Study on state of health for power transformer oil with multiple parameters

Evaluating the state of health for power transformer oil so as to realize its cascade utilization is of great significance to save resources and protect the environment. There are large amounts of information for transformer oil. The information include viscosity, condensation point, point of flammability, acid value, water content, water-soluble acid, oxidation stability, interfacial tension, breakdown voltage, dielectric loss etc. Parts of the information are of uncertainty. This increases the difficulty of oil evaluation and classification. In order to overcome the difficulties, the fuzzy comprehensive evaluation method for state of health for power transformer oil was proposed. This evaluation method is built on large transformer oil's monitoring information, and provides the basis for cascade utilization of oil. Firstly, select out the indexes that can be used for oil evaluation, and establish evaluation factor sets and evaluation sets, with the method of fuzzy comprehensive evaluation method. Secondly, using ridge shape distribution as fuzzy membership function, determine fuzzy matrix of each factor on different evaluation class respectively. And finally, use the hierarchical analysis method to determine the weight of each index, obtain the quantitative values of the evaluation by means of fuzzy matrix synthesis, and establish the fuzzy comprehensive evaluation method for state of health of power transformer oil. As for the oil of a transformer that was in operation, as long as the corresponding experimental data was got, the state of health can be obtained with the help of fuzzy comprehensive evaluation method. Take the transformer of Xing-Cheng substation for instance. Using the proposed evaluating method, the corresponding experimental data was analyzed. And the investigations results show that the method is rational and valid.