| Start mode and boot process of gas-steam combined cycle powergeneration units is different from the general steam turbine generator; thegenerator runs by the synchronous motor pattern for a period of time,absorbing power from the outside; in the entire startup process, the rotating speedof the generator is less than70%of the rated speed, which belongs to the lowfrequency operation, and the voltage of the generator is only17%of the ratedvoltage; the SFC is used during generator startup process. These put forward newrequirements for generator protection, such as how to prevent misoperation ofthe reverse power protection and frequency protection, and how to reduce theimpact on other protection.This paper analyzes the impact of the special conditions of the variablefrequency starting on generator protection and searches for solutions, and itresearches generator longitudinal and transverse differential protection and givesthe different criterion of the protection, it also puts forward some improvement toaccommodate special operating frequency conversion. According to the technicalparameters and operation characteristics of gas turbine on Beijing West ThermalPower Project, this paper establishes the model in ATP software, wich simulatesthe variable frequency startup process、 the internal faults and external faultsoccurring in power generation process by switch operation, and the simulationresults verify the correctness and practicability of the protection criterion. |
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