FR2551923A1 - VERY HIGH VOLTAGE ELECTRICAL TERMINAL - Google Patents

Abstract

THE INVENTION CONCERNS TERMINALS FOR VERY HIGH VOLTAGE. IT RELATES TO A TERMINAL WHICH INCLUDES SEVERAL CONDUCTOR PROJECTS 8 WHICH START RADIALLY FROM A CORE CONDUCTING CORE PART 9 WHICH FACILITATES THE CONNECTION OF SEVERAL CONDUCTORS; INSULATION MATERIAL 10 COVERS THE PROJECTS AND AT LEAST PART OF THE CORE. THE ELECTRICAL CONSTRAINTS 11 ARE LOCATED IN THE INSULATION AND ARE THEREFORE REDUCED IN THE SURROUNDING AIR. APPLICATION TO ELECTRICAL AND ELECTRONIC TERMINALS OPERATING AT HIGH VOLTAGE.

Description

The present invention relates to electrical terminals at very high

voltage.

  In electrical and / or electronic equipment using very high voltages of several kilovolts, problems arise in preventing corona discharge between parties with very different potentials. Problems are particularly important in the case of terminals which Multi-conductor junctions It is desirable in electrical or electronic equipment which utilizes very high voltages to use terminals which minimize the risk of corona discharges and which facilitate a close approximation of the elements to electrodes. high mutual potential differences, so that the size and more precisely the volume

  this equipment can be reduced to a minimum.

  According to the invention, a very high voltage terminal comprises a plurality of conductive projections which extend in a radial direction from a conductive core central portion, intended to facilitate the making of a junction between several conductors, and a region of an insulation material for covering the projections and a

  at least part of the soul part.

  The ends of the projections remote from the web portion may be rounded.

  The region of isolation material may have

  a dome-shaped outer surface and the web portion and the projections may be encased beneath the dome outer surface of the insulation material, and within it.

  The projections and the soul part can be

made in one piece.

  The soul part and the protrusions can be

  formed of a metal such as copper, and the insulation material may be a plastic such as polytetrafluoroethylene.

  The adaptation of the core portion may comprise a hole or a cavity or the like for the housing of the conductors, during the attachment of the core portion, for example

by welding.

  In addition, or alternatively, the core portion 5 may have a threaded connector, preferably surrounded at least in part by the dome-shaped surface, so that the risk of corona discharge from

of the connector are reduced.

  The high voltage terminal can be placed in a tank which is filled with an insulating fluid

such as an oil for example.

  Other features and advantages will become more apparent from the description which follows, made in

  reference to the accompanying drawings in which: Figure 1 is a plan view of a known type of dome-shaped terminal, with a graph showing the variation of the electrical stress in the terminal; Figure 2 is a plan view of a known type of dome-shaped terminal similar to the terminal of Figure 1 but covered with an insulating plastic, and also including a graph showing the variation of the stress; Figure 3 is a plan view of a small terminal covered with plastic, with a curve showing the variation of the stresses associated with the terminal; and FIG. 4 is a relatively schematic view

  in plan of an example of a terminal according to the invention, covered with a plastic material, with a graph which indicates the electrical stress associated with the terminal.

  The invention relates to the reduction of the effects of electrical stress concentrations around very high voltage terminals. These concentrations are formed especially around sharp corners and edges. In practice, sharp corners and edges are replaced by polished curved surfaces so they are smooth, having large radii of curvature as shown in Figure 1, with a curve 1 of stresses as shown, when using a terminal 2 of generally spherical shape The stress reduction is obtained by coating surfaces of generally spherical shape and curve of insulating materials so that a voltage drop occurs in the insulation material and causes a reduction of the electrical stress in the surrounding air This is represented by graph 3 of FIG. 2 shows the stress associated with a terminal 4 of generally spherical and curved shape surrounded by a material 5 of insulation made of a plastic material It should be noted that the constraint is also reduced in the latter case because of the increased radius

  the interface between air and insulation.

  Electrical stress in the insulating material

  can be increased by reducing the radius of curvature of an inner conductor 6 of the terminal which is surrounded by a material 7 of insulation as shown in Figure 3.

  This advantageously gives a corresponding reduction in the stresses in the surrounding air since the constraint

  is transferred to the insulating material 7 from the air.

  The radius of the inner conductor should be reduced to less than about 0.5 mm so that this enhancement is optimized as shown in curve 12, the stress in the surrounding air being minimal Obviously, in many applications, this improvement does not can not be easily achieved since terminals of more than half a millimeter must be used.

  A terminal can be made as shown in FIG. 4 in order to implement the phenomena which give this improvement. The terminal shown in FIG. 4 has projections 8 which project radially from a central portion 9 of the core, the projections 8 having rounded end portions and being incorporated so that they locally increase the stress in a surrounding sheath 10 of plastics material Thus, as indicated by curve 11 of FIG. 4, the stress increases in z 2551923 the sheath 10 of plastic material, so that the constraint

  is reduced in the surrounding air.

  Various modifications can be made to the arrangement shown schematically in FIG. 4, in the context of the invention and, for example, for the

  Conductor housing to be connected, the central core portion 9 may have screw connectors or may include one or more cavities for welding conductors.

  Although the arrangements described above are indicated as being surrounded by air, it should be noted that

  that the terminal can advantageously be immersed in an insulating fluid so that the risks of corona discharging are further reduced The use of such immersion in a fluid which increases the resistance to breakdown is well known and therefore does not describe it .

  The material of which the core portion 9 and the projections 8 of the terminal are formed is normally copper but any metal or other conductor may be used, and the insulation material is usually a plastic such as polytetrafluoroethylene although other types of insulation materials may be used.

Claims (8)

  1 terminal for very high voltage, characterized in that it comprises a plurality of conductive projections (8) extending radially from a central conductive part 5 core (9) which is intended to facilitate the realization   a junction between a plurality of conductors, and a region formed of an insulation material (10) for covering the projections and a portion at least of the core portion.   Terminal according to claim 1, characterized in that the ends of the projections (8) remote from the core portion are rounded.   Terminal according to one of claims 1 and 2,   characterized in that the insulating material region (10) is constructed to have an outer dome surface, and the web portion (9) and the projections (8) are encased under the outer surface thereof. dome shape of the   insulation material and inside of it.   Terminal according to one of the preceding claims, characterized in that the projections (8) and the core portion (9) are formed in one piece.   Terminal according to any one of the claims   characterized in that the web portion (9) and the projections (8) are formed of a metal, and the insulation material is a plastics material.   Terminal according to Claim 5, characterized in that the metal is copper and the plastics material is polytetrafluoroethylene.   Terminal according to any one of the preceding claims, characterized in that the adaptation of the core portion (9) comprises at least one hole, a cavity or a similar recess for the housing of the conductors intended to be connected with each other. conductive way to the soul part.   8 terminal according to any one of the preceding claims, characterized in that the core portion (9) has a connector provided with a thread which is at least   surrounded by the dome-shaped surface so that the risks of a corona discharge from the connector are reduced.   9 Terminal according to any one of the preceding revendica5 tions, characterized in that it is placed in a reservoir which, during operation, is filled an insulating fluid.