Wavelet-Based Flashover Prediction Using High-Frequency Components

Abstract

Abstract - In order to monitor operating performance of contaminated outdoor insulators, a wavelet-based flashover prediction method is proposed. In most cases, the low-frequency components, namely, fundamental, 3 rd , and 5 th harmonic components have been mainly used for the sake of the spectral analysis of the leakage current. However, in this paper, the detail coefficients of wavelet transform representing high-frequency components are used as important information to predict a flashover in the contaminated insulator. Experimental results verify that the proposed method has a superior capability for flashover prediction.Key Words : Flashover Prediction, Contaminated Insulator, Leakage Current, Wavelet Transform, High-Frequency Components*정 회 원 : Kyungpook National University, School of Electrical Engineering and Computer ScienceE-mail : songyc03@ee.knu.ac.kr접수일자 : 2010년 1월 27일 최종완료 : 2010년 3월 3일 1. Introduction With increasing application in wet and contaminated conditions, such as salt-fog environments, outdoor insulators are exposed to long-term humidity and severe contamination. Once the moisture on the insulator surface is condensed to form continuous wet film, leakage current will be driven by source voltage to pass through the conductive layer. Thermal energy produced by the current cause evaporation of the layer and formation of dry-band gaps. Once the electric field at these gaps reaches the breakdown strength of air, dry-band discharges will occur. Due to initiation and development of the discharges, flashover may take place and affect operating reliability of power systems. From the viewpoint of reducing costs and minimizing risk of damage to people Camcorderand property, it is urgent to develop methods for monitoring outdoor insulator performance in contaminated environments. Current methods include the equivalent salt deposit density (ESDD), optical measurements, and leakage current measurements. In particular, the leakage current can provide much useful information on the state of a contaminated insulators, thus, several approaches using the leakage current have already been introduced to monitor the contamination conditions of outdoor insulators, for example, deterioration pattern analysis, leakage current property comparison under various circumstances, spectral analyses, and stochastic analysis using a Hilbert transform and the level crossing rate [1-6]. However, in most case, the low-frequency components, namely, fundamental, 3