This article describes the partial discharge test in-site for 1 000 kV power transformers taking a variable frequency power supply as the test power source. The performance parameters and testing process of a 1 000 kV power transformer are analyzed. The whole test circuit is computed for validation

and the computation result is compared with the measured data. In addition

some anti-interference measures

such as detecting and locating partial discharge with ultraviolet

multipoint earthing of test circuit

and adding isolation transformer to test power source

are offered. This partial discharge test method has the advantages of smaller test equipment and flexible connection

and is worth while to propagate in ultra-high voltage projects.