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This article discusses an advanced method for estimating dc conductivity of oil using parameters evaluated under switching impulse voltage application. Firstly, the effectiveness of switching impulse application for assessing the condition of oil–paper insulation is investigated. Thereafter, the evaluated parameters under switching impulse voltage are fitted by Havriliak and Negami (HN) model for estimating the oil conductivity. The method is applied on oil-impregnated pressboards containing different moistures and a distribution transformer for experimental investigation. Moreover, the limitations of the proposed method are also discussed in this article. [ABSTRACT FROM AUTHOR]

This paper presents an advanced technique for calculating activation energy of oil-impregnated pressboard through dielectric response current measurement under switching impulse voltage at different temperatures. The proposed technique analyzes the measured impulse voltage and current signals to formulate its equivalent circuit at different temperatures. The equivalent circuit parameters are utilized to determine the shifting of ac conductivity curve along frequency axis with variations in temperatures. Based on the shifted ac conductivity curves at different temperatures, the corresponding activation energy of the insulation is estimated. The effectiveness of the proposed technique is investigated through a few laboratory prepared test samples. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the influence of surface charges on the discharge development across particle contaminated spacer surfaces for lightning impulse voltages. Results; Discussion; Conclusions.

The paper, prepared by CIGRE WG D1.25, presents the experience in practical application of sensitivity verification of the UHF partial discharge detection system for GIS after its introduction by ELECTRA Report in 1999. A detailed description of the two-step procedure, Step 1 in laboratory and Step 2 on-site, is given and supported by examples. Guidelines will help manufacturers and users in the effective application of the UHF method for PD detection on GIS and will permit to avoid technical misinterpretations. The procedure is described in details in CIGRE Technical Brochure. [ABSTRACT FROM PUBLISHER]

The paper, prepared by CIGRE WG D1.03 (TF 09), presents the guidelines for risk assessment procedure on defects in GIS based on PD diagnostics. The procedure, described in detail in CIGRE Technical Brochure 525, starts with sensitive PD measurement to detect the critical defects and follows with identification of the type of the defect and its location inside the GIS. This information taken together with other essential data from laboratory measurements, manufacturer's experience, design aspects and trend analysis of the PD activity, are the base for the estimation of the criticality of the defects. Finally, the risk assessment is performed based on the estimated dielectric failure probability and failure consequences that can be different in case of on-site testing or in service activity. [ABSTRACT FROM PUBLISHER]