Evaluation of the Performance of Glass Insulator String with Broken Units Under Artificial Pollution

Abstract

Glass insulators are more susceptible to vandalism and the presence of broken units can modify the supportability of the insulator string. It is necessary to know the influence of broken insulators regarding to the quantity and position in the string to verify the supportability of the remaining units. The aim is to evaluate the electrical performance of glass insulator strings with broken units in AC systems, under pollution conditions, in various configurations. The artificial pollution method used will be the solid layer according to the recommendations of IEC-60507, considering three levels of pollution for each configuration. The SDD (salt deposit density) values used were: 0.03, 0.07 and 0.10 mg/cm². In this work, 9 configurations were tested. The test was carried out under steam fog, applying the non-standardized method named RFO (Rapid Flashover), which has been used by some laboratories and proposed as an alternative to the up and down method. The tests identified that the position of the broken insulators in the string influences the breakdown voltage. The results show that glass insulator strings with broken units in random and intermediate positions may represent a more pronounced drop in the supportability when compared to the configurations in which these units are located at the ends, the one in which the broken units are close to the conductor presents the least loss of supportability.