US3371177A - Gas-blast circuit breaker with separable movable and isolating contacts - Google Patents

Description

Feb. 27, 1968 w. A FISH, JR

GAS-BLAST CIRCUIT BREAKER WITH SEPARABLE MOVABLE AND ISOLATING CONTACTS Filed March 5, 1965 2 Sheets-Sheet 1 AAA iVV

INVENTOR William A. Fish,Jr.

BY W664? ATTORNEY Feb. 27, 1968 A. FISH, JR REAKER WITH SEPARABLE MOVA BLE GAS-BLAST CIRCUIT B AND ISOLATING CONTACTS 2 Sheets-Sheet 2 Filed March 5, 1965 United States Patent 3,371,177 GAS-BLAST CIRCUIT BREAKER WITH SEPARABLE MOVABLE AND ISOLATING CONTACTS William A. Fish, in, Wilkins Township, Pittsburgh, Pa.,

assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 3, 1965, er. No. 436,774 8 Claims. (Cl. 200-148) ABSTRACT OF THE DISCLOSURE A compressed-gas circuit interrupter has a movable contact cooperable with a movable isolating contact disposed within a pressurized tank. An exhaust blast tube extends from the contact structure externally of the tank. During the opening operation, the arrangement is such that the movable contact first separates from the movable isolating contact and subsequently the movable isolating contact moves to an isolating position. The movable contact then returns to its closed position in the fully opencircuit position of the interrupter.

Both the movable contact and the isolating contact are pneumatically actuated by piston structures. The piston structure for the movable contact comprises first and second pistons secured to a piston rod movable through the head portion of an operating cylinder with one of the pistons serving additionally as a movable blast valve to the exhaust blast tube. A pneumatic control scheme insures that the piston structures of the movable and isolating contacts will be actuated in the right sequence.

This invention relates, generally, to circuit breakers and, more particularly, to circuit breakers of the gasfilled, dual-pressure type in which a blast of high pressure gas assists in arc interruption during opening of cont-act members of the breaker.

Prior sulfur hexafiuoride, SE gas-filled circuit breakers have been operated by a mechanical linkage actuated by a compressed air, pneumatic operating mechanism. The flow of gas for are interruption has been obtained from a mechanically driven puffer in low capacity breakers, or from a blast valve controlled fiow from a high pressure chamber to a low pressure chamber in high capacity breakers.

A modified dual-pressure scheme consisting of a moderate pressure inside the main breaker tank blasting into an auxiliary tank of gas at or near atmospheric pressure for interruption is disclosed in a copending application, Serial No. 416,262, filed December 7, 1964, by I. M. Teliord and assigned to the Westinghouse Electric Cor-v poration. A gas-operated control system using the pressure difierential between the high and low pressure chambers, thereby eliminating the need for a separate pneumatic operating mechanism and compressed air system, is disclosed in a copending application, Serial No. 419,044, filed December 17, 1964, by G. I. Easley and assigned to the Westinghouse Electric Corporation.

An object of this invention is to provide a simplified gas-operated control system for a circuit breaker.

Another object of the invention is to increase the speed of opening of a gas-operated circuit breaker, thereby opening the contact members and providing the contact sep 3,3 7 l, 177 Patented Feb. 27, 1968 ICC aration required for most efiicient quickly as possible.

A further object of the invention is to provide a delayed additional contact separation after interruption has occurred to prevent fiashover due to surge voltages, without increasing the contact separation beyond that required for eflicient interruption before a current zero, and thus an opportunity to interrupt, occurs, which can result in undesirably high are voltage and are energy.

Still another object of the invention is to operate the isolating contacts of a circuit breaker in a region of relatively high pressure high dielectric gas, thereby requiring a relatively small contact separation.

. A still further object of the invention is to incorporate a hollow contact member of the orifice type and a blast valve in the structure that operates the circuit interrupter of a circuit breaker.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a dual-pressure, gas-filled circuit breaker has a moderately high gas pressure in a main tank and a low gas pressure in an auxiliary tank. An interrupting contact of the orifice type is engaged by an isolating contact to establish a circuit through the breaker. Each contact is actuated by a gas-operated piston in a cylinder disposed inside the main tank and controlled by gas-operated valves. The interrupting contact is withdrawn first, separating the contacts and opening a blast valve incorporated in the interrupter cylinder to permit gas to flow through the orifice contact and a blast tube into the low pressure tank. At full travel the interrupting contact provides the necessary separation for efiicient interruption. After a short delay to permit completion of the interruption, the isolating contact is withdrawn to maintain and increase contact separation, and the interrupting contact is returned to its closed position, thereby stopping the flow of gas. 7

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the acarc interruption as companying drawings, in which:

tie-energized; and

FIGURE 1 is a diagrammatic view of one pole unit of a circuit breaker and control system embodying principal features of the invention, the contacts being shown in the closed-circuit position and the main control valves prises a generally cylindrical main tank 2, a pair of terminal bushings 3 extending through a wall of the tank 2, an interrupter operating cylinder 4, an interrupter 5, an isolator 6, a low pressure gas storage auxiliary tank 7, a compressor and filter 8, and an auxiliary switch operating cylinder 9. As shown, control valves A, B and C are mounted inside the main tank 2. A close valve 11 and a trip valve 12 are mounted externally of the tank 2.

