Gas-insulated load break switch and switchgear comprising a gas-insulated load break switch

Abstract

A load-break switch has a housing holding insulation gas at ambient pressure; a first main contact and a second main contact being movable relative to each other in an axial direction of the switch; a first arcing contact and a second arcing contact being movable relative to each other in the axial direction and defining an arcing region where an arc is formed during a current breaking operation, wherein the arcing region is located radially inward from the first main contact; a pressurizing system pressurizing a quenching gas during the current breaking operation; and a nozzle system arranged to blow the pressurized quenching gas onto the arc. The first main contact includes at least one pressure release opening to allow gas flow in a radial outward direction. A total area of the pressure release opening suppresses a reduction of gas flow out of the pressure release opening.

Claims

1. A gas-insulated load break switch, comprising: a housing defining a housing volume for holding an insulation gas at an ambient pressure; a first main contact and a second main contact, the first and second main contacts being movable in relation to each other in an axial direction of the load break switch; a first arcing contact and a second arcing contact, the first and second arcing contacts being movable in relation to each other in the axial direction of the load break switch and defining an arcing region in which an arc is adapted to form during a current breaking operation, wherein the arcing region is located, at least partially, radially inward from the first main contact; a pressurizing system having a pressurizing chamber for pressurizing a quenching gas during the current breaking operation; a nozzle system arranged and configured to blow the quenching gas, which is pressurized, onto the arc formed in a quenching region during the current breaking operation, the nozzle system having a nozzle supply channel for supplying at least one nozzle with the pressurized quenching gas; and an interruption chamber, the first main contact being arranged, at least partially, within the interruption chamber; wherein the first main contact includes at least one pressure release opening formed such as to allow a flow of gas substantially in a radial outward direction, wherein a total area of the at least one pressure release opening is configured such that during a supply of the pressurized quenching gas, a reduction of the flow of gas out of the pressure release opening is suppressed, wherein the total area of the at least one pressure release opening is less than 5 times of a cross-section of the nozzle supply channel, wherein the interruption chamber includes at least one gas outlet opening, a total area of the at least one gas outlet opening being at least the total area of the at least one pressure release opening and/or the total area of the at least one gas outlet opening being more than ⅓ of an area of a cross-section of the interruption chamber, wherein the at least one gas outlet opening is formed such as to allow, in co-operation with the at least one pressure release opening, the flow of gas substantially in the radial outward direction into an ambient-pressure region of the housing volume.

2. The gas-insulated load break switch of claim 1, further comprising a gas flow directing member configured and arranged to direct the flow of gas to a low electrical field region.

3. The gas-insulated load break switch of claim 2, wherein the gas flow directing member is configured and arranged to direct the flow of gas away from an external contacting terminal of the gas-insulated load break switch.

4. The gas-insulated load break switch of claim 1, wherein the first arcing contact has, at least in a contacting region with the second arcing contact, a substantially uniform cross-section, wherein the first arcing contact includes at least one gap extending in the axial direction of the load break switch, the gap having at least ¼ of an area of the substantially uniform cross-section of the first arcing contact.

5. The gas-insulated load break switch of claim 1, wherein the pressurizing system is a puffer system and the pressurizing chamber is a puffer chamber with a piston arranged for compressing the quenching gas on a compression side of the puffer chamber during the current breaking operation, wherein the piston includes at least one auxiliary opening connecting the compression side with an opposite side of the piston, wherein a total cross-section area of the at least one auxiliary opening is at least ⅓ of the area of a total gas outflow cross-section of the nozzle system.

6. The gas-insulated load break switch of claim 1, wherein the second arcing contact includes a hollow section extending substantially in the axial direction, the hollow section being arranged such that a gas portion from the quenching region flows from the quenching region into the hollow section.

7. The gas-insulated load break switch of claim 6, wherein the hollow section has an outlet for allowing the gas portion having flown into the hollow section to flow out at an exit side of the hollow section into an ambient-pressure region of the housing volume.

