Experimental Study of Electrical Breakdown Voltage of a Glass Insulator Strings with Different Numbers of Broken Units

This work presents results of a comparative study conducted on breakdown voltage measurements in a glass insulators string containing several units with broken glass part. String with 16 insulator units were tested simulating a transmission line of 230 kV. Two arrangements have been adopted: (i) seven good insulators and nine broken units and, (ii) six good insulators and ten broken units. The electrical breakdown voltage measurements have been carried out in dry and without pollution, in five different configurations. The experimental works have been conducted in industrial frequency and with switching impulse with positive and negative polarities. As a result, depend on the distribution and localization of the good insulators in the chain, the breakdown voltage values of the chain with six good insulators was higher than the chain with seven good insulators. A string with six good insulators in configuration #4 showed higher value of the electrical breakdown voltage than a string with seven good insulators in configurations #1 and #2.