The detection of partial discharges in transformer oil
Department of Electrical Engineering
Master of Science
Misra, Raj Pratap
Ball, W. H. Warren
Electric insulators and insulation--Oil
The level, meaning the number and the intensity Of partial discharges that occur in transformer oil per time period of applied pulse when a high voltage is applied can be used as a measure of the quality and remaining life of the oil. The level of partial discharges at a given applied voltage can be correlated with the degree of contamination of the oil by impurities such as water and conductive particles and can be used as an indicator of the proximity of the oil to breakdown. There are several approaches to the detection of partial discharges, e.g., acoustic measurements, electromagnetic measurements, and charge measurements.
In this study, a comparison was made among different types of partial discharge detectors. The radiated radio frequency (rf) emission of the partial discharges in the oil was simultaneously measured with the partial discharge currents detected by a capacitively-coupled detector. The discharges were measured under uniform field conditions and using a sinusoidal voltage of 60 Hz. A second experiment was run in which the currents due to the partial discharges were measured inductively and compared with those measured by the capacitively-coupled detector. The second experiment was run using an impulse voltage and a nonuniform field geometry. In both experiments, it was observed that the detector with capacitive coupling had greater sensitivity than either of the other two systems.
A discussion of the reasons for the differences in sensitivity along with a comparison of other discharge detection methods is included.
njit-etd1984-008 (90 pages ~ 5,229 KB pdf)
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Created March 23, 2004