WO2011159248A1

WO2011159248A1 - Switchgear with single-phase insulation comprising air and screens

Info

Publication number: WO2011159248A1
Application number: PCT/SE2011/050778
Authority: WO
Inventors: Bertil Moritz; Lars Hjort
Original assignee: Hm Power Ab
Priority date: 2010-06-18
Filing date: 2011-06-17
Publication date: 2011-12-22
Also published as: SE1050637A1; EP2583365A1; EP2583365A4; CN102986100B; SE534914C2; CN102986100A

Abstract

Switchgear for high voltage comprising a circuit breaker (2) of vacuum breaker type and a disconnector (7) arranged above each other in a single-phase insulated design. Operating shafts (3, 9) are arranged for the circuit breaker and the disconnector, respectively. Two different types of single-phase insulation is used for the circuit breaker and disconnector unit and for phase lines (8) going out from the switchgear. The single-phase insulation consists of air insulation and screen walls (6) between the phases of the circuit breaker and disconnector unit (2, 7) and of synthetic material, preferably shrinkable plastic (14), on the surface of the outgoing phase line (8).

Description

Switchgear with Single-Phase Insulation Comprising Air and Screens

Technical Field

The present invention relates to a switchgear for high voltage comprising a circuit breaker and a disconnector arranged in series above each other in a single- phase insulated design and having operating shafts for the circuit breaker and the disconnector, respectively.

Such switchgears are known since long as well as each one of the components included therein.

Background Art

As a first example of the prior art and the technical field to which the invention relates, a switchgear that is adapted for alternating voltages within the 10 kV range may be mentioned, and that has a circuit breaker unit and a disconnector unit, wherein these are mutually vertically orientated close to each other and placed within a compartment electrically insulating by means of air at normal pressure.

In such switchgears, it has been proposed that the circuit breaker unit is actuatable by first members for electric connection and disconnection. In a similar way, the disconnector unit is electrically connectable and disconnectable by means of second members.

In case of switchgears of the nature indicated above, it is previously known to construct different air-insulated switchgears, where, however, it has turned out that such switchgears, from a breaker and insulation point of view, require great insulation distances and thereby give rise to great construction volumes.

In that connection, it has turned out that a selected insulation distance has to take into consideration the instantaneous humidity of the air and its contents of salts and contamination, which in practice has turned out to require great and bulky compartments and chambers for such switchgears.

With the purpose of reducing the requisite insulation distance, it has also been proposed to have the entire switchgear, or at least parts thereof, built in into a hermetically closed "tank", of a gas-proof or air-proof design, as well as to fill this tank with a gas under a positive pressure, for example with sulphur hexafluoride (SF₆) gas. Such a tank should then contain different mechanical parts, which either will be connected to voltage, i.e., have a normal phase voltage or principal voltage (usually different out-of-phase three-phase voltages), or be earth connected to have earth potential (0 level).

The reasons for using a contained SF₆ gas under a positive pressure are that this gas has turned out to be efficient as an arc-preventing or breaking medium, in order to, in a better and faster way than in a pure air insulation, be able to extinguish occurring electric arcs, foremost in connection with a switching off of high powers and high alternating currents and under high voltage. SF₆ has also better insulating properties, which is utilized to get shorter insulation distances. However, the SF₆ gas is a greenhouse gas and requires, therefore, an intricate and expensive handling, not only because it requires a utilization of a gas-tight container or tank, but also since it contributes negatively to the greenhouse effect.

In addition, in each breaking sequence, this gas has turned out to give rise to residual products that are aggressive from a corrosion point of view.

There are also previously known different other designs of circuit breaker units, for instance such designs when a generated electric arc should be

extinguishable by means of a directed strong air current or air shock, put under a high positive pressure, and with the air current or shock being aimed directly to the propagation and length of the expected electric arc. This means, of course, extra equipment that complicates the construction of the switchgear and makes it more expensive.

In switchgears for three-phase networks, it is also previously known to single-phase insulate each one of the individual, energized conductors going out from the switchgear in such a way that possibly occurring flashovers only can occur between one of said phases and earth potential and never directly between the phases. This has turned out to require a complex geometrical design of the utilized parts and very bulky constructions within the switchgear.

It may also be mentioned that it is per se previously known to a generate negative pressure (vacuum) of an air volume surrounding a breaking point so as to contribute in reducing the development and/or the impact of an electric arc over the breaking point and also contribute to allow extinguishing the tendency to a generated electric arc. These so-called vacuum breakers are insulated in known designs having a complicated shape of solid insulation. The solid insulation is often epoxy casting resin. Baking in a complex geometry of movable parts in epoxy is a very expensive solution.

