Very Fast Transient Analysis of Transformer Winding Using Axial Multiconductor Transmission Line Theory and Finite Element Method

A transformer white box model based on multiconductor transmission line (MTL) theory in cylindrical coordinates has been developed. This model allows variable lengths in conductors to be incorporated into the MTL formulation. A 2D axisymmetric model for the windings is implemented using finite element method (FEM) to determine the per unit length capacitance and inductance matrices. The model is capable of producing voltage and current results in both the frequency and time domains for each turn in the winding. The results obtained using the proposed model has been compared with those from Numerical Electromagnetic Code (NEC) and measurements done by others. Applications of the proposed model in analyzing inter-turn voltages and the induced voltages on secondary windings have been investigated.