On the field test methods and precautions of cable fault tester

Nowadays, in the domestic cable fault test equipment market, there are a wide variety of types of instruments and instruments. In addition to our common cable fault testers, there have been a series of buried cable fault testers, street light cable fault testers, and low-voltage cables. Detector, cable ground fault tester, mine cable fault tester, etc.
On-site cable fault test method
1, the basic steps of high-voltage cable fault testing The basic steps of cable fault testing: In general, according to the following steps to test:
1) Find out the cause of the fault and the basic condition of the cable, such as whether the fault is caused by the operation or the pre-test. Is it a new cable or a long running cable? The approximate length of the cable? Is there any connector in the middle of the cable? There have been failures, whether the cable is buried directly or in cable trenches, cable types, etc.
2) It must be clear that both ends of the cable must be disconnected from other lines to ensure that the cable is not charged and the environment surrounding the cable is in a safe state.
3) The tester must pay attention to, each time before connecting with the cable, connect the phase wire of the cable to the ground with a short-circuiting wire. When the power is switched on, one end of the short-circuit wire must be grounded first, and the other end should be connected to each phase of the cable. *Electricity. For other electrical appliances, such as capacitors, test transformers, etc., before wiring and removing the connection cable, it is also necessary to pay attention to the first power and then the wiring. In short, to form operating habits, not afraid of trouble, before each operation, first pay attention to whether the operation of electrical appliances and the circuit connection, first put * electric operation.
4) When testing, first use the low-voltage pulse function of the flash tester to perform full-length test on each phase of the cable to see if the test waveforms are the same when using the three-phase armored test. For most high-impedance faults, the test waveforms for each phase are the same. For low-impedance faults and high-impedance faults with open-phase faults, the fault phase test waveform does not match the full length of the test cable, so that the fault distance can be directly measured with low-voltage pulses.
5) When using the high-voltage flashover test, whether the cable fault is a high-impedance fault or a low-impedance fault, the high-voltage flashover method can be used for testing. For low-resistance or disconnection faults that can directly measure the fault distance with low-voltage pulses, high-voltage flashovers are usually used for verification tests and precise determination of fault points.
During the high-voltage flashover test, it should be noted that no matter whether the cable is single-phase fault or multi-phase fault, when testing one fault phase, other cable phase lines should be short-circuited with the cable armor to reduce the interference of other cables and improve Test accuracy.
6) After the high-voltage flashover test is completed and the fault distance is determined, fault fine point determination can be performed. When the sound-magnetic synchronous fixed point instrument is used, fault fixed point and path detection work can be performed synchronously.
2. Precautions during the test process Fault test safety issues are divided into tester safety and equipment safety. The safety of testers should pay attention to the grounding and discharge of the instrument, and the safety of the equipment is mainly the correct wiring. In addition to operating according to the instructions, pay attention to understanding the following points:
1) "One-point grounding" and "Multi-point grounding separately": when the flashmeter is tested by high-voltage flashover, the high-voltage loop is required to be grounded, ie, the high-voltage test transformer and the grounding terminal of the capacitor are directly connected to the cable armor (the armoring must be grounded. ), use the shortest line to directly connect the equipment, do not connect too long, this is mainly to ensure that the test waveform standards, easy to analyze. For instruments such as the operation box and the flash detector that we have to operate directly, the protective grounding wire can be connected to the ground separately. Generally, it should not be connected with the high-voltage grounding wire. This ensures that if the high-voltage grounding wire is not connected properly, Operators' safety.
2) Safe discharge and discharge of electricity: When the high-voltage flashover test is performed, the high voltage of the high-voltage pulse capacitor and the test cable is mainly used. Use a special resistance band to put * electric charge. The use of a grounded insulating rod to directly discharge the power, and the inrush current is too large, will affect the service life of the high-voltage pulse capacitor.
3) DC power supply: Use a flash detector with a DC power supply function. Try to use a DC power supply for high-voltage testing when testing. This prevents high-voltage surge currents from hitting the flicker meter through the AC power cable.

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