High-Frequency Current Transformer Design and Implementation Considerations for Wideband Partial Discharge Applications

High-frequency current transformers are popular noninvasive inductive wideband sensors. Despite the simplicity in design and operational principle, implementation of such sensors for partial discharge (PD) applications requires careful consideration, particularly in the higher frequency range where traveling wave attenuation and distortion are relevant. First, the role of design variables, including core materials, winding design, and shielding practices on sensor sensitivity and frequency characteristics (transfer impedance), is presented. Next, the suitability of the constructed sensors for PD applications is assessed. The designed wideband sensors are suitable for laboratory applications with standard measurement circuits and controlled conditions. The low-level magnitude and frequency spectrum of the discharge pulses hinders signal integrity in relation to the placement of the sensors within the measurement circuit, signal amplification, and pulse repetition rate (pulse resolution). To enable the most stringent detection levels under 1 pC, efforts are needed in distortionless amplifier design and interference mitigation.