Search

Article presents experimental analyses of faults in winding of transformers and rotating electric machines. The first part of article deals with the possibilities of diagnostics for windings electrical machines. The second part of article deals use of frequency method SFRA (Sweep Frequency Response Analysis) for analyse winding fault. Finally, the article presents experimental measurements of diagnostics for analysis of the windings in distribution transformer and rotating electric machine. On both of the investigated machines is analyzed internal winding fault.

The paper presents a stand for measuring the oil absorption rate during impregnation of electrotechnical pressboard or other porous materials. The stand allows for accurate record of absorbed oil volume and the time in which it was absorbed. It was found that the time needed to complete impregnating of pressboard is about 2×106 s. At this time, pressboard absorbs the insulating oil in a volume of approx. 25.6% its volume. This means that the free spaces occupy about 25.6% of pressboard volume. The testing of the pressboard free surface showed that it is about 10 m2 per cm3. Based on these data, it was found that the average value of capillary diameter in the pressboard is about 25.6 nm.

In the paper presents compares the DC conductivity of the insulating oil manufactured by Nynas and electrical pressboard Pucaro companies impregnated with the same insulating oil with different moisture contents. The study of conductivity for both materials were made for the measuring temperature in the range of 20 °C to 80 °C and measuring voltages in the range from 20 V to 1000 V. In the Arrhenius plots for both materials were been performed linear approximations of experimental results. On the basis of Arrhenius plots for the oil and the sample for the pressboard, for all measuring voltages, the value of the activation energy value of the DC conductivity and the determination coefficient R2 was determined. The value of the determination coefficient close to one indicates the high accuracy of conductivity measurements. Comparing the activation energy value of the DC conductivity for insulating oil and pressboard impregnated with the same oil, it can be concluded that the conduction in pressboard is not caused by the presence of oil in the solid component of the paper-oil insulation.

This article is focused about for electronic proposal measuring system of moisture analysis by return voltage method (RVM) for power oil transformers. RVM method is wide state specifying method which is not set in standards but in many cases is a method which is determining a clear and exact result. The results have mainly shows moisture content, content of conductive impurities in oil and degree of aging of paper insulation impact.