This paper describes the linearity calibration of power sensors using the setup for the direct comparison method. To achieve sufficient dynamic range an attenuator is used. The S-parameters of the attenuator need not be known because the effective attenuation can be calculated from two sets of measurements on the device under test. This way the linearity is traced to a monitoring power sensor instead of the Sparameters of the attenuator. The method is verified with a bilateral comparison.
High-frequency current transformers are popular noninvasive inductive wideband sensors. Despite simplicity in design and operational principle, implementation of such sensors for partial discharge applications requires careful consideration, particularly in the higher frequency range where traveling wave attenuation and distortion is relevant. First, the role of design variables, including core materials, winding design, and shielding practices on sensor sensitivity and frequency characteristics (transfer impedance) are presented. Next, the suitability of the constructed sensors for partial discharge 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 most stringent detection levels under 1 pC, efforts are needed in distortionless amplifier design and interference mitigation.Index Terms-current transformers, frequency-domain analysis, high-voltage techniques, partial discharge measurement, time-domain analysis.
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