United States Patent: 3553406

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( 72667 of 72667 )

United States Patent	3,553,406
Boersma	January 5, 1971

CIRCUIT-BREAKER OPERABLE BY EXTINGUISHING GAS PRESSURE DIFFERENTIAL

Abstract

A gas blast circuit breaker comprising at least two cooperating movable contacts, of which each one is attached to a piston adapted to be driven by the extinguishing gas, the stroke of one contact and its piston being smaller than that of the other contact and its piston, the piston having the smallest stroke being used to start the opening operation of the circuit breaker and to open a valve, the opening of said valve allowing extinguishing gas to escape and to extinguish the switching arc and effecting the exposure of the piston having the greater stroke to the pressure of the extinguishing gas, and means for automatically effecting a delayed reclosing operation of the circuit breaker.

Inventors:	Boersma; Rintje (Harmelen, NL)
Assignee:	N.V. COQ (Utrecht, NL)
Appl. No.:	04/716,808
Filed:	March 28, 1968

Foreign Application Priority Data


Apr 14, 1967 [NL]			67.05277

Current U.S. Class: 218/88

Current International Class: H01H 1/14 (20060101); H01H 33/28 (20060101); H01H 33/70 (20060101); H01H 1/12 (20060101); H01H 33/30 (20060101); H01H 33/83 (20060101); H01H 33/82 (20060101); H01h 033/86 ()

Field of Search: 200/148.2,148

Foreign Patent Documents


1,270,584	Jul., 1961	FR

Primary Examiner: Macon; Robert S.

Claims

I claim:

1. A gas blast circuit breaker comprising a container, at least two concentric compartments formed in said container, the outer compartment being filled with extinguishing gas under high overpressure, at least one pair of cooperating movable contacts accommodated in the inner compartment, at least one of said contacts being a nozzle contact having a central passage for the discharge of extinguishing gas during the opening operation of the circuit breaker, two cylinders, two pistons each piston being mounted for reciprocation in a cylinder, the first movable contact being attached to one of said pistons, the second movable contact being attached to the other one of said pistons, the stroke of the first movable contact and its piston being smaller than the stroke of the second movable contact and its piston, at least one spring, said pistons being adapted to be driven in the direction, in which the circuit breaker is opened, by the extinguishing gas, said spring being adapted to drive said pistons in the direction, in which the circuit breaker is closed, a valve surrounding said inner compartment and being constituted by two cooperating annular valve members, of which one is fixed to a stationary part of the circuit breaker and the other one is fixed to the second movable contact and its piston, the piston of the second movable contact forming a movable wall portion of the inner compartment, said valve being closed and separating the inner compartment and said discharge passage from the outer compartment, when the circuit breaker is in its closed condition, and said valve being opened directly after the opening operation of the circuit breaker has been started so as to allow extinguishing gas from the outer compartment to flow into the inner compartment, to act on the piston of the second movable contact and to escape through said discharge passage, a first passage connected to the cylinder space associated with the first movable contact and used for driving the latter in the direction, in which the opening operation of the circuit breaker is started, a first changeover valve provided in said first passage and adapted to be operated by an outside command, said first changeover valve being adapted to connect said first passage either with a low-pressure space, in which the gas pressure is lower than that in the outer compartment, or with said outer compartment, a second passage connected to the cylinder space associated with the second movable contact and used to help the latter to be driven towards its closed position, a second changeover valve provided in said second passage and adapted to connect said second passage either with a low-pressure space or with said outer compartment, a single acting third cylinder, a piston provided in said cylinder and connected to said second changeover valve for driving it towards its position, in which the second passage is connected with the outer compartment, a second spring acting on said second changeover valve and used to drive it towards its position, in which the second passage is connected with the low pressure space, and a conduit having a delaying action, said conduit connecting the active cylinder space of said third cylinder with a space, which in the closed condition of the circuit breaker is connected to a low-pressure space but, after the opening operation of the circuit breaker has been started, is in open communication with said outer compartment.

