US3379849A - Dual-pressure gas-blast circuit breaker with piston means and interrupting unit in closed tank - Google Patents

Description

Apnl 23, 1968 G. J. EASLEY 3,379,849

DUAL-PRESSURE GAS-BLAST CIRCUIT BREAKER WITH PISTON MEANS AND INTERRUPTING UNIT IN CLOSED TANK Filed Dec. 17, 1964 4 Sheets-Sheet 1 HIGH 4 PRESSURE RESERVOIR HIGH PRESSURE GAS STORAGE WITNESSES INVENTOR W WW Gilbert J. Eusley BY W W /r. M

v ATTORNEY Apnl 23, 1968 J EASLEY 3,379,849

DUAL-PRESSURE GAS-BLAST CIRCUIT BREAKER WITH PISTON MEANS AND INTERRUPTING UNIT IN CLOSED TANK Filed Dec. 17, 1964 4 Sheets-Sheet 2 TO HIGH 3,3 79,849 N MEANS 4 Sheets-Sheet 3 G. J. EASLEY ST CIRCUIT BREAKER WITH PISTO DUAL-PRESSURE GAS-BLA AND INTERRUPTING UNIT IN CLOSED TANK April 23, 1968 Filed Dec; 17, 1964 MEANS April 23, 1968 G. J. EASLEY DUAL-PRESSURE GAS-BLAST CIRCUIT BREAKER WITH PISTON AND INTERRUPTING UNIT IN CLOSED TANK 4 Sheets-Sheet 4 Filed Dec. 17, 1964 United States Patent 3,379,849 DUALPRESSURE GAS-BLAST CIRCUIT BREAKER WITH PISTON MEANS AND INTERRUPTING UNIT IN CLOSED TANK Gilbert J. Easley, Edgewood, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 17, 1964, Ser. No. 419,044 Claims. (Cl. 200-448) ABSTRACT OF THE DISCLOSURE An interrupting unit is mounted within a main tank filled with an arc-extinguishing gas at relatively low pressure, such as sulfur hexafluoride (SP gas. An operating cylinder and reciprocating piston are also mounted within the tank and effect contact separation within the interrupting unit. A high-pressure reservoir, containing the same arc-extinguishing gas, such as sulfur hexafluoride (SP gas at a higher pressure, is used to blast the established arc at the separated contact structure and also to effect opening and closing movement of the reciprocating piston. An extension of the piston rod is latched in both the open and closed-circuit positions and also mechanical- 1y effects operation of the auxiliary switches. The tank and the high-pressure rseervoir constitute a dual-pressure closed gaseous system for conserving and reusing the blasted (SP gas.

This invention relates, generally, to circuit breakers and, more particularly, to circuit breakers in which a blast of high pressure gas is utilized to assist in interrupting the are drawn between separated contact members of an interrupting assembly mounted inside a breaker tank.

Prior high capacity gas-blast circuit breakers of the double pressure type have performed satisfactorily, but have the disadvantages of high cost, and high mass of moving parts which makes ultrahigh speed operation difficult to attain. Furthermore, the operating mechanisms of prior breakers have required seals around operating shafts capable of retaining gas inside the breaker tank at a relatively high pressure.

An object of this invention is to provide a dual pressure gas-blast circuit breaker in which gas in the main tank is maintained at a pressure sufficient only for required insulation between live parts, and live parts to ground.

Another object of the invention is to provide a circuit breaker which does not require an external operating mechanism and an air compressor.

A further object of the invention is to eliminate interpole linkages, cranks and shaft seals from a circuit breaker structure.

Still another object of the invention is to utilize a small reservoir of high pressure gas to operate the contact members of a circuit breaker directly, as well as to provide a gas blast for are interruption.

