Influence of pollution constituents on DC flashover of high voltage insulators

This paper is aimed at the study of the influence of the chemical constitution of pollution on dc flashover discharge of high voltage contaminated insulators. It´s shown that the type of salt and salt mixture has an influence on the critical currents for both polarities but doesn´t affect significantly the critical voltages whereas the concentration of insoluble matters (Non Soluble Density Deposit, NSDD) has an influence on both critical current and critical voltage. The discharge parameters characteristics N and n depend on the chemical constitution of pollution, the concentration of NSDD and the polarity of voltage. It´s also shown that the most important constituent of the discharge column are water vapour and air; and the transfer of metallic ion has no significant influence on flashover voltage.