WO2013178787A1

WO2013178787A1 - High-voltage switch with multiple metal enclosures

Info

Publication number: WO2013178787A1
Application number: PCT/EP2013/061262
Authority: WO
Inventors: Per Skarby
Original assignee: Abb Technology Ag
Priority date: 2012-05-31
Filing date: 2013-05-31
Publication date: 2013-12-05
Also published as: EP2856487A1; EP2856487B1; KR102038724B1; CN104380422A; KR20150015478A; CN104380422B

Abstract

A switch comprises a first switching assembly (la) in a first metal enclosure (2a) and a second switching assembly (lb) in a second metal enclosure (2b). The two metal enclosures (2a, 2b) are electrically insulated from each other as well as from ground. This allows arranging a plurality of metal-enclosed switching assemblies in series while avoiding excessive electrical fields in any of them.

Description

High- oltage switch with multiple metal enclosures

Technical Field

The invention relates to a high-voltage switch having a switching assembly in a metal enclosure. The invention also relates to a method for operating such a switch.

Background Art

Circuit breakers for high-voltage applications typically may comprise a switching assembly having one or more electrical switches arranged in a metal enclosure. The metal enclosure is grounded, while the switching assembly is at high-voltage potential.

To provide a circuit breaker for even higher voltages, the size of the metal enclosure must be in- creased in order to keep the field strengths within acceptable limits. This is expensive and requires different circuit breaker components for different voltage ratings.

DE 10 2006 050 732 describes a circuit breaker using electrical switches arranged in series, with each switch located in an insulating enclosure. Impedance devices comprising grading capacitors are provided for distributing the voltage over the switches.

Disclosure of the Invention

Hence, it is a general object of the invention to provide a switch design that allows to switch even very high voltages while keeping cost low.

This object is achieved by the switch and the method of the independent claims. Various embodiments are given in the dependent claims or claim combinations. Accordingly, the switch comprises at least two metal enclosures, with a switching assembly arranged in each metal enclosure, wherein said switching assemblies are arranged in series and wherein said at least two metal enclosures are electrically insulated from each other. The two metal enclosures being electrically insu^¬ lated from each other, and in particular being insulated from ground, allows arranging a plurality of metal- enclosed switching assemblies in series wile avoiding ex^¬ cessive electrical fields in any of them.

The high-voltage switch can comprise, for ex^¬ ample, switching assemblies with high-voltage circuit breaking and/or high-voltage disconnecting function and/or high-voltage current commutating function. In particular, the high-voltage switch can be a high-voltage disconnector, a high-voltage circuit breaker, a high- voltage current commutating device, or similar devices.

In this design, the switching assemblies are arranged in series such that a high voltage can be switched. Each switching assembly is arranged in a metal enclosure, with the metal enclosures being electrically insulated from each other. This allows to keep the metal enclosures at different electrical potentials and therefore to reduce the electrical fields within them. Hence, smaller metal enclosures can be used.

The design is scalable in the sense that the same metal enclosure and switching assembly can be re^¬ used for different voltage ratings. For comparatively small voltage ratings, a single enclosure and switching assembly can be used. For larger voltage ratings, two, three or even more switching assemblies can be arranged in series, with each being mounted in its metal enclosures and the metal enclosures being mutually insulated.

In one embodiment, the switch comprises a first metal enclosure enclosing a first switching assembly as well as a second metal enclosure enclosing a second switching assembly. Further, the switch comprises a first and a second terminal. The switching assemblies are arranged in series between the terminals, such that they can interrupt a current flow between the terminals. Advantageously, the first terminal is electrically connected to the first metal enclosure and a second terminal is electrically connected to the second enclosure. Thus, the voltages between the enclosures and their switching assemblies remain comparatively small, even if the switch is switched off.

In yet other embodiments, the switch comprises, for each switching assembly, at least one impedance device arranged in parallel to the switching assembly or are arranged between the metal enclosure and a node between the switching assemblies. The impedance devices can have matching impedances in order to evenly distribute the applied voltage over the switching assemblies and/or to compensate for a stray capacitance from the conductor to ground.