A still further object of the invention is to simplify the control apparatus and system for controlling the operation of a gas-blast 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, an interrupting assembly, including a high pressure reser- Voir, an interrupting chamber, stationary contact fingers, a hollow movable contact member, an operating cylinder, and a double acting piston disposed inside the cylinder, is mounted inside a generally cylindrical main tank on the lower ends of two terminal bushings which extend through collars on the wall of the tank. A high pressure storage 3,379,849 Patented Apr. 23, 1 968 ice tank is mounted outside the main tank and connected to the high pressure reservoir by an insulating tube. The main tank contain sulfur hexafluoride, SP gas, at about 40 p.s.i.g. to provide suflicient insulation to ground and between open contacts. The storage tank and the reservoir contain SF gas at about 230 p.s.i.g., which is maintained at this pressure by a compressor connected between the main tank and the storage tank, thus forming a closed system. The movable contact is connected directly to the piston which is operated by gas from the high pressure reservoir and controlled by two pilot-operated valves disposed inside the main tank. A pilot-operated blast valve, also disposed inside the main tan-k, controls the flow of gas from the high pressure reservoir to the interrupting chamber. The operation of these three valves is controlled by magnet valves located externally of the main tank. An auxiliary switch is operated by a double acting piston disposed inside a cylinder located externally of the main tank and connected to the high pressure reservoir through two plunger operated valves mounted inside the main tank. The plungers are actuated by a rod on the piston which operates the movable contact member of the interrupter. A spring-biased latch pin releasably engages the piston rod to hold the movable contact member in the fully closed or the fully open position.

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 accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of a circuit breaker and control system embodying principal features of the invention;

FIG. 2 is a diagrammatic view of a modified latching scheme for the circuit breaker, the contacts of the breaker being closed;

FIG. 3 is a view, similar to FIG. 2, the contacts being open;

FIG. 4 is a diagrammatic view of a modified circuit breaker having three pole units mounted in one tank;

FIG. 5 is a view, in plan, of the circuit breaker shown in FIG. 4;

FIG. 6 is a view, in plan, showing the structure for operating the movable contact members of the circuit breaker illustrated in FIG. 4, the contacts being open;

FIG. 7 is a view, partly in section and partly in end elevation of the breaker illustrated in FIG. 4, the section being taken through one of the terminal bushings; and,

FIG. 8 is a View, similar to FIG. 7, showing an alternate bushing and current transformer arrangement.

Referring to the drawings, and particularly to FIG. 1, the circuit breaker shown therein comprises a generally cylindrical main tank 2, a high pressure storage tank 3 located underneath the main tank 2, a high pressure reservoir 4 disposed inside the main tank 2 and connected to the storage tank 3 by means of an insulating tube 5, and a compressor 6 connected between the main tank 2 and the storage tank 3. The main tank 2 contains an interrupting gas, for example sulfur hexafluoride (SP gas, at a relatively low pressure, for example 40 p.s.i.g., to provide suflicient insulation to ground and between open contact members of the circuit interrupter. The storage tank 3 and the reservoir 4 contain SF gas at a relatively high pressure, for example 230 p.s.i.g. The gas is maintained at the high pressure by means of the compressor 6 which, as previously explained, is connected between the low pressure main tank 2 "and the high pressure storage tank 3, thus forming a closed system. The main tank 2 is provided with removable end covers 7 for access to the interior of the tank.

An interrupter assembly 8 is mounted inside the tank 2 on the lower ends of two terminal bushings 9, each one of which extends through a cylindrical collar 11 at the top of the tank 2. The bushings 9 may be of a type well known in the art, each bushing having a flange 12 attached to an internal flange 13 on one of the collars 11. A current transformer 14 may be mounted around each collar 11. Each bushing 9 has a conductor 15 extending through the bushing. A metal sleeve 16 may be mounted inside the collar 11 in the space between the collar and the bushing 9 to provide a potential tap 17 in a manner well known in the art.

