint point as zero move the dash line to the fault point this way we can tell the distance between joint and fault point As Fig 2 19 shows 350M LOCA ZERO 1KM V 201 505 GAIN15 FUN RANG VOP ZOOM FILE BAL Fig 2 19 2 8 Measurement of VOP and Calibration If we need to test or calibrate the cable vop we can connect the instrument with one healthy pair to detect the waveform If the total length detected 1s aie not the same as the real length we can press DJ 7 under VOP menu until the detected length is the same as real length Then the set VOP is the real VOP of this cable we can keep this in file for this kind of cable For calibration we can save the waveform detected then shorten the far end of this cable compare these two waveforms move the cursor
4. 30V Width 160ns to 3 5us Automatically set according to ranges Balance control Range 82 to 600 Ohms Blind Area 2m DISPLAY Type High resolution LCD 320 240 pixel with backlight BRIDGE PARAMETER Poor Insulation Range Detected 0 30MQ Test Voltage 100V TEST MODE Balance Differential Bridge POWER Two Li Ion cells 5 hours for continuous use 5 minutes auto Tel 03 9023 0189 Fax 03 9700 0583 1 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator power off after last key operation CHARGING TIME 3 hours automatically CHINGER POWER Input 220V 50Hz AC Output 8 4V DC ENVIRONMENTAL Operating temperature Storage temperature Humidity 511 to 40 100 to 40 20 90 RH at 25 Table 1 ST880 Specifications Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 1 4 ST880 Layout and Appearance 1 4 1 The Instrument includes Main Unit One Test Cable Charger One CD PC software for data transfer Bag 1 4 2 Front Panel Fig 1 1 ST880 Front Panel amp Display area LCD to display the waveform and all messages D Function Buttons there are many buttons on the below and right sides of the LCD see what displayed correspondingly on LCD it will perform that function naso sz nxu zaunxx n
5. z zxzxzxnx ur nc aa z xxxz nOnarnm nm m m mmxmm n nc x zqu Tel 03 9023 0189 Fax 03 9700 0583 3 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator C c To svvitch on and off the LCD backlight D SIGNAL The test cable is plugged here B USB to use Flash Disk to transfer waveform 6 CHARGE Charge the instrument G CURSOR to move the cursor right left to determine the fault location 7 to svvitch on and off the instrument Je to convert different test mode Press once single test press this button more than 2 seconds it will be converted to automatic test 1 5 Operation The instrument interface 1s easy and friendly to use the operation 1s just like the ATM machine from the bank There are 12 blank keys around the LCD 6 at the bottom and 6 at the right If the ST880 is powered on the function of the keys will correspond to the nearest displayed function Tel 03 9023 0189 Fax 03 9700 0583 4 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Press here 1 500M V 201 50 GAIN15 500M 201 50 GAIN15 Press here Fig 1 3 Fig 1 4 For example if we power on the 51880 there will have the following functions displayed at the bottom of the LCD they are FUNC RANG VOP ZOOM FIND FILE LINE press RANG as Fig 1 3 shows then the right part of th
6. La If the diameter of the whole cable is the same we need only input the cable s length L If the cable has many different diameters we need input part diameters and part length of the cable See details in the third part The tester adopts intelligent bridge technology users only need to connect the line well input the length part diameters etc press some keys and then the fault point will be calculated out Tel 03 9023 0189 Fax 03 9700 0583 26 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 3 2 Bridge test interface introduction Use BRIDGE test lead to connect to the SIGNAL port power on ST880 press Mode to choose BRID mode as Fig 3 3 shows Fault distance Cable length X CableLength 00001 Fault distance BAL DIFF BRID Fig 3 3 Fig 3 4 Fault distance cable length 90 is the proportion value tested by the instrument the result will be displayed While for Cable length m needs the user to input the correct cable total length after testing After inputing the cable length press CAL the fault distance will display During the test the insulation resistance and the loop resistance will be displayed in the up of the screen The menu below the LCD are SEG these are used to inputcable length we will introduce later in this chpter Tel 03 9023 0189 Fax 03 9700 0583 27 E info telecomtest com au W http www telecomtest co
