Underground Wire Fault Locator

HM-6050 underground wire fault locator is networking cable fault test platform based on embedded computer platform. It is integrated USB communication technology, touch-screen technology and 3G communication technology,which greatly improved the performance of the instrument in practice and is simple to operate.

This cable fault locator provides you a specified cable management software to reduce your workload. The Underground Wire Fault Locator is composed four parts: a host computer system ,path tracer, cable fault locator and HV power supply .

Application

This Underground Wire Fault Locator is used for testing the faults of buried cable fast and precisely, meanwhile, it can be used for detecting the buried path and depth of a cable.

Main features：

1）Adopt special structure sounding-wave vibration transducer and low noise exclusive part as a previa amplification device to boost the sensitivity of the location and path-seeking greatly.

2）For overhead cable, only by connecting the transducer probe of our device to the fault cable or adjacent cable, the distance and the direction of the fault spot can be located easily and precisely.

3）Power frequency adaptive cancellation theory and hi-Q power frequency trapped wave technology increase the restrain and anti-interference ability to 50Hz power frequency signal in strong electric field, also narrowed the blind area. In instrumental function, adopts scoustoelectric synchro-receive and display technology, to get rid of the disturbing of the local noise effectively.

4）Easy to operate, you just need to turn on/off the power to test and don’t have to change channel or select function. Meanwhile, this powerful device is compose of modules and have compact structure and small in size, be convenient for carry.

Please follow procedures below to resolve cable fault quickly:

1. Analyze nature of cable fault and cable type.

Different cable type is tested by different method, different cable medium has different testing velocity, different cable has different voltage-resistant level. You need to know these information before test.

2.Test cable full length by and proofread wave velocity by LV impulse method.

Test full length of cable can help us to understａnd cable fault clearly and judge nature of cable fault (high impedance fault or low impedance fault). Meantime we can calculate wave velocity to make accurate test.

3. Choose proper test method, make rough test by cable fault locate host.

Different test method is for different cable fault. Low impedance fault (open-circuit or short circuit) is tested by LV impulse method, high impedance fault (leakage or flash-over) is tested by multiple pulse method or impulse HV flash-over method. Choose proper method test cable full length and fault approximate position.

Remark: Zo is characteristic impedance value. For electric cable it is usually between 10—40.

Low voltage flash-over method is simple, can be tested directly . You should pay attention to the wire connection and the DC high voltage added when you use high voltage flash-over method. The maximum voltage withstanding for oil paper cable and crosslinked polyethylene cable is 50KV and 35 KV, generally, you can not exceed these levels. The ground wire of high voltage device should be connected with the lead sheathing of the cable tested.

4.Test the path of cable by cable tracing tester

You must know cable route before precisely locating cable fault.

5. Locating fault point precisely by cable fault locator.

Connect HV device according to fixing point discharge mode and increase voltage according to cable characteristic and voltage resistance level. Locating cable fault position in a range of 1m.

Introduction of test method

1.Test theory

According to TDR theory, this device will send a series of electric impulse to tested cable, then receive reflection impulse due to impedance variation. We can according to electric wave transmitting velocity in cable and time duration of two reflection impulse inflection point to calculate the distance from test initial terminal to fault position by S=VT/2.

S represents distance from test initial terminal to fault position,

V represents electric wave transmitting velocity in cable,

T represents required time duration wave propagate in cable.

This system can test cable by 4 methods: Low voltage pulse method, multiple impulse method, , DC HV flash-over method and impulse HV flash-over method method.

2. Low voltage pulse method

Low voltage pulse method is used to test wave transmitting velocity in cable, cable full length, low-impedance(fault phase impedance is less than 1K) and open circuit fault,short circuit fault.

when testing faults, the cable can be considered as a evenly distributed transmission line. In according to transmission line theory, exert a impulse voltage in one end of the cable, this impulse will transmit through the cable in a certain speed( this speed is depends on the dielectric constant and the magnetic conductivity). In the fault-position or when the resistance is unevenly, the impulse will be reflected. Write down the transmission time span △T, △T times the transmission speed V, the position of the faults can be work out.

Lx = V· △T /2

Lx refers to the distance from beginning end to the fault point.

Measure the length of the cable：L＝V·T/2

Measure the impulse transmit speed：V＝2L / T

Add LV impulse to fault phase, the impulse will transmit to impedance mismatch point, like middle connector, T connector, short circuit point or terminal. These point will reflect impulse and it will be received by tester.

If transmission pulse is in same phase with reflecting pulse, the fault is open circuit fault or terminal open circuit fault. If in opposite phase, the fault is short circuit or low impedance fault.

If insulation resistance of fault point is lower than characteristic impedance even zero electric resistance, the fault is called low resistance fault or short circuit fault.

If insulation resistance is infinite or in normal but voltage can not reach to user end, the fault is called open circuit fault.

Connect fault phase and ground wire to input terminal of tester( another end of input wire connect to aviation plug), connect USB interface of test system to computer USB interface.

●Test velocity (low resistance fault, open circuit fault and short circuit fault)

For some cable, the wave transmission speed is unknown, we can test it if we know the full length of the cable.

Select “fault test"ａnd “TDR" in “work mode"menu. Input cable full length then press “Test" button, then press “Sample" button. Adjust “range"button according to waveform and baseline to get clear waveform.

If no waveform display or reflecting waveform is too small, please fine-tune input amplitude to re-sample.

If instrument crashes while sampling, indicate Error, press reset key to restore.

●Test fault(low resistance fault, open circuit fault and short circuit fault)

When you test cable fault, first select “TDR"in work mode menu, then select corresponding sample frequency and impulse velocity according to cable full length, then press “sample"button. Open circuit waveform or short circuit waveform will be displayed on screen(Shown as fig.above). Select one waveform from tn-pulse waveform and it will be displayed in “manual waveform area", locating fault position by cursor and you will get test result.

Unpacking inspection

Before unpacking for the first time, please follow the steps below for unpacking inspection.

1) After unpacking the paper, take out the backpack and the document bag, look up the manual and packing list,

2) Check the packing list to check whether all the accessories in the backpack are complete and intact.

3) Check whether the factory number of the packing box and the nameplate of the instrument and the warranty card are consistent

4) Power-on inspection, click the button according to the menu to confirm that the button function is intact, press the backlight, the LCD screen backlight is turned on, rotate the cursor knob, and the cursor on the screen moves accordingly to confirm whether the host function is intact.

Maintenance

When the malfunction of the instrument cannot be easily eliminated, you should not disassemble the machine for maintenance, please contact our company and we will serve you wholeheartedly. If the user disassembles the machine privately, the warranty is not provided.

Transportation and Storage

Transportation considerations

The instrument has been subjected to corresponding temperature test, humidity test, vibration test, impact test and other tests in accordance with group II specified in GB6587.1. However, please handle with care during transportation, protect from sun and moisture, and avoid severe impact.

Storage conditions, storage period and precautions

In order to facilitate the maintenance and use of the instrument, please pay attention to the following environmental requirements.

1. Storage temperature: -40℃～+50 ℃

2. Relative humidity: 40℃ (20～90) %RH

3. Atmospheric pressure: (86～106) kPa

When the instrument is not in use, the instrument should be stored indoors under the original packaging conditions, and not exposed to the sun or rain. The room should be ventilated and dry, and should not contain any gas to cause corrosion. There should be no severe mechanical vibration and shock around the instrument, and no strong electromagnetic field.