The damage of the transmission cable by external force, dampness, aging insulation, etc. will cause the line transmission failure, which will seriously affect the normal production and service life. In order to troubleshoot, you must quickly find the point of failure. Therefore, a cable fault tester is needed. Many people I don’t know how the equipment works. This article will introduce you to the working principle of the equipment.
1. The principle of the DC fault test method of the cable fault tester: The direct flashover method is suitable for measuring high-resistance flashover faults. In the actual test, the operation method and wiring diagram are basically the same as the flash method (no ball gap). The direct flash method can also be divided into voltage sampling method and current sampling method. We recommend using current sampling. When the DC high voltage acts on a certain value of the fault phase, the fault point is decomposed and short-circuited. At this time, the reverse direction is generated from the fault point. Convert voltage V10. The voltage propagates along the cable. When the fault is transmitted to the starting end, the impedance of the starting end is greater than the characteristic impedance of the cable, so the reflection is 2v10. This voltage continues to propagate backwards and short-circuit after the fault point. Therefore, the reflected voltage is -2v1. After the negative reflection voltage, it is transmitted to the beginning, so it goes back and forth several times, until the flashover discharges over and over again.
2. The principle of the cable fault tester affects the high-voltage flash test method: the flash method is suitable for the detection of high-resistance leakage faults. The flash test can also be used for other types of high resistance and low resistance faults. The test method is the same as the direct flash method. The difference is that the cable does not apply DC high voltage, but applies a surge voltage through the ball gap to make the fault click and discharge, and the reflected voltage (or current), the instrument records the transient state, and the waveform analysis is used to determine the location of the fault point. The main method of measuring high impedance and flashover faults. The same sampling method is divided into voltage sampling and current sampling. Of course, the subdivision can be divided into high-end and low-end voltage sampling, inductance and resistance sampling, start-up and terminal sampling. The current sampling wiring is simple, reliable, and easy to identify, so the current sampling method is recommended.
3. The principle of the low-voltage pulse test method of the cable fault tester: The present invention has the characteristics of simple operation, easy waveform recognition, and high accuracy. For short-circuit, low-resistance and disconnection faults, the method can directly determine the fault distance, even if there is no such thing. In case of failure, the low-voltage pulse method can also be used to measure the total length or speed of the cable before the high-voltage flashover test. Compared with the flashover test waveform, the waveform analysis is usually convenient and quick to determine the fault point.
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