It can be seen that the error of current transformers is mainly determined by the magnitude of excitation current, and in order to improve the accuracy performance of current transformers, it is fundamentally necessary to reduce the excitation current of current transformers. In order to reduce the error of the transformer, we can start by optimizing the structural parameters of the open close current transformer, such as selecting soft magnetic materials with high permeability and low eddy current losses as the iron core, increasing the number of turns in the secondary winding, increasing the cross-sectional area of the iron core, and reducing the length of the magnetic circuit. However, these measures have their own limitations in application, such as inconsistency with actual application situations or low cost-effectiveness. Therefore, in order to further improve the accuracy performance of open and close current transformers, other compensation methods must be considered.
In order to further reduce the error of current transformers and improve their accuracy, it is necessary to compensate the existing current transformers. By analyzing the equivalent circuit of current transformers and combining existing research results, a systematic induction and in-depth study of compensation methods for current transformers were conducted. Finally, the compensation methods for current transformers were elaborated from three aspects. The idea behind these compensation methods is as follows.
1. Compensation method for self extracting excitation current
The excitation current is the main source of current transformer error. If the excitation current can be effectively extracted and injected into the secondary load, then the current on the secondary load has a strict ratio relationship with the primary current, that is, there is no error, thus achieving the purpose of compensation.
2. Compensation method for external excitation current
The excitation current is the fundamental reason for the operation of current transformers and cannot be completely eliminated. If the excitation current is provided through an external circuit, the primary current converted to the secondary side in the equivalent circuit will be equal to the secondary current, and the secondary current will have no error, thus achieving the purpose of compensation.
3. Compensation method for providing secondary potential
The magnitude of excitation current is directly related to the voltage at both ends of the excitation impedance. If the voltage at both ends of the excitation impedance is reduced, the magnitude of the excitation current of the current transformer can be reduced. Therefore, if an appropriate potential is provided in the secondary circuit of the current transformer to make the voltage at both ends of the excitation impedance basically zero, then the excitation current is basically zero, achieving the purpose of compensation.