Author: Noyafa–CCTV Tester
Let's find out the mechanism and cause of cable failure. The mechanism of occurrence of electrical breakdown: electrical breakdown is when the voltage is high and the electric field strength is large enough, there are a few free electrons in the medium will be sent out under the effect of the electric field. Let's find out the mechanism and cause of the cable failure. mechanism and reasons. The mechanism of occurrence of electrical breakdown: electrical breakdown is that when the voltage is high and the electric field strength is large enough, a few free electrons in the medium will collide and dissociate under the effect of the electric field, and the free electrons collide with neutral molecules, which encourages dissociation And generate new electrons and positive ions.
These electrons and positive ions collide with other neutral molecules after obtaining electric field energy. This process continues to develop, making the electron flow in the medium."avalanche"If it is aggravated, it will cause the breakdown of the insulating medium, and the conductive channel will be formed, and the fault point is instantly short-circuited by the strong electron flow. In the cable fault test, the use of DC high voltage or impulse high voltage makes the cable fault click through. The effect time is very short, the principle of this method is attributed to electrical breakdown, thermal breakdown: thermal breakdown is the temperature of the insulating medium due to the heat generated by the dielectric loss of the cable insulating medium under the effect of the electric field. If the heat is greater than the heat radiated to the surrounding area, the temperature will continue to rise, and as the temperature continues to rise, the insulating medium will be scorched, cracked or partially fused, which will eventually lead to breakdown.
The effect of thermal breakdown lasts for a long time. It usually occurs during the operation of the cable. The root cause of the failure is external force damage, the quality of accessories is not up to standard, the quality of laying construction, and the third of the cable body. The basic process of cable fault test, fault diagnosis: the diagnosis process of fault type is the process of starting to understand and analyze the fault status of the cable.
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