The insulation level is the level that the transformer can withstand various overvoltages and long-term maximum operating voltage during operation, and is the withstand voltage level that cooperates with the protective arrester. It depends on the maximum voltage Um of the equipment.
According to the transformer winding end and neutral insulation level is the same can be divided into two kinds of insulation structure that is full insulation and sub-insulation. The winding end and the neutral point of the insulation level is the same can be divided into the same level of insulation is called full insulation; winding insulation level is lower than the wire end level is relatively low, can simplify the insulation structure, save material, Thus reducing the size of the host and manufacturing costs. But the grade insulation transformer only allows the use of 110KV and above neutral grounding system.
220KV and below the voltage level of insulation mainly by the frequency withstand voltage and lightning withstand voltage decision. For more than 220KV transformer in addition to frequency voltage and lightning withstand voltage, but also need to increase the operational impact withstand voltage, it is because the high voltage transformer insulation level is already very high, under the existing lightning protection measures, the atmosphere over The voltage is generally not as dangerous as operating over voltage. Because the insulation level is mainly determined by the operating voltage.
