Analysis Of Operation Property And Research Of Improvement Resolution For The Generator In Three Gorges Power Plant

Three Gorges power plant, using a large-scale hydropower generating units with the single capacity of 700 MW and total installed capacity of 18200 MW, is not only the centre-point of central China power grid and national grid, but also the key point that China's power system towards to the national network. Three Gorges of the transmission system is the cross-regional hub connecting the power grids. Thus, the generator operating whether safely or not will impact directly on the safety of the entire power system, and it is the large hydropower generating units which refuse to operate or function by error that will result in very serious consequences. Therefore, studying the high reliability and adaptability which large-scale hydro-generator group protection system holds has very important theoretical and engineering value. The computerized protection is synthesized on the basis of the application of the Generator-transformer set protection and actual problems in the Left Bank Plant.The characteristy of the generator, transformer protection is discussed and the reasons of their faulty occurrences are analyzed, and the digital protection abroad is researched, e.g. the SIMENS unit protection applied in Three Gorges Plant .Considering the 5-branch structure of the stator in TGHP, it's reasonable to install a complete longitudinally differential protection, split-phase protection and unbalanced protection in the neutral point, and the latter should be the prior choice for branched structure. Then the dual main protections' reliability is analyzed and a back up protection for large generators is discussed.The application and acting process of the negative power protection in TGHP is analyzed and it's necessary to install this protection for large turbines. And considering features of the unit and regulator in TGHP, locking is unnecessary for the negative power protection, and the valve values are set in two blocks, and the signal is delayed in a short time.According to the application and improvement of the field winding protection of TGHP, expound it's reasonable that large-capacity generator select the injecting-voltage rator grounding protection ,and solute the question that rator lose grounding protection before the generator running by the outing injecting-voltage power.That the temperature of the main current transformers conured in the multi-branch generator rising, occurred in the generator of VGS in the left bank of the Three Gorges Power Station, leads to the action of splitting phase and transverse differential protection ,thus to the result of stopping. According to this, the impaction of the current transformer to mainly protection is analyzed, and the result obtained from the scene practice shows that the installation is more reasonable, which the main current transformers conured in the multi-branch generator is located outside the generatorFinally the main shaft current protection and related non-electrical protections for large generators are analyzed, and the former is necessary for bearing metal resisting electrical corrosion, so Current transformer with TA is proposed in TGHP to measure the shaft current. Then the importance of the non-electrical protections such as over-speed protection and water-cooling generator's pure water system protection are discussed.