It is generally known that high-voltage transformers or else high-voltage inductors, for example having a rated voltage on the high-voltage side of, for example, 220 kV or 380 kV and a rated power of >100 MVA, are arranged in an oil-filled transformer tank for insulation and cooling purposes. In such a transformer the transformer bushing, introduces the high-voltage potential from the air side to the winding in the transformer tank. When pure air insulation is used, the distance between components at high-voltage potential and the earthed transformer tank should be up to 4 m or more, for example, depending on the voltage level. By means of oil-saturated paper or pulp, which can withstand very much higher field loading than air, the distance can be reduced considerably. If the high-voltage connection is led concentrically through a round opening into the tank, a distance between the inner conductor and the tank of, for example, 20 cm is sufficient.
It is furthermore known that domes can be used for this purpose in the region of the outgoing lines. Domes are rotationally symmetrical hollow bodies which can be made of a metal and have a hemispherical termination at one axial end with a mostly bent tube attachment for a conductor terminal and a tapering diameter at the other axial end. For improved insulation, these electrically conductive hollow bodies can be surrounded by a barrier, such as a double-walled barrier system which is made of an insulation material that is likewise arranged within the oil-filled transformer tank.
Such a barrier system, which can be matched to the basic shape of the metallic hollow body, is mostly produced from molded part modules which are made of a wet substance. This means that a layer of wet and therefore moldable pulp or some other insulation material is applied around a mold, the outer contour of which reproduces the inner cavity of the molded part to be produced, wherein the mold with the layer of insulating material surrounding it is then dried in a furnace and hardened.
It has proved to be disadvantageous in this respect, in particular, that the bent tube attachment is to be manufactured at a different angle to the rotational axis of the dome. Specifically, the angle of the tube attachment is determined by the conductor routing within the oil tank and depends predominantly on aspects of insulation. It is therefore possible that different angles of the tube attachment pieces of the three respective domes can be specified even in the case of a three-phase high-voltage transformer. In addition, high-voltage transformers are mostly unique or are manufactured at least only in minimal series, such that differences arise between the transformer types. It is disadvantageous that a transformer manufacturer therefore specifies a multiplicity of various molds for producing the insulation barriers.
In order to limit this variety of molds for the production of the insulation barriers, it is known to firstly produce a molded part without a tube attachment, to cut out a hole of the diameter of the tube attachment at the desired position in the hemispherical termination and secondly apply a tube attachment piece at the then individually stipulated angle, for example by adhesive bonding. This process uses additional working steps and reduces the ability of the molded part or molded part module used as the barrier to be insulated at the bonding point.
USPTO Backgrounds
USPTO Backgrounds