The main tank 2 contains a high-dielectric-strength electronegative gas, such as sulfur hexafluoride (SP gas, at a predetermined moderately high pressure. The auxiliary tank 7 contains SF gas at a lower pressure than the pressure of the gas in the main tank 2. The gas in the main tank 2 is maintained at the high pressure by the compressor 8 which is connected between the auxiliary tank 7 and the main tank 2 to form a closed system and returns gas from the auxiliary tank 7 to the main tank 2 after an interrupting operation. The auxiliary tank 7 is connected to the operating cylinder 4 through an insulating blast tube 13.

The bushings 3 may be of any suitable construction, each bushing having a supporting plate 14 attached to the lower end of a terminal conductor 15 which extends through the bushing. A current transformer 16 may be mounted around each bushing externally of the tank 2.

The control valve A is a three-way, normally closed, pressure pilot operated valve. The valve B is a three-way, normally closed, pressure pilot operated valve with an internal bleed between the pilot section and the outlet as indicated by the dotted lines b. The valve C is a straight-way, normally closed, pressure pilot operated valve. The fclose valve 11 is a straight-way, solenoid operated, normally closed valve of adequate capacity to pressurize the small pilot line to valve B. The trip valve 12 is a three-way, solenoid operated, normally closed valve of adequate capacity to pressurize or exhaust the small pilot lines to valves A and C. One each of the close and the trip valves is required per breaker unless single pole operation is desired, in which case one is required per pole. One each of valves A, B and C is required per pole.

As shown, a piston 17 is disposed inside the auxiliary switch operating cylinder 9. Contact members 18 and 19 are carried by a piston rod 21 attached to the piston 17. The lower end of the cylinder 9 is connected to the main tank 2 through a line 22. The upper end of the cylinder 9 is connected to a port Kin the isolator cylinder 6 through a line 23. When high pressure gas is admitted to the upper end of the cylinder 9, the piston 17 is retained in its lowermost position in view of the difierence in area of the two sides of the piston. When the high pressure gas is exhausted from the upper portion of the cylinder 9, the piston 17 is raised due to the gas pressure below piston 17. The function and operation of the auxiliary switch 24, which is operated by the piston 17, will be described more fully hereinafter.

The interrupter operating cylinder 4, the interrupter and the isolator operating cylinder 6 are shown in more detail in FIG. 2. The interrupter operating cylinder 4 comprises a base 25, an open-end cylinder 26, a first piston 27, a spring 28, a second piston 29 and a blast valve seat 31. As shown in FIG. 1, the base 25 is attached to the supporting plate 14 on the right-hand bushing 3. The cylinder 26 is divided into two compartments 32 and 33 by a partition 34. As previously explained, the compartment 33 has an open end 35. The piston 27, which is disposed in the compartment 32, has an integrally formed stem 36 which extends through the partition 34 into the compartment 33. The piston head 29 is attached to the end of the stem 36 by a nut 37. An O-ring seal 38 may be provided around the stem 36 in the piston head 29. A similar seal 39 may be provided in the rim of the piston head 29. Likewise, a seal 41 is provided at the joint between the cylinder 26 and the base 25.

The piston 27 also has an integrally formed rod portion or arcing probe 42 and an orifice contact member 43 which extend through the base 25. A plurality of contact fingers 44 slidably engage the orifice contact member 43 which encloses the arcing probe 42. The contact fingersv 44 are attached to the base 25. The spring 28 surrounds the stem 36 in the compartment 32 between the partition 34 and the piston 27. Thus, the piston 27 is normally held closed against the blast valve seat 31 to prevent gas from flowing through openings 45 in the wall of the orifice contact 43 into the low-pressure blast tube 13. The openings 45 connect the inside of the orifice contact 43 with the region 47 between the left-hand side of the piston 27 and the valve seat 31.

The piston 27 functions as a blast valve to control the flow of gas from the main tank 2 through the orifice contact member 43 into the auxiliary tank 7 through the blast tube 13. When the piston 27 is moved to the right to disengage the seal 31, the gas is permitted to flow through the orifice contact member 43, the openings 45, and the region 47 into the blast tube 13. Small bleed holes 46 are provided in the partition 34 for a purpose which will be described more fully hereinafter.