7. ai VOP VOP or the default VOP is 201 to use this to choose the right VOP If the cable VOP is not in the list just use these two to adjust 500M 201 50 GAIN15 FIND FILE 500M V 201 50 GAIN15 FUN RANG ZOOM Fig 2 10 Fig 2 11 2 4 4 ZOOM This is used to change the waveform display rate horizontally Press this button the LCD display will be as Fig 2 11 shows the waveform can be zoomed in zoomed out or reset Tel 03 9023 0189 Fax 03 9700 0583 18 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 4 5 FIND After the test 1s finished this 1s used to find the fault location also this menu can quit Wavelet Method Fig 2 12 shows details LOCA locate under such mode use this menu to relocate the cursor to the suspected fault location ZERO press once there will have a solid line appear at the location of dash line and this 1s the zero point of the coordinate If there 1s a joint near the fault location and there will have reflection set the joint point as zero move the dash line to the fault point this way we can tell the distance between joint and fault point MEMORY 8 a 2007 01 10 12 10 10 MEMO 1 500M Vz201 50 GAIN15 FUN RANG VOP ZOOM FIND 500M V 201 50 GAIN15 FUN RANG VOP ZOOM H ND FILE Fig 2 12 Fig 2 13 2 4 6 FILE To manage the waveforms as Fig 13 show please find details in 2 8 2 5 Conn
8. to the position where there 1s difference we can see that this 1s the cable length Repeat the above operation to calibrate the VOP Tel 03 9023 0189 Fax 03 9700 0583 23 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 9 File Management The ST880 can save 20 waveform they will be lost even the instrument is powered off 2 9 1 Enter into file management press FILE key we can enter into the file management the appearance is as Fig 2 20 shows The current waveform is displayed MEMO MEMORY 00 p MEMO 2007 01 10 12 10 10 PAGE PAGI 500M V 201 50 GAIN15 500M Vz201 50 GAIN15 FUN RANG VOP ZOOM FIND AL FUN RANG VOP ZOOM FIND Fig 2 20 Fig 2 21 2 9 2 Save the current waveform after entering FILE press MEMO to save the current waveform If there already have 20 waveforms the earliest one without being locked will be deleted Note if we want to save the waveform we should do it immediately If you review the filed waveforms first the current waveform will be deleted then we will have to do the test again uten 2 9 3 Review the filed waveforms press key it will display the waveform saved as 00 as Fig 2 21 shows The left corner of LCD will display MEMORY D l amp here 00 is the saved serial number amp shows that the waveform is locked shows the waveform is unlocked Press f PAGE or SQ button to review all saved wav
9. transfer the fault data to PC via cable or Flash Disk 1 2 Features STS80 combines the conventional TDR method and Bridge Method for fault detecting faults like open circuit short circuit poor insulation can be detected Multimeter function it can be used to detect isolation resistance and loop Automatic Detection advance and precise it can find almost all types of faults Manual Detection easy to detect it matches with automatic detection to give the operation a very precise result Waveform Storage ST880 can store 20 waveforms together with the fault time permanently it will not be lost even the instrument is powered off Wavelet detection technology used for long distance fault detection this can increase the detection range and accuracy Data transfer the operator can transfer the data in the ST880 to PC with a ST880 Cable Fault Locator Flash Disk The software installed in the PC can analyze the waveforms establish database for the waveforms and print if necessary Friendly Human Machine Interface HMI easy to use Internal recharging Li Ioh battery long life span and short charging time Small in dimension and light in weight easy to carry bag 1 3 Specifications RANGE 0 to s000m ERROR VOP is 200m us Max 1 m x2000m 8 2000m VELOCITY 100 to 300 m us default 201 m us GAIN 0 80dB TDR PARAMETER Amplitude Single 30V Double
10. 4m 4m 4m 4m 4A 45 49 49 CO CO CO CO CO CO CO CO CO 4 Co du 4 Co n CP 4 ea 4 CO CO CO CO el el ez C Co Co LK OMS Li m m m m m m m m m m m m m m m m m m o Fig 2 22 Tel 03 9023 0189 Fax 03 9700 0583 25 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Chapter 3 Bridge Method The fault resistance of poor Insulation is very high much more than the cable s surge impedance the pulse reflection is very weak and it is difficult to judge the fault point At this time we should use Bridge test mode The tester also has mega meter and ohmmeter function 3 1 Working Principle and in unit length the resistance 1s the same We assume that the resistance of the whole cable is R if we can test the resistance between the fault point and the other terminal is Ra and we know that the length of centre yarn is La and then we can get the following conclusion La Ra R L The centre yarn rate 1s changes according to the temperature and different diameters of line but the influence is the same in the range of the cable s length If we use Ra R this proportion calculation method we can remove the influence When testing the testing will calculate the Ra R automatically and then we should input some data in order to calculate the
