Author: Noyafa–CCTV Tester
What are the methods of cable fault detection? For cable fault detection, it usually needs to go through three main steps: fault type diagnosis, fault point location and accurate determination. The fault type diagnosis is mainly to determine the fault phase of the cable fault point. It is a high-resistance grounding or cable fault detection method. For cable fault detection, it usually needs to go through three main steps of fault type diagnosis, fault point location and precise determination.
Fault type diagnosis is mainly to determine the fault phase of the cable fault point. It is a high-resistance ground or a low-resistance ground, allowing the tester to choose the appropriate detection method. Fault point ranging is also known as pre-location.
Test cables are used for faulty cable core lines or online measurement and analysis of fault information. The distance to fault is initially determined, and the extent of the fault is minimized in order to pinpoint that point. Cable fault detection pre-location methods can generally be divided into two categories, namely classical methods, such as bridging methods; modern methods, such as low-voltage pulse methods, high-voltage flashover methods, etc.
Cable fault detection accurately determines the point based on a predetermined distance and accurately determines the actual location of the fault point. The precise point method mainly includes the acoustic point method, the induction fixed point method, the time difference fixed point method and the synchronous fixed point method. This paper mainly discusses the basic method of fault point pre-location.
For low impedance breakdown, short circuit and open circuit faults, a pulsed signal can be applied to the cable core. The signal is transmitted and reflected on the cable, and the pulse waveform is measured by a digital oscilloscope or a portable virtual oscilloscope to calculate the location of the fault point. The advantage of the low-voltage pulse reflection method is that it is simple and intuitive, does not require detailed cable materials, and can differentiate fault types based on the polarity of the reflected pulse.
Defects cannot be used to detect high impedance and flashover faults. The cable fault detects the echo phenomenon when the characteristic impedance of the transmission line changes, and applies a certain voltage to the cable core so that it will not burn through and generate discharge. The discharge pulses are transmitted and reflected in the cable, and the position ratio of the reflected pulses is measured by a digital oscilloscope to calculate the location of the fault point.
This method is suitable for high resistance breakdown, but the operator's safety is poor, and the waveforms are difficult to distinguish.
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