Gas-blast load-break switch

Abstract: A gas-blast load-break switch comprises a pressure storage chamber (13) for storing pressure of arc-extingui­ shing gas with arc energy generated by the disconnection between contacts (4, 7), and a suction chamber (14) inclu­ ding a piston (15) which is moved in connection with the cut-off movement of the movable contact (7). A gas flowing means (11) is provided such that the pressure raised by the arc energy is stored in the pressure storage chamber (13) before communicating the pressure storage chamber (13) and the suc­ tion chamber (14) and a gas chamber (22) formed on the side of the piston (15) opposite from the suction chamber (14). The volume of the gas chamber (22) is greater than those of the pressure storage chamber (13) and the suction chamber (14), and the distance of piston movement in the suction chamber (14) is longer than the contact length when the movable contact (7) is thrown into the fixed contact (4).

Description: The present invention relates to a gas-blast load-break switch and, more particularly, to a breaker switch including a negative pressure generating apparatus for forming blasting gas flow against an arc. A conventional gas-blast load-break switch of this type, as disclosed in the specification of U.S. Patent No. 4,511,776, comprises: within a sealed container containing arc extinguishing fluid such as SF₆ gas or the like, a fixed contact and a movable contact disconnectable to each other; a pressure storage device including a pressure storage chamber for raising the pressure of arc extinguishing fluid using the arc energy generated by the separation of those contacts; and a negative pressure generating device including a negative pressure chamber which generates negative pressure by the relative movement between a cylinder and a piston caused by the separating operation of the movable contact. By the above structure, the arc between the detached contacts will be extinguished by a blasting of gas flow directing from the pressure storage chamber to the negative pressure chamber, which gas flow is caused by the differential pressure between the initial pressure and rising pressure caused by the arc energy in the pressure storage chamber and the negative pressure in the negative pressure chamber. In the abovementioned prior art, the contact length L is predetermined between the movable contact and the fixed contact when the movable contact is thrown into the fixed contact, which length L is equal to the length of the piston movement defining the negative pressure chamber. Consequently, the movable contact moves by the distance L relative to the fixed contact during the breaking operation of the movable contact, the movable contact begins to be detached from the fixed contact and, at the same time, the negative pressure chamber initiates to communicate with the gas chamber located on the other side of the negative chamber from the piston. Succeedingly, the negative pressure chamber immediately communicates with the gas chamber on the other side thereof from the piston. In this case, therefore, the pressure by the arc energy cannot be satisfactorily raised up to achieve a complete extinguishment of the arc. For example, when an electric current of approximately 100 to 500 ampere is applied between the contacts, as the electric current being relatively lower, the arc is extinguished by merely the differential pressure between the initial pressure in the pressure storage chamber and the negative pressure in the negative pressure chamber. Further, when a higher electric current is applied between the contacts, the rising pressure caused by the arc energy in the pressure storage chamber is instantly risen up because of the fact that the arc energy is generated in proportion to the higher current, thereby to extinguish the arc. However, for example, when the contacts are subjected to an high-intensity electric current of approximately 1000 to 3000 ampere, the rising pressure produced by the arc energy in the pressure storage chamber is not sufficient. Therefore, it causes a problem that the arc generated between the contacts cannot be extinguished by the insufficient differential pressure between the initial pressure and rising pressure caused by the arc energy in the pressure storage chamber and the negative pressure in the negative pressure chamber. Furthermore, according to the abovementioned prior art, the volume of the gas chamber on the opposite side of the piston from the negative pressure chamber is predetermined to be smaller than those of the pressure storage chamber and the negative pressure chamber, which gas chamber is filled up with the heated fluid after extinguishing the arc. As a result, it also causes a problem that the temperature of the arc extinguishing fluid in the gas chamber is risen to an extent that insulating capacity of the arc extinguishing fluid itself is remarkably deteriorated and to lose its insulatability. A gas-blast load-break switch with the features set forth in paragraphs 2 to 6 of claim 1 is described in EP-A-0 382 145, which is an Art.54(3) EPC document. SUMMARY OF THE INVENTION An object of the present invention is to provide a gas-blast