Changes of iron losses during the service of distribution transformers

This article examines the issue of the increase in electrical energy losses in the iron cores of power transformers as a result of prolonged operation. A summary analysis of the results of measuring the losses of 200 pcs. power oil transformers after prolonged operation is provided. The results clearly show an increase in losses compared to the passport data provided by the manufacturing plant. The reasons for the increase were analyzed and compared for two different types of magnetic cores produced before and after 2000. The increase in idle running losses over five-year periods r% e determined using the Least squares method. Based on the statistical data from the measurements, a model is proposed for calculation of idle running losses using a linear dependence and an exponential function. The conducted research shows a good accuracy of the proposed approximation.