Abstract:

Cabinet A and cabinet B of generator protection group of a power plant respectively reported "protection action of stator zero sequence high voltage section", which caused unit trip. It was found that the generator outlet potential transformer(PT) B phase 5042PT was obviously overheated. The accident process, through the breakdown PT finish straight resistance, insulation, excitation characteristic curve, and no-load current test, PT interturn short circuit are the main reasons of the unit tripping. In view of how to find early export PT insulation fault, the corresponding measures to prevent cracking was proposed. Specification requirements must be strictly according to the forecast to complete generator export PT partial discharge, triple frequency withstand voltage test, etc. In addition, the trend analysis was carried out on the data of various routine pre-test projects to detect the abnormality timely. The analysis of PT turn-to-turn short circuit fault at the generator outlet plays a good role in finding out the safety hidden danger and improving the reliability of the equipment. The regular completion of relevant tests in accordance with the standard requirements and the emphasis on the trend analysis of test data can effectively reduce the occurrence probability of the same type of accidents and reduce the scope of accidents.

Key words: generator outlet PT, interturn short circuit, zero sequence voltage