The invention also relates to a method for operating the above switch. This method comprises the step of connecting a first one of the switching assemblies to a first high-voltage potential and a second one of the switching assemblies to a second high voltage potential in such a manner, that the switching assemblies are arranged in series between said first and said second potentials in order to interrupt the current flow between them.

Brief Description of the Drawings

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

Fig. 1 shows a view of a switch,

Fig. 2 shows a sectional view of a switch, Fig. 3 shows a switching assembly with several switches and/or switching gaps,

Fig. 4 shows a switch design with more than two switching assemblies, where the metal enclosures are held at intermediate potentials, and

Fig. 5 shows a sectional view of a further embodiment of a switch.

Modes for Carrying Out the Invention

Definitions

The term "high voltage" designates voltages typically exceeding 72 kV.

The term "a gas with elevated pressure" designates an insulating gas having a pressure exceeding at^¬ mospheric pressure, in particular exceeding 2 bars.

Embodiments

Figs. 1 and 2 show switches having a first switching assembly la and a second switching assembly lb. First switching assembly la is arranged in a first metal enclosure 2a, and second switching assembly lb is ar^¬ ranged in a second metal enclosure 2b.

Each switching assembly comprises one or more electrical switching units 4. A suitable switching unit may for example be based on the concepts presented in US 7, 235, 751 B2.

For example, each metal enclosure is filled with an insulating medium, in particular with a gas of elevated pressure, such as SF_S, for increasing the break^¬ down voltage.

The two switching assemblies la, lb are arranged in series and are interconnected by means of a conductive rod 5. The two enclosures 2a, 2b are mechanically interconnected by means of an electrically insulat^¬ ing cylinder 6, which encloses the conductor 5. Cylinder 6 can, for example, also be filled with an insulating gas of elevated pressure, such as SF_e, for increasing the break-down voltage. Furthermore, it may or may not contain partitions in order to separate the total volume of gas or insulating medium into one or several gas zones.

The switch can be arranged as a whole in ambient air in a so-called live tank configuration.

The switch comprises two terminals 8a, 8b, for connecting it to a line 9 to be interrupted. As mentioned, the first and second switching assemblies la, lb are arranged in series between the first and the second terminals 8a, 8b. Further, in the present embodiment, first terminal 8a is electrically connected to first metal enclosure 2a and second terminal 8b is electrically connected to second metal enclosure 2b.

The switchs of Figs. 1 and 2 further comprise a frame designated by numerals 10a - lOj . It has a first section 10a, 10b, 10c, a second section lOd, lOe, lOf and a third section lOg - lOj . First section 10a - 10c is mechanically connected to first metal enclosure 2a, second section lOd - lOf is mechanically connected to second metal enclosure 2b, and third section lOg - lOj mechanically connects the first and second sections to each other. At least third section lOg - lOj is electrically in^¬ sulating. For example, it comprises a plurality of rods lOg, lOh, lOi and lOj extending between the first and the second sections 10a - 10c and lOd - lOf, respectively.

Further, and as is best seen in Fig. 2, the switch comprises an electrically insulating suspension 12 for suspending the switch e.g. in a scaffolding 14. In the embodiment of Figs. 1 and 2, the suspension 12 com^¬ prises several suspension members 12a - 12d, at least one of which is connected to first frame section 10a - 10c and at least another of which is connected to second frame section lOd - lOf. It must be noted, though, that the whole switch can also be supported from the ground, e.g. by means of support insulators, rather than being suspended from a scaffolding 14.

