Power Transformer Running State Assessment Methods

In order to guarantee the security, reliability and economical efficiency of power system, power enterprise required that electrical equipment repair system change from regular maintenance to the state maintenance. The reliability of power equipment is vital to power system's safe operating. It is imperative for the CBM under the extension of power grid and the reform of electric power system. It is also a trend of developing power grid. As the ultimate element in the electricity supply chain, the safe operating of transformer is close correlative with the safety of the power system. So it is important to find out the state of running transformer. At present, more and more attention has been paid to the condition assessment of power transformer. Although some achievements have been obtained, there are still needs for the further investigation to this field. Therefore, on base of consulting a great amount of material, a deep research on the condition assessment method of the transformer using fuzzy comprehensive evaluation is done in this paper.Appropriate status parameter was chosen to assess the condition of the transformer by combining the existent achievement and the expert experience, considering the practical maneuverability. So electrical test, state parameter of dissolved gases in oil, parameter of oil characteristic and other factors(include the working atmosphere, operational data, maintenance record, operational aspect of accessories section),etc, are selected as the evaluation factors of fuzzy comprehensive evaluation to build model, which is advantageous to add more effective and sensitive state parameter in the sequel; At the same time the influence degree to the state of the power transformer is different according to each evaluation factor, adopt the improved analytic hierarchy process(IAHP)to confirm the weight distribution of every factor in models; according to the characteristic of evaluation factors, the relative impairment grade was introduced to reflect the influence degree between factors and state of power transformer, then the membership grade function of the relative impairment grade to the state of transformer is confirmed by fuzzy mathematics; To the state parameter of dissolved gases in oil, because of its one's own characteristic and importance, carry on state parameter reasoning by putting up the neural network to train the membership grade function, which have achieved the preferable result and have worth popularizing. Through the examination of actual transformer show that the assessment method for transformer condition is reasonable and satisfying. This method has the feature of good practicability, extension and flexibility, offering a way of getting the state of transformer and a guidance of transformer maintenance.