Design of a DC Residual Current Sensor Based on the Improved DC Component Method

Personal safety in low voltage direct current (LVDC) system is very important, while the occurrence of electric shock can be greatly reduced with the DC-residual current device (DCRCD). There are some defects in the application of DC component method based on magnetic modulation to make DCRCD. The DC component is not equal to zero after eliminating the leakage current signal, which may affect the subsequent detection of DC leakage and cause the malfunction of DC-RCD. In order to solve this problem, an improved DC component method was presented in this paper. A DC residual current sensor (DC-RCS) based on the single-core voltage-type magnetic modulation is designed. The DC-RCS is realized by adding two compensation circuits and a single-chip microcomputer. A detailed design procedure is described and an experimental prototype is used to validate it. The results show that the DC component can be compensated to approximately zero, thus the occurrence of malfunction can be effectively avoided.