Each switching assembly comprises an actuator for actuating its switches. A first actuator 15a is attributed to the first switching assembly la. It is at the potential of the first enclosure 2a and it comprises one or several actuating coils 15a" and an energy storage 15a' . Energy storage 15a' is mounted to first frame section 10a - 10c and feeds actuating coil(s) 15a" mounted in the first enclosure 2a for operating the first switching assembly la. A second actuator 15b is attributed to the second switching assembly lb. It is at the potential of the second enclosure 2b and it comprises at least one actuating coil 15a" and an energy storage 15b' . Energy storage 15b' is mounted to second frame section lOd - lOf and feeds at least one actuating coil 15b" mounted in the second enclosure 2b for operating the second switching assembly lb. As mentioned, each actuator 15a, 15b is at the potential of the metal enclosure 2a, 2b of its switching assembly la, lb; i.e. preferably the voltage difference between each actuator 15a, 15b and its respective enclosure 2a, 2b is less than 5 kV. If the enclosure may contain a plurality of contact members la, lb, 4 as indicated below in Fig. 3, the actuator needs to be electrically insulated therefrom.

The actuators 15a, 15b are electrically insulated from each other.

In operation, the actuators 15a, 15b are at high voltage potentials. Therefore, each actuator 15a, 15b comprises its own power supply with a galvanically insulated power feeder 16a, 16b, respectively. A "galvanically insulated power feeder" is a feed for feeding electrical power from ground potential to an elevated high voltage potential. Such feeds are known to the skilled person and can e.g. consist of a plurality of coupling capacitors in series creating a capacitive circuit between ground and high voltage potential that can be supplied by a high frequency source at ground potential (see for example US 2006152199 Al) . Other such power feeders may be based, for example, on inductive, hydraulic, pneumatic or mechanical principles.

In operation, the switch is connected with its terminals 8a, 8b to a line 9 to be interrupted.

When both switching assemblies of the switch are in their conductive state, the switching assemblies la, lb as well as conductive rod 5 are on the same high voltage potential. The metal enclosures 2a, 2b will also be on high voltage potential.

The primary voltage drop of the system voltage to ground occurs over suspension 12 and power feeders 16a, 16b, which have been built for that purpose and are easily adapted to the respective voltage ratings.

When the switching assemblies la, lb are switched off, i.e. when they are in their non-conductive state, there will typically be a high-voltage drop over the terminals 8a, 8b. In this case, the potential on conductive rod 5, i.e. at the electrical node 17 between the switching assemblies la, lb, will depend primarily on the impedances over each switching assembly, i.e. on the impedances between node 17 and the two terminals 8a, 8b, respectively, but also on the impedance between the enclosures 2a and 2b as defined e.g. by the length of cyl^¬ inder 6.

Further impedances that affect the voltage distribution are the impedances of the terminals 8a, 8b to ground and of node 17 to ground.

Three closed dashed lines 20 in Fig. 2 enclose the three major parts of the breaker that are electrically connected to each other and are therefore on the same potentials.

Ideally, if the design of the switch is symmetric, the impedances at both switching assemblies la, lb are equal and therefore the voltage drops over the switching assemblies la, lb are equal, as well, if the capacitance of conductor 5 to ground can be neglected. In order to compensate for asymmetries and/or for the effect of the stray capacitance of conductor 5 to ground, an ex^¬ emplary embodiment comprises auxiliary impedance devices 18a, 18b, which are close to equal and have e.g. absolute impedance values (at 50 Hz or 60 Hz) in the order of 1-10 ΜΩ. In other words, the impedance devices 18a, 18b shall provide a larger capacitance than the stray capaci^¬ tance of conductor 5 to ground, for example shall be larger by a factor 5 to 10. The impedance devices are typically capacitors having a capacitive and resistive part. Each switching assembly is arranged in parallel to one impedance device 18a, 18b, and all impedance devices are matched in order to evenly distribute the voltage applied to the switch over the switching assemblies la, lb. Alternatively, or in addition thereto, an impedance device 18c, as shown, can be arranged between the two enclosures 2a, 2b.

Alternatively to arranging the impedance devices 18a, 18b parallel to the switching assemblies la, lb, they can be inserted between the metal enclosure 2a, 2b and those terminals of the switching assemblies la, lb that are connected to node 17.

