Simulation of distribution of space charge in ±500kV converter transformer in DC tests

In DC withstand test and polarity reversal test, there would be space charge at interfaces of oil-paper insulation in converter transformer, which may excite partial discharge in subsequent tests. So it is important to study distribution of space charge in converter transformer. This paper simulated the distribution of space charge in a ±500kV converter transformer during DC withstand test, polarity reversal test and earth with finite element method. It was studied that the influences of changing resistivities of oil and paper on space charge distribution in ±500kV converter transformer. Based on the calculation of space charge, the study indicates that the ratio of resistivities of oil and paper has a great influence on distribution and release rate of space charge in ±500kV converter transformer.