Research on the Influence of Primary Load Imbalance on the Combined Transformer’s Error

According to the procedure, measurement of the error of three-phase three-element combined transformer should adopt three-phase detecting method that could detect the actual error. A three-phase three-element combined transformer has both current transformer and voltage transformer, and the distance between each of them is quite close, thus, the electromagnetic interference is unavoidable. Imbalanced primary load occurs frequently in power system operation. In order to study the effect of electromagnetic field in this complex situation on the error characteristics of combined transformers, the following work is carried out in this paper: developing a three-phase detecting test platform and working on the platform to carry out an experiment about the influence of primary load imbalance on the error of the three-phase three-element combined transformers. The experimental results show that the imbalance of the primary load will lead to great impact on the error of voltage transformer in combined transformer, the maximum ratio error is 0.25 and the phase difference could be up to 4.9’. The primary load imbalance has rare effect on the error of current transformer. In order to further verify the influences of the primary load imbalance on the three-phase three-element combined transformers’ error characteristics, a three-phase three-element combined transformer model is to be established and the error characteristics of three-phase three-element combined transformer will be simulated and analyzed under the imbalanced primary load. The proportion of combined transformer in power grid measurement is very large. It is of great engineering value and academic significance to study the error characteristics of combined transformer and ensure that it can accurately carry out electric energy measurement during operation.