A normal condition of the interrupter operating cylinder is the closed position, as shown in the drawing. The front compartment or chamber 32 formed by the cylinder 26, the partition 34, and the piston 27 is at low pressure. A region 48 between the piston head 29 and the partition 34 is also at low pressure. The region on the Iight-hand side of the piston head 29 in the compartment 33 is at high or tank pressure. A region 49 on the left-hand side of the piston 27 is also at high pressure. However, the piston is held in the closed position by the high pressure acting on the right-hand side of the piston head 29 and the force of the spring 28.

The movable isolator contact structure comprises a cluster of contact fingers 51 having a base 52 which is attached to a piston rod 53 by means of an arcing probe or horn 54. A plurality of contact fingers 55, attached to the base 56 of the isolator operating cylinder 6, slidably engage the piston rod 53.

The isolator operating cylinder 6 comprises the base 56, a cylinder 57 having a flange 53 attached to the base 56, and a piston 59 slidably disposed inside the cylinder 57. The piston rod 53 may be formed integrally with the piston 59. An O-ring gasket 61 seals the joint between the cylinder 57 and the base 56. A seal 62 at the right-hand end of the cylinder 57 is engaged by the piston 59 when the piston is in the closed position of the isolating contacts. An O-ring seal 64 is provided around the piston rod 53 Where it passes through the base 56. As shown in FIG. 1, the base 56 is attached to the supporting plate 14 on the left-hand bushing 3.

A port L and a region or chamber 63 formed by the piston 59, the base 56 and the seal 62 are permanently connected to the low pressure gas system. The tank pressure acting on the piston rod 53 acts as a permanent force attempting to drive the isolator to the open position. Thus, the isolator is closed or opened by pressurizing or exhausting the chamber 60 formed by the cylinder 57 and the piston 59.

The method of arc interruption is similar to that described in a copending application Serial No. 61,284, filed October 7, 1960, now US. Patent 3,154,658, issued October 27, 1964 to R. G. Colclaser and R. N. Yeckley and assigned to the Westinghouse Electric Corporation. High pressure gas is blasted into the hollow orifice contact member 43 and out through the openings 45 and the blast tube 13 into the low pressure tank. The orifice contact 43 is separated from the isolator contact 51 by moving the piston 27 to the right. When the piston 27 moves to the right, high pressure gas from inside the main tank 2 flows through the orifice contact 43, the openings 45, the region 47 and the blast tube 13 into the auxiliary low pressure tank 7.

Thus,- the, blast valve is incorporated in the operating cylinder that withdraws the interrupter contact 43. The sequence of operation is such that the interrupter contact 43 is first withdrawn, separating this contact from the isolator contact fingers 5,1 and opening the blast valve to.

permit high pressure gas from the main tank 2 to flow through the hollow orifice contact 43 in the manner previously described. At full travel, the interrupter contact 43 and the arc horn or probe 42 provide the necessary separation for efiicient interruption. After a short delay to permit completion of the interruption, the isolator piston rod 53 is withdrawn to increase and maintain contact separation. The piston 27 and the interrupter contact 43 then return to their initial or closed position by pressure equalization through openings 46, thereby closing the blast valve and stopping the flow of high pressure gas.

The opening, or interrupting operation is initiated by admitting high pressure gas to port F. This pressurizes the region 48 between the piston head 29 and the partition 34 and drives the orifice contact to the open position. This opens the blast valve, permitting gas to flow through the orifice contact into the blast tube, and separates the contacts, thereby drawing an are which is centered and transferred to the arcing probes 42, 54 by the flow of gas. The small bleed holes 46 through the partition 34 permit the pressure in the chambers 48 and 32 to equalize and the interrupter to be returned to its initial or closed position by the force of the spring 28 and the high pressure gas on the right-hand side of the piston head 29. The size of the bleed holes will determine the length of time the interrupter remains open, and may be selected to permit reclosure as soon as possible after allowing adequate time for interruption of the arc to be completed. When port F is again reduced to low pressure the cylinder will exhaust and the interrupter will remain in the normal, closed position. A check valve 69 between ports F and G, see FIGURE 1, also quickly exhausts the front chamber 32 of the cylinder so that the opening operations can be repeated quickly if desired.

As shown in the drawings, the breaker is in the closed position. The close valve 11, the trip valve 12 and the valves A and C are deenergized and closed. The isolator chamber is pressurized and the pilot of valve B is maintained at high pressure by the internal bleed connection, thus holding this valve in the open position and admitting tank pressure to maintain the pressurized condition of the isolator. The low pressure condition in the operating chamber of the interrupter is maintained through the exhaust connection of the normally closed valve A to the blast tube and the low pressure storage tank 7.

