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Extensive high resolution electro-optic Kerr field mapping measurements have been taken with transformer oil near 20°c using parallel plane electrodes and field strengths near 0.2 MV/m. Static field measurements have been extended to the transient period following the application of a step voltage. Significant space charge effects resulting in electrode fields being enhanced by a factor of up to 2...
PCB's are persistent ecological poisons. Hence the search for alternative dielectric liquids for use in fire-resistant transformers. One approach has been to use non-flammable vaporizable fluids such as the fluoroocarbon C8F160 which boils at about 101°C at atmospheric pressure.
Samples of two types of insulating oil used in transformers and switch-gear components in Egypt are experimentally tested to determine the breakdown-change of their dielectric constant and of their breakdown voltage. A standard oil tester is used to apply high voltage to the samples at two different rates and two different time intervals. The breakdown voltage of each sample is measured at the two...
Particle deposition occurs very rapidly and it modifies significantly the breakdown voltage and the metals content of transformer oil. This leads to unrealistic values not representative of the oil's condition in the transformer. It has been shown that particles in oil homogenization can be successfully achieved by 25 min of ultrasonic agitation for a I-liter volume of oil. This simple, rapid and...
An experimental study on the combined γ-radiation and heat effects on the electrical properties of transformer oil is presented. Several samples of fresh unused transformer oil of the type used in Egypt is irradiated in a γ-cell for different time periods, at the same radiation conditions. Each sample, one at a time, is then raised to a different pre-specified temperature. At this temperature, we...
The viscosity values may be fitted over the whole range 10−3 – 1012 by the Cohen Grest relation with great accuracy and a standard deviation less than 5 to 8 10−2. However to calculate the 4 C.G. - parameters it is necessary to get precise data over a large range of viscosities about 8 to 10 orders of magnitude. If it is not the case a 3-parameters equation as the VFTH relation may be sufficient for...
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