8. The gas-insulated load break switch of claim 1, wherein the nozzle includes an insulating outer nozzle portion; and/or wherein the nozzle is arranged, at least partially, at a tip end of the second arcing contact.

9. The gas-insulated load break switch of claim 8, wherein an insulating outer nozzle portion of the nozzle is arranged at the tip end of the second arcing contact.

10. The gas-insulated load break switch of claim 1, wherein the insulation gas has a global warming potential lower than the one of SF.sub.6 over an interval of 100 years, and wherein the insulation gas includes at least one gas component selected from the group consisting of: CO.sub.2, O.sub.2, N.sub.2, H.sub.2, air, N.sub.2O, a hydrocarbon, CH.sub.4, a perfluorinated or hydrogenated organofluorine compound, and mixtures thereof.

11. The gas-insulated load break switch of claim 1, wherein the insulation gas includes a background gas, the background gas being selected from the group consisting of: CO.sub.2, O.sub.2, N.sub.2, H.sub.2, air, in a mixture with an organofluorine compound selected from the group consisting of: fluoroether, oxirane, fluoramine, fluoroketone, fluoroolefin, fluoronitrile, and mixtures and/or decomposition products thereof.

12. The gas-insulated load break switch of claim 1, having a rated voltage of at most 52 kV.

13. The gas-insulated load break switch of claim 1, wherein the total area of the at least one gas outlet opening is more than ⅓ and less than ½ of the area of the cross-section of the interruption chamber.

14. A gas-insulated switchgear, comprising: at least one gas-insulated load break switch, each having: a housing defining a housing volume for holding an insulation gas at an ambient pressure; a first main contact and a second main contact, the first and second main contacts being movable in relation to each other in an axial direction of the load break switch; a first arcing contact and a second arcing contact, the first and second arcing contacts being movable in relation to each other in the axial direction of the load break switch and defining an arcing region in which an arc is adapted to form during a current breaking operation, wherein the arcing region is located, at least partially, radially inward from the first main contact; a pressurizing system having a pressurizing chamber for pressurizing a quenching gas during the current breaking operation; a nozzle system arranged and configured to blow the quenching gas, which is pressurized, onto the arc formed in quenching region during the current breaking operation, the nozzle system having a nozzle supply channel for supplying at least one nozzle with the pressurized quenching gas; an interruption chamber, the first main contact being arranged, at least partially, within the interruption chamber; wherein the first main contact includes at least one pressure release opening formed such as to allow a flow of gas substantially in a radial outward direction, wherein a total area of the at least one pressure release opening is configured such that during a supply of the pressurized quenching gas, a reduction of the flow of gas out of the pressure release opening is suppressed, wherein the total area of the at least one pressure release opening is less than 5 times of a cross-section of the nozzle supply channel, wherein the interruption chamber includes at least one gas outlet opening, a total area of the at least one gas outlet opening being at least the total area of the at least one pressure release opening and/or the total area of the at least one gas outlet opening being more than ⅓ of an area of a cross-section of the interruption chamber, wherein the at least one gas outlet opening is formed such as to allow, in co-operation with the at least one pressure release opening, the flow of gas substantially in the radial outward direction into an ambient-pressure region of the housing volume.

15. The gas-insulated switchgear of claim 14, wherein the at least one gas-insulated load break switch comprises at least two gas-insulated load break switches, wherein each load break switch includes an external contacting terminal for respective different voltage phases, and wherein each load break switch further includes a gas flow directing member, wherein the gas flow directing member is configured and arranged to direct the flow of gas away from the external contacting terminal and/or wherein the gas flow directing member is configured and arranged to direct the flow of gas away from an interphase zone between neighboring voltage phases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will now be described in greater detail with reference to the drawings in which:

(2) FIG. 1 shows a schematic cross-sectional view of a gas-insulated load break switch according to an embodiment;

(3) FIG. 2 shows a perspective view of a first main contact of the embodiment of FIG. 1;

(4) FIG. 3 shows a perspective view of an interruption chamber of the embodiment of FIG. 1;

(5) FIG. 4 shows a perspective view of a piston of the embodiment of FIG. 1; and

(6) FIG. 5 shows a schematic cross-sectional view of a switchgear having three gas-insulated load-break switches, according to a further embodiment.

