Interference mechanism of external current on heavy current transformer

In order to reduce the interference from stray flux of adjacent bus bars on the error of heavy current transformer (HCT) which always has a large diameter, the interference mechanism was investigated theoretically in details based on magnetic circuit. It was concluded that there were mainly two interference ways that the stray flux affected the error of HCT, and then it was further verified by experiments and finite element method (FEM). A formula was derived to calculate the error of HCT due to the interference. It was found that leakage flux around the core performed an important role in the error of HCT with a large diameter. Some methods were suggested to reduce the interference on HCT, especially when considering the nonuniform leakage flux along the large circumference of iron core.