A Passive RF Sensor for Detecting Simultaneous Partial Discharge Signals Using Time–Frequency Analysis

In this paper, a passive radio-frequency (RF) sensor has been presented for non-invasive radiometric detection of simultaneous partial discharge (PD) signals in high-voltage (HV) equipment. The sensor is a multi-resonator-based passive circuit with an antenna for capturing PD signals. The low-cost RF sensors are installed in HV sensing units for monitoring multiple units simultaneously. Each sensor captures PD signal and processes it with distinct spectral signatures as identification data bits and transmits the signal to a single sampling channel. From the captured RF signal, both the PD level and the source identification can be retrieved. Our proposed passive sensor addresses both aspects of PD monitoring, PD detection, and faulty source identification. Moreover, in identifying the data bits, the time-frequency analysis is utilized for superior detectability. This analysis enables the detection of multiple PD events separated by a defined time delay, although they occur at the same instance. Thus, the sensor can distinguish simultaneous PD occurrences from multiple sources, which is a novel contribution in PD detection. The proposed sensor system provides low-cost, passive condition monitoring of HV units in a distribution substation.

I. Introduction

Partial discharge (PD) detection and localization techniques have been developed since the early 1940s. The principle of measuring the level or severity of dielectric degradation in a power equipment is to estimate the change of temperature, pressure or electrical stress during PD [1], [2]. These changes result in different physically observable signals, including electrical [3] and acoustic pulses [4], ultraviolet ray, temperature variation [5], gas discharge [6] and RF emission [7], [8]. As a result, a number of methods have been found for detecting PD signals, which can be grouped into six categories, based on the PD manifestation that they measure. These are (i) Chemical detection, (ii) Electrical detection, (iii) Acoustic detection, (iv) Optical detection, (v) Infra- Red detection and (vi) Radiometric detection.