A Laboratory Investigation of Di-electric Characteristics of Electrical Insulation

Materials in Air and in Oil
1Lawal, A.O. and 2Resham D.
1Department of Electrical Engineering, Kwara State Polytechnic, Ilorin.
2School of Engineering and Physical Sciences, Herriot-Watt University, United Kingdom.
E-mail: lolasupo@yahoo.com

ABSTRACT

Electrical measurements of insulation in air and in oil were performed on four different types of insulating materials – two cellulose based and two polymeric materials. Extensive measurements were carried out in air and in oil on the selected
materials. Results of their breakdown voltages show higher values for insulations soaked in oil than those measured in air. It also shows that cellulose based materials have better performance in oil than polymeric, and they equally show a recovery rate of up to 70% in oil. All materials tested show averagely high breakdown strength for a long time (≥5hrs) before deterioration under stress. To confirm this, the materials were maintained in transformer oil at 100 deg. Celsius for five hours and then subjected to a high dielectric strength.