A Review of Online Partial Discharge Measurement of Large Generators

Abstract

Abstract:Online partial discharge (PD) measurements have long been used as an effective means to assess the condition of the stator windings of large generators. An increase in the use of PD online measurement systems during the last decade is evident. Improvements in the detection capabilities are partly the reason for the increased popularity. Another reason has been the development of digital signal processing techniques. In addition, rapid progress is being made in automated single PD source classification. However, there are still some factors hindering wider application of the system, such as the complex PD mechanism and PD pulse propagation in stator windings, the presence of detrimental noise and disturbances on-site, and multiple PD sources occurring simultaneously. To avoid repetition of past work and to provide an overview for fresh researchers in this area, this paper presents a comprehensive survey of the state-of-the-art knowledge on PD mechanism, PD pulse propagation in stator windings, PD signal detection methods and signal processing techniques. Areas for further research are also presented.

Unsupervised Monitoring System for Predictive Maintenance of High Voltage Apparatus

“…The plot in Figure 8b gives-on the same time scale of Figure 8a-the average apparent charge per cycle q a (t) computed as per (3); here, the values of q a (t) have been normalized in the range [0, 1]. The plot in Figure 8c provides-on the same time scale of Figure 8a-the residuals referred to the linear regression computed on the data plotted in Figure 8 as per (4). As specified in Section 2 the linear regression is computed after removing the data belonging to the transient zone.…”

“…A predictive maintenance apparatus monitors an electrical machine continuously to prevent a breakdown in the insulation system [1][2][3][4]. Electrical, mechanical and thermal stress sources systematically contribute to deteriorate motors.…”

Generator Insulation-Aging On-Line Monitoring Technique Based on Fiber Optic Detecting Technology

“…They also have different coefficients of expansion. Severe vibration can introduce cracks inside the thick epoxy mica and voids inside the mica facilitating PDs [48][49][50][51][52][53][54][55][56]. Of course, winding temperature would depend on load which will show up in the temperature trending profile in an online monitoring configuration.…”

Application of a Novel Wavelet Shrinkage Scheme to Partial Discharge Signal Denoising of Large Generators

“…Partial discharge (PD) measurements have been made on electrical equipment insulation for many years and proved to be a sensitive means of insulation condition assessment and fault diagnosis [1][2][3][4][5][6][7]. However, electrical equipment operates in a strong electromagnetic environment, and PD on-line measurements are extremely affected and hampered by electrical noise [2].…”

“…A too large decomposition level will increase calculation complexity without significant improvement in the denoising effect; a too small decomposition level cannot achieve desirable denoising results. In previous studies, it was determined based on prior knowledge about signal energy distribution in the wavelet domain [6] or through trial and error [9][10][11], which is expert-dependent and subjective. Automatic approaches are introduced in references [17,19] aimed at guaranteeing that most energy of the signal is decomposed into detail sub-bands.…”