Development and modelling of a new type of sensor for detecting current transients for power system protection

A new type of sensor is proposed to detect high frequency transients in currents and their initial polarities. The proposed sensing system replaces both high frequency signal sampling and processing by a simple detection coil wound on a ferrite core and an analogue electronic circuit. It is verified through laboratory experiments that transient occurrence, occurrence time, and initial transient polarity can be determined accurately. A detailed model of the sensor, including the dynamic hysteresis characteristics of the ferrite core, is developed and implemented on an electromagnetic transient simulation software, and verified through experimental measurements. Application of the developed model to simulate a transient current polarity comparison based protection scheme is demonstrated. The versatility of the proposed sensor compared to common digital signal processing based approaches, namely discrete wavelet transform and mathematical morphology, is highlighted using experimental waveforms.