As shown, the interrupting assembly 8 is of the single break type. If desired two or more breaks could be connected in series for each pole unit of the breaker. As shown in FIG. 1, only one pole unit is mounted in each tank 2. The interrupting assembly 8 includes the high pressure reservoir 4, an interrupting chamber 21 attached to the reservoir 4, a cluster of contact finger members 22 and an arc horn 23 disposed inside the chamber 21 and also attached to the reservoir 4 which, in turn, is attached to the lower end of the conductor 15 in one of the terminal bushings 9. A movable contact member 24, which engages the contact fingers 22 when in the closed position, is attached to a reciprocating piston 25 disposed in an operating cylinder 26 which is attached to the lower end of the conductor 15 in the other one of the terminal bushings 9. Contact finger members 27, which are attached to the end of the cylinder 26 through which the movable contact member 24 extends, slidably engage the contact member 24.

The contact member 24 is preferably of a tubular type having vent openings 28 provided in the wall of the tubular portion of the contact member, as described in a copending application, Ser. No. 612,284, filed Oct. 7, 1960, by R. G. Colclaser and R. N. Yeckley and assigned to the Westinghouse Electric Corporation. During an interrupting operation, high pressure gas is blasted into the open end of the tubular moving contact member 24 and out through the vents 28 into the main tank. The interrupting chamber 21 is preferably composed of a suitable high temperature material, such as polytetrafluoroethylene. The method of interruption is similar to that described in the aforesaid copending application. However, the method ofclosing, tripping, latching and operation of the blast valve is difierent, as will be described hereinafter.

The fiow of the interrupting gas from the high pressure reservoir 4 into the interrupting chamber 21 is controlled by a blast valve A. The valve A is a standard, two-way, pressure operated valve, which is controlled by a magnetic pilot valve A located in a control cabinet 29. The pilot valve A admits gas from the high pressure storage tank 3 to the operating cylinder of the blast valve A through a small insulating tube 31.

The operation of the piston 25 in the operating cylinder 26 is controlled by valves B and C, which are standard, pressure operated, three-way valves. When deenergized, each valve connects its end of the operating cylinder to the low pressure tank and shuts oif the gas from the high pressure reservoir 4. When the corresponding magnetic pilot valve B or C in the control cabinet for either valve is energized, high pressure gas is admitted through a small insulating tube 32 or 33 to the operating cylinder for the corresponding main valve B or C. Operating either main valve admits gas from the high pressure reservoir 4 through an insulating tube 34 to its end of the operating cylinder and at the same time shuts oil? the connection to the low pressure tank 2.

As shown, the contact member 24, the piston 25 and a piston rod 35 are attached together to move as a unit when the breaker is operated. It will 'be noted that the piston rod 35 is rather large in diameter. The purpose of this is to reduce the effective piston area for closing the contact members, since the force required to close the contact members is considerably less than that required to open the contact members quickly. In addition, the closing speed may be controlled further by providing a throttle 36, which is so located that it controls the flow of high pressure gas into one end of the cylinder 26, but does not restrict the flow of gas out of the cylinder. This is important in order to obtain a fast exhaust on a close-open operation.

As shown in the drawing, the opening into the righthand end of the cylinder 26 is so located that the piston closes off the gas escape passage as the piston reaches the open position of the contact members of the breaker. Thus, a cushioning effect is obtained at the end of the opening stroke of the breaker.

In order to provide a definite restraining force to hold the breaker in the fully closed or the fully opened position, a spring-biased latch pin 37 drops into one of the two depressions 38 or 39 in the piston rod 35. When the breaker is closed, the magnetic force tending to open the contacts even when very high fault currents are flowing is relatively low for the current loop shown, in the order of 50-100 pounds. Therefore, the restraining force of the spring biased latch pin in a depression need not be very great, and is easily overcome when high pressure gas is admitted to the operating cylinder to move the piston. The need for an open position restraining force is not as great, but is considered desirable to control rebound.

It will be understood that the arrangement of a springbiasd pin dropping into the depression is merely intended to illustrate a principle involved. The actual latch may be of whatever construction is necessary for reliable operation. One possibility is to utilize a groove inside a hollow piston rod and a spring-biased expanding ring in order to produce a balanced load on the piston rod. Another possibility is to utilize rollers on the pin or ring in order to reduce friction.