To sum up, it can be noted that known switchgears have required space- requiring and/or complicated designs and/or utilization of materials less suitable from an environmental point of view such as transformer oil, SF₆ gas and the like.

Summary of invention

The object of the present invention is to provide a switchgear wherein the above-mentioned disadvantages have been obviated and an air-insulated compact switchgear is obtained.

This object has been solved by using two different types of single-phase insulation for the circuit breaker and disconnector unit and for the phase lines going out from the down side of the switchgear.

In this way, the switchgear can be arranged independently of the atmosphere surrounding the switchgear. This is in particular achieved by the fact that the single-phase insulation of the circuit breaker and disconnector unit consists of air insulation.

The single-phase insulation of the phase line going out on the down side of the switchgear consists of synthetic material, preferably of shrinkable plastic attached to the phase line. Thanks to simple geometry, several types of insulating layers can be attached. As an alternative to shrinkable plastic, it is possible, for example, to dip the conductors in thermosetting plastic or thermoplastic. Another alternative is to lacquer the conductors with several layers.

By the circuit breaker included in the circuit breaker and disconnector unit, in this connection, a breaker is intended that can break currents of at least 2000 A and that does not require, e.g., SF₆ gas as a breaker medium or insulating medium. Therefore, a vacuum breaker known per se, or another circuit breaker that is compact without requiring SF₆ gas, is advantageously used as a break medium or insulating medium. This entails among other things an essential saving of space.

By a design according to the invention wherein the circuit breaker and disconnector unit is contained in a space where air at atmospheric pressure forms the single-phase insulation and where the space is separated from the part of the switchgear from where the phase line goes out, a considerable advantage is achieved in that the outgoing phase line can be directed in the desired direction independently of the direction of the actuator of the circuit breaker and

disconnector unit.

The separation of the space with the circuit breaker and disconnector unit from the down side of the switchgear, with the outgoing phase line situated thereon, consists advantageously of an electrically conducting bottom beam connected to earth. A plurality of bottom beams constitute together an earthed middle plane, floor. In particular, if this bottom beam is a part of the compartment or cupboard construction of the switchgear, a well accessible surface is obtained for earthing of the disconnector in its disconnection position.

The separating bottom beam advantageously carries a phase lead- through of a suitable electrically insulating material, such as thermoplastic reinforced with glass fibre (which is a considerably cheaper solution than hitherto used conventional lead-throughs of casting resin, epoxy, etc. The conductor going out from the circuit breaker and disconnector unit may, via the phase lead-through, be directly connected to the plastic-insulated phase line on the down side. By forming the phase lead-through with a creep distance, considerations can be given to possibly occurring impurities of the air insulation, such as moisture, salt content, dust particles and the like.

In one embodiment of the switchgear of three-phase systems, the phases in the space for the circuit breaker and disconnector unit are separated from each other by an electrically insulating wall. In this way, it is guaranteed that a flashover and an arcing between the phases are efficiently prevented. Since the single- phase insulation of the circuit breaker and disconnector unit consists of air insulation, neither is any pressure relief required for the tank in which the switchgear is contained, since by virtue of the single-phase insulation, the possibility of the formation of an electric arc between the phases is avoided.

By arranging the circuit breakers of the three-phase system in line with each other, whereby also the respective appurtenant disconnectors are in line with each other, a well suited extension of the respective operating shaft for the circuit breakers and the disconnectors is achieved. These operating shafts are

advantageously parallel to each other and are arranged to be operated

independently of manual action. By earthing the operating shafts, they can penetrate the walls separating the phases without requirement of tightness. A conceived electric arc always impinges on earth before it can reach another phase.

The manually independent operation of the switching on and off of the operating shafts is remotely released and is effected by means of spring forces acting on the operating shafts. Thus, the operating shaft of the disconnectors may, for instance, include or consist of a torsion spring, by the spring force of which connection and/or disconnection is effected.

By the switchgear according to the invention, there is obtained, as the single-phase insulation on the circuit breaker and disconnector unit side consists of air insulation at atmospheric pressure, a very advantageous possibility of expanding the switchgear by the interconnection of a plurality of switchgears wall to wall. In doing so, appropriate holes are made in the switchgear wall and the high-voltage feeders are brought directly between the interconnected switchgears. Thus, no special sealing against gas/air leakage to or from the atmosphere needs to be made.