11. ST880 Cable Fault Locator User Manual ST880 Cable Fault Locator All rights reserved No part of this manual shall be reproduced stored in a retrieval system or transmitted by any means electronic mechanical photo copying recording or otherwise without written permission from Shandong Senter Electronic Co Ltd Although every precaution has been taken in the preparation of this manual Shandong Senter Electronic Co Ltd assumes no responsibility for errors or omissions Neither is any liability assumed for damages resulting from the use of the information contained herein Declaration SENTER reserves the right to change specifications or designs described herein without any notice or obligations Tel 03 9023 0189 Fax 03 9700 0583 1 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator CONTENT Chapter EG CGT all M 0 Cieneral ThTOELHTIO LEOTE serrera orr O Orn OE O OE 0 NENNT 0 1 3 6 1 1 4 51880 Layout and Appearance 3 4 LO The Procedures Tor SECON 7 Chapter 2 Pulse Reflection TDR Detection 2222 10 01 ib 10 PAPAE Rees OIG ERE 11 20 Wavelet Method TQ CUS CIO aie conan a did 14 LATOR urma 15 19
12. e LCD will display 250M 500M 1KM 2KM 4KM and 8KM Press 500M as Fig 1 4 shows then the test range will be 500 meters Setting Press key to turn on the 51880 the welcome and time information will be displayed then press SET the ST880 will be entering the setting display as Fig 1 5 and 1 6 shows Welcome to ST880 Welcome to ST880 2007 01 01 12 30 30 2007 01 01 12 30 35 el CONT TIME Fig 1 5 Fig 1 6 Tel 03 9023 0189 Fax 03 9700 0583 5 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 1 CONT Contrast Set After entering SET press CONT then press INC to increase the contrast and press DEC to decrease the contrast as Fig 1 7 shows Welcome to ST880 Welcome to ST880 2007 01 01 12 30 35 2007 01 01 12 30 35 Fig 1 7 Fig 1 8 2 TIME Set After entering SET press TIME then choose SET on the right choose the time you want to set then press INC or DEC to adjust the time As Fig 1 8 shows After all these are done the ST880 will save the setting and memorize it the operator doesn t need to set it again The detailed setting and operation will be introduced later in this manual Tel 03 9023 0189 Fax 03 9700 0583 0 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 1 6 The Procedures for Detection 1 6 1 The judgment of the fault Based on the 51880 the telecom cable faults can be categor
13. ection 2 5 1 Test Lead plug the test lead to SIGNAL Tel 03 9023 0189 Fax 03 9700 0583 19 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 5 2 BALANCE mode connection pair fault use red clips of BALANCE test lead to clip the two conductors of the pair as Fig 2 14 shows For Earthing fault clip the earthing conductor and ground as Fig 2 15 shows 0000 k ik RUN m 1 lt Cau g c amp qo N _ _ _ 5 Differential Method connection the red clips of BALANCE test lead clamps the faulty pair the black clips of DIFFERENTIAL test lead clamps the healthy pair as Fig 2 16 shows AA Balance clips L L A Faulty Pair lt 49 l Diff Ss a RE Lr Can n Ees X Healthy pair 20 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 6 Automatic Test We can use Automatic Test first if the fault is complicated and gives no satisfactory result we can use Manual Test Press TEST button for more than 2 seconds it will enter into Automatic Test and gives fault waveform it 1s as Fig 2 17 shows 500M V 201 50 GAIN15 FUN RANG VOP ZOOM FILE Fig 2 17 2 7 Manual Test If the fault or cable condition is complicated then
14. eforms Tel 03 9023 0189 Fax 03 9700 0583 24 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 9 4 Lock the saved waveform if the operator wants to save one an PAGE waveform to avoid being deleted you can press PAGE GQ to the file you want to lock press LOCK you can lock it If you want to unlock it press LOCK again at the waveform to unlock it 2 9 5 Use USB disk for data transfer plug an USB disk to USB port press U DISK under FILE menu all saved waveforms will be displayed as list as Fig 2 22 shows press ENTER to select the highlighted waveform then there will have m appear it shows that the current 1s selected Then press FE T SEL SEL or ez to select the waveform you want to transfer or press S ALL to select all waveforms or press S ALL again to cancel the selection After you select what you want to transfer then press COPY to copy them to the USB disk Press EXIT to quit this operation iC 4 Cn 4 Co du 4 e 4 4 CI PO 4 4 C x xt r b br b ss S S r r QU BDS BB QDQU Q B SBS B S 00 Bus bi cd 4 amp ll li d cn cn 4
