Application of 20Hz Spoon feeding Stator Grounding Protection in 700MW Water turbine Generator Unit

As an essential source part of “Transmission of Electricity from West China to East China”, Laxiwa Power Station in Qinghai plays a vital role in 750kV electric net stand in Northwest China. It is a strategic project that can transmit the power as a whole “package” from electrical network in Northwest China to the network of West China. The principles applied in 3ω stator grounding protection and 3U₀ stator grounding protection are introduced. The stator grounding protection of 20Hz disemboguement to 100% stator grounding protection applied in this power station is demonstrated. The grounding protection measures and the working principles of these apparatuses are analyzed. Protection experiments of the whole unit and its test run of 72 hours are carried out before the power station works. The matters concerned in the test run on the locale and in the protection and maintenance of the whole unit device are concluded. Compared with the principle of the triple frequency harmonics, this kind of protection has more advantages. It is more sensitive and covers larger areas in test , and it has nothing to do with the operation of the dynamotors.