Although it is thought that an adaptation of the latch pin arrangement described above will do the job in the simplest manner, a more positive latching arrangement is shown in FIGS. 2 and 3. A pivoted latch member 41 is biased by a spring 42 to engage a projection 43 on the piston rod 35, when the contact members of the breaker are closed. A piston 44 is disposed inside a latch release cylinder 45, which is connected through a pipe 46 to the main control valve B which admits high pressure gas into the operating cylinder 26. When the valve B is operated to open the contact members of the breaker, gas is also admitted to the cylinder 45, thereby causing a piston rod 47 on the piston 44 to engage the latch member 41 to release the latch. Since the volume of the latch release cylinder is much smaller than the main operating cylinder 26, the latch will release before the pressure built up in the operating cylinder 26 is able to produce a high latch load.

In FIGURE 3 the operating piston 25 and the latch 41 are shown in the open position with the valve B still energized to maintain pressure in the latch release cylinder 45. When the valve B is deenergized, pressure is released from the cylinder 45 and the latch spring 42 will drive the piston 44 toward the right in the cylinder 45, and the latch 41 Will be returned to a position in which it will engage the projection 43 on the piston rod 35 when the contact members of the circuit breaker are closed.

In order to control the operation of an auxiliary switch directly by the position of the contact members of the circuit breaker, two three-way valves D and E are provided to control the admission of gas from the high pressure reservoir 4 to an auxiliary switch operating cylinder 51 containing a piston 52 for actuating the contact members of the auxiliary switch. The valves D and E are plunger operated valves actuated by a rounded projection 53 on the piston rod 35. The valve D is connected through a small insulating tube 54 to one end of the cylinder 51 and the valve E is connected through an insulating tube 55 to the other end of the cylinder 51, which is located in the control cabinet 29. When the breaker is closed, the

plunger on valve E is up, and the tube 55 is connected to the low tank pressure. The plunger on the valve D is depressed by the projection 53, and high pressure gas is applied to the tube 54 to actuate the piston 52 to the position shown in the drawing, which corresponds to the closed position of the contact members of the circuit breaker. When the breaker opens, the projection 53 moves to the right so that the plunger of valve D is released, and the plunger on valve E is depressed. This reverses the application of high and low pressure to opposite ends of the auxiliary switch cylinder to move the piston 52 to the other position. One auxiliary switch and one set of valves D and B will ordinarily be sufiicient for a three-pole breaker, but an individual switch and set of valves per pole may be used if single pole operation is desired.

The control cabinet 29 is utilized to house the gas compressor 6 and its controls, the magnetic pilot valves A, B and C, the auxiliary switch and its operating cylinder 51, and anti-pump relays X-Y, which control the magnetic pilot C of the three-way closing valve C. One set of magnetic pilot valves A, B and C could be used to operate all three poles, but it may be found desirable to use three sets of pilot valves in order to keep pilot tubes short and of equal length. Of course, three sets of magnetic pilot valves would be required if single pole breaker operation is desired. The magnetic pilot valves are all three-way valves so that high pressure gas is exhausted rapidly from the pilot tubes to the low pressure tank when the pilots are deenergized. This is especially important on close-open operations, and also to limit the amount of high pressure gas passed through the blast valve during an interruption.

As shown in the drawing, the electrical control for the circuit breaker is a conventional, anti-pump, X-Y scheme which controls the operation of the magnetic pilot valve C for the main closing valves C. The magnetic pilots for the blast valve A and the opening valve B are connected in parallel, so that their operation is initiated simultaneously when the breaker is tri ped by either a control switch CST or a protective relay PR. In case the gas pressure in the high pressure system becomes too low for reliable breaker operation, contacts LPC in the X coil circuit open to prevent the breaker from closing.

