EP2387057A1 - Gas-isolated high voltage switch - Google Patents

Abstract

The high-voltage switch has a contact arrangement with two arcing contacts (21, 31), of which one (31) is displaceably mounted against the action of a preloaded spring (33). When the contact arrangement is closed, the free ends of the two arcing contacts (21, 31) are supported on each other. When opening the contact arrangement, the two arc contacts separate only after a predetermined switching stroke. A resulting, compressed arc gas receiving arc zone (L) is then bounded by free ends of the two arcing contacts (21, 31) axially and by an insulating nozzle (40) radially outward.

In order to prevent the return of the displaceably mounted arcing contact (21) against the action of the prestressed spring (33) when a large short-circuit current is interrupted, the switch has a reset device (60) which communicates with the arc zone (L) and which increases with increasing pressure the compressed arc gas produced in the arc zone (L) generates a restoring force assisting the restoring force of the preloaded spring (33).

Description

TECHNICAL AREA

The present invention relates to a high voltage switch according to the preamble of claim 1.

Switches of the aforementioned type are designed as a circuit breaker and have a rated current carrying capacity of at least a few kA in the voltage range of more than a few kV. In general, these switches are used as a generator switch and therefore contain a loadable with high rated currents contact arrangement with two - each with a rated current and an arc contact containing - switching pieces, of which a Isolierdüse is attached to a first. The arc contact of the second contact piece is axially displaceable against the action of a preloaded spring in a fixed contact carrier. When the contact arrangement is closed, free ends of the two arcing contacts are supported on one another to form a contact force generated by the preloaded spring. When opening the contact arrangement, the two arc contacts separate only after a predetermined stroke of the contact pieces from each other. This results in a compressed arc gas receiving arc zone, which is bounded by the free ends of the two arcing contacts axially and radially from the insulating nozzle to the outside.

STATE OF THE ART

A switch of the type mentioned is described in CH 519238 , This switch comprises a housing which is filled with an insulating gas having arc extinguishing properties and accommodates a contact arrangement comprising two contact pieces movable relative to each other along an axis, each having a rated current contact and an arc contact formed as a nozzle tube. One of a drive movable first two contact pieces carries an insulating nozzle through which the arc contact of the second contact piece is guided when the switch is closed. This arcing contact is designed as a follow-up contact and is loaded with a prestressed spring. When the switch is closed, the follow-up contact is based on forming the formation of a sufficient contact force with its remote from the spring free end on the side facing away from the drive free end of the arcing contact of the first contact piece. When switching off the preloaded spring leads the follower contact over a defined distance to the first contact piece, whereby the stroke of the first contact piece is kept low and also in the initial phase of the shutdown drive energy compared to a switch is saved, in which overlap both arcing contacts with frictional engagement.

PRESENTATION OF THE INVENTION

The invention, as indicated in the claims, the object is to provide a switch of the type mentioned above, which requires only a small drive energy and yet characterized by a high reliability and a long service life.

The defined in claim 1 gas-insulated high-voltage switch according to the invention comprises a contact arrangement having two along an axis relative to each other movable contact pieces each having an arcing contact and a fixed to the first of both contact pieces insulating. In this switch, the arc contact of the second contact piece is mounted axially displaceable against the action of a preloaded spring in a fixed contact carrier, with the contact assembly closed free ends of the two arcing contacts to form a contact force generated by the prestressed spring supported each other and separate the two arcing contacts Opening the contact arrangement only after a predetermined stroke of the contact pieces from each other. A resulting, compressed arc gas receiving arc zone is bounded by the free ends of the two arcing contacts axially and radially from the insulating nozzle to the outside. The second contact piece has a restoring device which communicates with the arc zone, and generates the restoring force assisting the restoring force of the preloaded spring with increasing pressure of the arc gas generated in the arc zone. The restoring force and the restoring force act in the same direction . Both forces therefore act as a harder spring, as if the preloaded spring had a larger spring constant.

