Beriz Bakija

Long-term study of partial discharge and gassing behavior of alternative insulating oils for oil gaps

The paper describes the gassing behavior of alternative insulating oils in exposure to partial discharges. Mineral and ester-based oils were applied with partial discharge over a long-term period. The ambition is to verify, how far the mineral oil experience can also be applied to ester-based insulating oils. For this purpose, it is important to recognize the gassing behavior and additionally the dielectric strength- and loss factor- behavior of alternative insulating oils.

Effect of various polarizations to the breakdown voltage of oil impregnated paper insulation

In this Paper the polarization and depolarization behavior of oil impregnated paper by a DC voltage and its influence on the breakdown voltage by reversed polarity is presented. As Power transformers for HVDC applications are tested with a polarity reversal test before commissioning the insulation system is stressed with AC and DC fields. The behavior of the insulation system under this DC stress is not jet adequately investigated. To get a further understanding of the charge movement by applying a DC voltage polarization and depolarization current of oil impregnated paper insulation is measured. Furthermore the influence of a polarization of this insulation to the electrical performance by polarity reversal is investigated.