Vibration Simulation Of Three Phase Five Limb Transformer Under GIC

Geomagnetic storm disasters occurred now and then.The problem of the geomagnetic induced current(GIC)damage to the power transformer is gradually being concerned by the transformer designer,producer and operator.Especially with the increase of power grid scale and the increase of voltage level,the amplitude of GIC will increase and the phenomenon of transformer vibration and noise enhancement will become more serious.This will threaten the safe operation of the transformer,reduce the service life of the transformer,and adversely affect the physical and mental health of the surrounding residents.In order to obtain the vibration characteristics of power transformer under GIC,we set up a three-dimensional coupling model of the circuit-magnetic field-mechanical field of the transformer under GIC by analyzing the mechanism of transformer vibration under GIC.Also,we take the three-phase five column transformer as an example for simulation.The main research contents are as follows:(1)Based on the study of the magnetostrictive properties of silicon steel sheet,the calculation method of equivalent magnetostrictive force is proposed.On the basis of measuring the magnetostrictive curve of the silicon steel sheet,the calculation formula of the magnetic force of the iron core is derived by using the theory of elastic mechanics.(2)Based on the equivalent circuit of the transformer,the(7)A,?-A(8)method for solving the three-dimensional eddy current field and the basic theory of the transformer vibration,the three-dimensional coupling model of the circuit-magnetic field-mechanical field of the transformer under GIC is established.The model can be used to analyze the excitation current,magnetic flux density and the vibration displacement of the transformer.(3)Taking a three phase five column transformer as an example,we calculated the distribution of the vibration displacement of the iron core under di fferent GIC.We obtained the excitation current,magnetic flux distribution and the time domain and frequency domain characteristics of the transformer under different GIC.The simulation results verify the feasibility and correctness of the model and the method.(4)By the vibration simulation of different position of the transformer core at different GIC,we found the weak link of the transformer in vibration,and put forward the measures of reducing vibration and noise of the tran sformer.The simulation results and the model established in this paper can be used to guide the optimization design of the transformer structure,reduce the adverse effects of GIC on the vibration of the transformer,and promote the development of fault vibration monitoring method.