Showing papers by "Sivaji Chakravorti published in 2012"

A methodology for identification and localization of partial discharge sources using optical sensors

Abstract: The present work represents a methodology to detect the location of single as well as multiple Partial Discharge (PD) sources by optical method and to investigate the performance of optical sensors for this purpose. An experimental setup has been arranged in the laboratory for generation of PDs, optical sensing and analysis of the recorded signals obtained from multiple optical sensors. The analysis results prove the effectiveness of the methodology using optical sensors to find whether PD is occurring at single location or multiple locations. For identification of PD locations pattern recognition technique has been utilized by considering the received optical energy as a feature. For feature selection and classification two techniques have been evaluated, viz. Gaussian Mixture Model (GMM) and Support Vector Machine (SVM), and both have shown promising performance. SVM in regression mode was used for identification of unknown PD location/locations. In this case average accuracy obtained was 92.6% when PD is occurring at one location and 80.1% when PD is occurring at two locations. The obtained results indicate that, the proposed methodology can be used to locate partial discharges in high voltage equipment where the optical signals due to discharges find a path to get radiated towards the outer surface.

Identification of simultaneously occurring dynamic disc-to-disc insulation failures in transformer winding under impulse excitation

Abstract: A method for identification and localization of isolated as well as simultaneous dynamic series insulation failures in transformer winding has been proposed. Trained wavelet network has been employed to identify the fault characteristics, viz. location(s), nature(s) and type of unknown impulse insulation failures. The network identifies the simultaneous dynamic insulation failures using the cross-wavelet transform based features extracted from recorded winding currents resulting impulse excitation. Four different fault emulators have been used to emulate different combinations of simultaneous dynamic disc-to-disc insulation failures in transformer winding. It has been found that the developed network with extracted features has identified the fault characteristics of simultaneous dynamic series insulation failures of transformer winding insulation within ±9% of winding length with good accuracy. The characteristics as well as experimentation details of simultaneously occurring dynamic disc-to-disc insulation failure(s), cross-wavelet transform based feature extraction and wavelet based fault characteristics identification are explained.

Surface resistance modified electric field computation in asymmetric configuration using surface charge simulation method: a new approach

Abstract: A novel formulation has been proposed in this paper for the calculation of asymmetric electric field including surface resistance using Surface Charge Simulation Method (SCSM). The formulation has been tested for a partly conducting dielectric sphere placed in uniform sinusoidal field and also for an axi-symmetric post type insulator. Finally the method has been applied for computing the effects of resistivity on the field around the solid components of high voltage metal enclosed equipments having asymmetric geometries. The effects of surface resistivity on the field distribution for different examples have been reported in details. The results are in good agreement with those reported in previous literature for axi-symmetric insulator. For asymmetric spacers the results highlight the locations of field enhancement, which is practically significant for compact gas insulated systems.

Modeling of self consistent field due to volume charge using charge simulation method and method of characteristics line

Abstract: This paper presents a numerical solution of electric field that is modified by the presence of volume charge within the region of interest. The effect of the presence of volume charge within the region of interest has been studied for both uniform and nonuniform fields. Charge simulation method coupled with the method of characteristics line is used to provide the numerical solution for the charge modified field. These two techniques are applied iteratively to converge to a self-consistent field model between the two surfaces in xerographic process. Detailed results are presented in the paper to show how the presence of toner as volume charges affects the field distribution when they are present within the field of interest.