This month’s Featured Technical Paper is from the Proceedings of the 2018 International Conference of Doble Clients. The paper is titled: Design and Use Ester-Filled Transformers


For over one hundred years, power transformers have conventionally been insulated and cooled with mineral oil. A growing interest in sustainable alternatives has driven the development of alternative insulating liquids. Some users have been considering and others have already obtained transformers that have been designed to be filled with ester insulating liquids. The improved fire safety characteristics and the reduced environmental impact of these biodegradable liquids offer advantages that help to reduce operational risks. In addition, ester liquids possess a higher water saturation capability that contributes towards life extension of the cellulose insulation. However, in order to reliably take advantage of the benefits of ester insulating liquid characteristics, power transformers need to be carefully designed considering not only the dielectric properties of esters, but also their thermal, chemical and physical characteristics. Their differences from traditional mineral oil offer challenges that need to be incorporated in the transformer design, construction, processing and placing in service. In addition to the environmental, safety and life extension benefits, the higher thermal capability of ester liquids together with high temperature solid insulation materials offer increased design flexibility to create innovative solutions to prior existing constraints. The transmission mobile resiliency transformers, that Siemens provided Consolidated Edison Company of NY, utilized a hybrid insulation system, together with synthetic ester liquid to provide a compact, multi-ratio transformer design that maximized operational flexibility and minimized installation time. The implementation of these newer alternatives allows for innovative solutions to meet today's power system safety, sustainability and resiliency needs. 

Doble Service Agreement Clients

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