The closing operation of the circuit breaker may be understood by referring to the control circuit shown in the drawing. When contact members CSC of the control switch are closed, the X relay is energized which, in turn, energizes the magnetic pilot valve C. High pressure gas is admitted through the pilot tube 33 to operate three- Way valve C; this closes off the low pressure tank connection to the right-hand side of piston 25, and at the same time admits high pressure gas from the high pressure reservoir 4. Since the left-hand side of piston remains open to low tank pressure, the unbalanced force on piston 25 will overcome the latch pin and move the piston to the left to close the contact members of the breaker. Movement of the piston rod 35 will operate the auxiliary switch as previously described; this will close contact members 56 of the auxiliary switch to energize the Y relay which, in turn, opens up the C coil circuit and also deenergizes the X relay. When the valve C is deenergized, low tank pressure will once more be present on both sides of the piston 25. In the meantime, however, the latch pin 37 will have dropped into place to hold the breaker contacts in a definite closed position. The closing operation with this scheme should be very fast, the closing time being about five cycles, or less.

1 Referring again to the control diagram, when contact members CST of a control switch are closed, or protective relay contacts PR are closed, the magnetic pilots for the two-way blast valve A and three-way trip valve B are energized simultaneously. Operation of three-way valve B closes off the low pressure tank connection to the left hand side of piston 25 and at the same time admits high pressure gas. Since the pressure on the right-hand side of piston 25 is low, the unbalanced force on the piston will overcome the latch pin and move the piston to the right to open the contact members of the breaker. Operation of two-way blast valve A admits high pressure gas to the contact region in the interrupting chamber 21 for are interruption. Movement of the piston rod 35 will operate the auxiliary switch as previously described; this will open contact members 57 of the auxiliary switch to deenergize the coils A and B which causes the main valves A and B to shut off the high pressure gas flow. Since the mass of moving parts on this breaker is low compared to a breaker with conventional linkages, cranks and external operating mechanism, a two cycle interrupting time is possible.

A close-open operation is obviously a combination of a closing operation followed immediately by an opening operation. The only difference here is that the high pressure gas on the right-hand side of piston 25 must be exhausted quickly in order not to interfere with the contact opening speed. This is accomplished by using threeway valves for pilot valve C as well as main valve C. This exhausts high pressure gas in the pilot tube quickly for fast operation of main valve C which, in turn, exhausts high pressure gas from the right-hand side of piston 25 quickly. The main valve C is deenergized automatically at the end of the closing stroke as previously described. It will be noted that the throttle 36 for controlling the closing speed is so positioned that it does not affect the high pressure gas exhaust from the operating cylinder.

Since both the opening and closing operations are very fast, it will be possible to get very high speed reclosing of this breaker. A reclosing time in the order of about 10 cycles should be possible. It is obvious that this breaker would be readily adaptable to single pole reclosing if so desired.

On prior compressed air breakers, adjustment to obtain synchronization of the contact members on a three-pole breaker required opening the main breaker tank, which was inconvenient and time consuming. This would be even less desirable on an SP breaker where it would be necessary to remove the gas. With the present breaker, synchronizing of both closing and opening of the contacts on all three poles may be obtained without drawing gas from the tanks by making adjustments on the pilot valves in the control cabinet. If a separate set of magnetic pilot valves is used for each pole, adjustments may be made by changing the magnet air gaps. If a common set of magnetic pilot valves is used for all three poles, then the adjustment could be made by means of an adjustable throttle screw in the pilot tube leading to each main valve. It is expected that the throttle 36 ahead of each main valve C, previously described, will not require further adjustment after once being set to obtain the desired closing speed.

In the circuit breaker shown in FIGS. 4, 5 and 6 of the drawings, all three poles are mounted in a single tank 2'. This structure is particularly suitable for circuit breakers utilized on medium voltage power systems which are required to interrupt relatively high currents. Since the breaker is required to operate only at medium voltages, the pressure of the gas inside the main tank 2 may be maintained at approximately 15 p.s.i.g. which will provide sufficient insulation for voltages of 14.4 to 69 kv. This low pressure would exempt the tank from the ASME code, thereby reducing the tank cost. The high pressure reservoir 4 is omitted from inside the tank 2 and one high pressure reservoir 3 provided externally of the tank 2, thereby further reducing the cost of the breaker.