Characterized in that the arc zone communicates with the return device, a portion of the arc gas, which is formed when separating the arcing contacts by the switching arc, out of the arc zone to the reset device. It is built up in the reset device by the pressure of incoming gas from the arc zone, a restoring force. This restoring force is directed against the direction of the arc contact out of the arc zone out. At the beginning of a turn-off operation, therefore, the distance of the two arcing contacts from each other remains relatively small and is thus prevented that build up a high arc voltage and from this voltage, a large energy conversion in the switching arc can result. When undermining a large, in particular asymmetrical, short-circuit current, excessive contact erosion and strong contamination of the arc gas due to a large energy conversion in the switching arc are avoided at the beginning of the interruption process. The reliability and life of the switch are therefore significantly improved over a comparable prior art switch.

Since the return device supports the biasing force of the spring when switching off a large short-circuit current, the stiffness of the spring can be kept relatively small. When closing the switch so an undesirably strong contact bounce is avoided, which would occur when using a spring of high stiffness.

Apart from the arc contact of the second contact piece no further moving parts are required in the switch according to the invention, if the return device is designed as a piston-cylinder system and contains a communicating with the arc zone pressure chamber when the pressure chamber of a first end face of a piston of the piston-cylinder system is limited, and when a remote from the pressure chamber second end face of the piston with the smaller diameter than the piston having arc contact of the second contact piece is rigidly connected.

In order to prevent the penetration of arc gas into a volume of the piston-cylinder system separated from the pressure chamber by the piston, the arcing contact of the second contact piece is guided by a wall section of the contact carrier which shields the second end side of the piston from the arc gas.

A compact design of the switch according to the invention is ensured if a pressure chamber radially outwardly bounding hollow cylinder of the piston-cylinder system is held on the wall portion of the contact support.

In order to limit the pressure chamber radially inwardly by simple means, it is advantageous to attach a piston rod to the pressure chamber axially delimiting the first end face, and to mold into the arc contact of the second contact piece, the piston and the piston rod, an axially guided through the pressure chamber exhaust passage, which connects the arc zone to an exhaust space of the switch. This piston rod can be guided in an axially displaceable manner by a bottom of the hollow cylinder axially delimiting the pressure chamber.

The prestressed spring may be disposed in the pressure space and supported at one end on the first end face of the piston and at the opposite end on the cylinder bottom.

Advantageously, the arc zone is connected via an annular expansion space with the pressure chamber. The hot arc gas formed in the arc zone initially expands adiabatically into this expansion space on its way to the pressure chamber. Here it cools down and enters the pressure chamber at a comparatively low temperature. This low temperature contributes to the fact that the generally arranged in the pressure chamber spring has no relaxation.

The wall of the expansion space may be formed radially outwardly from a serving as a longitudinal guide of the insulating, held on the contact sleeve and radially inwardly from the arcing contact of the second contact piece, and it can be the expansion space via an annular gap between the Isolierdüse and the arcing contact of the second Switching piece is arranged to be connected to the arc zone and communicate via at least one channel with the pressure chamber, wherein the channel is guided through the wall portion of the contact carrier and the hollow cylinder.

BRIEF DESCRIPTION OF THE DRAWING

Reference to a drawing, the invention will be explained in more detail below. Here, the single figure shows a plan view of a guided along an axis A section through a preferred embodiment of a high voltage switch according to the invention, which is shown in the left part of the axis located part of the figure when interrupting a high short-circuit current and the right part of the axis part in the on state ,

The reference numerals used in the drawings and their meaning are listed in the list of reference numerals. Basically, the same or similar parts are provided with the same or similar reference numerals in the figures. For the understanding of the invention non-essential parts are not shown in part. The described embodiment is exemplary of the subject invention and has no limiting effect.

WAY FOR CARRYING OUT THE INVENTION

The high-voltage circuit breaker according to the invention shown in the sole figure is designed as a generator switch and is typically designed for a rated voltage of 24 kV, a rated current of 6.3 kA, a permissible short-circuit current of 63 kA and a nominal frequency of 50/60 hertz.

This switch has a housing 10, which with a

Arc extinguishing properties having insulating gas, based on about Sulfur hexafluoride and / or nitrogen and / or carbon dioxide, is filled by generally up to several bar pressure. The upper part of the housing shown in the figure has a hollow cylindrical insulator 11 and two metal plates 12, 13 each serving as a power connection, between which the insulator is flanged gas-tight. In the housing 10 a to the power terminals 12, 13 is electrically connected contact arrangement is provided which has two along an axis A relatively movable switching pieces 20 and 30. The switching piece 20 is connected to a drive, not shown, and - as indicated by a double arrow D - when closing along the axis A upwards and when opening along the axis A out.

