DE2534385A1 - ITEMS THAT CAN BE RECOVERED - Google Patents

Description

Moor House, London Wall, London EC2Y 5HP (England)

Heat-resilient_objects

The invention relates to heat recoverable articles and in particular heat-resilient objects for electrical insulation purposes and the coating of busbars for electrical equipment.

Heat-resilient objects are understood to be those that, for example, under heat and / or pressure from an original Shape deformed into a heat dimensionally unstable shape and in that heat unstable configuration have been held, for example by cooling by maintaining the pressure. Such items can be in return to their original shape by the application of heat alone.

Up to now, busbars have been electrically insulated by dipping them into an oil-filled container or by coating them with polyvinyl chloride or epoxy resin or resin-impregnated paper. However, such insulating coatings can withstand field strengths between 10 and 15 kilovolts per mm of thickness for a maximum of 1 minute. Oil-immersed bus bars work effectively up to 11 kilovolts when the edge-to-edge distance to the nearest parallel bar is at least 25 mm, but oil immersion tanks take up and are a lot of space

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difficult and make access to the busbars difficult.

The other insulation systems require a clearance from the top ■ surface to surface between the busbars from little! at least 50 mm if the rails have a working voltage of 11 kV exhibit. A closer placement of the busbars leads to corona discharge.

Under short-circuit conditions, the temperature of a busbar briefly rise to 250 ° C, after which the insulation must still be effective. Transformer oil resists While such temperature rises are successful, epoxy resins will chip as a result of thermal expansion while Coatings made of non-crosslinked polyvinyl chloride above a temperature of 100 ° C melts and of the Busbars dripping off.

The invention now makes it possible to use busbars that work, for example, at 11 kV, depending on the geometry to place the busbar parallel at a distance of 40 mm and under certain circumstances a field strength of at least 50 kV / mro to achieve when this voltage through the Isolation is applied therethrough for 1 minute.

The subject of the invention is therefore a heat-divisible Hollow body with at least one open end, one of which is heat-shrinkable capable sleeve, the inner surface of which at least partially with an electrically conductive lining such is provided that when the heat-recoverable article is shrunk onto a base, the electrically conductive Lining remains in contact with the socket over the entire length of the socket part, so that there are no gaps between the socket and lining, and at least an end portion of the inner surface of the sleeve with electrically insulating sealant is provided.

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■ ^? -

The invention also relates to a method for isolating connections or joints between busbars, in which the heat-resilient body according to the invention is shrunk on over the connection so that the connection ^{lies in a Faraday 1} cage and the closure means a barrier against the ingress of moisture.

The invention further relates to a T-shaped metallic brace Busbar that is surrounded by an electrically insulating cross-linked polymer material.

Finally, the invention relates to a kit that has a heat-resilient hollow body according to the invention, a T-shaped metallic busbar surrounded by an electrically insulating cross-linked polymer material and a heat-recoverable one Tube made of polymer material with an electric field strength of at least 50 kV / mm for 1 minute having.

The term "bus bar" is used herein to describe the terms "bus bar", "bus rod" and "bus shape" which are defined in ASTM B187-7 ^.

Generally there is a heat recoverable article according to the invention made of a material which is given the property of plastic or elastic memory can and has been expanded to a larger shape than its original shape under pressure and / or heat has been cooled in the expanded state. An object treated in this way retains its shape obtained by expansion at until it at least returns to the heat recovery temperature or a temperature range at which it is heated to its original or towards its origin lent shape goes back.

