Abstract: In view of the difficulty in detecting the uniform and non-uniform contamination of high voltage

（HV）glass insulators and the inaccuracy of risk assessment，a risk assessment method for HV glass insulators

based on a new leakage current indicator Rhi was proposed. The new leakage current index Rhiwas derived by the

leakage current of the 3rd，5th and 7th harmonics，according to the measured critical voltage gradient（Ec），using two bunch of 33 kV cap glass pin type insulator，the critical voltage stress test of polluted insulator in different top and bottom surface ratio（J）and wetting rate was carried out to evaluated the level of risk . In addition，the influence of the ratio of the equivalent soluble deposit density（ESDD）to that of non soluble deposite dentisty （NSDD）on insulator flashover was also analyzed. Finally，the experimental results show that the new index can predict the risk degree of insulator and the probability of flashover more accurately.

      Key words: polluted insulators；risk assessment；leakage current harmonics；fast Fourier transform；glass

insulator