This paper addresses the issue of current distortion and increased transmission errors of current transformer caused by DC bias.It proposes a quantitative method for calculating the secondary side current and transmission error of current transformer affected by DC bias.This method resolves the problem of reduced accuracy in existing calculation techniques when the current transformer experiences significant saturation due to DC bias.The nonlinear magnetization characteristics are divided into unsaturated and saturated regions.By using the relationship between the initial and final values of the TA current curve in both regions

an analytical expression for the secondary side current of the TA under DC bias is derived.The fundamental component is then solved

enabling the quantitative calculation of the current transformer’s angle and ratio differences under DC bias.The accuracy of the theoretical formulas is validated through Simulink simulations.The results also show that as the DC bias current increases

both the ratio difference and angle difference remain stable initially and then increase linearly.