Novel winding for a gas-insulated transformer

There are numerous operational problems with the technology of oil-filled transformers including their considerable mass and associated civil engineering. In addition, blast walls, acoustic baffles or sufficient space are required to protect surrounding buildings in an urban environment. In an attempt to answer these problems, a 20 kVA, single-phase prototype gas-insulated transformer, that employs atmospheric air as its cooling and insulating medium and uses a novel woven winding, was designed and built. This has clearly demonstrated the feasibility of woven winding, gas-cooled transformers that can operate at an average current density of 2.4A.mm-2 without the aid of powered cooling systems. Success was due to the use of a novel woven winding comprising a copper warp and a PTFE weft. As a consequence of the improved gas flow through this winding and the absence of any insulating cover on the copper strands, the thermal characteristics have been enhanced to a point where this technology is comparable with that of conventional oil-paper insulated transformers, without the accompanying weight, cost and environmental considerations associated with the latter.