Identyfikacja obecności osadów w izolacji transformatorów energetycznych

Omówiono zasadę szacowania zawilgocenia izolacji papierowo-olejowej transformatorów metodą skojarzonego pomiaru "RVM-PDC". Stwierdzono, że skojarzony pomiar "RVM-PDC" poprawia jakość szacowania, zwłaszcza w transformatorach o niejednorodnej morfologii izolacji. Przedstawiono przemysłowy miernik realizujący pomiar w trybie "RVM-PDC". Metoda ta, po uwzględnieniu badań olejowych, daje możliwość identyfikacji osadów na części aktywnej transformatorów. Zaprezentowano przykłady identyfikacji osadów na obiektach rzeczywistych.

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The principle of moisture contents assessment in transformer paper-oil insulation by means of the joint RVM-PDC measurement is described. Such a measurement is based on using the first two steps of the RVM method for additional determining of the insulation setup time characteristics of charging and discharging currents. The difference between these currents with capacitance of windings allow calculating cellulose conductivity which is the function of tempera-ture and moisture contents. In this way it is possible to assess the water contents on the basis of two various electrical phenomena: polarization and conductivity. It was found that the joint RVM-PDC measurement increased the quality of assessment, especially for transformers of non-homogenous morphology of insulation. This method, together with additional consideration of oil tests, allows sludge identification on the active part of transformers. The principle of identification is based on finding large differences of the moisture level assessment from RVM and PDC tests. The sludge presence on the insulation surface can be treated as equivalent of additional moisture contents. In such a case the RVM test gives too high results of water contents in cellulose. On the contrary, the PDC test is not significantly influenced by this effect. The more sludge on the insulation, the more visible this phenomenon is. The insulation ageing also results in physicochemical changes of oil properties, especially in the losses coefficient tg?, acidity, resistivity and furans contents (2-FAL). The analysis of results obtained from insulation electric tests and oil physicochemical tests allows determining if the insulation is with unbalanced water contents in the paper and oil or with sludge presence. Some examples of sludge identification performed on real objects are shown. The internal inspection of the transformer confirmed positive diagnosis on sludge presence.