The use of low frequency heating techniques in the insulation drying process for liquid filled small power transformers

Effectively removing the moisture from the cellulose insulation is a key process in the production of power transformers and to ensuring the trouble-free operation of the power transformer for years of service. The quality of the drying of the insulating material is critical in meeting dielectric requirements and assuring trouble free service for users. Micafil Vakuumtechnik AG of Zurich, Switzerland, a pioneer in the development and manufacture of a low frequency heating (LFH) drying process equipment, has developed a new LFH process for ABB liquid filled small power transformers manufactured in South Boston, Virginia. This process was developed to meet South Boston´s very stringent drying requirements for small power transformer core and coil assemblies that are processed in their own tanks with the transformer tank serving as a vacuum chamber. The drying process has proven to be very successfully in the removal of the moisture from the cellulose insulation and insuring that the insulation power factor is consistently under 0.5 %