How to detect faults in a DC grounding system with a clamp-on ammeter
Transformer, substation, distribution room DC bus system grounding if there is a problem, detection or search is very troublesome work. Usually staff use a multimeter to find the segments, not only affects the efficiency of work and find also unsafe. Need to DC line, a section of a section of the measurement, so that part of the high-voltage equipment out of protection, a serious impact on the problem.
Without affecting the work of the DC system, online to find the DC bus fault grounding method. Substation DC system grounding line mainly using low-frequency signal injection method, DC leakage current detection method and pull method. The injection method is easily affected by the distributed capacitance; pulling method can not be the existence of parasitic circuit grounding branch line; DC leakage current detection method needs to be installed in the branch DC leakage current sensor, subject to the device cost constraints, the sensor sensitivity can not be guaranteed, the sensitivity of the line is limited.
All three methods can not ensure that the selection of the correct line. Therefore, the DC leakage current detection method is slightly improved, the leakage current measurement is changed to a high-precision DC clamp-on ammeter. DC clamp leakage current meter test substation DC system positive or negative conductor grounding, the grounding leakage current is the largest; when the grounding resistance is larger, the leakage current is smaller, may be less than 1mA. so, direct measurement of grounding leakage current clamp ammeter must meet: 1, can be measured clamped into the core (single-core or multi-core), 2, can test the resolution to be very small (microampere clamp ammeter), 3, high precision. Small error
The positive and negative lines of the DC line together with the clamp that measure DC leakage. The AC fire line zero line clamped together to measure the AC leakage. Clamp the ground line to measure the leakage current of the grounding line. Clamp the main line to measure the current of the main line.