15. egmented If it diplay as Cable Length 0000m the underlined number is blinking take 1580m as example press it will be Cable Length 1000m then press to the second number press MX five times it will be 1500m then press and press ADJ eight times now Cable Length 1580m After input the number press CAL to calculate the result vvill be displayed as Fig 3 13 shows isolation 2 5 M Loop resistance 1500 Ohm Fault distance Cable length 60 0 Cahle Length 1580 11 Fault distance 048 I Please wait Fig 3 13 3 6 3 Input method for segmented cable Under some condition the cable detected consists of different diameter lines then we need have different cable length method or the result will be not correct 33 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Press SEG there will have a table display on the LCD as Fig 14 shows The sequence is from far to near for the segmentation if there is only two the 3 part should all be 0 isolation 2 5 M Loop resistance 1500 Ohm Fig 3 14 ali a ADJ u Use ADJ and P to input the number if it need to enter next p column just use SPACE After inputing all numbers press CAL to get the result Press SEG Again it will quit this segment input Tel 03 9023 0189 Fax 03 9700 0583 34 E in
16. fo telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Chapter 4 Data Analysis Software All the test result data can be transferred to the PC through the USB port the help pls see it on the management software on line help Chapter 5 Power The instrument adopts rechargeable Li battery when the battery 1con in the screen shines and meanwhile the tester sends out sound it means that the tester low battery The tester adopts intelligent charge management when charge the tester the charge indicator always shines It will last for five hours when charge the tester Please notice that don t use other chargers When charge the tester users can t use the tester When connect with the charger in start state the tester will shut off automatically and when charge the tester users start the tester the charge will stops automatically Chapter 6 Troubleshooting 6 1 Failure to Turn on the Power Treatment please recharge 6 2 Sudden dead or mess display Treatment because of strong interference power off and then power on For the other complex troubles do not open the 51880 to try to settle that yourself instead of calling the sales service 5 3 Contact Please contact us as soon as possible if there is any problem about ST880 including this manual Tel 03 9023 0189 Fax 03 9700 0583 35 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Telecom Tes
17. ized to the following kinds 1 Open Circuit one conductor or a few conductors are broken the communication is impossible For this kind of cable fault we can use TDR method Pulse Reflection for location 2 Low resistance cross fault for this type of fault it can be categorized into three type conductor earthing one pair cross and different pairs Under this condition the 1solation impedance will drop tremendously to very low level maybe a few hundred or thousand This will influence the communication or sometimes impossible For this kind of fault we can use TDR method to detect the faults If the waveform 1s difficult to judge we can also use BRIDGE method to detect 3 Poor Isolation the isolation material of the conductors of the cable is facing water or humidity this will lower the isolation resistance and makes poor communication quality maybe impossible For this kind of fault it 1s similar to 2 fault but with higher fault resistance a few thousand Ohm to 30M Ohm this kind of fault 1s not very serious We can not use TDR method to detect but BRIDGE method After the cable faults we should use MegaOhm meter mutimeter to tell the fault type and fault degree so that we can choose proper detecting method We should also consider the following conditions like the time range the environment the weather condition and any other factors Only this way we can roughly judge the fault type and what method we can use