load-break switch which can positively extinguish the discharge current arc, of a lower or higher intensity, and which has an excellent insulating capacity. This object is achieved by the gas-blast load-break switch defined in claim 1. Owing to the arrangement of the invention, when the movable contact is disengaged from the fixed contact, the suction chamber is not communicated with the gas chamber defined on the opposite side of the piston from the suction chamber enables the rising pressure generated by the arc energy to accumulate in the pressure storage chamber. As a result, when the gas gas passage or flowing means communicates the suction chamber and the gas chamber located on the side of the piston opposite the suction chamber during the piston movement, the rising pressure caused by the arc energy can favorably be activated to positively extinguish the arc. Also, because the volume of the gas chamber is relatively large, the temperature of the heated arc extinguishing gas introduced into the gas chamber can be lowered, thus contributing to maintain the insulating capacity. Other objects, characteristics and advantages of the present invention will be fully explained hereinafter with reference to embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertically cross-sectional view showing a cut-off breaker of a gas-blast load-break switch according to one embodiment of the present invention; Fig. 2 is a horizontally cross-sectional plan view showing a three-phase cut-off breakers in a triple type gas-blast load-break switch which makes use of a principle of the cut-off breaker of Fig. 1; Figs. 3 to 6 are cross-sectional views illustrative of different stages in breaking operations of the cut-off breaker of Fig. 1, respectively; Fig. 7 is a cross-sectional view of a second gas flowing means, taken along a line VII - VII of Fig. 2; Fig. 8 is a cross-sectional view showing a modified structure of the second gas flowing means shown in Fig. 7; and Fig. 9 and 10 are vertically cross-sectional views illustrating cut-off breakers of gas-blast load-break switches according to further embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described hereinafter with reference to the drawings. Fig. 1 is a vertically cross-sectional front view of a gas-blast load-break switch according to one embodiment of the present invention, a cut-off breaker of the switch being shown in a closed state. One end of a cylindrical sealed container 1 of the cut-off beaker is airtightly closed by a terminal end plate 2 and a bushing 20, and the other end is also airtightly closed by a terminal end plate 3 and a bushing 21. The container 1 is filled with arc-extinguishing gas such as FS₆ gas or the like. A fixed contact 4 is securely connected on an inner surface of one terminal end plate 2 within the cut-off breaker of the sealed container 1, and a fixed conductor 5 is securely connected on an inner surface of the other terminal end plate 3 within the sealed container 1 of the cut-off breaker. A movable contact 7 including a current collector 8 which is always in contact with the fixed conductor 5 contacts with the fixed contact 4. Accordingly, on a center axis of the cut-off breaker sealed container 1, the fixed contact 4, the movable contact 7, the current collector 8 and the fixed conductor 5 are disposed in alignment between the terminal end plates 2 and 3. The fixed conductor 5 is slidably fit in a groove formed at the central portion of the current collector 8. A lever 9a is connected to the movable contact 7 via a link 10 which is made of an insulating material. In turn, the lever 9a is connected to an operation system (not shown) by a common driving shaft 9. Fixed on an inner surface of the sealed container 1 of the cut-off breaker is an insulating nozzle 6 which divides the inner space of the closed container 1 into a pressure storage chamber 13 on one side of the nozzle containing a contact portion between both contacts 4 and 7 and a suction chamber 14 located on the opposite side thereof. The suction chamber 14 is defined by a surface on one side of a piston 15 connected to the movable contact 7 and a surface of the insulating nozzle 6 opposite to the surface of the piston. On the other side of the piston 15 from the suction chamber 14 a gas chamber 22 is formed. The gas chamber receives therewithin a system of connecting mechanism of the movable contact 7 comprising the link 10 and the lever 9a as well as a current collector ring mechanism section such as the current collector 8 and the like for electrically connecting the fixed conductor 5 and the movable contact 7. The volume of the gas chamber 22 is arranged larger than those of the pressure storage chamber 13 and the suction chamber 14, so that the temperature of heated gas introduced into the gas chamber 22 will be easily lowered so as to maintain favorable insulating capacity. The inner surface of the sealed container 1 in the cut-off breaker which slidingly contacts with the outer periphery of the piston 15 is formed with a recessed portion which serves as a first gas flowing means 11, communicating the suction chamber 14 and the gas chamber 22 at the closed condition illustrated in the drawings