Before determining the cable fault, the tester must first determine the nature of the cable fault, in addition to mastering the performance and operating methods of the machine, in order to adopt appropriate working methods and test methods.
First, use a megohm or multimeter to measure the insulation resistance between each opposite ground and phases at one end of the cable. According to the resistance value, determine whether it is a low-resistance short circuit or a disconnected open circuit, or a high-resistance flashover fault.
1. When the resistance is lower than 100 ohms, it is a low-resistance fault, 0 to tens of ohms is a short-circuit fault, and the resistance is extremely high to infinitely large as an open circuit or disconnection fault. Whether the wire is broken, you can also connect the cable terminal to a universal meter to measure the resistance of the two phases that are short-circuited at the beginning to confirm. This type of fault can be directly measured by the low-pulse method.
2. When the resistance is very high (hundreds of megabytes and gigabytes) and there is instantaneous discharge during high-voltage tests, such failures are generally called flashover failures, which can be determined by the DC high-voltage flash test method.
3. High resistance fault: The resistance value is higher than the low resistance fault, and it is determined by the DC high voltage flash test method during the high voltage test.
4. Determine the points after rough testing in a certain way. If necessary, find the cable path and measure the cable length or distance.
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