18. let Method Fig 2 3 shows the waveforms with and without using Wavelet Method The solid line is waveform after using Wavelet Technology while dash line is using conventional TDR technology We can see from the comparison that the fault waveform 1s much obvious for Wavelet than TDR 500 250 m Amplitude 200 400 B 900 1000 Lenqthim 8 Fig 2 3 Waveform comparison TDR and Wavelet Methods Working Method for Wavelet Test Start under FUNC menu press W let button to enter the wavelet test method There will have TAY display after entering this method on the right upper location of LCD Stop to quit the Wavelet method has three ways first one is to press W let button again second method 1s to choose the range except 4Km and Km under RANG menu the third one is to press TEST button for a while it will convert to Automatic Test then it quits the Wavelet method After quitting this 14 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator method this MAY will disappear Application it is only used for the long distance gt 2Km detection when we choose this method the default range 1s at 8Km If the operator wants to set the range at 4Km you can just do it Operation this method can only support manual test Under Wavelet method p press TEST button to the detection We can press GAIN o lt button t
19. m au ST880 Cable Fault Locator 3 3 Multimeter function Bridge test can also have 100V Megaohm and Ohm meter function it can be used to test isolation resistance and loop resistance 3 3 1 MegaOhm Meter function Any red and black one of the test lead can be used for this function For example the user wants to test the insulation resistance between one conductor to ground the RED 1 connect the conductor the black one connects with the ground as Fig 3 5 shows Press TEST the screen will display the test result in a short while Assume the insulation resistance is 1 2 MQ red crocodile chip clamp red guide line and displays Red 1 Black 1 2M Red 2 Black No loop If use RED 2 and Black clip it will display Red 1 Black oo Red 2 Black 1 2M No loop J N o S RED 1 LIL L L nr i CE K em n don t use Black Coon amp bU Fig 3 5 MegaOhm Meter Connection Fig 3 6 Ohm Meter Connection 28 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au m s Black x dontuse ST880 Cable Fault Locator 3 3 20 Ohm Meter Function RED 1 and RED 2 test lead can be used to have Ohm Meter function the connection is as Fig 3 6 shows 3 4 Connection Method for Bridge method We will the poor isolation for line to earth 3 4 1 Determine the faul
20. o adjust the Gain for suitable waveform But Gain should not be too big 2 4 TDR method Press E key to power on ST880 the first show is welcome interface and the current time at this time can be adjusted adjustment methods please see this chapter I 5 Setting then enter into TDR test method It is as Fig 2 4 shows COMP 6 8 9 SOOM V 201 50 GAIN15 mmo 500M V 201 50 GAIN15 575 RANG VOP ZOOM Mei C Mode Fig 2 4 Fig 2 5 In Fig 2 4 1 15 solid cursor 2 is waveform 3 1s dash cursor 4 is the distance 15 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator between the solid cursor and dash cursor 5 1s the battery indicator 6 1s the current test range 7 15 the current VOP 8 15 the current display rate 9 is the current gain In Fig 2 5 A Menu area is all menus for the ST880 B Menu area is all menus highlighted menu in A Menu area C Mode 15 the testing mode now in use Balance Differential or Bridge Mode Conversion Press Mode button it will display as Fig 2 6 shows Then press BAL Balance Diff Differential or BRID Bridge to choose one method We will introduce the BRIDGE method in Chapter 3 BAL DIFF BRID 500M V 201 50 GAIN15 FUN RANG VOP ZOOM Fig 2 6 Fig 2 7 Here we will introduce the functions for each menu Tel 03 9023 0189 Fax 03 9700 0583 16 E info telecom
21. pletely Tel 03 9023 0189 Fax 03 9700 0583 8 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 1 6 4 Pinpointing of the fault According to the fault distance detected with the reference of the drawing to determine the fault location Maybe sometimes the file is not complete we can estimate the rough location of fault according to the information we gathered Example if there is any joints within the fault distance range we can tell that the fault point 1s at the Joint location Tel 03 9023 0189 Fax 03 9700 0583 9 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Chapter 2 Pulse Reflection TDR Detection TDR method is suitable to detect Open Circuit and Low Resistance Cross Fault 2 1 Working Principle Electrical pulses are transmitted into the cable and a portion of the pulse energy will be reflected back to the instrument from cable discontinuities or faults The fault characteristic impedance Zi will be different from the cable characteristic impedance Zc the reflection coefficient 1s p Zi Zc Zi Zc 1 The reflection pulse voltage 1s Un pU1 Z1 Zc Zi Zc Ui 2 From the equation 1 when the cable has Open Circuit fault Zi oo p 1 then the reflection pulse is positive see Fig 2 1 A While the cable has Short Circuit fault 41 0 p 1 the reflection pulse is negative see Fig 2 1 B Under normal condition the fa
22. t Solutions Melbourne Australia Tel 03 9023 0189 Fax 03 9700 0583 E mail info telecomtest com au Tel 03 9023 0189 Fax 03 9700 0583 36 E info telecomtest com au W http www telecomtest com au