DETAILED DESCRIPTION

(7) Reference will now be made in detail to the various aspects and embodiments. Each aspect and embodiment are provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one aspect or embodiment can be used on or in conjunction with any other aspect or embodiment. It is intended that the present disclosure includes such combinations and modifications.

(8) Within the following description of embodiments shown in the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment applies to a corresponding part or aspect in another embodiment, as well.

(9) FIG. 1 shows a schematic cross-sectional view of a gas-insulated load break switch 1 according to an embodiment. In FIG. 1, the switch is shown in an open state. The switch has a gas-tight housing 2 which is filled with an electrically insulating gas at an ambient pressure. The shown components are arranged within the housing volume 2 which is filled with the gas.

(10) The switch 1 has a first arcing contact (e.g., a stationary pin contact) 10 and a second arcing contact (e.g., a movable tulip contact) 20. The fixed contact 10 is solid, while the movable contact 20 has a tube-like geometry with a tube portion 24 and an inner volume or hollow section 26. The movable contact 20 can be moved along the axis 12, in an axial direction A, away from the stationary contact 10 for opening the switch 1.

(11) The switch 1 further has a first main contact 80 and a second main contact 90 designed to carry and conduct a nominal current during nominal operation. In an opening operation, the second main contact 90 is moved away from the (stationary) first main contact 80, and the current from the main contacts 80, 90 is taken over by the arcing contacts 10, 20.

(12) The switch 1 further has a puffer-type pressurizing system 40 with a pressurizing chamber 42 having a quenching gas contained therein. The quenching gas is a portion of the insulation gas contained in the housing volume of the switch 1. The pressurizing chamber 42 is delimited by a chamber wall 44 and a piston 46 for compressing the quenching gas within the puffer chamber 42 during the current breaking operation.

(13) The switch 1 further has a nozzle system 30. The nozzle system 30 comprises a nozzle 33 connected to the pressurizing chamber 42 by a nozzle channel 32. The nozzle 33 is arranged axially outside the tulip contact 20. In embodiments, several nozzles may be arranged at different azimuthal positions along a circle about the axis 12; and the term “nozzle” herein preferably refers to each of these nozzles.

(14) During a switching operation, as shown in FIG. 1, the movable contact 20 is moved by a drive (not shown) along the axis 12 away from the stationary contact 10 (to the right in FIG. 1b) into the open position shown in FIG. 1. Thereby, the arcing contacts 10 and 20 are separated from one another, and an arc forms in an arcing region or quenching region 52 between both contacts 10 and 20.

(15) The nozzle system 30 and the piston 46 are moved by a drive (not shown), during the switching operation, together with the tulip contact 20 away from the pin contact 10. The other chamber walls 44 of the pressurizing volume 42 are stationary. Thus, the pressurizing volume 42 is compressed and the quenching gas contained therein is brought to a quenching pressure which is defined as the maximum total pressure (overall, i.e. neglecting localized pressure build-up) within the pressurizing chamber 42.

(16) The nozzle system 30 then blows the pressurized quenching gas from the pressurization chamber 42 onto the arc. For this purpose, the quenching gas from the pressurization chamber 42 is released and blown through the channel 32 and the nozzle 33 onto the arcing zone 52. Thus, the quenching gas flows towards the arcing zone 52. From the arcing zone 52, the gas flows in a predominantly axial direction away from the arcing zone.

