A study of defective characteristics on HVAC insulators for 33 kV distribution system

This research compared the electrical characteristics of insulators for 33 kV distribution system of Provincial Electricity Authority of Thailand. The insulator used in this present work is suspension type, class 52-1. The breakdown voltage of defective insulators in dry and uncontaminated condition under AC voltage is compared. The insulators were arranged into 3 main formats: (1) three good insulators and one broken insulator (2) two good insulators and two broken insulators (3) one good insulator and three broken insulators. The 1^st and 3^rd formats were subdivided into four arrangements while the 2^nd format was subdivided into 6 formats depending upon the position of good and broken insulators. Test results showed that the value of breakdown voltage depended upon the position of good and broken insulators. Also, the breakdown voltage of the 2^nd format with the 5^th subdivision, good insulators were at 1^st (top) and 3^rd positions while broken insulators were at 2^nd and 4^th positions, was highest. The insulator installation for testing and its atmospheric correction factor followed ANSI C29.1-1988.