Characterization of a Signal Conditioning Circuit Based on Envelope Detection for the Detection of Partial Discharges in UHF

The radiometric acquisition of partial discharges in the UHF spectrum requires acquisition equipment with high sampling rates and bandwidths, which makes detection more expensive. The use of signal conditioning circuits to reduce the acquisition hardware requirements is a practice with the potential to decrease the price of monitoring the quality of electrical insulation by partial discharges. However, the signal conditioning circuit electronic components should be characterized for the efficient phenomenon detection, since the strengths and weaknesses of the each one of these components can be detected, improved, and even combined to obtain a more effective monitoring system. In this way, the characterization of a partial discharge detection system, that uses a signal conditioning circuit based on envelope detection, is performed in this work to verify the operability of the selected electronic components for this purpose. The partial discharge detection is performed by a Circular Printed Monopole Antenna (PMA) and the signal conditioning circuit is composed by filter, low noise amplifier (LNA) and a Schottky diode-based envelope detector. The transmission coefficient of filter was measured, the figures of merit of LNA like transmission coefficient, noise figure and 1dB compression point were measured. Furthermore the envelope detection was verified with the frequency spectrum of conditioning signals. The proposed circuit was able to trace the envelope of partial discharge pulses and reduce their acquisition rate by 87 times.