23. t area the two ends are called near end and far end the near end will connect the instrument 342 Tund one line with relatively low resistance from all faulty lines as line under tested open it with any other equipments or lines 3 4 5 Then find one well isolated line as assistant open it with all other equipments of lines at both ends The resistance to ground of healthy line should be much higher faulty line the higher the better 3 4 4 Shorten the healthy line with the faulty line 3 4 5 Plug the test lead into SIGNAL socket RED 1 clip clamps to Healthy Line and RED 2 to faulty line any B clamps to ground The detailed connection is as Fig 3 7 shows Fig 3 7 Connection for Grounding Fault Tel 03 9023 0189 Fax 03 9700 0583 29 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 3 4 6 Cross fault connection is similar to grounding fault but the black clip is different as Fig 3 9 and 3 9 shows Far End Fig 3 9 Cross between Different apair fault Connection 3 4 7 tis really important for the connection please pay attention RED and RED 2 should correspond to the loop at far end Tel 03 9023 0189 Fax 03 9700 0583 30 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 3 5 Bridge Method Test Procedure Be careful with the connection before test Press TEST then it will display Please Wait the instrument will meas
24. test com au W http www telecomtest com au ST880 Cable Fault Locator 2 4 1 FUNC Function For basic control function they are used under Manual Test Press FUNC it will display as Fig 2 7 shows SAVE to memorize the current displayed waveform for comparison use COMP to compare the current waveform with saved one If it is comparison for faulty pair and healthy pair the position with great difference will be the fault point See Fig 2 20 BAL if the range is 250m press BAL to balance automatically this makes the waveform much easier to tell W let press one time to enter into the Wavelet testing method There will have AY displayed as Fig 2 8 shows Press it again it will quit this detection method adyust the gain 500m SkM V 201 20 GAIN 09 FUN RANG VOP ZOOM FIND FILE 500M V 201 50 GAIN15 VOP ZOOM Fig 2 8 Fig 2 9 2 4 2 RANG Range Press RANG there will display 250M 500M 2KM 4KM and 8 at the right part of LCD as Fig 2 9 shows Tel 03 9023 0189 Fax 03 9700 0583 17 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 4 35 VOP velocity of propagation It is used to choose suitable vop according to different cable type the display is as Fig 2 10 shows 201 plastic cable 201 m use 192 Filled Polyethylene cable 192m use 160 Oil Cable 160m use 216 Paper Pulp cable 216m use
25. tomatic test Gain is adjusted automatically while for manual test it is adjusted manually Tel 03 9023 0189 Fax 03 9700 0583 12 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator Balance there is to match impedance to eliminate the effect of transmitting pulse to receiving signal and make the reflection pulse more obvious For automatic test BALANCE 1s adjusted automatically while for manual test it 1s adjusted manually BALANCE amp Differential Methods for Balance method it only connects the faulty conductor pair all points that not match will be displayed from waveform including the faulty point and joints So if the fault is not obvious it 15 difficult to tell the waveform difference of faulty point and joint Then now we can use Differential method to test that 1s connect one good pair and one faulty pair to the instrument then the different point of these two pairs will be displayed it 1s easier to tell the faulty waveform For Differential method it is not necessary to adjust the balance For real fault detection we can use Balance Method first 1f 1t 1s difficult to analyze the waveform we can use Differential Method Tel 03 9023 0189 Fax 03 9700 0583 13 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 3 Wavelet Method Detection Wavelet method is used for long distance fault detection Comparison after using Wave
26. ult is usually poor isolation the absolute value of reflection coefficient is less than 1 Reflection Reflection Pulse iti Tranzmit A Open Circuit Fault VVaveform B Short Circuit Fault VVaveform Fig 2 1 Tel 03 9023 0189 Fax 03 9700 0583 10 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 2 2 Concepts Waveform We can know the cable condition through the waveform displayed using TDR method so it is key factor to understand the waveform if we use TDR method VVaveform for Open Circuit fault is upward while the Short Circuit waveform 15 downward sim A Open Circuit Fault VVaveform B Short Circuit Fault VVaveform Fig 2 2 Fault Distance The start position of reflection waveform is fault location Move the cursor to the pulse waveform start that is the position of there 1s ereat change as Fig 2 2 the dotted line shows the number displayed on the screen 1s the fault distance If the curor is at other location the value displayed has no sense For Automatic Test the instrument can set the fault distance automatically but sometimes it need to correct manually if necessary Test Range For choosing range it is very important we can only detect the cable within the range If the cable we are testing 1s beyond the range we have chosen then the condtion of the beyond part will not display we will know nothing about it So
