Study On Protection Setting Calculation Software Design For Large-Scale Generator-Transformer Group

Large-scale generator-transformer group is the core of modern power system, itssecurity and stability is of great significance for the entire grid. For a long time, comparedwith the grid relay protections, the large-scale generator-transformer group’s relay thecorrect action was low. The main reason is the complex structure of large generator, morepossible types of fault, extremely complicated configuration of generator-transformerprotection unit, different protection programmer and the principle of implementation fromdifferent manufacturers, difficult calculation corresponding to internal fault and hightechnology requirements about setting calculation. In addition, setting values by manualcalculation that is cumbersome, complex. Moreover, human negligence will inevitably leadto security vulnerabilities exist. After the separation power network and power plant,protection setting calculation will mainly borne by the party in power plants, there is anurgent need to development a setting calculation software about generator-transformergroup protection. Based on setting calculation of Three Gorges Power Station undergroundgenerator-transformer group protection, key technical problems of setting calculationsoftware about generator-transformer group protection have been researched and analyzedin this paper.Firstly, the protection configuration scheme and the setting calculation of the largegenerator-transformer group relay protection have been analyzed in this paper. Moreover,general schemes of setting calculation software about generator-transformer groupprotection have been presented combine with the database technology and VC++languagein this paper. For the purpose of setting calculation, The schemes of the software have beendivided into several major module containing graphical modeling and fault analysis, settingcalculation, sensitivity calibration, customized inventory management as well as severalmajor features such as database management module, and basic design idea and functionalrequirements of all modules have been presented in this paper.Fault analysis is of great difficulty for the generator-transformer group. this articlefocus on the generator-transformer group’s electrical characteristics under the situation of variable group of fault and abnormal status, then analysis the equivalent circuit model andthe sequence circuit, the equivalent circuit model and simplified circuit model for thegenerator internal faults are given. With the help of Guide of Calculating Setting of RelayProtection for Large Generator and Transformer, and relevant guidance documents andspecifications, an in-depth analysis of generator-transformer unit protection principle andmethod of setting is made, including the differential protection and loss of excitationprotection of generator, and longitudinal differential protection for power transformer.Study on the special problems of a number of protections setting process has been made.The article analysis the versatility problem in software design and graphic modelingmethod, and shows the basic structure of a software framework.