Life Assessment Of Transformer Based On Condition Monitoring

Transformer is one of the important equipments in power system. With the development of the system, the number of the transformers is increasing. Now, large numbers of transformers have been close to or run to the end of the design life. Replacing all of them needs lots of money. However, some transformers still can run for some time due to maintenance. If they are replaced, it will cause unnecessary waste. Therefore, reasonable assessment of the life of the transformer and utilizing the equipment effectively can improve the economy of the power system.Many traditional assessment methods for predicting the initial life by destructive testing are made through the sample. Although the aging model considers the combined effects of Electric-Heart-Machinery, the model assumes that the electric field and mechanical strength of the device during operation remained unchanged. It's failed to take reasonable maintenance for lengthen the life and lacks self-correction ability.. It's a far cry from the actual state.This paper presents a new method of life assessment based on condition monitoring technology, which introduces the state assessment into the life assessment. On the basis of the state parameters, it constructs a comprehensive assessment system including the hottest temperature, electric field strength and partial discharge as indicators. By analyzing the hottest temperature and electric field strength induced changes with the time to estimate the life. For partial discharge, through analysis the character of insulating material in different stages, according to the differences of the discharge characteristics and the historical data, we can educe the life of the insulating material now. Finally, comprehensive analysis the results of the three index, we can estimate of the overall life of the transformer by assigning different weights.This method makes the initial state data combined with existing state data. A more reasonable assessment of transformer life, not only can improve the security and reliability of the power system, but also can save the cost of the transformer replacement. Life assessment of transformers is a multi-attribute decision problem. A more accurately life assessment needs to introduce more state variables.