| With the increase of the generator's unit capacity, the short current of the generator has increased sharply, which made ordinary circuit breakers can not meet the demand of breaking capacity. For the purpose of safety and reliability, isolated phase enclosed bus developed rapidly and generator-transformer-circuit unit wiring are widely used. This is inconvenient for the regular operation, especially the danger of quick auxiliary power switching in the accident. Auxiliary power may fail by the failure of quick switching. So the reliability of auxiliary power is relatively low.Over the last decade,in electrical engineering design of large power plants ,Whether or not high capacity thermal generators(600MW and above) need to install the generator circuit breaker(GCB) is a problem that brings up many arguments and disagreements. The application of GCB could overcome some drawbacks to a large extent,hence it improves availability of generating units and system reliability. With the development of national power, relatively loose control of construction funds and high reliability requirement of progress of economy and society, meanwhile under the influence of major institutional reform of power system and the shift in power system operating mechanism of market economy structure, it is very necessary to make new discussion on this controversial question. With the combination of availability of generating units and economical efficiency, this thesis analyses the comprehensive benefits of application of GCBThis dissertation analyses the optimization of plant wiring of auxiliary power with the application of GCB. Also auxiliary power is checked under the N-1 mode of operation. The results meet the requirement of operations.This paper makes a detailed research on technological advantage of generator circuit breaker: simplifies the procedure of operation,diminishes extent of generators and transformers accidents, simplifies quick auxiliary power switching and synchronization operation, improves the reliability, facilitates test and maintenance. Using Monto-carlo logical / mathematical model, two schemes which is with and without GCB are compared and analyzed respectively。It is pointed out that the application of GCB could improve the availability of high capacity generating unitsThis thesis also presents the conception and goal of general economic benefit assessment, along with steps and procedure. With indexes extracted from technical and economical analysis of installing GCB—economical efficiency and reliability, we assessed the economic benefit of GCB installation based on DEA/AHP method and obtained effective sequence of different conditions under one of which GCB is installed, and the other not, in practical operation WaiGaoQiao power station, offering certain references on whether GCB should be installed on 2×1000MW generators in WaiGaoQiao NO.3 power station.Finally, on the basis of theory research, this thesis studies on the simulation of generator with and without circuit breaker。Through the simulation of various kinds of failures of main transformer high side, generator terminal current or negative-sequence current are studied. By the results of simulation, we know that with the same failure point generator terminal current or negative-sequence current decreases, if GCB are installed. Hence it shortens the repairing time and reduces the economic loss.Through the above technical and economic comparison and analysis, the first stage investment on large generator with GCB is more than that without GCB. But it simplifies the procedure of auxiliary power switching, improves the protection level of generator,main transformer and high voltage station transformer , simplifies synchronization operation, facilitates test and maintenance, shortens the repairing time, reduces the economic loss, improves the availability of generator, and operation cost is less by the application of GCB. The investment of GCB can be made up within a few years. So it is recommended that GCB should be installed. |
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