Research On Fault Diagnosis Of Hydropower Generator Excitation System

With rapid development of hydropower industry, the requirement for safe, steady and reliable operation for excitation system is higher. A good excitation system able to help to improve the hydroelectric system stability and secure the technical and economic target. It is important to implement fault diagnosis and state assessment of excitation system accurately, as it could help to promote smooth operation of system which results to higher system efficiency, lesser cost of labor and time.In this article, an EXC9000 excitation system used by Dongfeng hydraulic power plant located in Wujiang, Guizhou Province is studied. The SCR circuit of power cabinet is hardcore of excitation system. And electric circuit failure and overheating failure of SCR are simulated. The operation of excitation system is measured by SCR temperature. The details are as follows:Firstly, the physical structure of SCR and circuit structure of three-phase bridge rectifier are investigated, thus conduct conditions are identified. Matlab is used to simulate failures for different SCR inside three-phase bridge rectifier. Various kinds of failures can be recognized by summarizing the simulation waveform pattern. To make the 7 groups of different control angle under single fault waveform as the training sample, locate the accurate fault SCR in three-phase bridge rectifier.Then,to dealing with the situation that the SCR is easily overheat and its temperature value is hard to directly monitor,do the thermal simulation for SCR.At first,this article has made analysis of the heat dissipation theory of SCR,introduced the method of force air cooling and phase change cooling.Analysised the structure of EXC9000 excitation power cabinet then made modeling and simulation.Using simulation software Solidworks Flow Simulation to imitate the SCR radiating situation in the power cabinet.Modeling and simulation for two types of wind machine witch are equipped on EXC9000 excitation power cabinet respectively.The simulation result is concluded the camparison of the two fans' simulation effects.Which provided a reference for hydropower plants adopt different cooling methods.Finally,using the fuzzy analytic hierarchy process method to divided the function indexhierarchy of excitation system as a whole,in analytic hierarchy model of index layer elements were determined.Using the concept of fuzzy mathematics to power cabinet temperature index.For example on the running state of the plant staff can according to the views of the assessment more reasonable arrangement related maintenance,thus in a certain extent,improve the regular maintenance of redundancy and low efficiency.