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This paper aims at presenting results related to electrical breakdown of oil paper insulation systems by puncturing of paper insulation. In the investigations the used experimental setup is a needle-plane geometry with sheets of paper inserted in the oil gap. The voltage applied to the needle is a Lightning Impulse (LI) of positive polarity. The propagation of streamers was studied by an ultra-high-speed...
This article studies the apparent resistivity of mineral oil as a function of electric DC stress using theoretical and experimental methods for three different oils. The experimental measurement of the apparent resistivity is done using a cell with two bare Rogowski like electrodes separated by a 2mm gap. The dc current is measured after one hour and the stress is varied in steps. For low DC stress...
The aim of this paper is to develop a theoretical foundation of the reversed polarity method for measuring the mobility of ions in transformer oil. The results of the measurements of transient currents in oil, showing very distinct transient current peaks appearing after polarity reversal, are evaluated by computer simulations using an ion drift model. It is found from the analysis that the peaks...
Corona currents in air measured in a large scale coaxial geometry (douter = 1 m, dinner = 0.26 mm), under both DC and AC voltages of a triangular shape with frequencies in the range (1–50) Hz are analyzed. A computational model describing dynamics of positive and negative ionic charges is employed to examine the results of the measurements. The performed simulations show a good overall agreement with...
Conduction process in dielectric liquids usually occurs due to ion migration and is therefore characterized by concentration and mobility of the ionic charge carriers. For this reason accurately determining these parameters and especially ion mobility in insulating oils for HVDC applications needs to be done precisely. In this report various methods for determining ion mobility are described, including...
Nanotechnologies have potential to be used in transformer industry in enhancing material properties which may lead to a compact design of transformer and reduced manufacturing cost. In this publication, breakdown physics in nanofluids is studied for transformer insulation liquid. Several types of nanoparticles were selected and added into mineral oil. Breakdown voltage, streamer propagation velocity,...
Transformer oil is one of the most important and widely used of all dielectric liquids. Significant research into the insulating properties of transformer oil has been carried out. Much of this work has focused on the development of streamers, and how they can result in the electrical breakdown of the oil. Due to the complex nature of transformer oil no universally accepted model describing streamer...
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