The operating scheme is basically the same as that hereinbefore described in which the high pressure gas is used to operate the breaker contacts directly instead of by means of an external operating mechanism and linkages. The blast valve A, the opening valve B and the closing valve C are cont olled by magnetic pilot valves A, B and C, respectively, in the manner herein-before described. Likewise, auxiliary switch valves D and E are operated in the manner previously described. A single operating cylinder 26 and a single set of valves are utilized in this case to operate all three poles of the breaker.

The operating cylinder 26 and the control valves B and C are at ground potential, thereby making it unnecessary to insulate the pilot tubes for these valves. As shown in the drawing, the valves are located inside the main tank 2. However, the valves may be located outside the tank so that the main valves and pilot valves could by physically combined. There is a further possibility of combining valves A and B, since they are controlled by the same electrical circuit.

As shown in FIGS. 4 and 5, a pair of bushings 9' is provided for each pole unit of the circuit breaker. The inner ends of the bushings are aligned longitudinally of the tank 2, and the outer ends are tilted transversely of the tank as shown in FIG. 5. By tilting the bushings alternately in opposite directions, sufiicient space is provided for the bushing current transformers 14. Also, more than enough electrical spacing is provided between the external terminals of the bushing. Locating the bushings in line may give the impression of creating a rather long breaker, but such is not the case; a check on dimensions to get the required spacings and creepage distances between poles shows that this breaker is about -25 percent shorter than comparable three-tank oil breakers.

As shown in FIG. 4, the interrupting chamber 21, the stationary contact members 22 and the arc horn 23 for each pole unit are mounted on the inner end of the terminal conductor 15 in one of the bushings 9 of each pair of bushings. Collector fingers 27' are mounted on the inner end of the terminal conductor 15 in the other one of each pair of bushings. The main guiding and supporting of the movable contact member 24' for each pole unit is provided by a hole through the base of the collector fingers 27. Additional guiding is obtained by means of the collector finger tips.

As shown most clearly in FIG. 6, the movable contact members 24' for all three pole units are operated by two spaced insulated rods 61 which are joined by cross members 62, one of which is attached to each one of the movable contact members 24. A cross member 62 at the right-hand end of the rods 61 is attached to the piston 25 in the operating cylinder 26 by means of a rod 63, which is attached to the member 62 by means of a clevis 64. In this manner, the contact members for all three pole units are operated simultaneously by the piston 25.

It will be noted that there is a wide slot between the collector fingers 27 on two sides in order to admit the cross members 62 which connect the moving contacts to the insulating rods, thus keeping the spacing between bushings to a minimum. There are no insulating supports shown between the stationary contacts, however, these could be provided in the manner shown in the aforesaid copending application in order to facilitate removal of the complete three-pole contact assembly as a unit from the left hand end of the tank 2 for convenient maintenance.

FIG. 7 of the drawing shows an end view of the breaker and a cross section through one of the bushings 9'. The general location of the high pressure tank 3' and the control cabinet 29 is shown. Since the main breaker tank 2 must be mounted high enough to provide electrical code clearance between external live parts and the ground level, there is plenty of space underneath the main tank for the high pressure tank and the control cabinet.

The gas bushing 9' shown is in general similar to prior bushings utilized on SP breakers. However, the bushing is not handled as a unit, but is assembled in the breaker with separate upper and lower porcelains 65 and 66, respectively, which are held in position by the conductor stud 15. The bushings 65 and 66 are drawn against an internal flange 13 at the top of the collar 11' with suitable gaskets 67 and 68 disposed between the porcelains 65 and 66, respectively. Omission of flange bolts permits the use of smaller diameter current transformers.

