SEDL / STP / STP998-EB / STP26426S

An Engineering Model for Streaming Electrification in Power Transformers

Roach, JF
Senior research scientist, Research and Development Center, Westinghouse Electric Corp., Pittsburgh, PA

Templeton, JB
Manager, Shell Form Design, Power Equipment Division, Westinghouse Electric Corp., Pittsburgh, PA

Pages: 17    Published: Jan 1988

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Abstract

An engineering approach to assessing static electrification phenomena in power transformers is presented. A theoretical model is developed to estimate streaming currents and space charge accumulation around the hydraulic oil flow loop in a three-phase transformer. The streaming current model is applied to a 345-kV, 240-MVA three-phase auto transformer with shell form winding design. The influence of space charge on the electric field and potential distributions in the upper plenum is modelled by a one-dimensional theory. Significant electric stress enhancement at coil edges on alternate half cycles of applied a-c stress is predicted for the 240-MVA transformer. Potential failure modes in power transformers due to static electrification are discussed.