Study on Decomposition Gases of Various Ester Insulating Oils by Local Heating

Abstract

Recently, the use of ester-based insulating fluids in electrical equipment has been increased for reducing the environmental impact. However, the fault diagnostic techniques have not been established as those by DGA for mineral oil immersed electrical equipment. In our present study, in order to estimate the overheating temperature, the characteristics of gas generations from three types of locally heated ester-based insulating fluids (PFAE, FR3 and MIDEL7131) were investigated, with a temperature ranging from 300 to 700℃. The results reveal that the gas generation characteristics for ester-based fluids are greatly different from that of mineral oil. In addition, it was found that the gas generation pattern also changes with the type of ester oil. We succeeded in estimating the overheat temperature of oil filled electrical equipment with high accuracy by investigating and establishing the relationship between relative gas ratio and temperature.