This article mainly introduces a successful application case which used the partial discharge detection technology to diagnose the state of arrester.The high frequency CT and oscilloscope are used in on-site detection

for abnormal leakage current of arrester

and the PD defects inside arrester have been identified.At last

the type of discharge and the assessment of severity are determined through arrester partial discharge test in the laboratory.It is found that the surge arrester exist interior metal gap discharge by disassembling it

and the defect on the arrester has deadly threat.