The contactor 20 has in axially symmetrical arrangement a tubular arcing contact 21 and a contact surrounding this contact with rated current contact 22, whereas the contact piece 30 in axially symmetrical arrangement also includes a tubular arc-shaped contact 31 and the arcing contact 31 at a distance surrounding rated current contact 32, an external and an inner ring of contact fingers and therefore favors the transmission of high rated currents. The arcing contact 31 is slidably mounted relative to the rated current contact 32 along the axis A and is at the switch closed (right half of the figure) with its arcuate free end by means of a preloaded spring 33 to form a sufficient contact force on the likewise arc-free free end of the Arc contact 21 supported.

When switching piece 20 of the arcing contact 21 and the rated current contact 22 via a radially extending wall 23 are electrically connected. The switching piece 20 is a typically PTFE-containing insulating nozzle 40 is fixed, which is arranged between the arcing contact 21 and the rated current contact 22 and projects beyond the free ends. The arc contact 21 and the rated current contact 22 are electrically conductively connected via a radially extending wall 23 and define, together with the wall 23 and the nozzle 40, a heating volume 24 which communicates with an arc zone L when the switch is opened (left half of the figure) a switching arc S receives and is bounded by the facing free ends of the two arcing contacts 21, 31 axially and the insulating nozzle 40 radially outward. The heating volume 24 serves to receive compressed arc gas, which is formed when the switch is opened by the switching arc S in the arc zone and is supplied via a heating channel 25.

The switching piece 20 is guided gas-tight sliding and electrically conductive in a fixed, metal hollow cylinder 14 along the axis A. The hollow cylinder is electrically conductively attached to the plate 12 serving as a power connection. The hollow cylinder 14 and a central portion of the plate 12 form a fixed cylinder of a piston-cylinder compression device having a compression space 26. In the compression chamber 26 befindliches insulating gas is compressed when opening the switch with the help of the then downwardly acting as a piston switching piece 20. If the gas pressure in the heating volume 24 is smaller than in the compression space 26, the compressed insulating gas is conducted from the compression space 26 into the heating volume 24.

The contact piece 30 has a contact carrier 50 in the form of a pot. The contact carrier is attached to its acting as an edge of the pot end electrically conductive on the serving as a power connection metal plate 13. A acting as the bottom of the pot wall portion 51 of the contact carrier 50 has a central opening 51 a and carries a disposed inside the pot, the central opening coaxially surrounding hollow cylinder 52. In the wall portion 51 facing away from the end portion of the hollow cylinder 52 is a radially inward extended cylinder bottom 53 integrated, in which a central opening 53 a is formed. In the outer edge region of the wall portion 51, the nominal current contact 32 and inside a sleeve 34 are electrically conductively attached in a coaxial arrangement outside.

The hollow cylinder 52 is part of a piston-cylinder system 60 which has a communicating with the arc zone L pressure chamber 61. This pressure chamber is bounded in the axial direction by the cylinder bottom 53 and by an end face 62 a of a piston 62 guided in the hollow cylinder 52. In the radial direction, it is limited to the outside by the hollow cylinder 52 and inwardly by a piston rod 63 attached to the end face 62a. The piston rod is guided through the opening 53 a in an exhaust space P of the switch, which communicates via openings, not shown, with the interior of the housing 10. The Piston 62 is rigidly connected at its end face 62b remote from the pressure chamber 61 to the arcing contact 31 having a smaller diameter than the piston 62. The arcing contact 31 is led out through the opening 51 a from the space enclosed by the hollow cylinder 52 space. The wall portion 51 therefore shields the end face 62 b from arc gas which expands through the insulating nozzle 40. In the arcing contact 31, the piston 62 and the piston rod 63 an axially guided through the pressure chamber 61, nozzle function exhibiting exhaust channel 35 is formed, which connects the arc zone L with the exhaust chamber P of the switch.

The prestressed spring 33 is arranged in the pressure chamber 61 and is supported on the cylinder bottom 53 with the formation of the contact force with its lower end on the end face 62a and with the opposite upper end.