The present bushing differs from the prior bushings in that a solid stud conductor is used, and the gas connection to the interior of the bushing is through a small hole 69 in the flange 13'. A small filter may be provided to keep out solid are products, such as powder.

Another difference is that the encapsulated current transformers 14 are mounted around the tank collar instead of an extension of the upper porcelain. In this case, the tall metal collar 11 is required anyway with the horizontal tank construction.

Another alternate arrangement for the current transformers and bushings is shown in FIG. 8. In this case indoor type current transformers are mounted inside the tank collar 11' on a support 71 attached to the inside of the collar 11'. Secondary leads 72 are brought out through suitable seals in a connecting member 73 on the collar 16. The bushing shown is of the condenser type in order to obtain the smallest possible diameter for the current transformers 14. No porcelain is required on the lower end of the bushing, and the interior of the upper porcelain 65 is filled with SP gas through a small filtered opening 69' in the flange 13' attached to the top of the collar 11. The bushing flange forms the top cover for the current transformer pocket.

Although the tank collar 11' must be taller in order to mount the current transformers 14 around the ground sleeve 74- of the condenser bushing, the collar is not much larger in diameter, due to the small diameter of the condenser bushing. In addition to providing the smallest possible current transformer, this arrangement has the advantage of a natural fiashover path across the ouside porcelain to ground around the outside of the current transformer which is desired for differential relaying schemes. This eliminates the need for an electrode gap 75 required in the arrangement shown in FIG. 7.

From the foregoing description it is apparent that the invention provides a circuit breaker having the following advantages:

(1) Low cost due to elimination of external operating mechanism, air compressor, operating rods, cranks and shaft seals.

(2) High speed opening, closing and reclosing due to low mass of moving parts.

(3) High speed close-open operation due to utilization of three-Way valves.

(4) Readily adaptable to single pole reclosing.

(5) Low side thrust on bushings.

(6) Main tank at low gas pressure uses minimum amount of gas and permits use of lower cost tank.

(7) Simplified gas control scheme made possible by a latch pin arrangement to hold the breaker in definite closed or opened position.

(8) Breaker does not slowly change position when gas pressure is lost.

(9) Minimum gas sealing problem-no shaft seals and no large piston seals.

(10) Eliminates heavy accelerating spring and possible elimination of shock absorbers due to the cushioning effect obtained during the opening operation.

(11) Improved blast valve operation over prior mechanically operated valve-no delay on close-open operation.

(12) Opening and closing synchronizing of contacts possible without opening the tank.

The circuit breaker shown in FIGS. 4, 5 and 6 has the following additional advantages:

(1) Single operating cylinder and set of valves for three-pole breaker.

(2) No synchronizing problem between poles.

(3) No high pressure reservoir required inside the breaker tank.

(4) Operating cylinder and valves are at ground potential.

(5) Low gas pressure in breaker tank may eliminate ASME boiler code inspection, thereby lowering the tank cost.

(6) Novel alternating position of bushings permits use of shortest possible single tank.

Since numerous changes may be made in the above described construction, and ditferent embodiments of the invention may be made without departing from the spirit and. scope thereof, it is intended that all subject matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a dual-pressure gas-blast type of circuit breaker employing a substantially closed gaseous system for conserving and reusing the blasted gas, in combination, a main tank containing an interrupting gas at a relatively low pressure yet having a higher dielectric strength than air at atmospheric pressure, a reservoir containing the same kind of gas at a relatively high pressure, an interrupting chamber mounted inside the main tank, a stationary contact member disposed inside the interrupting chamber, a movable contact member engaging the stationary contact member, an operating cylinder mounted inside the main tank, a reciprocating piston having a piston-rod extension disposed in the cylinder and connected to the movable contact member, valve means for controlling the flow of gas from the high pressure reservoir into opposite ends of the cylinder to operate the piston to open and close the contact members in the interrupting chamber, a blast valve for controlling the flow of a high-pressure blast of gas into the interrupting chamber, auxiliary switch means for controlling the operation of the valve means and the blast valve, control valves (D, E) disposed immediately adjacent the operating cylinder for controlling the operation of the auxiliary switch, and said control valves being directly actuated by a projection on the piston-rod extension.