2. A gas blast circuit breaker as claimed in claim 1 in which the conduit having a delaying action connects the active cylinder space of said third cylinder with said the said first passage provided with the first changeover valve.

3. A gas blast circuit breaker as claimed in claim 1 in which the conduit having a delaying action connects the active cylinder space of said third cylinder with the inner compartment.

Description

The invention relates to a gas blast circuit breaker comprising a switching chamber adapted to be filled with compressed extinguishing gas, at least one discharge space to collect the discharged extinguishing gas, at least one pair of cooperating switching contacts provided in said switching chamber, at least one of said contacts being formed as a nozzle contact and cooperating with a valve system which separates the switching chamber from the discharge space, when the circuit breaker is in its closed position, but connects during the opening operation the switching chamber and the discharge space with one another so as to allow the extinguishing gas to escape from the switching chamber to the discharge space and thereby to extinguish the switching arc, said switching contacts being both adapted to be moved and being each coupled for their movement with a cylinder-piston system driven by the extinguishing gas, said contacts being, during the opening operation, first driven together and in engagement with one another in the opening direction through a part of the opening stroke and thereupon separated from one another owing to the arrest of the switching contact which, in respect of the opening movement, is the rearmost one by a stop member and to the continued movement in the opening direction the switching contact which, in respect of the opening movement, is the foremost one, a spring for closing the circuit breaker, said spring acting on said foremost switching contact, and means for supplying, during the opening operation, the cylinders of both switching contacts with compressed extinguishing gas from the switching chamber one somewhat later than the other, so that the foremost switching contact is first driven by the cylinder-piston system of the rearmost switching contact and thereupon by its own cylinder-piston system.

A gas blast circuit breaker of this kind is disclosed in the British Pat. specification 821,069. In this circuit breaker the switching chamber is supplied with compressed extinguishing gas from the outside, when the circuit breaker has to break the electric circuit. Consequently, the extinguishing gas is not at once available to move the switching contacts in the opening direction. Moreover in this circuit breaker only one of the two cooperating switching contacts can be formed as a nozzle contact. For the exact operation of this circuit breaker many passages and slide valve members must be exactly attuned to one another, which makes the construction of the circuit breaker complicate. Alteration of the duration of the gas blast is not possible without drastic modification of several details of the circuit breaker. The circuit breaker remains in the opened condition till the supply of extinguishing gas to the switching chamber is cut off and the pressure in said chamber is brought back to the original low value.

The invention has for its object to provide a gas blast circuit breaker of the mentioned kind, in which the switching chamber is already filled with extinguishing gas under high pressure in the condition of rest of the circuit breaker, both cooperating switching contacts may be formed as nozzle contacts and the duration of both the gas blast and the complete switching cycle can be adapted in a simple manner to the prevailing conditions. It consists in that the cylinder of the cylinder-piston system of the form foremost switching contact is a double acting cylinder, of which, during the switching operation, the cylinder space meant for the closing movement of said contact is supplied with compressed extinguishing gas from the switching chamber a predetermined space of time after the cylinder space of the cylinder-piston system coupled with the rearmost switching contact and meant for starting the opening operation has been supplied with gas from said chamber, so as to enable the closing spring to move the foremost switching contact again towards the rearmost switching contact, to close again the valve system between the switching chamber and the discharge space and to restore the circuit breaker to its closed condition. In this circuit breaker the switching chamber contains already in the condition of rest extinguishing gas under high pressure, so that extinguishing gas is directly available for each opening operation. Moreover, the blast of extinguishing gas is maintained till the circuit breaker has been closed again. This is of great importance, when the electric circuit is not interrupted in time by the isolator switch connected in series and cooperating with the circuit breaker.

