Known high-voltage transformers or high-voltage inductors, for example, having a rated voltage on the high-voltage side of 220 kV or 380 kV and a rated power of >100 MVA, for insulation and cooling purposes, can be arranged in an oil-filled transformer tank. A so-called transformer bushing has a useful function in a transformer of this type. A high-voltage potential is led through the bushing from an air side to a winding in the transformer tank. In the case of pure air insulation, the distance between components at high-voltage potential and the earthed transformer tank—depending on the voltage level—can be up to 4 m or more. By an oil-impregnated paper or cellulose, which can withstand a higher field stress than air, the distance can be decreased. If a high-voltage connection is led into the tank concentrically through a round opening, then a distance between an internal conductor and a tank of 20 cm, for example, can suffice.
Known spherical caps are used for this purpose in the region of the outgoing lines. These are rotationally symmetrical hollow bodies composed of a metal which have a hemisphere-like termination with a usually angled pipe attachment for a conductor connection or a conductor bushing at one axial end and a tapering diameter at their other axial end. For improved insulation, these electrically conductive hollow bodies can be surrounded with a double-walled barrier system composed of an insulation material, which is likewise arranged within the oil-filled transformer tank.
CH 695 968 A5 describes a spherical cap of this type, but has a disadvantage that the insulation barriers can be laborious to manufacture, and has an insulation capability that is able to be improved.
For example, the insulation barriers are spaced apart by insulation rings into which spacer blocks are latched. This is laborious to manufacture and also not optimal in terms of insulation technology because components having sharp edges at points are used within a region that exhibits a voltage gradient and is to be electrically insulated. The use of spacer blocks can be disadvantageous particularly in the hemisphere-like regions of the barriers because there is a particularly high risk of the insulation barrier that is to be spaced apart bearing merely on corner points of the spacer blocks.
The possibility of electrical connection of the spherical cap to a screening pipe can prove to be disadvantageous. This is because high-voltage outgoing lines can be individually manufactured items which are subject both to their own manufacturing tolerances and to the manufacturing tolerances of an oil transformer upon installation into the latter. Compensation of such tolerances is either possible by a mechanically particularly pliable connection between the screening pipe and the spherical cap, which can be undesirable for stability reasons, or relatively high forces are applied permanently via the spherical cap, in order to fix the components in the desired position, which can likewise be undesirable.