Despite lots of research have been carried out

the equivalence between natural contamination and artifi-cial contamination tests hasn’t been satisfactorily solved

the flashover voltages obtained from the natural contamina-tion tests are always slightly higher than that obtained by the artificial contamination tests. In this paper

the naturalcontamination tests and the artificial tests of glass insulators had been carried out in the Kunming UHV test base. Byusing the flashover voltages as index

three different ways of contamination brushing by the ESDD and NSDD are de-signed

the influence of different contamination brushing methods on the equivalence between artificial contamina-tion test and natural contamination test is studied. Based on that

the influences of contamination brushing by the saltcomposition and by the surface conductivity on the flashover voltage are studied to find the contamination brushingmethod which has the closest flashover voltage to the natural contamination. Test results show that brushing contami-nation by the overall ESDD and NSDD is the most convenient way

brushing contamination by the surface conductivi-ty has the closest flashover voltage with the natural contamination tests

brushing contamination by the salt composi-tion times. Furthermore

in order to analyze the reasons for the difference between the flashover voltage of artificialcontamination test and natural contamination test

the influences of salt composition and contamination distributionon flashover voltage are investigated.