To control the circuit breaker the latter may be constructed in such a manner, that the cylinder space of the cylinder-piston system coupled with the rearmost switching contact and meant for starting the opening operation and the cylinder space of the cylinder-piston system coupled with the foremost switching contact and means meant for the closing operation are each connected to a passage comprising a throwover valve adapted to connect the relevant cylinder space either with the high-pressure switching chamber or with a low-pressure space, the first one of said throwover valves controlling the rearmost switching contact being operable from the outside and the second one of said throwover valves controlling the foremost switching contact being operated by a spring and a cylinder-piston system, of which the active cylinder space communicates through a conduit having a delaying action with the said cylinder space of the cylinder-piston system coupled with the rearmost switching contact. When in this pneumatic system the first throwover valve is brought into the position, in which the cylinder of the rearmost switching contact is supplied with extinguishing gas from the switching chamber and the opening operation is started, the second throwover valve is brought a predetermined space of time later into the position, in which the cylinder space cooperating with the foremost switching contact and meant for the closing operation is also supplied with extinguishing gas from the switching chamber and the circuit breaker is restored to its closed condition. By varying the passage area of the conduit having the said delaying action the duration of the switching cycle can be adapted to the prevailing circumstances in a simple manner.

If it must be avoided that, during the closing operation, the foremost switching contact bumps with considerable force against the rearmost switching contact, when the latter is still out of its position of rest, whereby the often brittle lining being adapted to resist to the action of the switching arc and covering the surfaces of the switching contacts exposed to said arc could be damaged, a construction is recommended, in which the cylinder space of the cylinder-piston system coupled with the foremost switching contact and meant for the closing operation is connected to a passage comprising a throwover valve adapted to connect said cylinder space either with the high-pressure switching chamber or with a low-pressure space and said throwover valve is operated by a spring and a cylinder-piston system, of which the active cylinder space communicates through a conduit having a delaying action with a chamber on the low-pressure side of the valve system cooperating with the switching contacts and provided between the switching chamber and the discharge side. Preferably, the chamber on the low-pressure side of said valve system is provided between said valve system and the inlet opening of the or each nozzle contact. In that case the cylinder space of the rearmost switching contact can be discharged directly after the latter contact has been reached its stop member during the opening operation, so that the rearmost switching contact is restored to its position of rest by the pressure of the extinguishing gas and, if necessary, by stabilization spring, before the foremost switching contact has ended the reclosing movement or even has started said movement. During its reclosing movement the foremost switching contact then cannot bump against the rearmost switching contact with appreciable force, so that the danger of damaging the lining of the switching contacts, said lining, consisting for instance of a brittle sintered tungsten-alloy, is considerably reduced.

The invention will be elucidated with the aid of the accompanying drawing. In the drawing is:

FIG. 1 partly an axial sectional view, partly an elevational view of a gas blast circuit breaker according to the invention,

FIG. 2 on a larger scale an axial sectional view of the switching element of said circuit breaker and

FIG. 3 on a larger scale an axial sectional view of a variant of the switching element shown in FIG. 2.

In the drawing 1 is a metal vessel to be connected with earth, in which an inner wall is provided which consists of insulators 2, 3, 4 and contact rings 5, 7. The space 7 between the vessel and said inner wall is filled with insulating material of high dielectric strength. In the thus formed double walled vessel the switching element is mounted. This element is held in place by insulators 8, 9 and provided with electrically conductive contact holders 10, 11, which are electrically conductively connected through connecting contacts 12, 13 with the contact rings 5, 6. Attached to these contact rings 5, 6 are the connecting conductors 14, 15 for the connection of the circuit breaker with the outer electric circuit. This circuit breaker is only meant to interrupt the circuit. To keep the circuit open and to close the circuit an isolator switch (not shown) must be connected in series with the circuit breaker.

From FIG. 2. it appears, that the contact holders 10, 11 comprise electrically conductive hollow blocks 16, 17 which are spaced apart by a tubular insulator 18. The block 16 carries a conductive tube member 19 having a central passage 20 for the discharge of extinguishing gas. A first nozzle or switching contact 21 is slidably mounted in this tube member. The block 16 carries also a cylinder 22, in which a plunger piston 23 is mounted for reciprocation. This piston is loaded by a relatively weak closing spring 24. The nozzle or switching contact 21 is rigidly attached to the plunger piston 23.

