US 3622725 A
Description (OCR text may contain errors)
'11.; United States atom 1111 3,622,725
 Inventor Lorne D. McConnell  References Cited Radnor, UNITED STATES PATENTS 2f:- 5 1 1970 2,537,474 1/1951 Mejean 200/83 B gf g 2,911,507 11/1959 Wood 200/148 E  Assignee l-T-E Imperial Corporation FOREIGN PATENTS Philadel hia, Pa, 715,182 8/1965 Canada 200/83 J Primary ExaminerRobert S. Macon 54 PRESSURE CONTROLLER FOR GAS CIRCUIT Faber Sofie BREAKER ll claims4 Drawing Figs ABSTRACT: The pressures of a low-pressure and high-pres- 152 1 us. C1 200/148 E, sure region of two-Pressure g circuit breaker are pp to 200/148 B pistons carried on a common rod so that the pistons and rod [5| Int. Cl l-l0lh 33/80 move to a predetermined P0Sition when the Pressure  Field of Se r h 200/148 ference between the two pressure regions is below a given value. The motion of the rod turns on a compressor which operates until a desired pressure ratio is Obtained P16553065 4 N r ,e /d
F/L 75,6 1 6// 44,404 016 56 mm for J fll/f/fl 1.9 3 I 55117 1444 V6 PATENTEHNUV 2 1 3.622.725
SHEET 1 OF 2 5 JE/vrae 42 l 4% 1 PRESSURE CONTROLLER FOR GAS CIRCUIT BREAKER RELATED APPLICATIONS The invention of the present application may be used in gascircuit breakers of the type shown in application Ser. No. 680,778, filed Nov. 6, I967, in the name of John H. Golota, entitled ADJUSTABLE CONTACT NOZZLE AND RETRACTABLE ARCING CHAMBER FOR GAS BLAST CIRCUIT BREAKERS and application Ser. No. 823,] I5, filed May 8, 1969, in the name of Otto Jensen, entitled GAS BLAST CIRCUIT INTERRUPT ER USING MAIN MOVA- BLE CONTACT AS BLAST VALVE, both of which are assigned to the assignee of the present invention.
THE PRIOR ART Circuit breakers are well-known which employ a two-pressure closed gas system particularly those using sulfur hexafluoride as the gas. In these devices, sulfur hexafluoride from the high-pressure system is forced through the are drawn by the contacts of the system and into the low-pressure system. It is necessary with this type of circuit interrupter to have a control means to assure that the pressures are maintained in the highand low-pressure systems within specific limits to assure interrupting capability, proper pneumatic operation where the gas is also used to operate the contacts, and insulation integrity after the contacts are opened.
As the ambient temperature and enclosed gas volumes change, these pressures may vary over relatively wide but acceptable ranges. Therefore, a compressor, which is used to pump gas from the low-pressure region to the high-pressure region which is controlled by pressure measurements alone is not practical since it will cause compressor operation under many situations where the pressure difference is suitable for the breaker operation.
One control arrangement for controlling compressor operation in the type breaker to which the invention may be applied is shown in US. Pat. No. 3,129,309, in the name of McKeough et al. This patent describes a switch for a compressor where the switch is operated in response to gas density and, to this end, requires temperature compensation of the pressure measurement. Switches of this type are expensive and difiicult to apply to a breaker, particularly when the pressurized volume to be controlled is at line potential and relatively inaccesible. That is, it is difficult to sense the temperature with fluid-type sensors, or the like, at such an inaccessible region. For this reason, it is the common practice to place temperature sensors at some region other than at the pressurized volume directly adjacent the contacts, thereby leading to possible inaccuracies in control where the temperature of the volume being monitored is different from the temperature of the volume immediately adjacent the contact region. Accordingly, it is possible to reach relatively unsafe pressure conditions which are indicated as being safe. Moreover, this type system is costly in that it requires both pressure and temperature inputs and in that fluid bulbs must generally be mounted at considerable distances from the controller and connected to the controller by long capillary tubes. Thus, the controller itself, and the necessary mounting structure and other auxiliary equipment for the controller, add considerable cost and complication to the equipment.