The reference symbol E designates an expansion space whose wall is formed radially outward from the sleeve 34 and radially inward from the arcing contact 31. The bottom of the expansion space is formed by the insulating nozzle 40 and the ceiling of the wall portion 51. The expansion space E is connected to the arc zone L via an annular gap 41, which is bounded radially outward by the insulating nozzle 40 and radially inward by the arcing contact 31. In the wall portion 51 of the contact carrier 50 and in the hollow cylinder 52 guided channels 54 connect the expansion space E with the pressure chamber 61st

When the switch is closed, the current is conducted mainly from the terminal 12 via the hollow cylinder 14, a sliding contact, not shown, the rated current contacts 22, 32 and the contact carrier 50 to the terminal 13. When switching off a short-circuit current, the drive D leads the contact piece 20 down. The in the switch-on position (right half of the figure) supported on the arcing contact 21 arc contact 31 is in this case tracked by the biased contact spring 33 while maintaining the required contact force. This contact force is also present after disconnecting the rated current contacts 22, 32 and after commutation of the current in a connecting wall 23, the arc contacts 21, 31, a sliding contact, not shown, and the wall portion 51 containing current path. As soon as the end face 62b of the piston abuts against the wall section 51, the two arc contacts 21, 31 separate and form between the mutually opposite free ends of the switching arc S. The arc S generates hot, pressurized gas, which on the one hand via the heating channel 25th expands into the heating volume 24 and passes to the other via the exhaust passage 35 and a formed in the arc contact 21, nozzle function having exhaust passage 27 into the interior of the housing 10. When approaching a zero crossing of the current to be disconnected, the gas stored in the heating volume 24, assisted by compressed insulating gas from the compression space 26, inflates the arc S, which leads to an interruption of the current.

When switching off a large, typically asymmetric, short-circuit current occurs in the arc zone L, a particularly high gas pressure, which acts on the arcing contact 31 with a counter to the biased spring 33 acting force. At the same time, the two arc contacts 21, 31 repel due to strong electrodynamic forces. On the prestressed spring 33, therefore, a significant counterforce acts when switching off such a short-circuit current. In order to prevent the contact 31 from being returned upward upon interruption of an asymmetric short-circuit current against the movement of the contact piece 20 and against the force of the spring 33, a portion of the arc gas from the arc zone will pass through the annular gap 41, the expansion space E and the channels 54 guided in the pressure chamber 61. This gas builds up a pressure in the pressure chamber 61, which acts on the piston 62 and thus also the contact 31 with a restoring force. This restoring force is proportional to the pressure of the arc gas present in the arc zone L and supports the biasing force of the spring 33. Thus, at the beginning of the power interruption, an undesirably large distance between the two arcing contacts 21 and 31 and, accordingly, a high arc voltage are avoided. Namely, a high arc voltage substantially increases the energy converted in the switching arc S and leads to excessive contact erosion and gas contamination even at the beginning of the interrupting operation, thereby drastically reducing the reliability and life of the switch.

The flow cross section of the annular gap 41 is substantially smaller than the flow cross section of the expansion space E respectively. that of the flow channels 54. Therefore, the arc gas guided from the arc zone L into the pressure space 51 expands adiabatically into the expansion space after leaving the ring gap. As a result, the pressure and the temperature of the arc gas expanding into the expansion space E are reduced. Since the expansion space has sufficient gas tightness due to the sleeve 34 sliding on the jacket surface of the insulating nozzle 40 and the arc contact 31 closing the central aperture 51a, the major part of the cooled arc gas flows out of the expansion space E via the channels 54 into the pressure chamber 61 Pressure of the guided gas in this space is considerably smaller than the pressure of the arc gas in the arc zone L, this pressure is still sufficient to prevent the return of the arcing contact 31. This is achieved in that the return-preventing restoring force is achieved by an effective in the pressure chamber 61 piston surface F ₁ , which is seen to be several times greater in the arc space L opposite pressurized piston surface F ₂ , the open, a base point of the switching arc supporting end of the arcing contact 31 is formed.

Because of the strong cooling of the arc gas in the expansion space E and because of the comparatively short residence time of the cooled arc gas in the pressure chamber 61, the spring 33 has no relaxation and can fulfill their after-running and contacting comprehensive functions easily. Since the piston-cylinder system 60 acting as a return device supports the biasing force of the spring 33 when switching off a large, in particular asymmetric, short-circuit currents, the stiffness of the spring can be kept relatively small. When the switch is closed, this avoids undesirably strong contact bounce that would occur when using a spring of high rigidity.