In the embodiment of Fig. 2, the impedance devices 18a, 18b are arranged within the metal enclosures 2a, 2b. Alternatively, and as shown in the embodiment of Fig. 5, the impedance devices 18a, 18b can be arranged outside the enclosures 2a, 2b, and can be arranged outside insulating cylinder 6 where there is more room to accommodate them. In the embodiment of Fig. 5, the impedance devices 18a, 18b each extend from an enclosure 2a, 2b to the node 17 between the switching assemblies la, lb. For this purpose, a node terminal 19 is arranged between the two switching assemblies la, lb, advantageously at equal distances from both switching assemblies. Node terminal 19 is electrically connected to conducting rod 5 and extends outside insulating cylinder 6. For example, insulating cylinder 6 is split into two halves and node terminal 19 is arranged at the flanging point of the two halves. The two impedance devices 18a, 18b are each con^¬ nected to node terminal 19 at one of their ends, and to the enclosures 2a, 2b at their other ends.

The impedance devices 18a, 18b are, for example, capacitors, e.g. rated to some hundred kV each (e.g. 300 kV) . They act as grading capacitors and have a capacitance of at least 100 pF, in particular in the range of some 100 pF to some few nF.

For further illustration of the above, some embodiments are mentioned once more:

In embodiments, the metal enclosures 2a, 2b are electrically insulated from each other by a solid in^¬ sulator, in particular by an electrically insulating cylinder and/or by an electrically insulating third section of a frame of the switch.

In embodiments, the metal enclosures 2a, 2b are electrically insulated from each other by the electrically insulating cylinder 6 as disclosed in Fig. 1, 2, 6 and the accompanying description.

In embodiments, the metal enclosures 2a, 2b are electrically insulated from each other by the electrically insulating third section lOg, lOj of the frame 10a, lOj of the switch as disclosed in Fig. 1, 2, 6 and the accompanying description.

In embodiments, the metal enclosures 2a, 2b are electrically insulated from ground, in particular by a solid insulator 16a, 16b or a support insulator.

In embodiments, metal enclosures 2a, 2b are electrically insulated from ground by the galvanically insulated power feeders 16a, 16b of the power supply of the actuators 15a, 15b, as disclosed in Fig. 1, 2, 6 and the accompanying description.

In embodiments, the metal enclosures 2a, 2b are arranged in series to one another. In embodiments, each metal enclosure 2a, 2b is closed in a gas-tight manner.

In embodiments, the first metal enclosure 2a enclosing the first switching assembly la and the second metal enclosure 2b enclosing the second switching assembly lb are each closed in a gas-tight manner.

In embodiments, the switch is a high-voltage switch for ac or dc applications, in particular a high- voltage disconnector, a high-voltage circuit breaker, or a high-voltage current commutating device.

Notes

In the above embodiment, the switch comprises two switching assemblies la, lb arranged in series. It can, however, comprise even more switching devices arranged in series, with each switching device mounted in its metal enclosure and with neighboring metal enclosures being electrically insulated from each other. With this design, the switch can be scaled to even higher voltages while reusing the same switching assembly and metal enclosure designs.

As mentioned, each switching assembly 2a, 2b comprises one or more electrical switching units 4. Fig. 2 shows an embodiment with two such switching units 4. If several switching units 4 are provided, at least some of them are advantageously arranged in series for increasing the withstand voltage of the switching assembly.

In contrast to a metal-clad dead tank switch with a single switching assembly, the metal enclosures 2a, 2b are not connected to ground. In the embodiment above, the metal enclosures 2a, 2b at the ends of the series arrangement of switching assemblies la, lb are connected (via a low-impedance connection) to the terminals 8a, 8b, respectively. Alternatively, the connection between the metal enclosures and the terminals may be of higher impedance. In this case, the impedances between the terminals and the adjacent metal enclosures as well as the impedances between neighboring metal enclosures are advantageously balanced such that (i) the voltage drops are the same, or at least approximately the same, over all switching assemblies, and (ii) the potential of each metal enclosure is in the center, or approximately in the center, between the potentials input and output terminals of the switching assembly that it encloses. An example of such a switch with three switching assemblies la, lb, lc and three metal enclosures 2a, 2b, 2c is shown in Fig. 4. Impedance devices Z are provided between each metal enclosure 2a, 2b, 2c and a node 17 between two neighbouring switching assemblies, and optionally between an end-side metal enclosure 2a and 2c and its neighbouring terminal 8a and 8c, respectively. At least the absolute impedances values of all impedance devices Z are chosen to be equal, or at least to be sufficiently similar, in which case the above conditions (i) and (ii) are met if the impedances to ground are neglected.

