Voltage Distribution Of Transformer Windings Under VFTO

In Gas Insulation Substations(GIS),the splitting operation of indoor or outdoor isolation switches(QS),circuit breakers(QF),or the occurrence of short-circuit faults have a great potential to cause steep pre-wave overvoltage.Also known as VFTO(Very Fast Transit Over voltage),when such a voltage waveform invades the transformer coil,it will cause a very uneven voltage distribution,causing the insulation of the transformer winding coil to be damaged.Therefore,Accurate calculation of the over-voltage distribution of transformer windings under the action of VFTO and summary of impact laws are of great importance to ensure the stability of transformer insulation and ensure the safe and reliable operation of Transformer.According to this background,this paper,combined with the winding coil of the oil-immersed power transformer produced by Zhongrong Electric Power Co.,Ltd.,simulated and compared the potential distribution of the transformer windings under the ultra-fast transient overvoltage,and based on the multi-wire transmission theory.A multiconductor transmission line mathematical model of winding is established,and the corresponding mathematical model is simplified taking into account the boundary condition constraints.The electrical parameters of winding are obtained by means of finite element software and energy function method.The frequency domain expression of parameters is obtained by vector matching and volumetric method,and the differential equations are solved by spatial discrete and finite element theoretical analysis method.Finally,the advantages of the finite element method are verified and the conclusion of voltage distribution is obtained by the actual measurement and simulation of the single Transformer winding model.The results of the comparison analysis verify the scientific nature and accuracy of the proposed method in this paper.At the same time,this method is applied to ensure the insulation performance of transformer windings by putting forward reasonable and feasible overvoltage protection measures.