LIST OF REFERENCE NUMBERS

10

casing

11

insulator

12, 13

Metal plates, power connections

14

hollow cylinder

20

switching piece

21

Arcing contact

22

Current Rating Contact

23

connecting wall

24

heating volume

25

heating duct

26

compression chamber

27

exhaust port

30

switching piece

31

Arcing contact

32

Current Rating Contact

33

contact spring

34

shell

35

exhaust port

40

insulating

41

annular gap

50

contact support

51

Wall section of the contact carrier

51 a

Opening in the wall section

52

hollow cylinder

53

cylinder base

53a

Opening in the cylinder bottom

54

channels

60

Piston-cylinder system, reset device

61

pressure chamber

62

piston

62a, 62b

End faces of the piston 62nd

63

piston rod

A

axis

D

drive

e

expansion space

F ₁ , F ₂

Pressurized piston surfaces

L

Arc zone

P

exhaust space

S

Switching arc

Claims (9)

A gas-insulated high-voltage switch having a contact arrangement comprising two contact pieces (20, 30), each movable relative to each other along an axis (A), each having an arcing contact (21, 31) and an insulating nozzle (40) secured to the first (20) of both contacts the arc contact (31) of the second contact piece (30) against the action of a prestressed spring (33) in a fixed contact carrier (50) is mounted axially displaceable, wherein in the closed contact arrangement free ends of the two arcing contacts (21, 31) to form a the contact force generated by the preloaded spring (33) are supported on each other, and in which the two arcing contacts (21, 31) when opening the contact arrangement only after a predetermined stroke of the contact pieces (20, 30) from each other and thereby a compressed arc gas receiving arc zone (L) is formed by the free ends of the two arcing contacts (21, 31) axially un d) is bounded radially outwards by the insulating nozzle (40), characterized in that the second contact piece (30) has a restoring device (60) which communicates with the arc zone (L) and which compresses as the pressure in the arc zone increases Arc gas generates a restoring force supporting the restoring force of the prestressed spring (33). Switch according to Claim 1, characterized in that the return device is designed as a piston-cylinder system (60) and contains a pressure chamber (61) which communicates with the arc zone (L), that the pressure chamber (61) from a first end face (62a). a piston (62) of the piston-cylinder system (60) is limited, and in that a from the pressure chamber (61) facing away from the second end face (62b) of the piston (62) with the smaller diameter than the piston having arcing contact (31) of the second contact piece (30) is rigidly connected. Switch according to claim 2, characterized in that the arcing contact (31) of the second contact piece (30) is guided by a second end face (62b) of the piston (62) against the arc gas shielding wall portion (51) of the contact carrier (50). A switch according to claim 3, characterized in that the wall portion (51) of the contact support (50) is a the pressure chamber (61) radially outwardly bounding hollow cylinder (52) of the piston-cylinder system (60) is held. Switch according to claim 4, characterized in that on the pressure chamber (61) axially delimiting the first end face (62a) is a pressure chamber radially inwardly bounding piston rod (63) is mounted, and in that the arc contact (31) of the second contact piece, the Piston (62) and the piston rod (63) an axially through the pressure chamber (61) guided exhaust channel (35) is formed, which connects the arc zone (L) with an exhaust space (P) of the switch. Switch according to claim 5, characterized in that the piston rod (63) axially displaceable by a pressure chamber (61) axially bounding bottom (53) of the hollow cylinder (52) is guided. Switch according to Claim 6, characterized in that the prestressed spring (33) is arranged in the pressure chamber (61) and is supported on the cylinder bottom (53) with one end on the first end face (62a) and with the opposite end. Switch according to one of claims 3 to 7, characterized in that the arc zone (L) via an annular expansion space (E) with the pressure chamber (61) is connected. Switch according to claim 8, characterized in that the wall of the expansion space (E) radially outwardly of a longitudinal guide of the Isolierdüse (40) serving, on the contact carrier (50) held sleeve (34) and radially inwardly from the arcing contact (31) of second switching piece is formed, and that the expansion space (E) via an annular gap (41) which is arranged between the insulating nozzle (40) and the arcing contact (31) of the second contact piece (30) is connected to the arc zone (L) and with the pressure chamber (61) via at least one channel (54) communicates, which is guided through the wall portion (53) of the contact carrier (50) and the hollow cylinder (52).

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