110kV System Main Transformer Neutral Grounding Study

In the construction of the power grid, it involves many aspects about how to select the neutral grounding mode correctly, which is related to the reliability of the system. The main factors about the selection of neutral grounding mode include the short-circuit current,protection configuration, as well as insulation level, and so on. With the adoption of a small reactance grounding way, it can not only make the overvoltage get decreased to some extent, but also can make the large current generated by direct grounding to have a further decline. As well, it can reduce the frequency of failure occurrence of the neutral grounding because of ground clearance, which improves the safety, reliability and stability of the entire power system and reduces the production cost of the transformer.And it greatly increases the social and economic benefits.In this paper, with the comparison of the advantages and disadvantages of various transformer neutral grounding modes and the corresponding influence it has on power system reliability, zero sequence protection and insulation level, etc, the 110 kV transformer neutral grounding via low reactance was put forward based on the superiority and its practical value. At the same time, the advantages of small reactance grounding was verified by using PSCAD software to build the model, it also calculated the available range of reactor reactance value. Through the researches, it can provide theory basis for the scheme of 110 kv system transformer neutral grounding via reactor as well as lays theoretical basis for transformation of 110 kv substation by neutral grounding via small reactor.