U.S. Pat. No. 3,423,553 to Pratsch also shows a pressure controller where, again, temperature compensation is used with a step-type control rather than continuous control being used in the control loop. This device is subject to all the disadvantages described above, and introduces errors into the temperature-sensing measurement because of the step-type control action.
SUMMARY OF THE INVENTION In accordance with the present invention, the compressor of a two-pressure gas circuit breaker is controlled to maintain a given pressure ratio between the two systems. More specifically, the interrupting capability of a gas circuit breaker is largely determined by the existence before and during operation of the contacts of an adequate pressure ratio between the two systems. The required pressure ratio is essentially independent of temperature. Moreover, in most gas circuit breakers, the highand low-pressure gases will be disposed in close proximity in the interrupter area so that differences between high and low pressures in the interrupting area willbe substantially the same temperature so that temperature changes will not affect operation of the pressure control system.
Accordingly, and in accordance with the invention, a pres sure ratio switch is provided which is connected at one end to a high-pressure region and at its other end to the low-pressure region of a gas circuit breaker. A mechanically movable member, which is acted upon by these two pressures, is then arranged to move to a given position only when the pressure ratio between the high and low-pressure system falls below a given value. In this situation, the compressor is automatically switched on in order to restore the pressure ratio to some value above a given value at which point the mechanical member movable by the pressure ratio between the highand low-pressure regions deenergizes the compressor operation.
One specific pressure transducer which can be used, in accordance with the invention, is a rod having differently sized pistons at its opposite ends having areas which are related to one another by a factor equal to the pressure ratio-which is to be maintained between the highand low-pressure regions. These two pistons are then connected to one another by a suitable connecting rod which is arranged to drive a switch, or other control element, responsive to movement of the rod. The low-pressure region is then connected to the larger-area piston and the high-pressure region is connected to the smaller-area piston, with the two pistons being disposed to tend to move in opposing directions.
When the ratio of high pressure to low pressure is less than the ratio of piston areas, the piston will tend to move, thereby causing the movement of their connecting rod and the actuation of the compressor to restore the desired pressure ratio. A small biasing spring may also be provided to provide a biasing load on the piston assembly, which is the equivalent of a load of one atmosphere on each of the pistons in opposition to the normal direction of motion of the pistons. By this means, the motion of the pistons and their connecting rod is responsive to absolute-pressure ratio rather than gauge-pressure ratio. The absolute-pressure difference is more representative of the interrupting ability of the breaker than is the difference in gauge values so that the addition of this bias substantially improves the adequacy of the control to assure conditions proper to breaker operation.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is schematically illustrates the pressure-control device of the present invention as applied to a typical and schematically illustrated two-pressure gas circuit interrupter.
FIG- 2 is a top view of a pressure compressor constructed in accordance with the present invention.
FIG. 3 is a cross-sectional view of FIG. 2 taken across the section line 3-3 in FIG. 2.
FIG. 4 is an end view of FIGS. 2 and 3 as seen from the lefthand ends thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically illustrates the present invention and its application to a typical two-pressure closed gas system circuit interrupter. For specific circuit interrupters of this type, reference is made to the structures shown in copending application Ser. Nos. 680,778 and 823,! 15, noted above.