and also in the beginning of breaking operation. This gas flowing means 11 is maintained for communicating the suction chamber 14 and the gas chamber 22 only when the piston 15 moves the distance L₁ in a direction of breaking the circuit. The inner surface of the sealed container 1 of the cut-off breaker at the right hand side of the first gas flowing means is formed with a sliding surface which is brought into closed contact with the outer periphery of the piston 15. Continuous to the sliding surface, there is on the inner surface of the container a second gas flowing means 12 which is formed with an enlarged portion 12A communicating the suction chamber 14 and the gas chamber 22. The second gas communicating means 12 initiates to work when the piston 15 moves for breaking operation by the distance L₂ from the initial switch-closed position shown in Fig. 1. It is distinguished from the above-described first gas flowing means 11 which shuts off from communication between both chambers during the breaking operation for a length from the end portion of the first gas flowing means, i.e., the end of the distance L₁ to the terminal portion of the sliding surface, i.e., the end of the distance L₂. The working distance L₂ of the above-described second gas flowing means 12 is predetermined larger than the contact length L₃ between both contacts which is obtained when the movable contact 7 is thrown into the fixed contact 4. As a result, the rising pressure caused by arc energy will be stored within the pressure storage chamber 13. The difference between the above-described first gas flowing means and the second gas flowing means will be further described with reference to Figs. 3 to 6 illustrating some stages in the breaking operations. Fig. 3 shows a closed condition of the cut-off breaker, with the fixed contact 4 being in contact with the movable contact 7 within the pressure storage chamber 13, while the suction chamber 14 communicates with the gas chamber 22 through the first gas flowing means 11 formed between the inner surface of the sealed container 1 of the cut-off breaker and the outer periphery of the piston 15. The route of current is established between the bushing 20, the terminal end plate 2, the fixed contact 4, the movable contact 7, the current collector 8, the fixed conductor 5, the terminal end plate 3, and the bushing 21, and the remaining routes other than the current route are electrically insulated by an ordinal way. When the driving shaft 9 is rotated clockwise by means of an operating device (not shown) in response to a breaking command signal, the movable contact 7 is driven rightwardly by the actuation of the lever 9a and the like 10, as shown in Fig. 4. In this case, the volume of the suction chamber 14 becomes larger, however, it does not cause negative pressure because the first gas flowing means 11 which communicates the suction chamber and the gas chamber 22. Therefore, in the beginning of the breaking operation, the suction chamber 14 does not create reaction force against the movement of the operation device, so that the size of the device can be made smaller. However, when the piston 15 moves the distance L₁ to reach the position of Fig. 4, the first gas flowing means 11 is blocked, thereby causing to generate negative pressure in the suction chamber 14, and proceeding to the state in Fig. 5. Before it reaches the position as shown in Fig. 5 (a state when the piston 15 has moved the distance L₂), the movable contact 7 is dislocated from the fixed contact 4, causing the rise of gas pressure in the pressure storage chamber 13 due to the generated arc. When the movable contact 7 comes out of the throat portion of the insulating nozzle 6, a gas flow which directs from the pressure storage chamber 13 through the suction chamber 14 is formed. The arc is blasted by this gas flow. If the breaking-current is small, the arc is extinguished by the blasting, however, if the breaking-current is large, the pressure of the suction chamber 14 is immediately risen up to a maximum level due to the gas flow accelerated by the arc energy from the storage 13. For the reason, the blasting does cannot be continued satisfactorily. But, when the piston 15 reaches the state shown in Fig. 6, the second gas flowing means 12 communicates the suction chamber 14 and the gas chamber 22 so as to make the pressurized gas in the suction chamber 14 flow into the gas chamber 22, thereby to form a gas flow which enables to extinguish the arc. The second gas flowing means 12 leading to the gas chamber 22 is formed between the inner surface of the sealed container 1 of the cut-off breaker and the outer periphery of the piston 15, so that the gas flow flowing into the gas chamber 22 is directed toward the cut-off direction of the movable contact 7 and at the same time, it also enables to serve the space of the gas chamber 22 for gas blasting, which volume has not yet been utilized. Then, the heated gas flows into the gas chamber 22 and lowers its temperature by the gas chamber 22 which has a larger volume than those of the pressure storage chamber 13 and the suction chamber 14, to thereby maintain the insulation. The terminal end position of the movable