The present switch is for example used for switching high voltages and low currents, e.g. at the location of device 10 in Fig. 2 of WO 2011/057675, the content of which in its entirety is herewith made part of the disclosure by reference.

The high-voltage switch can comprise, for example, switching assemblies with high-voltage circuit breaking and/or high-voltage disconnecting function and/or high-voltage current commutating function. In particular, the high-voltage switch can be a high-voltage disconnector, a high-voltage circuit breaker, a high- voltage current commutating device, or similar devices.

The switch can be used for dc as well as ac applications .

In a typical example, it can e.g. be used for switching a dc voltage of 640 kV using two switching assemblies la, lb and metal enclosures 2a, 2b each being rated for approximately half that voltage. In this case, a typical distance between the two metal enclosures 2a,

2b can be in the order of some meters, such as 5 m - 6 m.

While there are shown and described presently preferred embodiments of the invention, it is to be dis^¬ tinctly understood that the invention is not limited

thereto but may be otherwise variously embodied and prac^¬ ticed within the scope of the following claims.

Reference numbers la, lb, lc: switching assemblies

2a, 2b, 2c: metal enclosures ! 4: switching unit, switching contact members j 5: conductive rod ] 6: insulating cylinder

8a, 8b: terminals

9: power line

10a, 10b, ... , 10j : frame j 10a, 10b, 10c: first section of frame j lOd, lOe, lOf: second section of frame

lOg, lOh, lOj : third section of frame, insulated section

12; 12a, 12b, 12c, 12d: suspension j 14: scaffolding j 15a, 15b: actuators

Claims

1. A high-voltage switch comprising a switching assembly (la, lb), wherein the switching assembly (la, lb) is arranged in a metal enclosure (2a, 2b) , characterized in that the switch comprises at least two metal enclosures (2a, 2b) , with a switching assembly (la, lb) arranged in each metal enclosure (2a, 2b) , wherein said switching assemblies (la, lb) are arranged in series and wherein said at least two metal enclosures (2a, 2b) are electrically insulated from each other.

2. The switch of claim 1, wherein each switching assembly (la, lb) comprises an actuator (15a, 15b) for actuating the switching assembly (la, lb), wherein the actuators (15a, 15b) of the switching assemblies (la, lb) are electrically insulated from each other.

3. The switch of claim 2, wherein each actuator (15a, 15b) is at a same potential as the enclosure (2a, 2b) of the switch it actuates.

4. The switch of any of the claims, wherein each actuator (15a, 15b) comprises a power supply with a galvanically insulated power feeder (16a, 16b) .

5. The switch of any of the preceding claims, comprising

at least a first metal enclosure (2a) of the metal enclosures (2a, 2b) enclosing a first switching assembly (la) of the switching assemblies (la, lb) ,

at least a second metal enclosure (2b) of the metal enclosures (2a, 2b) enclosing a second switching assembly (lb) of the switching assemblies (la, lb), and a first and a second terminal (8a, 8b) , wherein said switching assemblies (la, lb) are arranged in series between said first and said second terminals (8a, 8b).

6. The switch of claim 5, wherein said first terminal (8a) is electrically connected to the first metal enclosure (2a) and the second terminal (8b) is electrically connected to the second metal enclosure (2b) .

7. The switch of any of the claims 5 to 6, further comprising an electrically insulating suspension (12) for suspending said switch.

8. The switch of any of the claims 5 to 7, comprising a frame (10a, 10j ) having a first section (10a, 10b, 10c) connected to said first enclosure (2a), a second section (lOd, lOe, lOf) connected to said second enclosure (2b), and a third section (10g, lOj) connecting said first (10a, 10b, 10c) and said second (lOd, lOe, lOf) sections, wherein said third section (lOg, lOj) is electrically insulating.