In FIG. 1, there is illustrated a main housing 10 having a high-pressure region 11 and low-pressure region 12 separated by a barrier 13. A stationary contact, schematically illustrated as consisting of flexible contact fingers I5, is connected to a terminal 16 over the conductor 17. The high-pressure chamber 11 contains a movable contact, schematically illustrated as movable contact 18, which is connected to terminal 19 over the lead 20. A suitable operating mechanism 21, of any desired type, is operatively connected to movable contact 18 to move contact 18 toward and into engagement with stationary contact or to the disengaged position shown. A blast valve 22 is also provided, which permits communication, through the stationary contact 15, of high-pressure chamber 11 and low-pressure chamber 12 when the blast valve 22 is open. A blast valve operating mechanism 23, which may be operatively coupled to the operating mechanism 21, is provided to open the blast valve from its schematically illustrated tubular seat 24 during opening and closing of movable contact 18 with relation to stationary contact 15 so that a blast of gas will flow through any are drawn between movable contact 18 and stationary contact 15 to extinguish the arc. Preferably, this gas will be sulfur hexafluoride.
In order to insure proper interruption operation, it has been recognized, in accordance with the invention, that it is necessary to maintain a particular pressure ratio between the pressure in chambers 11 and 12. Note that the pressure differential may vary and that the system responds to ratio only. To help maintain this ratio, there is provided a compressor 30, which may operate through a check valve 31 and filter-dryer 32 such that gas will be forced into chamber 11 until a particular pressure is reached and gas is removed from chamber 12 so that, after a gas blast action, the gas in chamber 12 can be removed to return it to its desired low-pressure condition. The pressure of high-pressure volume ll may vary from about 200 pounds per square inch to about 260 pounds per square inch over a temperature range of from about 30 to 80 C. The low-pressure chamber 12 will vary from about 34 pounds per square inch to about 80 pounds per square inch over the same temperature range.
Typically, at normal ambient temperatures of about 30 C., the chamber 11 can be at a nominal pressure of about 235 p.s.i.a. while the low-pressure chamber can be at a pressure of about 40 p.s.i.a. This gives a pressure ratio of 6.1. At C., the high pressure is 212 p.s.i.a. and the low pressure is 35 p.s.i.a. for a pressure ratio of 6.06. At 80 C., the high pressure is 263 p.s.i.a. and the low pressure is 46 p.s.i.a. for a ratio of 5.73. Thus, these temperature-dependent pressures have a pressure ratio that is approximately constant over the full temperature range and can be represented by the fixed areas of two opposed pistons.
The operation of the breaker will result in a drop of the high pressure by about 10 p.s.i. and a corresponding increase in the low pressure. This would change the pressure ratio to about 4.5, which is a large variation which can readily be used to operate the control system.
In accordance with the invention, the pressure ratio of the pressures in chambers 11 and 12 is measured and maintained since, if this pressure ratio is maintained, the circuit interrupter will be effective over a wide temperature range. Thus, a pressure controller 40 is provided which is connected to the high-pressure chamber 11, over conduit 40a, and to the lowpressure chamber 12 over the conduit 40b. Contained within controller 40 is a movable member 42, having a large-area piston 43 and a small-area piston 44 which are exposed to the pressures of chambers 12 and 11, respectively. The areas of pistons 43 and 44 are so sized as to be a ratio of 6.! to 1. Accordingly, when the pressure ratio between high-pressure chamber 11 and low-pressure chamber 12 exceeds this value, the pistons 43 and 44 will be moved to the left and, when the pressure ratio is reduced below this value, they will move to the right. The rightward movement of pistons 43 and 44 operates the compressor control 50 which, in turn, turns on the compressor 30 to reestablish the desired pressure ratio between chambers 11 and 12. Once this desired pressure ratio is obtained, pistons 43 and 44 again move to the left to deactivate compressor control 50 which, in turn, turns off compressor 30. It will, of course, be obvious that the compressor control 50 may operate other suitable circuits such as indicator or alarm circuits.
In order to guard against a mass gas loss to atmosphere because ofa leak in tank 10 or the failure of compressor 30 to establish a proper pressure ratio, a suitable pressure sensor 60 may be connected to the low-pressure chamber 12. Pressure sensor 60 may then be connected to a suitable alarm and/or other control circuitry which could, for example, prevent the operation of the circuit breaker until suitable pressure conditions are reestablished. If desired, a second pressure sensor 62 can be coupled to the high-pressure chamber 11 and drive a suitable high-pressure chamber alarm 63.