Accordingly, each switchgear can be prepared for such combining by the corresponding switchgear walls being provided with a removable cover plate. When combining two or more switchgears, these cover plates are removed and the respective bus-bars in the respective switchgear are bolted to each other. This implies a considerable advantage in relation to known switchgears, in particular in relation to such ones having SF₆ gas-insulated closed tanks, where it is not possible to directly gain access to the bar system. In these known switchgears, it is necessary to provide the switchgear units with lead-throughs and expensive so- called Elbow cable connections in order to allow combining and interconnecting the same.

Moreover, it is advisable that the air-insulating inner space of the switchgear is in free fluid communication with the surrounding outer atmosphere. This is advantageously effected via filters.

Brief description of drawings

Further advantages and embodiments of the switchgear according to the invention will be clear from the following description, which is provided in connection with the appended drawings, wherein Fig. 1 shows a side section through the switchgear according to the invention, Fig. 2 shows the switchgear according to Fig. 1 in perspective but without operating mechanism and rotated 180°, and

Fig. 3 shows a section Ill-Ill through the switchgear according to Fig. 2.

Description of embodiments

The following description of the switchgear according to the present invention illustrates the principal structure thereof in a three-phase application for a high voltage network.

Thus, in the section view according to Fig. 1 , there is shown an

exemplifying three-phase embodiment of the switchgear according to the invention as seen from the side. The switchgear is contained in a covering 1 forming an inner space and consisting of a sheet metal tank. Each phase R, S, T embraces a circuit breaker 2, preferably of the vacuum type, above a disconnector 7. Via a link 4 having an insulating part 17, a first operating shaft 3 is arranged to manoeuvre the contact connection 5 of the circuit breaker 2 to and from, respectively, the incoming voltage feeding bar 13. A second operating shaft 9 is arranged for manoeuvring the disconnector 7 between an earth contact 18 and a breaker contact 19. The operating shafts 3 and 9 are controlled by means of an operating mechanism 12 (not shown in more detail and known per se). It is manually independently controlled by remote control.

Via a pin insulator 15, the circuit breaker and disconnector unit 2, 7 is mounted on a bottom beam 10. The pin insulator 15 is made as a lead-through of glass fibre-reinforced thermoplastic for a line 8 going out from the switchgear at the foot. This line 8 extends further to a lead-through 1 1 going out from the covering 1 of the switchgear, on the outside of which lead-through, connection may be effected for distribution of electricity to other apparatuses.

The essential feature of the switchgear according to the invention is best seen in Fig. 2, wherein the switchgear is shown in perspective and wherein the same reference designations are used as in Fig. 1 for components corresponding to each other. The feature is to be found in the combination of two different single- phase insulations, on one hand the one consisting of air at atmospheric pressure, which generally is prevalent within the covering 1 of the switchgear as well as outside the same, and on the other hand the one that the outgoing line 8 is provided with. Accordingly, the line 8 is made as a metallic conductor insulated with shrinkable plastic 14 or another insulating material, as is illustrated by the detailed enlargement shown in Fig. 1 . In spite of only air at atmospheric pressure being used as single-phase insulation in the remaining parts of the switchgear, this means that the switchgear can be made compact.

Simple plane insulating screens 6, which have been arranged between each one of the phases R, S, T within the area of the circuit breaker and disconnector unit 2, 7, form single-phase insulation in the upper space. These screens 6 guarantee that no flashovers will arise between the different phase voltages. Therefore, a disconnection of the disconnector 7 only means that a possible electric arc arises upon the contact knife movement of the disconnector 7 toward the earth contact 18, which is arranged on the bottom beam 10 and to which the disconnector 7 is connected in its off-state.

Since requirements are often made that the lines going out from the switchgear via the lead-through 1 1 should be directed in the same direction as the operating shafts 3, 9, problems with the geometry of the routing of the lines 8 and the insulation caused thereby often arise. By the insulation technique that characterizes the present invention, this problem has been entirely obviated.

In addition, by providing the lead-throughs 1 1 with each a cap 16, a good transition between conductor and lead-through has been obtained. Preferably, this cap is made of silicone rubber. Outside the lead-through 1 1 , that is, the part being inside the tank, there may be arranged hydrophobic silicone rubber of a special shape 20, which increases the creep distance. This prevents creeping flashovers and simultaneously allows a more compact embodiment. Accordingly, a good insulation capacity is obtained even if the used air insulation would be impaired by impurities in the form of moisture, salts, dust particles and the like. This means in addition that the space inside the covering 1 can communicate freely with the atmosphere prevailing outside the switchgear. Suitably, a filtered hole is made in the wall of the covering 1 for ventilation depending on air pressure changes in the atmosphere.

