EKSPLOATACIJA TURBOGENERATORA SA SMETNjAMA U SISTEMU HLAĐENjA VODOM NAMOTAJA STATORA

The paper describes the disturbance in the water cooling system of the stator windings, as a consequence of the deposition of copper oxides in the "hollow" conductors of the stator bars. The presence of copper oxide deposition is determined on the basis of monitoring the water temperature of individual hydraulic circuits, which consist of bars of the upper and lower layer of windings, as well as on reducing the total flow and increasing the pressure difference at the inlet and outlet of demineralized water for winding cooling system. In accordance with the operating instructions, the generator operated with a rated load for more than three years, until reaching the upper limit of the difference in water outlet temperature between individual hydraulic circuits, when the generator load was reduced to about 70% of the rated load. Chemical rinsing of the stator windings by the CUPROPLEX® Offline Cleaning method was organized during the overhaul in year 2020. Before rinsing of the windings, the water flow of individual hydraulic circuits was measured and it was determined in which bars there is a decrease in flow due to the accumulation of copper deposits. In addition to the four cycles of chemical rinsing of the complete stator winding, two cycles of rinsing were performed separately through the bars in which the flow was less than 50%. After successful chemical rinsing, the tightness of the windings was checked and high voltage insulation electrical tests were performed. In the further generator operation with rated load, all parameters are in accordance with the operating instructions