FIGS. 2 to 4 show one specific apparatus which could be used for the pressure controller 40 of FIG. I, where the device has very small frictional forces and where the device is compensated for atmospheric pressure. More specifically, the pressure controller consists of a body 70 which has cylinder chambers 71 and 72 in its opposite ends. A threaded opening 73 is formed in the bottom of cylinder 71 and threadably receives an adjustable collar 74 which contains suitable tool receiving openings, such as opening 75. A piston rod 76 is then slidably disposed within collar 74 and the left-hand end of rod 76 receives a large-area piston 77 secured to the end of rod 76 by the nut 78. The right-hand end of rod 76 is slidably received in opening 80 of rod 81. The right-hand end of rod 81 defines a high-pressure piston within cylinder 72 as will be later described.
A sleeve is then threaded onto the left-hand end of rod 81 and is fixed in position as by pin 91. The sleeve 90 then moves relative to the operating arm 92 of a standard microswitch 93 which has an operating button 94 engaged by operating arm 92 to operate microswitch contacts 95 which are schematically illustrated, and are connected to the microswitch terminals 96 and 97, respectively. Microswitch 93 is secured in a suitable chamber formed in body 70 and is held therein by its brackets 98 and 99 and screws 100 and 101, respectively. The left-hand end of body 70 then receives a cap as by suitable bolts which are contained in bolthead depressions 111 to 114, which bolts extend through cap 110 and into suitable tapped openings in body 70.
A central channel 120, which contains a suitable fitting receiving thread means, is provided for a low-pressure connecting line which is to be connected to the left-hand surface of piston 77. in a similar manner, a cap is secured to the right-hand end of body 70 and contains a suitable fitting receiving thread 131 for making a high-pressure line connection to the right-hand end or rod 81.
Roller diaphragm is then clamped over the left-hand surface of piston 77 by the clamp 141 and the outer flange of the diaphragm 140 is captured between cap 110 and the lefthand end of body 70. A port 140a is formed through the wall of chamber 71 to permit easy movement of piston 77 within chamber 71. Roller diaphragms of the type of roller diaphragm 140 are commercially available and the specific diaphragm 140 may be of the type sold under the trade name Bellofram Rolling Diaphragm. A specific diaphragm of this type used for diaphragm 140 carried the type number 41-] 12-87 Wall C. In a similar manner, the rod 81 receives a rolling diaphragm 150, which is held thereon by the clamp 151 and screw 152, with its outer flange clamped between cap 130 and the right-hand end of body 70. Rolling diaphragm I50 was of the type number 4-5037 Wall A. The use of rolling diaphragms in this application is extremely desirable in that they provide a seal for the low-pressure and high-pressure regions while avoiding the need for close tolerance and highly finished surfaces which would otherwise be necessary with a sliding seal to reduce frictional load to a minimum. Clearly, however, standard sliding seals could be used in the place of rolling diaphragms 140 and 150.
The pressure ratio to be maintained by the controller of FIGS. 2 to 4 will be the ratio determined by the cross-sectional area of chamber 71 relative to the cross-sectional area of chamber 72. In the particular embodiment of the invention discussed in FIG. 1, this ratio is about 6.1 to 1. Clearly, however, any desired pressure ratio could be selected.
A small compression spring 155 is then carried between collar 74 and rod 81, thereby biasing rod 81 to the right. Spring 155 is designed to provide a force, equal and opposite to the net atmospheric pressure loads effective on the nonpressureized sides of piston 77 and rod 81.
