The dynamic load adjustment of power transformers based on the inner temperature

Abstract

The inner temperature of power transformers is one of the major factors of the life of insulation life and the load operation mode in transformers. So it's of great significance to predict and calculate the inner temperature of transformers precisely in different loads and ambient temperature, which could be used to assess the surplus useful life and the safety performance of transformers. When the inner temperature of transformers is too low, it's evident that the load capacities of the power transformers are in half-load or less, which might reduce the economic benefit. However, when the inner temperature of transformers is too high, Not only do the ageing rating of insulation structure in power transformers is accelerated, but also the dielectric loss angle because of the aging products, which could prompt the inner temperature in power transformers higher. As a result, the remaining useful life of power transformers is decreased, and all kinds of partial discharge might happen for the degradation of the insulation structure in power transformers. Therefore, in order to make a balance between an integral remaining life of transformers and economical benefits, it's necessary to predict, calculate and monitor the inner temperature of power transformers, which could guarantee the operation mode safely and economically in some certain circumstance. In this paper, the influence of the inner temperature of transformers to the aging of insulation structure is first introduced. Then the relationship between the inner temperature of transformers and load in summer and winter is analyzed by thermal circuit model, from which we obtained the top-oil temperature of a certain transformer in different ambient temperature. And the data we measured shows that there is certain accuracy of the data we calculated by using thermal circuit model, and the maximum error between the data we calculated and measured is lower than 5°C. So there is a convenient way to estimate the inner temperature of transformers and guide the model of lifting loads. Besides, in the premise of remaining life and normal operation of transformers, the estimation of the inner temperature of transformers could be used to prompt economic performance.