The overcurrent site test on a 500 k V/400 MVA high power main transformer installed at on nuclear power plant is performed at 1.1 times rated current and power frequency by way of full capaci-tance compensation

thus reducing the power capacity needed dramatically and keeping the test at site feasible. In this paper

the scheme of site over current test for the transformer is designed based on the capacitance compensation calculation result and the site is performed successfully. It is proved by the test result that the compensation result is good and compensation and calculation method is accurate and effective.