contact 7 during breaking operation is preset by a stopper which is arranged such that the proximal end or the right end portion of the movable contact 7 abuts against the distal end or the left end portion of the fixed conductor 5. Consequently, even when the excessive pressure which exerts force applied against the piston 15 causes it toward the right direction to be acted over a predetermined stroke, the current collector 8 will not be broken as in the case of the conventional type shown in Fig. 11 and also, the structure of the invention is simpler than that of an exclusive stopper of the conventional breaker. Fig. 2 is a horizontally cross-sectional plan view illustrating of three-phase cut-off breakers integrally connected and housed within the triple type common sealed container 1. The structure of each cut-off breaker is substantially identified with that shown in Fig. 1. In each partition wall between the neighboring cut-off breakers or at the separation location of each phase, a through hole 12A for mutually communicating adjacent gas chambers 22 is provided, which serves to make the weight of the breaker much lighter. In this structure like Fig. 1, each of second gas flowing means 12 restricts gas flow in a direction of the breaking operation of a movable contact 7 so as to make it flow into the large volume gas chamber 22, whereby the high temperature gas is rapidly lowered, thereby to regulate the gas pressure in a range permissible for establishing the favorable insulation, as well as to obtain substantially the same effect as the abovementioned first embodiment. Fig. 7 is a vertical cross-sectional view showing the sealed container of the cut-off breaker taken along a line VII - VII of Fig. 2, which illustrates the second gas flowing means 12. According to this embodiment, a recess is formed all around the inner surface of the sealed container 1 of the cut-off breaker. Alternately, there also can be provided as shown in Fig. 8, a spline type second gas flowing means 12 comprising a plurality of recesses which are formed on the inner peripheral surface of the sealed container and spaced apart from one another. In this connection, so long as the enlarged gas flow area required when the higher electric current has to be cut off is obtained, its configuration and number is not limited. Fig. 9 is a vertical cross-sectional view of a cut-off breaker according to another embodiment of the present invention. Comparing with the first embodiment of Fig. 1, the embodiment shown in Fig. 9 differs from the first embodiment with respect to the first and second gas flowing means 11, 12. According to this embodiment, a portion exposed to high temperature gas which may contribute to extinguish the arc is formed of an insulating material having an insulating nozzle 6 integral therewith. Particularly, an insulating cylinder 23 integrally formed with the insulating nozzle 6 is attached on the inner surface of the sealed container 1 of the cut-off breaker, the first and the second gas flowing means 11, 12 being provided by defining recesses on the inner surface of this insulating cylinder. According to this embodiment, even when the sealed container 1 of the cut-off breaker is made of metal, an insulation capacity between the high-tension arc section such as both contacts 4, 7 and the sealed container 1 of the cut-off breaker can favorably be maintained. Fig. 10 is a vertical cross-sectional view showing further embodiment of a cut-off breaker according to the present invention. The difference between this embodiment and first embodiment shown in Fig. 1 resides on the arrangement of the stopper which serves to electrically contact between a movable contact 7 and a fixed conductor 5 and to protect the movable contact 7 from overrunning. That is to say, the stopper is arranged in such a manner that a current collector 8 is attached on the left end of the fixed conductor 5 which is securely mounted on a central conductor of a bushing 21 in order that the right end of the movable contact 7 is to be inserted into the groove portion of the fixed conductor 5. In this embodiment, similar to the first embodiment shown in Fig. 1, the overstroke of the movable contact 7 can be prevented with a simple structure. As is described above, according to the present invention, the second gas flowing means is defined between the inner surface of the sealed container of the cut-off breaker and the outer periphery of the piston adjacent the suction chamber. After a movable contact is separated from the fixed contact and a certain period of time is expired, the second gas flowing means enables communication between the suction chamber and the gas chamber, which is located on the other side of the suction chamber from the piston, whereby the rising pressure caused by the arc energy can be stored in the pressure storage chamber, which rising energy is applied to the arc for the reliable extinguishment of the arc. Further, the volume of the gas chamber is formed larger than those of the pressure storage chamber and the suction chamber. So that the temperature of the heated gas streamed into the gas chamber can be promptly cooled, thereby to maintain its insulation capacity.

