Behavior modeling of a type B RCD

Unlike to current transformer, a residual current sensor is highly sensitive to the input leakage current and core material. It senses the leakage current that is produced due to faulty condition in the electrical circuit or unintentional body touch to the equipment through conductive tracking of the insulation medium. The leakage current which the sensor detects consists of ac residual current with fixed or multiple frequencies, pure dc, half or full wave pulsed dc and mixed leakage current along with high frequency. A conventional current transformer will not be able to detect such current. At the outset, the paper explains in detail about various sensing technologies applicable to a residual current device. MATLAB simulation result shows the effect of different input leakage current upon the output characteristics of CBCT. Pspice simulation explains about the signal conditioning of the CBCT output for actuation of the tripping mechanism of the RCD. Later part of the paper explains about its behavior modeling due to external magnetic field interference. It suggests about means of shielding against external magnetic field. Transient electromagnetic analysis shows that by means of shielding the CBCT using a low permeable material, the performance of RCD can be improved.