Improvement of Insulation for Rotating Machine by Dry Ice Method

This paper presents the improvement of rotating machine insulation by the powerful blast-cleaning, dry ice method. In this work, the large synchronous generator, 16.25 MVA 6.9 kV and 78,240 running hour, was investigated and analyzed. The characteristic of insulation such as polarization and depolarization current (PDC), polarization index (PI) and dielectric loss tangent (tan δ) were measured according to the IEEE standard 43-2013. After cleaning with dry ice blasting, the insulation of generator has improved remarkably. The charging current is decreased due to removal of conductive layers from the insulation surface. For other parameters, polarization index and loss tangent are increased 52.03% and decreased 11.66% respectively. Furthermore, the operation time of dry ice method is very short when compared with traditional cleaning methods, resulting in reduced maintenance downtime and increased more productivity.