Research on the insulation reliability for the lead exit of 1000kV transformer

The construction features of self-made UHV lead exit in China are analyzed, and the test scheme and test items are determined. The insulation reliability test instrument was designed and manufactured, which allows the lead exit to be tested independently from the transformer or reactor. According to the V-t characteristic of oil-paper insulation, the long-term insulation property under power frequency voltage with 10-hour was proposed as the main test item to evaluate the insulation reliability of UHV lead exit, and the partial discharge (PD) level was taken as the characteristic parameter to study the electrical performance with long duration voltage. Based on the analysis of PD circuit combined two connection mode, a method of distinguishing the PD position was presented to exclude the interference of bushing PD. The test result shows that the product is qualified with high reliability and has good insulation performance.