Dependency of Dielectric Strength of Kaolin on Processing Method

This paper presents experimental results of a study to determine the dependency of dielectric strength of kaolin on processing methods. Two sets of electric insulators were made of porcelain; one set was made by wet pressing, while the second set was made by dry pressing. The porcelain were made from mixtures of kaolin, ball clay, flint, and feldspar compacted into discs of diameter 2.5 mm at pressures of 100 MPa before being fired to a temperature of 1250°C. The results show that the dielectric strength of electric insulators made by dry pressing exhibited generally higher dielectric strengths than those made by wet pressing. In addition, the study shows that dielectric strength of the insulators were much higher when tested while immersed in high grade transformer oil, than when they are tested while in air. The highest values when tested in oil and air were 22.5 kV, and 10.7 kV respectively.