The improvement of the cable fault test technology should adopt different methods for different types of faults. It is also necessary to constantly introduce new technologies and new equipment. At the same time, we must also explore new equipment and develop new functions. Such as the use of audio signals sent to the cable, the test technology at the fault point to receive the signal, and the use of T16/910 cable fault tester SDC series of high-fidelity cable fault flash detector accurate location of the fault. These devices can control their measurement error within a few tens of centimeters, find the fault point directly for processing, and improve the efficiency of fault detection.
Fault test method
The equipments used in the past include cable detectors, flash detectors, cable pathmeters, and fixed-point fault detectors. The most popular test method at present is the flash test method, which includes flash flash and direct flash, the most commonly used flash method. Flash flash test has high precision, simple operation, safety and reliability. Its equipment is mainly composed of two parts, namely high voltage generator and current pulse meter. The high voltage generating device is used to generate DC high voltage or high voltage, which is applied to the faulty cable to force the fault point to discharge and generate a reflected signal. The current pulse meter is used to pick up the reflected signal to measure the fault distance or directly measure the open circuit, short circuit or low resistance fault with the low voltage pulse.
The following briefly describes the test method based on the fault point resistance:
(1) When the resistance of the fault point is equal to infinity, it is easy to find the fault of open circuit by measuring with low-voltage pulse method. Generally speaking, the pure open fault is not common, usually the fault is a relatively high-impedance earth fault or phase-to-phase fault, and it is relatively or phase-to-phase. Low resistance faults coexist.
(2) When the fault point resistance is equal to zero, it is easy to find the short circuit fault by the low-voltage pulse method, but it is rarely encountered in actual work.
(3) When the fault point resistance is greater than zero and less than 100 kilohms, it is easy to find a low-impedance fault by low-voltage pulse method measurement.
(4) The flashover fault can be measured by the direct flash method. This fault is generally present inside the connector. The fault point resistance is greater than 100 kilohms, but the value changes greatly and each measurement is indeterminate.
(5) The high-impedance fault can be measured by the flashover method. The fault point resistance is greater than 100 kilohms and the value is determined. Generally, when the test current is greater than 15 mA, the test waveforms are repetitive and can overlap. When a waveform has one emission and three reflections and the pulse amplitude gradually weakens, the measured distance is the distance from the fault point to the cable test end; otherwise The distance from the point of failure to the end of the cable test.
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