The Research On New Technology Of Protection And Relay Coordination Software For Large Generator-Transformer Unit

With the large generator-transformer unit beening applied more and more in powergrid, In order to guarantee the safe and stable operation of large generator-transformer unit,require the relay protection device of large generator-transformer unit to work very well.Then it requires a constant researching and improving of large generator-transformer unitprotection and relay coordination technique. This paper discusses the research on newtechnology of protection and relay coordination software for large generator-transformerunit.With the Three Gorges power station beening put into operation, large water turbinegenerator and main transformer protection expose some new technical problems. Centeringon these problems, this paper gives suggestions on how to improve largegenerator-transformer unit protection configuration: such as, configuring reverse powerprotection, frequency protection, isolating switch non-whole phase peotection for largewater turbine generator; and scheme of generator injection type stator or rotor groundingprotection double configuration etc.Beening the main protection of transformer, there is still a weakness for differentialprotection to identify inrush current and sympathetic inrush. With the configured of GCB inlarge generator-transformer unit, the no-load closing of transformer becomes more common,which increases the impact of inrush current and sympathetic inrush on transformerdifferential protection. In order to prevent the misoperation of transformer differentialprotection, more perfect method to discriminate inrush current and sympathetic inrush isneeded urgently. Based on the analysis of the formation mechanism of inrush current, thispaper researchs the influence of voltage amplitude, closing angle, initial remanence, corematerial of thransformer, etd, on inrush current while no-load closing of transformer, bymeans of a combination of digital simulation testing and dynamic simulation testing.The workload of large generator-transformer unit relay coordination is heavy, becauseits configuration is complex. After the separation of power grid and power plant, it’s urgentto develop relay coordination software for large generator-transformer unit to fits the needs of staff of protection in power plants. With the author’s experience in the relay coordinationof the Three Gorges underground power plant generator-transformer unit, considering thecharacteristics of the relay coordination, this paper researchs the development of relaycoordination software for large generator-transformer unit.The relay coordination of large generator-transformer unit has the followingcharacteristics:1. The calculation of short circuit inside generator is complex.2. The typeof relay coordination principle is multiple and complex, the system parameter is complex,the number of values based on experience or test is huge.3. It needs to fill the complexvalue list of different protection device. Therefore, besides the needs of power grid relaycoordination, the relay coordination software for large generator-transformer unit needs tobe designed facing the protection device, the datebase of the software is more massive, andmust have the function that users can intervene in relay coordination process. With theapplication of software design theory, this paper completes requirement analysis andstructure design of relay coordination software for large generator-transformer unit,completes the development of the software user interface, and forms the implementationscheme of software function modules and datebase.