(17) Referring to FIGS. 2 to 4, elements of the switch of embodiment of FIG. 1 are shown in a perspective view. FIG. 2 shows a perspective view of the first main contact 80, FIG. 2 shows a perspective view of the interruption chamber 70, and FIG. 3 shows a perspective view of the piston 46.

(18) Referring back to FIG. 1 in a synopsis with FIGS. 2 to 4, the first main contact 80 of the embodiment comprises pressure release openings 85, of which two are shown in FIG. 2. The pressure release openings 85 may be provided circumferentially in regular or irregular intervals; moreover, it is possible that only one pressure release opening 85 is provided in the first main contact. The entirety of all pressure release openings 85 may be referred to as “pressure release opening 85” herein.

(19) The pressure release opening 85 of the embodiment shown in FIGS. 1-4 is formed in a circumferential wall of the first main contact 80 and extends in the axial direction A. Thus, the pressure release opening 85 allows a flow of pressurized quenching gas out of the arcing region 52 in a radial outward direction.

(20) The pressure release opening 85 is configured such that a flow of the pressurized quenching gas, which extends by the heat of the arc in the arcing region 52, is substantially not reduced. In other words. The total area of the pressure release opening(s) 85 is large enough not to cause any gas flow reduction of the quenching gas, e. g. a reduction of the gas flow volume.

(21) In the embodiment of FIGS. 1-4, the total area of the pressure release openings 85 is more than 4 times of the cross-section of the nozzle supply channel which supplies the nozzle 33 with the quenching gas, while at the same time being less than 5 times of the cross-section of the nozzle supply channel. In this way, a sufficient current conduction is ensured, and the insulation gas heated up by the arc, having reduced dielectric properties (lower insulation properties) than the same insulation gas in a colder state, is efficiently directed away from the arcing region in between the contacts, thereby helping to prevent any dielectric re-strike (re-ignition) of the arc from occurring.

(22) In the embodiment of FIGS. 1-4, the switch 1 further comprises an interruption chamber, see FIG. 3. The first main contact 80 and the second main contact 90, as well as the first arcing contact 10 and the second arcing contact 20, are arranged inside the interruption chamber 70.

(23) The interruption chamber 70 has gas outlet opening 75. The total area of the gas outlet openings 75 is at least the total area of the pressure release openings 85. Thereby, the hot insulation gas is directed out of the interruption chamber 70 into an ambient-pressure region of the housing volume 2. In the shown embodiment, the total area of the gas outlet openings 75 of the interruption chamber 70 is more than ⅓ of the area of a substantially uniform cross-section 71 of the interruption chamber 70, wherein the substantially uniform cross-section 71 is provided at least in a region where the first main contact 80 is arranged.

(24) Optionally, the total area of the gas outlet openings 75 of the interruption chamber 70 is more than ⅓ and less than ½ of the area of the substantially uniform cross-section 71 of the interruption chamber 70.

(25) In the embodiment of FIGS. 1-4, the piston 46, shown in more detail in FIG. 4, is provided with auxiliary openings 47, e. g. in a flange portion of the piston 46, which connect the compression side with an opposite side of the piston 46. In FIG. 4, a total cross-section area 48 of the at least one auxiliary opening 47 is at least ⅓ of the area of a total gas outflow cross-section of the nozzle system. A sufficient amount of cold insulation gas may flow to the moving main contact (the second main contact 90) and cover its contacting region. The cold gas has a higher insulation level and may therefore help to prevent re-strikes in this region.

(26) In the piston 46 which holds the second main contact 90, a central opening 49 is provided which leads to a hollow section 26. The hollow section is arranged such that a portion of the quenching gas having been blown onto the arcing region 52 is allowed to flow from the arcing region 52 into the hollow section 26, and from there through an outlet of the hollow section 26 into the bulk housing volume 2 of the load break switch 1.

(27) In embodiments, a double flow design may occur at the tip of the nozzle 33, wherein the insulation gas accelerates into different possible directions. The hot gas may therefore split into a portion which flows radially outward and is released into the housing volume through openings 75, 85, and into another portion which is released through the outlet of the hollow section 26 into the housing volume of the switch 1.