The block 17 carries a conductive tube member 25 which is partly formed as a cylinder. A second nozzle or switching contact 26 is mounted for axial movement in this tube member. The nozzle or switching contact 26 is attached to a piston 27 which is adapted to reciprocate in the cylinder space of the tube member 25.

In the shown closed condition, that means in the position of rest of the circuit breaker, the nozzle or switching contact 21 connects a circular series of resilient contacts 28 mounted in the tube member 19 with a circular series of corresponding contacts 29 mounted in the tube member 25, so that a conductive connection is established between the tube members 19 and 25, the blocks 16 and 17 and the contact holders 10 and 11. During the opening operation the nozzle or switching contacts 21 and 26 are first moved together upwards, till the piston 27 is arrested by a stop member 30. Thereupon the nozzle or switching contacts 21 and 26 are separated from one another, since the nozzle contact 21 continues to move upwards. As soon as the switching contacts have been started to move in the opening direction a valve system formed by a valve rim 31 of the plunger piston 23 and a packing ring 32 of the tube member 25 is opened, whereby the extinguishing gas under the relatively high pressure of about 14 atm. contained in the high-pressure switching chamber 33 confined within the blocks 16,17 and the insulator 18 is admitted to the nozzle or switching contacts 21, 26. When a little later the nozzle or switching contacts 21, 26 are separated from one another a blast of extinguishing gas escapes from said chamber 33 through said contacts and the passages connected thereto latter to the discharge spaces 34, 35 (FIG. 1), which are interconnected by a conduit 36. The insulating space 38 outside the switching element is filled with extinguishing gas through a conduit 37. In the spaces 34, 35, 38 a considerably lower gas pressure of say 3, 5 atm. is maintained. The extinguishing gas may be SF.sub.6-gas. This gas can be sucked through a filter device 39 out of the low-pressure spaces 34, 35 by a pump 40 and pumped back through a conduit 41 to the high-pressure switching chamber 33 (FIG. 1). Although in the condition of rest of the circuit breaker the gas pressures in the spaces 34, 35, 38 may be equal, a construction is recommended, in which the space 38 is separated from the spaces 34, 35. In that case the disintegration products of the extinguishing gas cannot enter the insulating space 38 and less gas has to be passed through the filters 39.

To control the nozzle or switching contacts the active cylinder space 42 of the cylinder 25, in which the piston 27 attached to the rear most nozzle contact 26 reciprocates, is accessible through a passage 43 comprising a throwover valve 44, by means of which said cylinder space can be connected either through a port 45 to the high-pressure switching chamber 33 or through a port 46 to the low-pressure space 38. In the rest condition, that means in the closed position of the circuit breaker, the cylinder space 42 communicates with the low-pressure space 38 and the valve 44 is forced into the illustrated end position by the spring 47, in which position the port 45 to the high-pressure switching chamber 33 is closed. Furthermore, the active space 48 of the cylinder 22 of the foremost nozzle or switching contact 21 is accessible through a passage 49 comprising a throwover valve 50, by means of which the cylinder space 48 is connected either through a port 51 to the high-pressure switching chamber 33 or through a port 52 to the low-pressure space 38. The valve 50 is forced in the illustrated end position by a spring 53, in which position the port 51 is closed and the port 52 is open, and it is adapted to be driven by a cylinder 54 and a piston 55 to the other end position, in which the port 51 is opened and the port 52 is closed. The cylinder space 56 of the cylinder 54 comprising the piston 55 is connected with the passage 43 and the cylinder space 42 of the rearmost switching contact 26 by a tube of insulating material having a delaying action on the flow of gas to and from said cylinder space 56.

