In the power distribution system, zinc oxide arrester can effectively prevent the power distribution system was struck by lightning.

In the three-phase four-wire power distribution system, when the lightning strikes the high-voltage side, the voltage drop caused by the lightning current flowing through the grounding resistor and the residual voltage of the zinc oxide arrester are added together to act on the transformer windings to easily breakdown the insulation. When the zinc oxide arrester grounding wire and transformer housing connected together and grounded, so that the voltage on the high-voltage winding only zinc oxide arrester sheath residual voltage, but this time has increased the transformer housing potential may occur from Shell to the transformer low-voltage winding reverse flashover. In order to prevent this inverse flashover, the low voltage side of the transformer is also connected with the neutral point in the shell, so that the potential of the low voltage side is also increased accordingly. This zinc oxide arrester sheath grounding lead, the transformer neutral point, the shell together and grounded method, the so-called trinity; lightning protection grounding protection method can effectively prevent equipment damage caused by lightning.

However, when the distribution transformer high-voltage side of the mine, the zinc oxide arrester action, the lightning current flowing through the grounding resistance of the pressure drop in the low-voltage side of the neutral point, the low-voltage side of the outlet at this time is equivalent to the wave through the wire grounding. Therefore, most of the voltage drop is added to the low-voltage winding, but also by the inductive effect, high-voltage winding will appear high voltage ratio, the high-voltage winding voltage limit by the zinc oxide surge arresters, the high voltage distribution along the high-voltage windings, High voltage windings produce the maximum on the neutral point, possibly breaking nearby insulation. At the same time the high voltage along the high voltage winding longitudinal voltage is also very large, it is likely to breakdown high voltage winding layer or turn insulation. Therefore, construction should try to reduce the grounding resistance, transformer maintenance should pay attention to improve the high-voltage winding neutral point insulation level. In addition, when the low-voltage side of the mine, the low voltage insulation margin than the high pressure, according to the ratio of high-pressure side of the fold, it is possible to first high-voltage side insulation breakdown, but also low voltage electrical insulation breakdown, Animal casualties. Therefore, according to this situation, low voltage surge arresters should also be installed on the low voltage side of the transformer.


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