(28) Some possible applications for the load break switch 1 are a low- or medium voltage load break switch and/or a switch-fuse combination switch; or a medium-voltage disconnector in a setting in which an arc cannot be excluded. The rated voltage for these application is at most 52 kV.

(29) By applying the openings for the flow of hot gas, as described herein, to a low- or medium-voltage load break switch, its thermal interruption performance can significantly be improved. This permits, for example, the use with an insulation gas being different from SF.sub.6. SF.sub.6 has excellent dielectric and arc quenching properties, and has therefore conventionally been used in gas-insulated switchgear. However, due to its high global warming potential, there have been large efforts to reduce the emission and eventually stop the usage of such greenhouse gases, and thus to find alternative gases, by which SF.sub.6 may be replaced.

(30) Such alternative gases have already been proposed for other types of switches. For example, WO 2014/154292 A1 discloses an SF.sub.6-free switch with an alternative insulation gas. Replacing SF.sub.6 by such alternative gases is technologically challenging, as SF.sub.6 has extremely good switching and insulation properties, due to its intrinsic capability to cool the arc.

(31) The present configuration allows the use of such an alternative gas having a global warming potential lower than the one of SF.sub.6 in a load break switch, even if the alternative gas does not fully match the interruption performance of SF.sub.6.

(32) In some embodiments, due to the openings that prevent an accumulation of the hot gas while still maintaining a sufficient current carrying capability, this improvement can be achieved without significantly increasing the machining for the involved parts.

(33) An application of the load break switch 1 is in a switchgear. A schematic sectional view of a switchgear 100 is shown in FIG. 5. In FIG. 5, by way of example, the switchgear 100 is a three-phase AC switchgear 100; as such, it comprises three load break switches 1a, 1b, 1c, each for switching one of the phases and each configured as a gas-insulated load break switch 1 as disclosed herein.

(34) In the switchgear 100 of FIG. 5, parts of the switches 1a, 1b, 1c containing the movable contacts 20, 90 (not shown in FIG. 5) are each connected to a respective supply line 115a, 1, 115b, 115c for the respective phase. The movable contacts 20, 90 retract from the contact counterparts in the upper part of FIG. 5. A gas flow directing member 110a, 110b, 110c is provided at each of the switches 1a, 1b, 1c which houses the insulation chambers and the stationary contacts. External contacting terminals 101a, 101b, 101c are led out of the gas flow directing members 110a, 110b, 110c for establishing an external connection, from the stationary contacts, e.g. to a busbar (not shown).

(35) The gas flow directing members 110a, 110b, 110c each have an opening 112a, 112b, 112c through which the flow of hot gas which occurs within the gas flow directing members 110a, 110b, 110c during an arcing event passes. The gas flow directing members 110a, 110b, 110c have their respective openings 112a, 112b, 112c direct away from the external contacting terminals 101a, 101b, 101c. Furthermore, the openings 112a, 112b, 112c also direct away from a zone in between the phase, i.e. an interphase zone 105 between the first phase and the second phase, and an interphase zone 106 between the second phase and the third phase.

(36) As such, the hot gas is directed away from neighboring phases. In FIG. 5, the openings 112a, 112b, 112c allow the gas to flow out in the upward direction of FIG. 5, and laterally into a direction which is substantially perpendicular to a direction of alignment of the switches 1a, 1b, 1c (i.e., in FIG. 5, the gas flow is allowed in a direction perpendicular to the plane of projection).

(37) Thus, the hot gas is directed away from an interphase zone 105, 106 which is a zone of high electrical field stress in the switchgear 100. Consequently, the interphase zone 105, 106 will not experience a reduced insulation level, as the hot gas is directed away from the interphase zone 105, 106, e.g. towards walls or roof of the switchgear 100 where the electrical stress is low.