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Examples of preferred materials used for the formation of heat-shrinkable sleeves or heat-recoverable Pipes suitable according to the invention can be found in British patents 1,337,951, 1,337-952 and I.303,432, whose Disclosure hereby expressly included in the present application; message is recorded. The materials disclosed there; are tracking current resistant and thus have an advantageous property of busbar insulation to protect against j Creep up. ■

The electrically conductive putter according to the invention can consist of any polymer material which has been given electrical conductivity by the incorporation of conductive fillers, for example carbon black or metals in flake or powder form, such as silver flakes or copper powder. It is essential that the lining during use on _(its length communicating with the sleeve in close contact with the totally of voids and gaps is free. To this \ purpose as a feed, a putty, a hot melt adhesive or heat curing adhesive is advantageously used Polyisobutylene or rubbers, for example butyl rubber or rubbers based on epichlorohydrin, to which suitable plasticizers and additives that modify the adhesive strength have been added if necessary. Suitable hotmelt adhesives are copolymers of ethylene, for example ethylene / vinyl acetate and ethyl en / acrylic ^- acid, called each of these adhesives may contain conventional additives such as processing aids, and antioxidants, if necessary, contain..

However, the lining can also consist of a plastic that is normally not regarded as an adhesive, into which it is conductive Fillers have been incorporated. Examples sol-! rather materials are polyolefins such as vinyl chloride, polyvinylidene fluoride and homo-, co- or terpolymers of hexafluoro-

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ethylene. The putter may advantageously be formed from these materials \. ^!

A particularly advantageous method for producing the heat! Resilient objects according to the invention is the <Double extrusion, where sleeve and lining are extruded and drawn together at the same time (e.g. disclosed in British patent specification 1 .Oj5j5 «959) · The object obtained can be subjected to irradiation for the purpose of crosslinking. The penetration depth of the radiation can be varied, so that the material is at the borderline between socket and! electrically conductive putter for the purpose of intimate connection of these ■ both are networked.

Sleeve and feed can \ also be extruded separately from each other, whereupon the chuck then introduced into the sleeve and
is firmly connected to this. The material of the lining and / or the sleeve can be crosslinked before or after this stage; Likewise, the putter can have the property of being plastic
or elastic memory as desired.

The open end portion or ends of the heat shrinkable; capable sleeve according to the invention are with an electrically insulating adhesive, putty or a thermosetting adhesive ' fabric that can be sealed to create a barrier against | the ingress of moisture under the sleeve through the or to form the open ends. i

The T-shaped one-piece metallic busbar according to the invention is a very useful replacement for the usual vertically connected busbar system! because the smooth surface significantly reduces the corona discharge; will. The electrical isolation of
T-shaped metallic busbars according to the invention
is effected by a cross-linked polymer material that is on
Space is formed over the metallic busbar. Before-

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partial materials are in the British patents:

1.337.951, I.337.952 and I.303.432. ,

The crosslinked polymer material according to the invention has advantageous a field strength of at least 30 kV / mm (1 minute).

While the articles of the invention are particularly useful for insulating busbars, they can as well can also be used for insulation from other electrical conductors.

Several objects according to the invention are described below by way of examples in conjunction with the drawings

Figure 1 shows a longitudinal section through an object according to the invention.

FIG. 2 shows an isometric view of FIG. 1 over one another connected busbars.

FIG. 3 shows the section from FIG. 1 in an isometric view after shrinking onto the connected busbars.

Figure 4 shows in isometric view a crosslinked polymer body that is in place around a T-shaped metal object was molded around.

In Figures 1 and 2, (1) is a heat recoverable article according to the invention. A heat-shrinkable sleeve (2) is equipped with an electrically conductive lining (3) and an electrically insulating closure means (4). As shown in Figure 3, the sleeve (2) shrinks when the object is heated, whereupon the chuck (3) is forced towards the busbars. The lining can, if desired, be melted or softened enough to fill in any gaps and irregularities (not shown ).

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The following examples are intended to explain the invention:

example 1

Bolted busbar connections are insulated and
the voltage at which the discharge begins ("discharge
inception voltage "; breakdown voltage), is used against the
Distance from busbar connection to earth applied.

Busbars
connection no

Polyisobutylene heat-shrink tube made of heat-insulating type - containing putty, capable of shrinking poly

ethylene contains polyethylene! fiendes pipe i

conductive polyisobutylene;

P ^ ttef ^S - - - containing '

Cap- butyl rubber- butyl rubber-

medium - - adhesive tape adhesive tape i

The graphic representation (FIG. 5) shows the essential improvement in the breakdown voltage, in particular at
low distances from connection to earth in the insulation of screwed busbars according to the invention is achieved. The numbers of the individual curves correspond to the numbers of the bolted or screwed busbars.

