Studies on Performance of Contaminated Insulators Energized with DC Voltage

Several types of insulators with a variety of contaminants and test methods were tested using dc voltages. A thyristor controlled dc power source provided a sufficiently stiff source for dc contamination testing. The dc performance is influenced by the contamination degree both for soluble and insoluble materials, contamination uniformity, insulator shape and relationship of total leakage distance to insulator diameter. Generally, the performance with dc shows linearity with respect to string length, but the dc values are generally lower than with ac.