Retrofit with Hybrid Insulation System of a Failed Power Transformer

Retrofit of power transformers using high temperature aramid insulation materials in the windings based on the hybrid insulation system has developed over the last two decades. By taking advantage of the higher thermal withstand properties of such insulation materials, a failed unit could be redesigned to increase its average winding rise to 95degC. The windings can then be redesigned to reduce the cooling space but replaced with more active material, thereby optimising the use of the available space within the core window. This approach enhances the transformer retrofit scope and flexibility which includes capacity expansion or loss reduction and improved reliability of the retrofitted transformers.