Investigation of Destructive and Healing Effects on the Temperature and Moisture Rise in terms of Dielectric Strength of Transformer Insulation Oil

Abstract

Transformer insulation oil is a crucial material for power transformer. Dielectric strength is one of the most important parameters of transformer insulation oil. Dielectric strength of insulation oil provides reliable operation of electrical equipment. Dielectric strength of insulation oil is a measure of the oils superior ability to withstand electrical stress without failure. Dielectric strength test involves applying alternative voltage at a controlled rate to two electrodes immersed in the insulation oil. Gap is a specified distance. When the current arcs across gap the voltage value recorded at that instant is the dielectric strength value of insulation oil. Dielectric strength of transformer insulation oil is also known as breakdown voltage of insulation oil. In this study, breakdown voltage of insulation oil was investigated under the influences of temperature and moisture. Breakdown voltage tests were applied in the standards IEC 156/95, ASTM D1816/97 and VDE 0370/Part5/96 test conditions for three different insulation oil types. Experimental results of the dielectric strength of transformer insulation oil were investigated during temperature and moisture non-equilibrium. The obtained results were compared with different temperature and moisture values in actual power transformer. Destructive and healing effects of temperature and moisture parameters were examined.

Key words: Dielectric strength, Insulation oil, Temperature, Moisture, Transformer