Example 2

Company frequency test

A tube (Raychem BBIT) made according to the third aspect of the invention is lengthwise shrunk onto a busbar. On the outside surface of the tube is over
A conductive paint applied over a length of 7 cm. A semi-conductive pipe is only placed over the edges of this connection

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Line, leaving 5 cm of the paint uncovered, shrunk. The voltage sent through the conductor rail is increased by 5 kV from 15 kV in 1-minute intervals increases. The paint layer is grounded. For comparison, the Raychem BBIT tube is replaced by a commercially available heat shrinkable PVC pipe replaced.

Results: Pipe thickness
(mm) pipe 1.86 Raychem BBIT 2.3 heat shrink
PVC pipe

Breakdown Breakdown i voltage voltage | (kV, effective) (effective, kV / mm)

70 37.5

35 15

Example 3

Comparison of the impulse withstand voltages

The insulated busbars are produced according to Example 2. The pulse voltage is found by increasing the Voltage in steps of 5 kV each; 5 pulses at each test level are applied. It gets more positive with a pulse Polarity (1/50 η sec.) According to B.S. 923, 1972, worked.

Results:

Tube thickness withstand voltage withstand voltage tube (mm) kV (impulse) (peak, kV / mm)

Raychem BBIT 1.9 105 55

heat shrink

PVC pipe 1.98 60 30

The results from Examples 2 and 3 show that the surface-to-surface separation of bus bars is reduced; can be achieved by using a material with improved breakdown and withstand voltage properties.

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Claims (1)

253A38B Claims before Heat-restoring hollow body with at least one open heather, containing a heat-shrinkable sleeve, 'the inner surface of which is at least partially provided with an electrically conductive putter, which according to! Shrinkage of the article onto the substrate is in seamless contact with the sleeve over the entire length of the relevant part of the sleeve and wherein the or at least one open end part of the inner surface of the body is provided with an electrically insulating closure means ¹ . 2) Body according to claim 1, characterized in that the material of the sleeve is crosslinked. 3) body according to claim 1 or 2, characterized in that at least the outer surface of the sleeve is leakage current resistant '. ', 4) body according to claims 1 to j5> characterized in that the total length of the inner surface of the heat shrinkable Sleeve is provided with an electrically conductive putter and the or each end portion of the inner surface of the putter with an insulating sealant is provided. ^! 5) body according to claims 1 to 3, characterized in that ■ that the central part of the inner surface of the heat-shrinkable Sleeve is provided with an electrically conductive putter and the or each end portion of the inner surface the sleeve is provided with an insulating sealant. 6) body according to claims 1 to 5 * characterized in that the electrically conductive putter made of a polymer material 609810/0593 253438b - Io - rial, which has been made conductive by incorporating electrically conductive fillers. 7) body according to claim 6, characterized in that the Polymer material of the electrically conductive putter a putty! a hot melt adhesive or a thermosetting adhesive \ is. ! 8) body according to claim 6, characterized in that the Polymer material of the putter is cross-linked. 9) Body according to claim 8, characterized in that the putter is heat-shrinkable. 10) body according to claims 1 to 9 »characterized in that that the insulating sealant is a putty, a hot melt adhesive or a thermosetting adhesive. 11) method for the insulation of busbars, characterized in that that you have a heat-resilient body according to claims 1 to 10 over the connection point can shrink, the sealant seals against the ingress of moisture. 12) T-shaped metallic busbar, characterized by a covering made of an electrically insulating cross-linked Polymer material. 15) busbar according to claim 12, characterized in that the polymer material is resistant to tracking. j 14) kit consisting of a heat-resilient molded body according to one of claims 1 to 10, a T-shaped metallic busbar according to claims 12 or lj> and | a heat-resilient tube made of polymer material with 60 98 10/0 593 253438b - li - a dielectric strength of at least 30 kV / now (1 minute). 6098 10/0593