Before using the low-voltage cable fault distance finder to determine the fault point of the cable, the tester must understand the structure of the cable and the insulation material of the cable, and determine the insulation condition of the cable line and fault properties, so as to select the appropriate measurement method according to different fault properties, and quickly and accurately determine the distance of the fault point. Otherwise, many unexpected problems will be encountered during the practice test, which will bring difficulties to the practice test work. First of all, use a megohmmeter or a multimeter to measure the insulation resistance between each phase and each phase at one end of the cable. If the measured insulation resistance is high, the continuity test of the conductor should be performed, that is, connect the cable at one end of the cable. The three-phase conductor is short-circuited and grounded, and the measurement is repeated at the other end to determine whether the conductor is blown.
According to the experimental results, the general fault properties can be divided into the following categories: 1. The insulation resistance of one core or several cores of the low-resistance fault or short-circuit fault cable to ground or the insulation resistance between cores is lower than 200W. Generally, there are single-phase grounding, two-phase short-circuit and grounding, and three-phase short-circuit and grounding. Such faults are measured by low-voltage pulse method. 2. The broken wire fault cable has one core or several core conductors that are not connected, and sometimes it is accompanied by the phenomenon of grounding through resistance.
Such faults can be tested by the low-voltage pulse method. 3. The insulation resistance of one core or several cores to the ground of the flashover faulty cable may be relatively high, but when the DC voltage is applied to the cable to a certain value, a sudden breakdown occurs. Most of these faults are found in preventive experiments, and the fault is measured by the direct flash method in the pulsed current method.
4. The insulation resistance of one core or several cores of the high-resistance fault cable to ground may be lower than the normal value but higher than 200W between the cores. In this case, the fault resistance is not very high, and the DC voltage cannot be applied. Pulse current should be used. Shock flashover measurement in working methods. The use of low-voltage cable fault distance meters Low-voltage distance meters Shenzhen Noyafa Electronic Technology Co., Ltd.
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