Allowance for insulation ageing in the new concept of accelerated life tests of high-voltage power transformers

It is pointed out that the existing system of type and acceptance tests of high-voltage transformer insulation does not take into account insulation aging, which is particularly objectionable with respect to equipment with reduced insulation levels. The authors propose a novel concept of accelerated life tests based on integrated simulation of basic operating loads both periodic (surge) and long-term ones, by performing a long-term accelerated test simulating the working conditions, with exposure of the test object and/or its insulation to periodic operating surges (overvoltages and overcurrents). This test replaces a group of conventional individual acceptance tests and provides more ample and more precise information on the performance and dependability of the equipment. The test procedure was checked in a test of a small lot of 1600 kVA 35 kV power transformers