Introduction: The variable frequency method is used to carry out the long-time induced overvoltage withstand test of Laxiwa 800kV Step-up transformer. The test conditions, selection of main test equipment and measures against interference are studied in the paper, which provides reference for other transformer tests with 800kV or higher voltage class.
Key words: power transformer, long-time induced over-voltage withstand test, variable frequency method, Laxiwa hydropower station
Laxiwa hydropower station is the station with largest installed capacity along Yellow River basin, even in the north of China now. The low voltage side voltage of its 800kV step-up transformer (260MVA single-phase double-winding transformer) is 18kV; its turn ratio is the largest among the 750kV-stage transformer; besides, low-voltage winding to ground capacitance is greater 1.3 times than that of 750kV step-down transformer. Estimation of main parameters of long-time induced overvoltage withstand test for 800kV step-up transformer, selection of test equipment and anti-interference measures are studied in the paper based on characteristics of 800kV step-up transformer. Besides, problems occurring during the test are analyzed and summarized.