Distributed Parameter Transformer Model And Its Application In Transformer Inter Turn Fault Analysis

As one of the most important components in the power system and the core equipment for power transmission,power transformers face more and more threats to their operational safety.It is of great significance for the safe operation of power grid to analyze the fault characteristics quickly and accurately and find out the minor faults of power transformer in time.Therefore,it is of practical significance to deduce a transformer model considering the distributed parameter characteristics of transformer windings,and to study the internal and external faults of transformer based on the model and the variation characteristics of internal electrical quantities of transformer when calculating faults.The main contents of this paper are as follows(1)According to the distributed parameter modeling idea,the transformer winding is divided into infinite number of "units" cascaded,and through calculus,mathematical induction and other mathematical theories,a time-domain transformer distributed parameter model is derived,which can be used for transient process analysis and takes into account the characteristics of winding distributed parameters.The model can be used to calculate the changes of current and voltage with time and position on transformer windings.(2)Through frequency response analysis and genetic algorithm,the objective function of strengthening resonance point weight is used to calculate the winding parameters of transformer distributed parameter model,and the influence of different number of "units" and different constraints on the calculation results of winding parameters is compared;for core hysteresis parameters,based on J-A model,the secondorder oscillation particle swarm optimization algorithm and GA algorithm are compared The influence of different parameters in J-A model on the characteristic quantity of hysteresis loop is analyzed,and the calculation method of dynamic inductance used to reflect the hysteresis characteristics of core is derived.(3)According to the calculation requirements of distributed parameter transformer model,a sinusoidal representation and analysis method of transient signal based on Hilbert transform is studied.Theoretical derivation and simulation results show that the method can accurately fit the transient signal of power system.The steady-state component is separated from the transient component while retaining the attenuation characteristics of the transient component,and the time-domain expression and its higherorder derivative of the transient signal are obtained.(4)The correctness of distributed parameter transformer model in steady state and transient state is verified by simulation.On the basis of three-phase operation,the difference of working characteristics of transformer under light load and normal load is compared.For the internal fault of transformer,the correction method of distributed parameter transformer model is given to coordinate with the calculation of voltage and current of transformer under the condition of inter turn fault and phase to ground fault,and the correctness of the correction model is verified by simulation.(5)Based on the transient signal analysis method and the modified distributed parameter transformer model,using the original secondary side fault recording data of the transformer,the inter turn fault discrimination conditions and the calculation method of the turn ratio of the fault section are derived,and the feasibility of the discrimination conditions and calculation method is verified by simulation.