Shunt reactor is an essential device in extra-high voltage（EHV） long distance transmission system. In order to judge the overall insulation performance of 750 kV shunt reactor in operation

we studied and proposed an on-site partial discharge（PD） test method for 750 kV shunt reactor based on frequency conversion resonance technology

calculated the loop parameters

and selected the test devices. Moreover

taking the impact of low-pressure environment at high altitude into account

we put forward the corresponding optimization measures on the external insulation of the equipment. Based on the theoretical studies

the on-site partial discharge tests of shunt reactor were carried out in 750 kV substation. The test results show that the partial discharge capacity of tested reactor is less than 290 pC

which is lower than the standard value

thus the reactor can operate normally. Therefor

the test method and this set of test device can be applied to a 750 kV shunt reactor PD test under high altitude conditions.