Abstract:
This research studies and compares the dielectric characteristic of various insulator types
line-post class 57-2, pin-post class 56/57-2, pin class 56-2 and suspension class 52-2 used in 24 kV
distribution systems operated by Metropolitan Electricity Authority (MEA). In Bangkok and nearby
area, most insulators are contaminated from sand or soil dust caused by traffic or industries. Most of
contaminated ingredient, CaSO2 and NaC1, are soluble. This contamination causes the insulator to
flashover and then the distribution system will be affected. In this present work, five levels of
contamination following in IEC 507 (1991), 0.025 mg/cm2, 0.05 mg/cm2, 0.1 mg/cm2 and
0.4 mg/cm2 were used to study the flashover characteristics of insulators. The contamination which
consists of kaolin, water and sodium chloride in a certain amount was sprayed through the surface
of insulators and then left until the surface was dry. The results showed that each type of insulator
has different flashover voltages depending on its size and structure.