Research On The Short Circuit Calculation Model Suitable For Relay Protection Setting Calculation

Relay protection setting calculation is an important basic work,which guarantees the safe operation of power grids.At present,due to the large amount of calculation of setting calculation,the AC protection setting calculation needs simplified models to improve the calculation efficiency.With the rapid development of power system,the scale of power system network expands and the structure and the operation mode are more and more complex,which presents a new challenge to the existing element models of power system in setting calculation.Therefore,in this paper,the models of generator,load and series compensation are studied in depth.The main research contents are as follows:A generator model for backup protection setting calculation is presented.The impacts of generator models on faults of backup protection setting calculation are analyzed,which have the impacts of generator models on different backup protection setting calculation confirmed.According to the characteristics of the sub transient generator model and the stage generator model,the generator model suitable for backup protection setting calculation is presented.On DSP-BPA,through the southern power grid examples,the rationality and validity of the model are verified.The model improves the accuracy of backup protection setting calculation and has a good practicality.A load modeling method suitable for setting calculation is proposed.The impacts of loads on the fault calculation are analyzed.The impact factors of loads on node voltage and short circuit current are obtained.According to the impact factors,a load sifting method suitable for setting calculation is presented.The impacts of different load models on the fault calculation are studied and the suggestions of using load models are presented.Simulation results of IEEE standard test system show that the size,position and model of loads have influences on fault calculation results.And the load sifting method can not only ensure the accuracy of fault calculation results,but also greatly reduce the amount of calculation.Considering the MOV action characteristic,a series compensation modeling method is presented to solve the fault calculation.The equivalent model of series compensation is analyzed.Based on the node admittance matrix,nonlinear equations of the fault calculation are formed,which consider the MOV action characteristic.The Newton-Ralph method is used to calculate the short-circuit current and the equivalent capacitive reactance of series compensation,which has accurate fault calculation realized.Simulation results verify the rationality and validity of the method.