9. The switch of claim 8, wherein said third section (lOg, 10j) comprises a plurality of rods extending between the first section (10a, 10b, 10c) and the second section (lOd, lOe, lOf) .

10. The switch of any of the preceding claims, further comprising an electrically insulating cylinder (6) connecting two of the metal enclosures (2a, 2b), and a conductive rod (5) being arranged in said cylinder (6) and connecting the switching assemblies (la, lb) in said two metal enclosures (2a, 2b) .

11. The switch of claim 10, wherein said cylinder (6) is filled with an insulating gas under elevated pressure .

12. The switch of any of the preceding claims, wherein said metal enclosures (2a, 2b) are filled with an insulating gas of elevated pressure.

13. The switch of any of the preceding claims, wherein each switching assembly (la, lb) comprises several electrical switching units (4).

14. The switch of any of the preceding claims, further comprising, for each switching assembly (la, lb), at least one impedance device (18a, 18b, Z) being arranged in parallel to each switching assembly (la, lb) or being arranged between the metal enclosure (2a, 2b) and a node (17) between the switching assemblies (la, lb) , wherein the impedance devices (18a, 18b, Z) have matching impedances in order to evenly distribute a voltage applied to the switch over the switching assemblies (la, lb) and to compensate for a stray capacitance from the conductor (5) to ground.

15. The switch of claim 14, further comprising

an electrically insulating cylinder (6) mechanically connecting two of the metal enclosures (2a, 2b),

a conductive rod (5) arranged in said cylinder (6) and electrically connecting the switching assemblies (la, lb) in said two metal enclosures (2a, 2b) , and a node terminal (19) arranged between said two switching assemblies (la, lb), electrically connected to said conductive rod (5) and extending outside said insulating cylinder (6),

wherein said impedance devices (18a, 18b) are arranged outside said insulating cylinder (6) and are connected to said node terminal (19) .

16. The switch of any one of the preceding claims, wherein the metal enclosures (2a, 2b) are electrically insulated from each other by a solid insulator, in particular by an electrically insulating cylinder (6) and/or by an electrically insulating third section (lOg, 10j) of a frame (10a, lOj) of the switch.

17. The switch of claim 10 and 16, wherein the metal enclosures (2a, 2b) are electrically insulated from each other by the electrically insulating cylinder (6) .

18. The switch of claim 8 and 16, wherein the metal enclosures (2a, 2b) are electrically insulated from each other by the electrically insulating third section (lOg, lOj) of the frame (10a, lOj) of the switch.

19. The switch of any one of the preceding claims, wherein the metal enclosures (2a, 2b) are electrically insulated from ground, in particular by a solid insulator (16a, 16b) or a support insulator.

20. The switch of claim 4 and 19, wherein the metal enclosures (2a, 2b) are electrically insulated from ground by the galvanically insulated power feeders (16a, 16b) of the power supply of the actuators (15a, 15b) .

21. The switch of any one of the preceding claims, wherein the metal enclosures (2a, 2b) are arranged in series to one another.

22. The switch of any one of the preceding claims, wherein each metal enclosure (2a, 2b) is closed in a gas-tight manner.

23. The switch of claim 5 and 22, wherein the first metal enclosure (2a) enclosing the first switching assembly (la) and the second metal enclosure (2b) enclos^¬ ing the second switching assembly (lb) are each closed in a gas-tight manner.

24. The switch of any one of the preceding claims, wherein the switch is a high-voltage switch for ac or dc applications, in particular a high-voltage disconnector, a high-voltage circuit breaker, or a high- voltage current commutating device.

25. A method for operating the switch of any of the preceding claims, comprising the step of connect^¬ ing a first one of said switching assemblies (la, lb) to a first high-voltage potential and a second one of said switching assemblies (la, lb) to a second potential, such that said switching assemblies (la, lb) are arranged electrically in series between said first and said second potentials .