The breaking step voltage and current of on-load tap changer in two-core phase shifting are closely related to on-load conditions.To determine the effects of on-load conditions on technical parameters of the on-load tap changer

by introducing the working principle and operational characteristics of two-core phase-shifting transformer

we deduced a practical and accurate formula about step voltage under the conditions of on-load.Taking a 230 k V/150 MVA two-core phase-shifting transformer as an example

we verified the accuracy of the proposed formula by comparing the MATLAB/SIMULINK simulation results with the results obtained by the formula.Then

we analyzed the relationship between the step-voltage and the load characteristics.It is demonstrated that more accurate technical parameters of the on-load tap changer can be determined by the calculation method based on the on-load conditions.Furthermore

a conclusion is drawn that the step-voltage increases with the growth of power factor by analyzing the influence of the load power factor on the maximum step-voltage.