27. ure the isolation resistance and loop resistance and display the result on the top It is as Fig 3 10 shows Isolation 2 5 M Loop resistance 1500 Ohm Red 1 Black 1 2M Red 2 Black No loop Fault distance Cable length Fault distance Cable length X CableLength 00001 X CableLength 00001 Fault distance Fault distance Please wait Please wait Fig 3 10 Fig 3 11 If the far end is not shortened it will display as Fig 3 11 shows with no loop appear Please check the connection and test again Tel 03 9023 0189 Fax 03 9700 0583 31 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator If the connection is correct we will get the detection result displayed as Fig 3 12 shows This needs around 1 minute Isolation 2 5 M Loop resistance 1500 Ohm Fault distance Cable length 60 0 5 Cable Length 00001 Fault distance Please wait Fig 3 12 3 6 Input the total length to calculate the fault distance 3 6 Know the cable length If you want to get the cable length there are two methods One is to get the drawings and know the cable length Two is use TDR method to have the total length Please be noted that the input method if different for segmented and non segmented cable Tel 03 9023 0189 Fax 03 9700 0583 32 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator 3 6 2 Input method for cable non s
28. we need to use Manual Test 2 7 1 Select Range it should be longer than the total cable length better have 30 more 2 7 2 Adjust VOP with different cable type adjust the vop with reference to the Table 2 2 7 3 Test press TEST once the waveform will be displayed on the LCD Move the cursor to the start point of the reflection pulse the distance value appeared on the upper right location is the fault distance If it 1s hard to 21 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator view the reflection pulse adjust RANGE to redo the test 2 7 4 Gain adjustment if the waveform amplitude is too big or small the T GAIN operator can adjust it with GAIN or under FUNC menu ai i or to increase or decrease the gain the instrument will press G display waveform accordingly 2 7 5 BALANCE if the range is 250m press BAL to balance automatically this makes the waveform much easier to tell 2 7 6 Waveform Memory and Comparison If you are not sure about the fault distance detected just press SAVE under FUNC menu to memorize the waveform then test one healthy pair without any parameter changing then press COMP to compare the two waveforms The point where there is great difference 1s fault point but not joint point It is as Fig 2 18 shows A point is fault point while B point is joint COMP B Joint A Fault
29. when we choose the test range it should longer than the total length of the cable maybe 30 more For example we know the total length of the cable detected is 1500m then we choose 2000m range is correct If the cable length is 950m we can not choose 1000m range 2000m range is better 11 Tel 03 9023 0189 Fax 03 9700 0583 E info telecomtest com au W http www telecomtest com au ST880 Cable Fault Locator VOP velocity of propagation From the above parts we can see that to detect distance is in fact detecting time Pulse velocity times transmitting time is distance so we must know the precise transmitting velocity first The VOP differs from different conductor isolation material and has nothing to do with the conductor diameter For example the VOP of plastic cable 1s 200000K m s or 200m us We have saved some normally used material VOP in the instrument the operator can choose from the list for the VOP see Tab 2 Isolation Material for Cable VOP m s 6 Hh n s _ Tab 2 VOP for Different Isolation Material The same type of cable may have different VOP for it 1s from different manufacturer if we want to know the exact VOP of some cable we should do the calibration please find details from 2 8 for calibration method Gain the gain can adjust the waveform amplitude displayed on LCD it is usually adjusted to the level suitable to view but without distortion For au
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