Diagnosis For Turn-to-Turn Short Circuit Of Rotor Windings In Turbo Generator

As the basic equipment of generating, synchronous machines play very important role in safety and stability of the whole power system. Developing on-line diagnosis to find fault in turbo-generator timely and effectively has become one of the important methods gradually to ensure the machine operating safely and reliably. Shorted rotor winding is a usual electric fault of synchronous machines. Based on the analysis of fault mechanism especially the magnetic characteristics of tum-to-turn short circuit of rotor windings in turbo generator, the paper studies the diagnose method, which combines the traditional method with the intelligent method, to identify the fault and the severity.This paper consists of four related parts as follows:The first part is concerning about the fault mechanism and the fault characteristics. The traditional on-line diagnosis methods are introduced, and the drawback of each method is put forward. At the same time, this part detailed the theory, the implementation and the application of the traveling wave method.In the second part, provided that the operating mode of the turbo generator keeps unchanged when the rotor winding appears fault, the magnetic motive force of the field winding will keep unvaried. Based on the analysis of the magnetic characteristics, an artificial nerural network can be built and the fault samples can be gained by theoretical arithmetic. The results of computation example show that the method can not only judge if shorted field turns exit but also estimate fault turns ratio.In the third part, in order to prevent shortcoming of the entrapment in local optimum of ordinary BP and the premature convergence of Basic GA, a new algorithm which combines BP with GA is presented, which is used to detect the rotor winding short. In the new algorithm, the method of coding, selection, crossover and mutation are modified. The results of computation example show that the method is feasible.In the last part, the relationship of the field current with the operational factors of the turbo generator is difficult to express exactly, belonging to the complexity of building the generator model and the difficulty of identifying generator parameters, GP algorithm is presented, which is better than other method in symbol regress. This method is shown to be effective by an example.