Since the inner space of the switchgear utilizes air at atmospheric pressure as phase insulation, an enlargement of the switchgear can be

accomplished with small means. Accordingly, two or more switchgears are combined to be placed wall-to-wall with each other. The only step that needs to be taken is to make holes for the running of the bus-bars 13 between the different combined switchgears. No step against gas or air leakage is required.

The description given above has been directed to a particular embodiment of the switchgear according to the invention. Of course, different modifications and further developments may be made without for that reason deviating from the general idea of the invention as expressed in the subsequent claims.

Claims

1 . Switchgear for high voltage comprising a circuit breaker (2) and a disconnector (7) arranged in series above each other in a single-phase insulated design and having operating shafts (3, 9) for the circuit breaker (2) and the disconnector (7), respectively, two different types of single-phase insulation being used for the circuit breaker and disconnector unit (2, 7) and for phase lines (8) going out from the switchgear on the down side, characterised in that the single- phase insulation is air insulation and screens (6) between the phases of the circuit breaker and disconnector unit (2, 7).

2. Switchgear according to claim 1 , wherein the single-phase insulation of the phase line (8) going out from the switchgear on the down side is of synthetic material (14) directly attached to the surface of the phase line (8).

3. Switchgear according to claim 2, wherein the single-phase insulation of the phase line (8) going out on the down side consists of shrinkable plastic (14) attached to the phase line (8).

4. Switchgear according to claim 1 , wherein the circuit breaker (2) is of vacuum breaker type.

5. Switchgear according to any of the preceding claims, wherein the circuit breaker and disconnector unit (2, 7) is contained in a space where air at atmospheric pressure and the screens (6) constitute the single-phase insulation, which space is separated from the part of the switchgear having the phase line (8) going out on the down side.

6. Switchgear according to claim 5, wherein the separation of the space for the circuit breaker and disconnector unit (2, 7) from the part of the switchgear having the phase line (8) going out on the down side consists of an electrically conducting bottom beam (10) connected to earth.

7. Switchgear according to claim 6, wherein the conducting bottom beam (10) constitutes a part of the compartment or cupboard construction (1 ) in which the switchgear is contained.

8. Switchgear according to claim 6 or 7, wherein the bottom beam (10) carries a phase lead-through (15) of thermoplastic for the lead-out of the outgoing phase line (8) that is plastic insulated on the down side and on the upper side of the phase lead-through (15) is connected to the down side of the circuit breaker and disconnector unit (2, 7).

9. Switchgear according to claim 7, wherein the compartment or cupboard construction (1 ) carries an outgoing lead-through (1 1 ) for the lead-out of the phase line (8) going out from the switchgear on the down side.

10. Switchgear according to claim 9, wherein the lead-through (1 1 ) is provided with a cap (16), preferably of silicone rubber.

1 1 . Switchgear according to claim 9 or 10, wherein, outside the part of the lead-through (1 1 ) being inside the compartment or cupboard construction (1 ), hydrophobic silicone rubber of a special shape (20) is arranged for the extension of the creep distance.

12. Switchgear according to any of the preceding claims, consisting of a three- phase switchgear having separate circuit breaker (2), disconnector (7) and outgoing phase line (8) arranged for the respective phase (R, S, T), the phases in the space for the circuit breaker and disconnector units (2, 7) being separated from each other by an electrically insulating wall (6).

13. Switchgear according to claim 12, wherein the circuit breakers (2) in the three-phase system are arranged in line with each other as well as the respective appurtenant disconnectors (7) to be operated by one operating shaft (3) for the circuit breakers (2) and one operating shaft (9) for the disconnectors (7), the operating shafts (3, 9) being mutually parallel.

14. Switchgear according to claim 13, wherein operation of the operating shafts (3, 9) is manually independent.

15. Switchgear according to claim 13 or 14, wherein the operating shaft (9) of the disconnectors (7) comprises a torsion bar.

16. Switchgear according to claim 15, wherein the switching on and off of the disconnectors (7) are effected by means of the spring force of the torsion spring (9).

17. Switchgear according to any of claims 12-16, expandable by

interconnection of a plurality of air-insulated three-phase switchgears wall-to-wall with each other with common high-voltage feeders (13), which, for each phase (R, S, T), are brought directly between the interconnected three-phase switchgears through openable holes in their walls.

18. Switchgear according to any of the preceding claims, wherein the air- insulating inner space of the switchgear is in free fluid communication with the surrounding outer atmosphere of the switchgear via filter.