The operation of the controller of F I65. 2, 3 and 4 is substantially identical to that described in connection with FIG. 1. Thus, the low-pressure side of a circuit interrupter is connected to fitting 120 and the high-pressure side is connected to fitting 131. So long as the pressure ratio ratio between the high-pressure and low-pressure chambers is greater than some given value, rods 76 and 81 will move to the left until there is a force balance. Under this condition, sleeve 90 presses on actuating arm 92 of microswitch 93, thereby operating the microswitch. This in turn, may be used with a suitable circuit, and in connection with FIG. 1, deenergize compressor 30. However, once the pressure ratio of the pressures at fittings 120 and 131 falls below a given value, piston 77 and rod 81 move to the right, thereby releasing arm 92 at a given position in the motion of sleeve 90 so that contacts 95 are operated to their opposite condition, and the compressor 30 of FIG. 1 is turned on.
Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.
The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:
1. In combination, a two-pressure closed system gas circuit breaker and a pressure control system therefor;
said two-pressure closed system gas circuit breaker comprising a high-pressure volume, a low-pressure volume, a blast valve connected between said highand low-pressure volumes and operable to produce a flow of gas therebetween, a pair of cooperable contacts disposed in a position whereby the flow of gas upon the opening of said blast valve will flow between said cooperable contacts, and operating means for temporarily opening said blast valve when said cooperable contacts open;
said pressure control system comprising a compressor connected between said highand low-pressure volumes for drawing gas from said low-pressure volume and applying gas to said high-pressure volume, a compressor control means connected to said compressor to turn said compressor on and off responsive to a predetermined pressure ratio between said highand low-pressure volumes; and a compressor control actuating means comprising first pressure responsive means connected to said low-pressure volume, second pressure responsive means connected to said high-pressure volume, and movable output means connected to said first and second pressure responsive means and movable in a first direction responsive to a pressure ratio between said highand low-pressure volumes above a given value and movable in a second direction responsive to a pressure ratio between said highand low-pressure volumes below a given value, said movable output means being coupled to said compressor control means.
2. The combination of claim 1 wherein the gas filling said highand low-pressure volumes is sulfur hexafiuoride.
3. The combination of claim 1 wherein said highand lowpressure volumes are adjacent one another.
4. The combination of claim l wherein said high-pressure volume is held at a pressure of about six times that of said lowpressure volume.
5. The combination of claim I wherein said first and second pressure responsive means comprise first and second pistons, respectively; and wherein said movable output means comprises a rod means interconnecting said first and second pistons. i I I 6. The combination of claim 5 wherein said rod means comprises first and second members in abutting connection to one another.
7. The combination of claim 5 wherein said second piston has an effective area greater than the effective area of said first piston by a ratio about equal to the desired pressured ratioto be maintained between said highand low-pressure volumes.
8. The combination of claim 1 which further includes absolute pressure compensating means; said absolute pressure compensating means comprising biasing means connected to said movable output means and applying thereto a biasing force equivalent to the force of one atmosphere.
9. A pressure controller for maintaining a given pressure ratio range between a highand low-pressure volume which are connected to a compressor for forcing gas into said highpressure volume; said controller having an output connected to said compressor to turn on said compressor when said pressure ratio is below a given value; said controller comprising:
a. a first piston having first and second opposite surfaces and movable within a first cylinder;
b. a second piston having first and second opposite surfaces and movable within a second cylinder;
. connection rod means connecting together said first surface of said first and second pistons whereby said first and second pistons on said connection rod means can move as a unit;
d. high-pressure connector means for connecting the pres sure of said high-pressure volume to said second surface of said first piston and low-pressure connector means connecting the pressure of said low-pressure volume to said second surface of said second piston;
e. electrical circuit switching means coupled to said connection rod means and connected to generate an output signal on said output when said connection rod means moves to a given position, indicating a pressure ratio between said highand low-pressure volumes which is below said given value.
10. The pressure controller of claim 9 wherein said second piston has an area greater than the area of said first piston by about the ratio of pressures which is to be maintained between said high and low-pressure volumes.
11. The pressure controller of claim 9 which includes first and second rolling diaphragm seal means extending between said first and second pistons, respectively, and their said respective first and second cylinders.
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