Scott G. McMeekin

Rolling element bearings are a critical component of rotating machines, and the presence of defects in the bearings may eventually lead to machine failure. Hence, early identification of such defects and severity assessment may avoid malfunctioning and breakdown of machines. Vibration signal features are often used to build fault diagnosis and fault classification systems. In this article, a novel refined composite multiscale dispersion entropy (RCMDE)-based feature is proposed using a nonlinear mapping approach using the generalized Gaussian distribution (GGD)-cumulative distribution function (cdf) with the different shape parameter $\beta $ . This work combines the GGD dispersion entropy (DE) algorithm within the RCMDE framework with a feature selection algorithm, which is then used as input to a multiclass support vector machine (MCSVM) model for categorizing rolling element bearings’ fault conditions. The proposed method is validated using Case Western Reserve University (CWRU), Jiangnan University (JNU), and Southeast University (SEU) datasets. The experimental analysis shows that the GGD-RCMDE features are better in terms of classification accuracy, precision, recall, and F1-score when compared with the existing approaches.

Electrical treeing (ET) can irreversibly deteriorate the insulation of polymeric power cables leading to a complete failure. This paper presents the results of an experimental investigation into the effects of unipolar and polarity reversing DC voltages on electrical tree (ET) and partial discharge (PD) behavior within high voltage direct current (HVDC) cross linked polyethylene (XLPE) cable insulation. A double needle configuration was adopted to produce non-uniform electric fields within the insulation samples, potentially leading to electrical trees. The development of trees was monitored through an optical method and the associated partial discharge signals were measured through an electrical detection technique, simultaneously. The analysis of the results shows reasonable relation between the formation of ETs and the type of the applied voltages. The polarity reversing attribute of the test voltages has a pronounced effect on formation and growth of electrical trees. This implicates an interaction between the space charges that accumulate within polymeric materials and the operational polarity reversing electric fields, which causes insulation degradation. Therefore, study of influencing HVDC operational parameters on insulation degradations can contribute to improvements in cable design and advancement in insulation diagnostic strategies applicable in HVDC systems leading to more effective asset management.

The aim of this paper is to investigate the various effects of climate conditions on outdoor insulators in coastal areas as a result of saline contamination under acidic and normal cold fog, determining significant electrical and physico-chemical changes on the insulator surface and considering the effect of discharge current, electric field distribution and surface roughness. To replicate similar conditions near the shoreline, experimental investigations have been carried out on insulation materials with the combined application of saline contamination and acidic or normal cold fog. The test samples included silicone rubber (SiR), ethylene propylene diene monomer (EPDM) and high-density polyethylene (HDPE), which were used as reference. The materials are of the same composition as those used in real-life outdoor high voltage insulators. All samples were aged separately in an environmental chamber for 150 h for various saline contaminations combined with acidic and normal cold fog, and were generated by means of the adopted experimental setup. This analysis represented conditions similar to those existing near the shoreline exposed to saline and acid spray during winter and early spring. Electric field and discharge current along polymeric samples were examined under acidic and normal cold fog. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopic (SEM) were used to probe the physico-chemical changes on the samples surface and investigate the hydrophobicity recovery property after aging tests. Finally, a comparative study was carried out on polymeric samples before and after being exposed to the acidic and normal cold fog based on the results obtained from the experiment. Research data may provide references for the better prediction of surface degradation as well as for the better material coating and design of external insulation.

Silicone rubber insulators are replacing the conventional ceramic and porcelain insulators rapidly in power transmission and distribution industry. Very limited field knowledge is available about the performance of silicone rubber insulators in polluted and contaminated environments and therefore need further investigation. A comprehensive analysis of silicone rubber sheets (intended for coating outdoor insulators) was carried out in this paper based on experimental results. The main performance parameters analyzed were arc inception voltage and flashover voltage. Dependence of these parameters on equivalent salt deposit density (ESDD), non-soluble salt deposit density (NSDD), relative humidity, ambient temperature, fog rate, dry band formation, dry band location and number of dry bands were investigated extensively. Insulator orientation and its effect on performance were also studied. The authors believe that this paper will provide a comprehensive knowledge about the flashover characteristics of silicone rubber insulators under humid, contaminated and dry band conditions. These results could be used in the selection and design of silicone rubber insulators for polluted environments.

The Finite Element Method (FEM) is commonly used for electric field simulation. This paper presents, for the first time, the calculation of the electric field intensity on one phase of a 245-kV OIP condenser bushing by FEM considering the effect of metallic-contained colloids deposition on the outer surface of lower porcelain. The distribution of the electric field on the surface of the bushing is calculated and the location of maximum electric field intensity of the bushing is determined. The spots having the maximum electric field intensity are the vulnerable areas from which the partial discharge may initiate. The extension of stained area due to the trapping effect of electric field is been considered.

Depositing very thin organic films on the surface of arrays of asymmetric split-ring resonators (A-SRRs) produces a shift in their resonance spectra that can be utilized for sensitive analyte detection. Here we show that when poly-methyl-methacrylate (PMMA) is used as an organic probe (analyte) on top of the A-SRR array, the phase and amplitude of a characteristic molecular Fano resonance associated with a carbonyl bond changes according to the spectral positions of the trapped mode resonance of the A-SRRs and their plasmonic reflection peaks. Furthermore, we localize blocks of PMMA at different locations on the A-SRR array to determine the effectiveness of detection of very small amounts of non-uniformly distributed analyte.

This paper presents a real-time implementation of partial discharge (PD) signal de-noising based on wavelet analysis. The results show that the Second Generation Wavelet Transform (SGWT) removes effectively white Gaussian noise (WGN), requires a smaller footprint and is less computationally intensive than the Discrete Wavelet Transform (DWT), reducing the cost for the hardware implementation. It is implemented on an OMAP-L138 processor as part of a real-time DSP-based PD monitoring system and its performance is determined. The throughput of SGWT de-noising, at different decomposition levels, using both cacheable and non-cacheable external mobile DDR memory addresses, is then evaluated.