Energizing the solenoid 72 of the trip valve 12 admits high pressure to the pilot 73 of the valve A which opens and admits high pressure to the interrupter operating cylinder through the port F. The interrupter opens, permits gas fiow through the interrupting orifice and recloses after a short delay as previously explained. The trip valve 12 also admits high pressure to the pilot 74 of the valve C which opens and exhausts the pilot 71 of valve B to low pressure. This permits valve B to close, thus exhausting the isolator cylinder to the low or auxiliary tank pressure through the connection of the exhaust port to the low pressure system.

The piston 17 in the auxiliary switch operating cylinder 9 is operated by the pressure change at port K of the isolator, thus opening the contact members 19 of the auxiliary switch 24 and deenergizing the solenoid 72 of the trip valve 12. The trip valve returns to its normally closed position, exhausting the pilots of valves A and C which return to their normally closed positions. This exhausts the interrupter operating cylinder and isolates the pilot 71 of valve B except for the internal bleed connection which maintains the valve B in the normally closed position. The isolator cylinder thus remains exhausted through valve B to the low pressure system and the breaker remains open.

Since the interrupter operation is initiated by pressurizing a very small volume and the isolator opening is initiated by exhausting a relatively large volume, the interrupter contact 43 will open sooner than the isolator contact 51. The desired time sequence and time intervals of interrupter open, isolator open and interrupter reclose can readily be obtained by selection of the proper size of gas passages.

Energizing the solenoid 75 of the close valve 11 admits high pressure to the pilot 71 of the valve B which opens and admits high tank pressure to the isolator chamber, thus closing the breaker. The pressure change at port K operates the auxiliary switch to open its contact members 18 and deenergize the solenoid 75 of the close valve 11. The pilot 71 of valve B is maintained at high pressure by the internal bleed connection and the breaker stays closed.

The gas flow capacity of the valve C should be greater than that of the close valve 11 to assure pneumatically trip-free operation of the isolator. Any standard, nonpumping electrical control scheme which provides sealin on both closing and opening operations is applicable to this circuit breaker.

From the foregoing description, it is apparent that the invention provides a circuit breaker in which the fast contact separation required for two or three cycle interrupting time is readily obtainable. The physical disturbance on interruption is kept to a minimum by completing the interruption with ideal contact separation, after which the separation distance is increased by operation of the isolator to prevent flashover due to surge voltages. Hence, the contact members are always in a region of high pres sure, high dielectric strength gas and the danger of flashover is reduced.

Certain features of the present invention are set forth and claimed in US. Patent 3,333,077, issued July 25, 1967 and assigned to the same assignee of the present invention.

While the invention has been shown and described, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit and scope thereof.

We claim as our invention:

1. A compressed-gas circuit interrupter including means defining a pressurized container, a movable contact separable from a movable isolating contact disposed within said pressurized container, means defining an exhaust passage disposed adjacent said contacts and leading out of the pressurized container, operating means for first efifecting opening separating motion of the movable contact, a later isolating opening movement of the movable isolating contact and a final reclosing movement of the movable contact, said operating means comprising an operating cylinder having a cylinder head with an aperture therethrough, a piston rod extending through said aperture and having first and second pistons secured thereto, said piston rod being connected to the movable contact to cause the opening and reclosing movement thereof, the first piston and the cylinder head defining a first chamber, one side of the second piston and the other side of the cylinder head defining a second chamber, the other side of the second piston being exposed to the pressure within said container, means for pressurizing or exhausting the second chamber, and pressure equalizing passages extending through the cylinder head to effect reclosing movement of the movable contact.

2. Tl e combination of claim 1, wherein the first piston additionally serves as a blast valve to control the exhausting flow through the exhaust passage.

3. The combination of claim 1, wherein spring means biases the movable contact in a closing direction.

4. The combination of claim 1, wherein the movable contact is hollow and the exhausting flow is directed therethrough.

5. The combination of claim 1, wherein the isolating contact has a piston secured thereto, and means defines a permanent low-pressure portion about the closing side of said piston.

6. The combination of claim 1, wherein the means for pressurizing or exhausting the second chamber comprises straight-way gas-pilot-operated valve controls the pilot a gas-pilot-operated three-way control valve disposed section of the first-mentioned valve. within the container and actuated by a three-way solenoidoperated tripping control valve disposed externally of the R f r n 'Clted g fl j b t d t 1 1 h th 5 UNITED STATES PATENTS ne com mm 1011 accor ing 0 cairn w erein e a piston operating the movable isolating contact is actuated gi i g et by a three-way gas-pilot-operated control valve disposed 3189717 6/1965 T a i within the container and having a bleeder connection ommaza between the pilot section and the exhaust outlet thereof. 10 ROBERT S MACON Primary Examiner 8. The combination according to claim 7, wherein a

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