Simulation of internal fault of three-phase five-leg transformer

In traditional internal fault models of power transformers based on winding analysis,the leak flux and the eddy effect of iron-leg are ignored and the non-linearity of iron-leg is less considered.In order to adequately describe the transient process of power transformer internal fault and find out internal fault causes,a simulation model is established with the magnetic circuit method,which is based on the structural model of three-phase five-leg transformer and considers eddy effect,leak flux and non-linearity.The magnetic flux linkage equations and voltage equation are established according to the magnetic circuits and the magnetic conductance equation is listed according to the relations among magnetic flux,current and magnetic circuit.The method to determine the parameters of simulation model is given,which is closely related to transformer structure.The model is applied in the simulation of fault with long recovering time and the simulative result is same as that of virtual value calculation.The transient trend of simulation is basically in accord with that of experiment,which proves the validity of proposed model.