Calculation of over-voltage distribution of transformer windings under very fast transient over-voltages（VFTOs）is very important to insulation design of electric transformers.In order to investigate over-voltage distributions of large-scale electrical transformer windings under VFTOs

a model using centralized parameters is presented in this paper.For the first several easily-burnt windings

neglecting frequency-varied impedance effect

each winding is modeled as one unit

and other windings are modeled every two windings as one unit

then a multi-conductor transmission line model（MTLM）for transformer windings is proposed.Transient over-voltage distributions are computed via the Lax-Wendroff difference method with third-order precision

and the frequency-varied parameters are dealt with by the vector fitting method to deduce transient computational formulas based on the Lax-Wendroff difference method.Computational results are consistent with the simulation ones of the electromagnetic transient program（EMTP）

which verifies the feasibility and validity of the proposed algorithm.