GB2080037A

GB2080037A - Gas-blast Circuit-interrupter

Info

Publication number: GB2080037A
Application number: GB8121364A
Authority: GB
Original assignee: AEI
Current assignee: AEI
Priority date: 1980-07-14
Filing date: 1981-07-10
Publication date: 1982-01-27
Also published as: GB2080037B

Abstract

A gas blast electrical circuit interrupter of the type incorporating a generally tubular contact (4) axially slidable relative to a contact (5) and connected to a puffer cylinder (2) co- operating with a fixed piston (3) for delivering a gas blast between the contacts (4, 5) during separation, incorporates an insulating piston member (6) supported by an insulating part (7) of the contact (4) so as to be axially slidable relative thereto. The piston member (6) is pierced by a passage (10) between two of its opposed surfaces, both of which are normally acted upon by pressurised gas from the puffer cylinder (2). The relative areas of these surfaces are such that during contact separation the piston member (6) initially abuts the contact (4) until a passage (12) is uncovered by the contact (5), resulting in a first gas blast and a loss of pressure on the surface of the piston member (6) remote from the contact (4). The piston member (6) is then forced away from the contact (4) releasing a second, high pressure, gas blast. <IMAGE>

Description

SPECIFICATION Gas Blast Circuit Interrupters This invention relates to gas blast electrical circuit interrupters of the type incorporating, within a gas filled enclosure, a pair of contacts at least one of which is movable between a closed position in which it engages the other contact, and an open position in which the contacts are spaced from each other, at least one of the contacts being of tubular form, and means being provided for delivering a rapid flow of arc extinguishing gas into the arcing space between the contact making faces of the contacts and through the tubular contact or contacts when the contacts are separated. Such interrupters will hereinafter be referred to as of the type specified.

It is known for interrupters of the aforesaid type to incorporate an insulating member mounted at the contact making end of a tubular one of the contacts and urged against the contact nozzle by a spring to prevent the release of compressed arc extinguishing gas between the member and the nozzle into the region between the contacts, during the early part of the interrupting stroke. The higher pressure achieved ensures more effective arc extinction.

According to the invention an electrical interrupter of the type specified incorporates a piston member which is supported adjacent the contact making end of one of said contacts and is movable axially relative thereto between a first position in which it is held when the contacts are closed, and in which it forms a barrier between one or more delivery passages for the pressurised gas and the bore of the or each said tubular contact, and a second position in which it permits the gas to be released rapidly into the arcing space following separation of the contacts, the piston member having opposed surfaces against which the pressurised gas acts as the contacts separate, the disposition and relative areas of which are such that over an initial part of the separating movement of the contacts the pressurised gas acts to oppose movement of the member from the first to the second position, and delays the -commencement of the rapid gas flow into the arcing space.

A puffer cylinder is preferably used to provide the quantity of pressurised gas for arc extinction.

Use of this invention enables a higher pressure of pressurised gas to be provided, increasing the efficiency of arc extinction.

Use of this invention enables higher gas pressures to be developed as the action of the pressurised gas against a suitable surface provides a greater force opposing movement of the piston member away from the first contact than has been hitherto provided by use of a spring. The area of said suitable surface may be arranged to provide a convenient force opposing said movement of the member as required.

The said piston member preferably includes a conducting part which serves to complete the circuit between the contacts when the interrupter is closed.

Preferably the other of the said contacts carries spring means which resiliently engages a part of the piston member when the contacts are closed and urges it into said first position.

Preferably the piston member is slidable within a cylinder coaxial with and projecting beyond the contact making end of the movable contact, and defines, with the cylinder, an annular cavity when the piston member is in the closed position, the piston member having a first surface which abuts the delivery passage opening or openings when the contacts are in the closed position, one or more openings connecting the delivery passage with the cavity, and at least one further opening which, in the closed position of the contacts is closed by a surface of the other contact but which after contact separation, connects the cavity with the arcing space, the gas pressure acting on a surface of the piston within the cavity as the contacts initially separate being such as to maintain the member in the first position, until the passage of gas through said further opening reduces the pressure in the cavity sufficiently to allow the gas acting on the first surface of the piston member to force the member away from the delivery passage or passages and to be released rapidly into the arcing space.

The invention may be better understood from the following description of an embodiment thereof, by way of an example, with reference to the accompanying drawing, Figure 1.

Figure 1 is a split sectional illustration showing an interrupter with the contacts both open and partially closed.

