Hebei North Grid Old Transformer Anti-Short Circuit Ability Evaluation Analysis And Management Measures

According to the ability withstand short circuit of transformer is provided by the transformer manufacturers, and lack of uniform specification and test standards. And aging and deterioration of the old transformer, its performance parameters will change accordingly. With the development of the grid, short-circuit current will change. All mentioned above will cause the transformer to meet the current short-circuit resistance requirements, and this thesis have done some research on those mentioned above.Firstly, this paper chooses an old transformer to conduct short-circuit current test in JIBEI Electric Grid. According to the test results, judge the damage extent of transformer, and decide whether to increase the current to continue testing by using short-circuit impedance method, low-voltage pulse method, capacitance method and frequency response method to test the transformer. And then get the real ability withstand short circuit of transformers and verify the test results by disassembling the tested transformer. Refer to the data which get from test, correct the ability withstand short circuit of transformer which is manufactured by the same company.Secondly, this paper presents a new type algorithm of calculating the probable maximum short-circuit current. Because the real short circuit current is influenced by many factors,and we can not get the correct short circuit current. This paper takes advantage of transformers parameters and measured short circuit currents backstepping the equivalent impedance of the system, calculate the short circuit current using the parameters, and then can get the maximum short circuit current which flow through different winding under different situation. Through the proposed algorithm, we can verify whether the ability withstand short circuit of the old transformers is qualified.Thirdly, this paper proposed suitable measures according to the result of evaluating the old transformers. This paper combines the existing measures of improving the ability withstand short circuit of transformer, and analysis the feature of these measures and scope from the cost, the performance and reliability. Give the corresponding recommendations to according to actual situation. At last, this paper develops a software system based on the research and makes the proposed algorithm and conclusion facilitating the practical promotion and application. The software can calculate the short-circuit current, assess short circuit ability of transformer and put forward the governance measures automatically, and then can modify the software database according to the actual changes in the grid achieve improving the management efficiency and eliminating hidden dangers timely.