Electric field distribution along the surface of high voltage polymer insulators and its changes under service conditions

This paper investigates the electric field distribution along the surface of high voltage polymer insulators and its enhancement due to water droplets by means of computational simulations and laboratory experiments. Different factors affecting the electric field distribution are analyzed through finite element method simulations. Among them, the presence of a grading ring and water droplets on the insulator surface are studied. The insulator surface is simulated for dry conditions, as well as its changes under wet conditions. Additionally, radio-influence voltage (RIV) measurements are performed on a 138 kV polymer insulator. A model for the presence of humidity on the housing is presented and its effect on the field distribution is discussed. The results show that the electric field enhancement along the surface is considerable and reaches values that cause corona and early ageing of the material