A Comparison between Piezoelectric Sensors Applied to Multiple Partial Discharge Detection by Advanced Signal Processing Analysis

Abstract

The development of sensors applied to failure detection systems for power transformers is a critical concern since this device stands out as a strategic component of the electric power system. Among the most common issues is the presence of partial discharges (PDs) in the insulation system of the transformer, which can lead the device to total failure. Aiming to prevent unexpected damages, several PD monitoring approaches have been developed. One of the most promising is the Acoustic Emission (AE) technique, which captures the acoustic signals generated by PDs using piezoelectric sensors. Although many studies have proved the effectiveness of AE, most signal processing approaches are strictly related to the frequency analysis of PD signals, which can hide important information such as the repetition rate of the failure. This article presents a comparison between two types of piezoelectric transducers: the microfiber composite (MFC) and the lead zirconate titanate (PZT). To ensure the detection of multiple PDs, time–frequency analysis was carried out by short-time Fourier transform (STFT). Intending to compare the sensibility of the transducers, the AE signals were windowed, and the root mean square (RMS) value was extracted for each part of the signal. The results indicate that spectrogram and RMS analysis have great potential to detect multiple PD activity. Although MFC was two times more sensitive to PD detection than the PZT sensor, PZT presents a higher frequency response band (0–100 kHz) than MFC (80 kHz).

Use of DSLR and Sonic Cameras to Detect and Locate High-Voltage Corona Discharges

“…Acoustic methods are widely recognized as capable of detecting partial discharges, as described in the IEC TS 62748:2016 international standard [ 53 ]. They often use piezoelectric sensors jointly with suitable signal processing approaches [ 54 , 55 ]. For the detection and location of corona discharges, an NL sonic camera has been used, whose main characteristics are summarized in Table 2 .…”

Localization of Dual Partial Discharge in Transformer Windings Using Fabry–Pérot Optical Fiber Sensor Array

“…The general acoustic localization method involves the use of piezoelectric transducers (PZTs) that are magnetically attached to the metal shell of the transformer tank [8]. The position of the partial discharge source is inferred by utilizing the time difference between the arrival of ultrasonic signals generated by partial discharge at different piezoelectric transducers [4,[9][10][11][12][13].…”

Assessment of Rogowski Coils for Measurement of Full Discharges in Power Transformers

“…Partial discharges (PDs) are low-energy ionization processes that occur due to a local field concentration in a dielectric material [3]. On the other hand, full discharges (FDs) perform the complete disruption of the dielectric and can occur permanently or in random periods [4][5][6]. PDs and FDs are characterized as electric non-conformities that emit UV radiation, current pulses, and acoustic and electromagnetic waves, causing a progressive deterioration of the insulation components.…”

“…In experimental tests, full discharges were induced in an oil-filled transformer, and the current signals produced by the Rogowski coils were compared using Power Spectrum Density (PSD) [2]. The Short-Time Fourier Transform (STFT) [6] was applied to detect repetitive discharges. The results indicated that the Ferrite core demonstrates high sensitivity in the frequency band between 0 and 1 MHz.…”