10kV system power plant adopts small current grounding system with arc suppression coil grounding, and there are many external power supply lines. Because of the insulation of insulators, cables and other reasons, 10kV single-phase grounding operation is often caused. Although it does not affect the electrical equipment, this kind of fault causes phase voltage rise, which poses a great threat to the insulation performance of the system, and often causes the expansion of the accident, resulting in two-phase short circuit Circuit or three-phase short circuit, affecting production.

Without small current grounding line selection, when single-phase grounding fault occurs, it is impossible to quickly confirm which line the fault line occurs on, which poses a threat to the production. It takes a long time and difficult to find the grounding fault line by power cut and transmission switching, and affects the production. Therefore, when single-phase grounding occurs in the system, in order not to affect the safe power supply of the whole system, we should quickly and accurately find the fault line, cut off the fault line, and avoid the occurrence of accidents, so it is very necessary to install the small current grounding line selection device.

Manager Wang of the power plant purchased the small current grounding line selection device from our company, which was installed on the control panel of the main control room after consideration, and monitored the 10kV system circuit and 10kV distribution cabinet circuit of the gas boiler at the same time. After a period of trial operation, there are three grounding items, one of which is instantaneous grounding, and the accuracy of selection cannot be judged. By analyzing the fault data and waveforms recorded in the fault recording graph, and according to the current imbalance, all zero sequence current transformers are checked. It is found that the models of zero sequence current transformers on site are inconsistent and the transformation ratio is different, which easily leads to the misselection and misselection of small current grounding line selection device. In order to solve the problem, the person in charge of the site plans to replace all zero sequence current transformers with the same type of zero sequence current transformers of our company.