A seminar at the forthcoming CWIEME Berlin exhibition will reveal how cellulose paper and mineral oil insulating systems in distribution transformers can still meet today’s ever-tightening cost and efficiency restrictions – thanks to a few smart modifications.
Proven and reliable, mineral oil-impregnated paper has been the insulation of choice in distribution transformers practically since their invention. Yet amid increasing pressures to lower costs, increase efficiency, and lessen environmental impact, the use of ester- or vegetable-oil impregnated paper as an alternative has become a hot topic for transformer manufacturers and suppliers at CWIEME exhibitions of late.
WEIDMANN hopes to add another hot topic…the paper itself. For the past 10 years, the international transformer insulation specialist has turned its attention to developing new papers.
“Many companies are on the hunt for alternative transformer insulation materials and there is actually a lot we can do to make the tried and tested system better,” says Kevin Biggie, Senior Innovation Engineer at WEIDMANN ELECTRICAL TECHNOLOGY AG.
Traditionally manufacturers use the same standard kraft cellulose paper throughout the transformer. Engineers at WEIDMANN, however, have discovered that by tailoring the properties of the paper to the differing insulation requirements of windings within the transformer, significant gains can be made in both cost and efficiency.
No more one-size fits all
“We found that in the low-voltage winding, the mechanical properties of the paper took precedence, whereas in the high-voltage winding, the electrical properties were more important,” he says. “Using a combination of different papers, we are able to reduce the amount needed and improve the overall performance of the insulation."
In both cases, the drying properties of the paper are also important but especially in the high-voltage winding. Cellulose paper naturally contains a certain amount of water yet can accelerate the ageing and decrease insulation performance once in service.
“Ideally the insulation should have no residual moisture, which is why we have developed papers to have advanced drying properties,” Mr. Biggie says. “That means that a manufacturer can save some processing time and cost in the factory or, using the same process, reach a lower moisture content level. What’s more, the fact we use less paper has an indirect drying benefit since there’s less water to begin with.”
Mr. Biggie will be discussing WEIDMANN’s research into distribution transformer insulation papers at the CWIEME Berlin exhibition in Germany on the 5th May, 15:25-16:05.
In particular he will present the TUF-Flex® and INSULutions® DPE papers that the company has developed specially for low- and high-voltage windings respectively.
Visitors to the exhibition will also have the opportunity to discuss these, as well as the recently-launched INSULutions® STRIP-Flex K paper for improved performance with narrow-strip high-voltage winding machines, on the WEIDMANN stand (4.2/F10).
“When it comes to improving the cost and efficiency of insulation in distribution transformers, there’s no need to reinvent the wheel,” Mr. Biggie concludes. “Rather a few smart changes to the choice and combination of papers can make a world of difference.”