Under the influence of DC bias, the iron core of the current transformer is prone to saturation, causing the ratio error to shift towards negative direction and the phase error to shift towards positive direction, resulting in measurement inaccuracy. This paper discusses the principle of the impact of DC bias on the error of current transformers, introduces a new type of anti-DC bias current transformer, which has anti-DC bias function compared to traditional current transformers. The paper briefly describes the verification requirements, methods, and schemes of
anti-DC bias current transformers, and conducts a large amount of experimental verification work. The paper also develops an AC / DC standard current transformer based on self-excited oscillation flux gate technology and magnetic integrator technology with an accuracy level of 0.02, which can measure both DC and AC, and has been applied in the error verification of anti-DC bias current transformers, achieving good results.