2. The dual-pressure gas-blast type of circuit breaker of claim 1, wherein latch means releasably engages the piston-rod extension to retain the contact members closed.

3. The dual-pressure gas-blast type of circuit breaker of claim 1, wherein solenoid valve means disposed externally of the tank actuates the valve means and the blast valve, and switching means located remotely from the circuit breaker controls the energization of the solenoid valve means.

4. The combination of claim 2, wherein fluid-pressure actuated means (44) releases the latch means, and the valve means initiates operation of said fluid-pressure actuated means. i

5. A multi-pole dual-pressure gas-blast type of circuit breaker employing a substantially closed gaseous system for conserving and reusing the blasted gas, comprising a generally cylindrical elongated main tank containing an interrupting gas at a relatively low pressure yet having a higher dielectric strength than air at atmospheric pressure, a reservoir containing the same kind of gas at a relatively high pressure, a pair of terminal bushings extending through the elongated tank for each pole, said bushings being spaced longitudinally of the tank and tilted in opposite directions transversely of the tank, an interrupter mounted inside the tank for each pole, each interrupter including an interrupting chamber supported by one terminal bushing, a stationary contact member disposed inside each chamber and a movable contact member slidably supported by an adjacent bushing, elongated insulating means movable longitudinally and connecting the movable contact members together, a single operating cylinder mounted inside the tank, a reciprocating piston disposed inside the cylinder and attached to said longitudinally movable insulating means, and valve means controlling the flow of gas from the reservoir into the cylinder to operate the piston to open and close the contact members.

6. The combination of claim 5, wherein the single operating cylinder within the tank is at ground potential.

7. The combination of claim 5, wherein the reciprocatingpiston has a piston-rod extension, and projections on the piston-rod extension operate valves for initiating operation of the auxiliary switch.

8. The combination of claim 5, wherein an auxiliary high-pressure tank is disposed below the elongated main tank.

9. The combination of claim 5, wherein a single blastvalve is provided for injecting high-pressure gas simultaneously into all of the interrupting chambers.

10. A multi-pole dual-pressure gas-blast type of circuit breaker employing a substantially closed gaseous system for conserving and reusing the blasted gas, comprising a generally cylindrical elongated main tank containing an interrupting gas at a relatively low pressure yet having a higher dielectric strength than air at atmospheric pressure, a reservoir containing the same kind of gas at a relatively high pressure, a pair of terminal bushings extending through the elongated tank for each pole, said bushings being spaced longitudinally of the tank and tilted in opposite directions transversely of the tank, the inner ends of said bushings being aligned longitudinally of the tank, an interrupting chamber and a stationary contact member therein mounted on the inner end of one of each pair of bushings, a movable contact member slidably mounted on the inner end of the other one of each pair of bushings, elongated insulating means movable longitudinally and connecting the movable contact members together, a single operating cylinder mounted inside the tank, a reciprocating piston disposed inside the cylinder and attached to said longitudinally movable insulating means, valve means controlling the flow of gas from the reservoir into the cylinder to operate the piston to open and close the contact members, a blast valve controlling the flow of gas from the reservoir into the interrupting chambers, and magnet valves disposed externally of the tank for controlling the operation of said valve means and said blast valve.

References Cited UNITED STATES PATENTS 3,163,737 12/1964 Gonek et al. 200-148 3,214,542 10/ 1965 Yeckley et al. 200- 3,246,108 4/1966 Colclaser et al. 200-148 FOREIGN PATENTS 1,304,411 8/ 19612 France.

533,574 9/ 1931 Germany.

646,847 9/ 1937 Germany.

517,622 2/ 1940 Great Britain.

ROBERT S. MACON, Primary Examiner.

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