The cable laying area is wide and the environment is often complex. When a fault occurs, the difficulty of maintenance will be greatly enhanced. Without cable fault detectors, power workers tend to spend longer on cable repairs. Then, cable fault detection The cable laying area is wide and the environment is often complicated. When a fault occurs, the difficulty of maintenance will be greatly enhanced.
Without cable fault detectors, power workers tend to spend longer on cable repairs. So, what faults can the cable fault detector generally detect? Today, the editor's article mainly explains the problem in this regard. 1. Low resistance fault The cable insulation material is damaged and a ground fault occurs.
Use a megohmmeter on site to measure the insulation resistance Rf less than 10Z0 (Z0 is the wave impedance of the cable, generally 10 to 40Ωbetween). On-site low-voltage power cables and control cables have a high probability of low-resistance faults. 2. Open circuit fault The continuity of the metal part of the cable is damaged, resulting in disconnection, and the insulating material at the fault point is also damaged to varying degrees.
The insulation resistance Rf measured with a megohmmeter on site is infinite (∞), but during the DC withstand voltage test, there will be electrical breakdown; check the continuity of the core wire, there is a breakpoint. The scene generally occurs in the form of one-phase or two-phase disconnection and grounding. Cable fault detector can solve this problem.
3. High resistance fault The cable insulation material is damaged and a ground fault occurs. The insulation resistance Rf is more than 10Z0 measured with a megohmmeter on site, and electrical breakdown will occur during the DC high voltage pulse test. High-resistance faults are cable faults with high probability of high-voltage power cables (6KV or 10KV power cables), which can account for more than 80% of the total faults.
4. Flashover fault The insulation material of the cable is damaged and flashover fault occurs. The insulation resistance Rf measured with a megohmmeter on site is infinite (∞), but in the DC withstand voltage or high voltage pulse test, there will be flashover electrical breakdown. Flashover failures are difficult to detect, especially when newly laid cables are subjected to preventive tests and flashover failures occur.
The field generally uses the DC flashover method for detection. 5. Breakdown fault In actual work, the cable insulation damage event triggered by the preventive test is habitually called cable breakdown. Such faults all occur under the DC test voltage, and the insulation damage is electrical breakdown, the grounding point is generally intact with lead wrap or copper skin, and there is no obvious external deformation (except mechanical trauma).
The cable breakdown faults are mostly simple ground faults, the ground faults are relatively high, the fault point is dissected, and the insulating material has no carbonization point, but the aging structure of carbon holes and water branches can be found through the instrument. 6. Operation failure It refers to the fact that the power system of the factory is in operation, the cable feeder of the cable feeder, the motor, and the cable lead of the transformer, the voltage fluctuation of the high-voltage secondary circuit or the grounding signal is found (the grounding trip of the power component with grounding protection occurs). A cable failure determined by the possibility of failure of other power components. The characteristic of this type of failure is that it is not clear.
The extreme form of cable operation failure is cable blasting (such as phase-to-phase short circuit caused by two-point grounding); another part of the operation fault develops into cable breakdown fault (such as cable aging, insulation defect) due to the failure of withstand voltage during the stop point inspection. Wait). If you don't know which faults can be detected by the cable fault detector? You may wish to read the above-mentioned content carefully, and you will have the answer you want.
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