Due to the closed structure and complex components

the determination and location of the partial discharge（PD） defects on composite apparatus have always been difficult problems. Based on the testing method of ultrasonic and ultra high frequency（UHF）

this paper introduces a new method of bridge connection by capacitive arm in the highfrequency（HF） to detect the PD defects. By using the variety of testing methods and making experiments after dismantling

this paper carries out a detailed analysis of suspension discharge case in a 220 kV composite apparatus

the analysis results show that:the method of bridge connection by capacitive arm in HF can effectively assist to determineand locate the PD defects;by verifying the variety of testing methods mutually

the accuracy of PD determination andlocation can be improved;by comprehensively using the ultrasonic-ultrasonic location method and combining ultrasonicand UHF location method

defect interference elimination and precise location can be realized

and the efficiency of equipment maintenance can be effectively improved.