Claims: A gas-blast load-break switch comprising three contact units in a sealed container (1) filled with arc extinguishing gas, each contact unit including a fixed contact (4) and a movable contact (7) detachable from each other, both contacts being disposed within said container (1), a pressure storage chamber (13) including a contact space and an insulating nozzle (6) with a throat portion through which said movable contact (7) extends when it engages the fixed contact (4), a suction chamber (14) formed on the side of said insulating nozzle (6) opposite the pressure storage chamber (13) and including a piston (15) connected to said movable contact (7), a space formed within said sealed container (1) on the side of the piston (15) opposite the suction chamber (14) and serving as a housing for an operation lever (9a) which drives said movable contact (7) and as a gas chamber (22) having a volume greater than those of the pressure storage chamber (13) and the suction chamber (14), and gas passage means (11, 12) provided on an inner surface of said sealed container (1) adjacent said suction chamber (14) for connecting said suction chamber (14) with said gas chamber (22) and separating them during the movement of said piston (15), the distance (L₂) of said piston movement in said suction chamber (14) being longer than the contact length (L₃) when said movable contact (7) is thrown into said fixed contact (4), wherein the gas spaces (22) of the three contact units are interconnected via through-holes (12A) formed in said sealed container (1). The switch of claim 1, wherein said suction chamber (14) is formed such that the outer peripheral surface of said piston (15) is brought into sliding contact with the inner peripheral surface of said sealed container (1) when the piston (15) moves, and said gas passage means (11, 12) comprises an enlarged section on the inner peripheral surface of said sealed container (1), which enlarged section includes recessed portions (11, 12) spaced apart from one another. The switch of claim 1, wherein an insulating cylinder (23) is disposed on an inner peripheral surface of said sealed container (1), said suction chamber (14) is formed such that the outer peripheral surface of said piston (15) is brought into sliding contact with the inner peripheral surface of said insulating cylinder (23), and said gas passage means (11, 12) defined on the sliding contact portion of said insulating cylinder (23) and said piston (15). The switch of claim 1, wherein said sealed container (1) includes a pair of terminal end plates (2, 3) opposite each other, a fixed conductor (5) securely fixed on one (3) of the terminal end plates is coaxially disposed in alignment with respect to said movable contact (7), a grooved portion is defined on either one of the facing portions of said fixed conductor (5) and said movable contact (7) so as to make the other facing portion slidably fit into said grooved portion, and the terminal end position is regulated at said contact portion between said fixed conductor (5) and said movable contact (7). The switch of claim 4, wherein said gas space (22) is formed so as to house said contact portion. The switch of claim 1, wherein said suction chamber (14) is formed such that the outer peripheral surface of said piston (15) is brought into sliding contact with the inner peripheral surface of said sealed container (1), and said gas passage means (11, 12) is defined on the sliding portion which is in contact with the piston (15).

Inventors: HONDA HARUO, ITOU SYUNJI, SEKI TAKAHIDE, TSUBAKI TOHRU, HONDA, HARUO, ITOU, SYUNJI, SEKI, TAKAHIDE, TSUBAKI, TOHRU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1990
Main classification: H01H33
IPC codes: H01H33