Abstract: A transformer coil comprises low and high voltage windings wound on a supporting construction and immersed in a main insulation material. The transformer coil has also a first barrier arranged proximate the low voltage winding and a second barrier arranged proximate the high voltage winding. Each of the first and second barriers is gas-tight and semiconductive so that gas bubbles potentially released during immersion in the main insulation material are unable to migrate to a high electric field region during the casting process or during apparatus operation.

Abstract: An electrical device includes a magnetic core, a bobbin extending about and partially covering the magnetic core, wherein the bobbin is made of a thermally conductive dielectric material, wherein the bobbin further comprises an outer body connectable to an inner body, wherein the inner body comprises at least a first contact element being formed as a rib that is configured to directly contact a surface of the magnetic core.

Abstract: A dry high voltage (HV) instrument transformer in the form of a HV current transformer includes a core casing having a secondary winding, a top housing, a primary winding, and a dry bushing, wherein the core casing comprises an insulation containing an electrically insulating material made of PES nonwoven impregnated and cured with low viscosity epoxy. The dry HV instrument transformer in the form of a HV voltage transformer includes a bottom tank housing, a cast of a primary winding module with an embedded screen surrounding the primary winding, a field grading disc, and a core, wherein the cast of the primary winding module is made of an insulating composite containing an electrically insulating material made of PES nonwoven impregnated and cured with low viscosity epoxy.