Study On Setting Of Protection For Huge Hydro-generator And Transformer Group

Hydro-generator and transformer groups are commonly adopted at large hydropower stations at present. To ensure their safe and steady operation, the protection of generator and transformer not only need complete functions, but also have to solve major problems of setting calculation, based on the analysis of generator-transformer and its protection. Moreover, advanced suggestion about protection operation should be proposed.This paper mainly discussed the setting calculation subject of generator-transformer groups of Right Bank Power Station of Three-Gorges. According to three types of generators and tow types of main connection, a setting scheme which is suitable for different conditions is pointed proposed, and the setting calculation is completed based on the setting scheme, moreover, a setting value list matching the protection device is formed. Further more, the paper discussed some major problems in the setting calculation, involving main protection, loss of field protection and inverse time characteristic protection.To ensure the sensitivity and reliability of protection, the setting scheme is proposed based on the analysis of generator-transformer and its protection. The setting scheme is that getting initial setting value based on related guidelines and operating experience, adjusting the setting value with the result of prototype tests, and checking the sensitivity of main protection by the generator internal fault transient simulation software. Meanwhile, the main criterion and setting method of transverse differential protection is improved, after the analysis of the result of dynamic simulation test.During setting loss of field protection, the impedance criterion, admittance criterion and their relationship are studied. Meanwhile, the composition of stator side criterion and the difference of setting thoughts are researched. Considering the end-heating is boosting at leading phase operation, it's better to add a monitoring and alarming stage in the loss of field protection, to ensure the safe of huge hydro-generator at the special operating mode.The problem that the inverse time characteristic of huge generator is difficult to match the operation equation is studied. After analyzing tow common setting methods, a new setting method based on the least square method is proposed, in order to fit the character of generator. To solve the matching difficult thoroughly, an implementation method which uses datum to fit inverse curve is proposed. The setting result is applied at generator-transformer groups of Right Bank Power Station of Three-Gorges. These generator-transformer groups have good operation condition at present.