DE1638176A1 - Device to prevent glow discharges between two insulated conductors of different potential, especially in rotating machines - Google Patents

Description

Op / ub

Public limited company Brown, Boveri & Cie., Baden (Switzerland)

Device to prevent glow discharges between two insulated conductors of different potential, especially in the case of rotating machines

In the case of large rotating machines, two winding bars can be placed directly next to each other in the phase separations in the stator whose conductor potential during operation is by the amount of the line-to-line voltage or the nominal voltage of the machine be apart. During the stress test, the full test voltage even occurs at these points. Daaber in the winding head the distances between the bars cannot be increased significantly for structural reasons, can be found here under Under certain circumstances, discharges in the air or gas gaps of the »phase separations develop even at the operating voltage, which are very undesirable. In the conventional designs, this is often avoided by the fact that the phase separations with; have been provided with a semiconducting filling,

109826 / 013S ^ ₁ "

BATH ORIGINAL

in most cases, the filling compound also serves as a mechanical support.

Such a filling of the space between the winding head parts by means of a filling compound, which usually consists of a with a semiconducting lacquer impregnated with a material, e.g. glass fabric, allows very small rod spacings but not necessarily permanent in the long run. This is due to the fact that the cavity-free production of a filling this type is practically impossible, and also because of the hardness of the filling compound and as a result of vibrations between the rod insulation and the filling compound, the latter becomes brittle and fine cracks can arise. the gradual destruction of the filling compound by glow discharges inevitably leads to a decrease in their mechanical strength, so that they also do their additional job as Support no longer fulfilled.

With the constantly increasing size of the machines with correspondingly higher nominal voltages results in the need to create a device that eliminates the glow discharges between two insulated conductors of different potential, especially with rotating machines with high nominal voltage, prevented. According to the invention, this is achieved in that at least the conductors facing each other

109826/0135 BAD ORlGlNAi,

a conductive surface is provided in the critical area, which is located in the conductor insulation, the surface of which is covered on all sides with semiconducting corona protective coatings., and that the conductive coatings are electrically connected to one another and at least their edges are covered with an additional semiconducting coating.

An exemplary embodiment of the invention will be explained in more detail with the aid of the drawing:

Figure 1 shows in longitudinal section the phase separation of two bar conductors in the head part of a generator winding, while the Figure 2 illustrates the same rod conductors in cross section along the line A-A of Figure 1.

At least the opposite broad sides in the head part of the two adjacent bars 1 are in the phase separation with conductive coverings 2, most expediently in the form of conductive paints, Mistake. These coverings 2 extend below the surface of the conductor insulation 4 in the longitudinal direction of the Bars up to the points at which the bars diverge, i.e. the coverings in the present example are in critical area between the two bends in the end winding, where the parallel bars are very close to each other come. The edges * of the coverings 2 are covered on all sides with a semiconducting coating 3, which is in the critical area also fully embraces the rod inside the insulation. JDle lei-

109826 / (TM «5th

BATH ORIGINAL

- a - 1b38176

tend coverings 2 as well as the semiconducting coverings 3 v / ground during the production of the usual insulation layer 4, e.g. by By painting or by inserting suitable thin foils, with a half of this insulation on the outside 3; e conductive coating 5 is applied as a corona protection.

The conductive coverings 4 are above conductive contact strips 6 and a conductive support element located between them in the gas gap 7 with each other in conductive connection. This support element 7j, for example, consisting of a semiconducting, fiberglass-reinforced plastic, also serves to distance the rods. Because the capacitance between the conductive Linings 4 and the copper conductor is approximately the same size in both bars 1, the linings 4 and the one in between Part of the insulation layer and the gas gap to half the voltage between the conductors of the two bars 1 brought. The overlying layer of insulation 4, which is additionally provided with a semiconducting corona protection coating 5 is only used to control the build-up of tension at the edges of the pavement on the rod surface so that none Glow discharges occurred.

With the arrangement described, a suitable Voltage control fully relieves the gas gap in the phase separations and relieves the stress in the Glimmer-resistant rod insulation laid. In this way, minimal rod spacing in the phase separations and an improvement of the glow behavior achieved during the voltage test

109826/0135

BATH ORIGINAL.

~ 5 - 115

will. There is also a constant mechanical Strength of the end winding supports and increased operational safety. Finally, better cooling is also achieved, since the gas gap does not have a semiconducting hatred fill out.

109826/013 ^

BAD ÖRIGMÄL

Claims (2)

11 Device for preventing glow discharges between two insulated conductors of different potential, in particular with rotating ilaachinen high nominal voltage, thereby marked that at least on the facing A conductive surface is provided on the sides of the ladder in the critical area the surface of which on all sides is provided. and that this Leir.bel'ip; e ale trlsch iiiit each other are connected and at least their edges are still covered with an additional semiconducting coating. 2. Device according to claim 1, characterized in that the conductive linings of adjacent conductors by means of dio conductor insulation brought out contact strips are electrically connected to one another. J. device n & ch claim 2, characterized in that the connection of the contact strips of neighboring conductors an electrically conductive support element is carried out, which is arranged between the conductors. Corporation BROWN, BOVERI & CIE. , 10987R / 0135 BATH ORIGINAL