The sides of the insulated enclosure for the interrupter containing sulphur hexafluoride under a pressure of 6 bar, may be seen at 1. A movable puffer cylinder 2 and fixed piston 3 provide pressurised gas for arc extinction. The puffer cylinder 2 is connected to a contact tube 4 which is mechanically driven by an interrupter actuating mechanism (not shown) into or out of engagement with a fixed contact 5. An annular member comprising an insulating part 6 mounted within a cylindrical insulating part 7 also cooperates with the fixed contact 5 when the interrupter is closed. The insulating part 6 of the annular member slides axially within the part 7 relative to the contact tube 4.When the movable contact tube 4 is moved towards the interrupter the closed position of the insulating part 6 abuts against a spring loaded ring 8 surrounding the fixed contact 5, which ring serves to position the part 6, and also holds the part 6 in contact with the end of the tube 4. In this position an annular cavity 11 is formed between the parts 6 and 7 of the annular member at a region from the end of the contact tube 4 as shown. Further movement of the contact tube 4 causes it to engage the fixed contact 5, the spring 9 being compressed by the part 6.

During the opening movement of the interrupter, gas is compressed in the puffer cylinder 2 by movement of the latter towards the fixed piston 3. Compressed gas is fed through apertures 10 into the annular cavity 11. Ports 12 connect the cavity 11 to the space between the contacts 4 and 5. When the interrupter is closed these ports 12 are obstructed by the fixed contact 5 so that gas pressure may build up in the cavity 11. In the closed position, the exterior surface of the puffer cylinder 2 slidingly engages contact fingers 1 3 which are electrically connected to the contact 4, and thereby forms an electrical connection between the contacts 4 and 5.The pressurised gas acts on the walls of the cylinder 11 urging the insulating part 6 away from a stop on the insulating part 7 and, with the assistance of the spring loading of the ring 8, retaining it during the initial stages of opening movement in contact with the end of the contact tube 4, preventing the release of pressurised gas from the puffer cylinder 2. Even when the insulating part 6 disengages from the ring 8 it tends to be held in contact with the nozzle 4 by the pressure acting in the cavity 11 since the area of this cavity on which the pressure acts is greater than that where the insulating part obstructs the nozzle. When sufficient gas has escaped through the ports 12, the insulating part 6 moves away from the nozzle enabling the gas from the puffer cylinder 2 to be expelled rapidly between the end of the contact tube 4 and the part 6 and thereby extinguishing the arc between the contact nozzles. By this means the main flow of arc extinguishing gas is delayed, permitting a higher pressure of the gas to be obtained resulting in more efficient circuit interruption.

Claims

1. A gas blast electrical circuit interrupter of the type specified incorporating a piston member which is supported adjacent the contact making end of one of said contacts and is movable axially relative thereto between a first position in which it is held when the contacts are closed, and in which it forms a barrier between one or more delivery passages for the pressurised gas and the bore of the or each said tubular contact, and a second position in which it permits the gas to be released rapidly into the arcing space following separation of the contacts, the piston member having opposed surfaces against which the pressurised gas acts as the contacts separate, the disposition and relative areas of which are such that over an initial part of the separating movement of the contacts the pressurised gas acts to oppose movement of the member from the first to the second position, and delays the commencement of the rapid gas flow into the arcing space.

2. An electrical circuit interrupter according to Claim 1 in which the source of pressurised arcextinguishing gas is a puffer cylinder.

3. An electrical circuit interrupter according to Claim 1 or Claim 2 in which the piston member is of generally annular cross section and is supported coaxially at the contact making end of the movable contact.

4. An electrical circuit interrupter according to, any preceding Claim in which the piston member' comprises a conducting part which serves to complete the circuit between the contacts when the interrupter is closed.

5. An electrical interrupter according to any preceding Claim in which the other of the contacts carries spring means which resiliently engages a part of the piston member when the contacts are closed and urges it into said first position.

6. An electrical circuit interrupter according to Claim 3 in which the piston member is slidable within a cylinder coaxial with and projecting beyond the contact making end of the movable contact, and defining, with the cylinder, an annular cavity when the piston member is in said first position, the piston member having a first surface which abuts the delivery passage opening or openings when the contacts are in the closed position, one or more openings connecting the delivery passage with the cavity, and at least one further opening which, in the closed position of the contacts is closed by a surface of the other contact but which after contact separation, connects the cavity with the arcing space, the gas pressure acting on a surface of the piston within the cavity as the contacts initially separate being such as to maintain the member in the first position, until the passage of gas through said further opening reduces the pressure in the cavity sufficiently to allow the gas acting on the first surface of the piston member to force the member away from the delivery passage or passages and to be released rapidly into the arcing space.

7. An electrical interrupter substantially as described hereinabove with reference to the accompanying drawing.