RI, TVI and AN characteristics of HVDC insulator assemblies under contaminated condition

The results of investigations into radio interference, television interference and audible noise characteristics of full-scale insulator assemblies for DC±600 kV HVDC transmission lines under contaminated and wet conditions are discussed. The interference levels during partial discharges were measured and found to be nearly the same as those as those of existing AC 500 kV transmission lines. Emphasis was placed on the characteristics of partial flashovers known as specific sparkovers under DC voltage on one or a few units in a string. The interference levels during partial flashovers were much higher than those during partial discharges. An insulator with a high flashover voltage, such as one having a diameter of 460 mm, was effective in preventing partial flashovers, at least up to a voltage of ±650 kV