Analytical Studies of HV Insulators in Saudi Arabia: Theoretical Aspects

Digital computer studies of long contaminated insulator strings have been carried out using linear, lumped circuit models. These studies enhance the evaluation of voltage distribution, currents, phase angle and wattage for each unit on the string for practical combinations of uniform and nonuniform distribution of contamination. The variations in performance as a function of numerous, stray capacitance and shielding fields are carried out for a wide range of pollution index, tower design varying at different areas, and conditions of Saudi Arabia. The studies are extended to the physics of the evaluation of the voltage distribution and phase angle variations along the insulator string as the surface is changed from clean, to dirty, to contaminated, to polluted. The iteration technique is used to explore the effect of nonlinearities in resistance as a function of temperature variations and current limits. Changes in surface resistance due to the liberated energy, which dries the contamination or arrests the accumulation of moisture upon the insulation surface, are considered in these studies. Studies are carried out on a per-unit basis to simplify the adoption of the results to insulator strings used at different voltage levels, under any degree of uniform or nonuniform distribution of contaminants along the insulator string.