Search

This study presents two different methods under uniform and non-uniform pollution layer in order to measure and calculate the leakage current (LC) of silicone rubber insulators. Experimental test for evaluating the LC analysis of polluted insulator have been done in a laboratory clean fog chamber. The electric field and potential distributions were obtained from finite element method software for 3D models. The mathematical background and circuit theory are described in details by a section of insulator and using the extended form factor formula. The surface conductivity used in the calculations was extracted from the measured LC after wetting rate. LC characteristics under 1 : 1, 1 : 2, 1 : 5 and 1 : 10 ratios of top to bottom surface salt deposit density on polymeric insulators are studied. To verify the proposed models of this study, the results of experimental data and two other approaches are compared with together before dry-band formation. Moreover, a dynamic LC model under uniform pollution layer has been introduced and extended in order to calculate the LC when the formation of dry-bands along the insulator surface occurs. The dynamic model is drawn from experimental data and measured surface conductivity. [ABSTRACT FROM AUTHOR]

In this paper, an experimental test results on silicon rubber insulator with voltage of 20 kV have been shown. Artificial aging on insulator has been done using solid layer methods according to IEC60507 standard. Leakage current waveforms during the experimental studies were measured. Normally Fast Fourier transform method used to find the harmonic spectrum in the leakage currents. Three states of analysis are considered. In the first state, it is done with nominal voltage and without arc. In the second state, it is done in the presence of dry band arcing and corona discharge and in the last case, continuous arc is investigated and in each state harmonic analysis is performed. It is observed that in second state the third harmonic components increase rather than in the first state. Artificial aging on insulator has been done using solid layer methods according to IEC60507 standard. Leakage current waveforms during the experimental studies were measured. Eventually, to distinguishing pollution intensity, equivalent salt deposit density calculations are implemented. At the end, finite element method has been investigated for the results of water droplets existing on the surface of silicone rubber materials and electric field distribution along the surface of insulator. [ABSTRACT FROM AUTHOR]

Every few years, some samples of insulators should be taken from overhead lines to monitor their operational condition. Since most insulators are not installed in standard atmospheric conditions, their performance evaluation using flashover voltage needs a correction factor to obtain the real breakdown voltage from test results. In this article, the validity of IEC spark over atmospheric correction factor for this purpose was studied. Moreover, the effect of pollution on the leakage current of silicone rubber insulators has been evaluated. Finally, the results have been analyzed to find appropriate correction factors and to discover the relationship between insulators' leakage current and their status. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) radiation decreases the hydrophobicity of silicone rubber (SiR) insulators. Lack of hydrophobicity on the surface of such insulators lowers the flashover voltage and increases the Leakage Current (LC) of insulators in the moist environment. This paper presents the artificial UV radiation effects on three types of 20 kV SiR insulators in a chamber with nine UV-C lamps (50 W/m2) for up to 5000 hours. To simulate the moist environment, solid layer method is applied according to IEC 60507 that includes artificial pollution deposition on the insulator surface. Fast Fourier transform of the LC waveforms indicates that the third and the fifth harmonic components are quite sensitive to any incremental discharge on the insulator surface. This sensitivity makes the frequency spectrum of the LC a good criterion to distinguish three distinct SiR insulator situations under the electric stress: 1) no discharge, 2) dry band arcing/corona discharge and 3) continuous arc. Thermogravimetric analysis (TGA) and scanning electron microscope images depict that the polluted insulators include much larger degraded parts under electric stress after aging. Measurements also show that the flashover voltages and the hydrophobicity of aged insulators decrease as the UV exposure time increases for different levels of moisture and pollution. [ABSTRACT FROM AUTHOR]