The valve 44 can be pulled by means of a pull-rod 58 into a position, in which the port 45 is opened and the port 46 is closed, so that extinguishing gas under high pressure is admitted into the cylinder space 42 and both nozzle or switching contacts 26 and 21 are moved with great speed in the opening direction by the piston 27. The result thereof is that the valve system 31, 32 is opened and the plunger piston 23 which, in the cylinder space 48, is still loaded by low-pressure gas from the space 38 is forced upwards with great force by the gas under high pressure contained in the switching chamber 33. The piston 23 then takes the nozzle or switching contact 21 along and the contacts 21 and 26 are separated from one another, so that the switching arc set up between said contacts is extinguished by the gas escaping through said nozzle contacts. However, at the same time the extinguishing gas under high pressure flows through the delaying conduit 57 to the cylinder space 56, which has the effect, that a predetermined space of time later the valve 50 is pulled into the right hand end position, so that gas under high-pressure is supplied through the port 51 and the passage 49 to the cylinder space 48 and high pressure will be exerted on the piston 23 in the cylinder space 48. The gas pressures on both sides of the piston 23 will then be equal, so that the spring 24 will be able to force said piston downwards. In the meantime the piston 27 and the rearmost contact are forced back to their position of rest both by the pressure of the escaping extinguishing gas and the force of a weak stabilization spring 59, so that the valve system 31, 32 is closed again. The time interval between the filling of the cylinder space 42 and the filling of the cylinder space 48 with extinguishing gas under high pressure is so chosen by adjusting the delaying action of conduit 57 as to guarantee that the contacts 21 and 26 are kept spaced apart at maximum distance a sufficient space of time to extinguish the switching arc by the escaping gas. After the circuit breaker has been restored to its closed condition the rod 58 is released and the valve 44 is moved to the left by the spring 47, so that the cylinder space 42 is again connected trough the port 46 with the low-pressure space 38. Thereafter the cylinder space 56 is connected again with the low-pressure space 38 through the tube 57, so that the valve 50 is also brought back into the left-hand end position, in which the cylinder space 48 is in open communication with the low-pressure space 38. The circuit breaker is then restored to the condition of rest, that means to its closed position.

In the circuit breaker shown in FIG. 2 it can happen that the nozzle or switching contact 26 is brought back into its position of rest so slowly, that the reclosing nozzle or switching contact 21 overtakes the contact 26 and bumps against the latter with great force. The danger thereof is that the rather brittle protective lining 64, 65 of the nozzle or switching contacts 21, 26 is damaged. In order to avoid this danger the tube 57 of the circuit breaker shown in FIG. 3 is connected to a chamber 63 through a conduit 60 comprising a choke opening 61, of which the cross-sectional area can be adjusted by means of an adjusting screw 62. This chamber 63 is located on the low-pressure side, that means on the side remote from the high-pressure switching chamber 33, of the valve-system 31, 32 and in front of the inlet openings of the nozzle or switching contacts 21, 26.

In the embodiment shown in FIG. 3 the valve 50 is pulled in the right-hand end position a predetermined space of time after the opening of the valve system 31, 32. In that position of said valve the cylinder space 48 is connected to the high-pressure switching chamber 33. It will be apparent that valve 50 will be restored to its position of rest only after the valve system 31, 32 has been closed again at the end of the closing stroke of the contact 21. This means, that the pull-rod 58 may be released directly after the nozzle or switching contact 26 has been arrested, during the opening operation of the circuit breaker, by the stop member 30, so that the valve 44 is brought back into its left-hand position much earlier. Since in that position the cylinder space 42 communicates again with the low-pressure space 38 the nozzle or switching contact 26 is driven back with great speed by the high-pressure extinguishing gas escaping from the switching chamber 33 and the spring 59 and it will then reach its position of rest long before the nozzle or switching contact 21 has completed its opening stroke and the following reclosing stroke. As in the closed position of the circuit breaker the nozzle or switching contacts 21, 26 do not touch each other, the danger of forcing, during the reclosing operation of the circuit breaker, the nozzle or switching contact 21 with great force against the returning nozzle or switching contact 26 and damaging thereby the protective linings 64, 65 of the contact surfaces exposed to the switching arc is avoided with certainty.

* * * * *

Current U.S. Class:	218/88
Current International Class:	H01H 1/14 (20060101); H01H 33/28 (20060101); H01H 33/70 (20060101); H01H 1/12 (20060101); H01H 33/30 (20060101); H01H 33/83 (20060101); H01H 33/82 (20060101); H01h 033/86 ()
Field of Search:	200/148.2,148