US3185895A

US3185895A - Pressure-control circuits for gas-type circuit interrupters

Info

Publication number: US3185895A
Application number: US144705A
Authority: US
Inventors: Gilbert J Easley
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1961-10-12
Filing date: 1961-10-12
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25
Also published as: GB971280A

Description

G. J. EASLEY May 25, 1965 PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Filed Oct. 12, 1961 3 Sheets-Sheet 1 PRESSURE SWITCH (NORMAL PRESSURE CONDITION) .l. 0- CST 99 l l I Fig. INVENTOR Gilbert J. Eosley BY (Z2: M ATTORNEY WITNESSES May 25, 1965 G. J. EASLEY 3,185,895

PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Filed Oct. 12, 1961 3 Sheets-Sheet 2 Fig. 2

83 68 w Fig. 3 f

k J 79 80 i I 8| I 83 PRESSURE SWITCH lov 5 y 1965 G. J. EASLEY 3,185,895

PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Filed Oct. 12, 1961 3 Sheets-Sheet S PRESSURE SWITCH Fig. 4

United States Patent 0 PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Gilbert J. Easley, Edgewood, Pin, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a

corporation of Pennsylvania Filed Oct. 12, 1961, Ser. No. 144,705 9 Claims. (Cl. 317-59) The present invention relates broadly to pressure-control circuits for gas-type circuit interrupters and, more particularly, to a pressure-control circuit for a gas-type circuit interrupter utilizing a minimum number of pressure switches.

As Well known by those skilled in the art, certain gastype circuit interrupters depend upon their interrupting integrity upon the pressure condition of the arc-extinguishing gas present within the sealed interrupting casing. For example, in a gas-type circuit interrupter, such as that set forth in United States patent application filed November 18, 1959, Serial No. 853,974, by Robert L. Hess, James M. Telford and Gilbert J. Easley, now United States Patent 3,114,815, issued December 17, 1963, and assigned to the assignee of the instant application, there is disclosed and claimed a novel type of circuit-interrupting structure in which a puffer element is moved with the movable contact structure to inject a blast of arcextinguishing gas into the arcing region. Such areextinguishing gas is completely enclosed in a surrounding casing, within which the separable contacts of the breaker are disposed and actuated. A sealed drive shaft extends laterally out of the pressurized casing for the interrupter; and mechanical opening and closing motion is transmitted into the interior of the sealed casing by means of the drive shaft. As a result,opening of the circuit interrupter of the aforesaid application is effected by rotation of the aforesaid drive shaft, which not only effects contact separation within the pressurized enclosure of the interrupter casing, but also mechanically effects driving motion of the puffer element to inject a gas blast through a suitable orifice and into the arc to effect the extinction thereof. In such a type of circuit interrupter it is necessary to maintain a minimum pressure of the arc-extinguishing gas within the circuit-interrupter casing.

If the pressure of the gas within the interrupting casing drops below a minimum value, opening of the breaker under such conditions is hazardous; and, in addition, closing of the breaker may result in considerable free arcing during such a closing stroke. It is, therefore, desirable to sense the pressure conditions within the circuit-interrupter casing, and should the pressure drop too low, to prevent closing and tripping of the breaker. At the option of the utility customer, tripping of the breaker may be obtained as the pressure conditions drop to the lower hazardous value.

It is, therefore, a general object of the present invention to provide an improved gas-type circuit interrupter in which control is obtained over the operating conditions of the breaker dependent upon the pressure of the arcextinguishing gas within the interrupter casing.

A more specific object of the present invention is to provide an improved pressure-control circuit for a gastype circuit interrupter in which a minimum number of pressure switches are employed for effecting the desired control.

It is known that, since a definite minimum operating gas pressure is established on gas breakers below which the breaker should not be operated, it is desirable to provide pressure operated switches to perform three functions when minimum operating pressure is reached:

(1) Energize an alarm or warning light to Warn the operator of an abnormal condition.

"ice

(2) Open the closing control circuit of the operating mechanism to prevent closing or reclosing the breaker.

(3) Open the trip circuit of the operating mechanism to prevent tripping the breaker, or, at the utility customers option, automatically trip the breaker open.

Generally, these functions are performed by separate pressure switches, but the present invention is particularly concerned with providing an improved control means for performing all three functions with only a single pressure switch. Since expensive temperature-compensated (density) pressure switches must be used on sealed gas breakers, it is very desirable to limit the number of pressure switches used. Accordingly, it is a further object of the present invention to provide an improved, simplified and dependable pressure-control circuit for a gas-type circuit interrupter in which many of the various functions for controlling the breaker may be obtained utilizing only a single pressure switch.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

MG. 1 is a diagrammatic control scheme for a gas-type circuit interrupter showing an application of the principles of the present invention, the contacts of the interrupter being illustrated in the closed latched position, and a normal pressurized condition being presumed to exist within the pressurized interrupter casing;

FIG. 2 is a side elevational view, partially in vertical section, of a single pressure switch utilizing micro-switch contact structure suitable for use in the pressure control scheme of FIG. 1;

FIG. 3 is a fragmentary schematic circuit illustrating a modification of the pressure-control circuit of FIG. 1, wherein the low pressure cutout for the closing control functions at minimum operating pressure instead of at the alarm pressure, the micro-switches of the pressure switch being adapted for differential pressure operation; and

FIG. 4 is a fragmentary schematic view of a modified type of pressure control scheme associated with the same type of gas circuit interrupter as shown in FIG. 1, again the contact structure being assumed to be in the closed latched position, and normal pressure conditions existing within the sealed interrupter casing.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a gas-type circuit interrupter. As shown, the gastype circuit interrupter 1 generally comprises contact structure 2 separable within a pressurized casing 3. Preferably, the casing 3 is filled with a suitable arc-extinguishing gas, such as sulfu-r-hexafluoride (SP gas at a suitable pressure, say 45 p.s.i.g.

Opening separating motion of the movable contact 5 toward the right, as viewed in FIG. 1, away from the relatively stationary contact 6 is effected by a rotatable drive shaft 7, connected by a linkage 8 to a movable insulating puffer cylinder 9 slidable over a fixed cylindrical insulating guide ltl affixed to the breaker casing 3 by a support 11. A relatively fixed piston 12 is provided, which cooperates with the movable operating puffer cylinder 9 to effect a compression of gas within the region 13. It will be obvious that pressure arising within the region 13 will cause an ejection of arc-extinguishing gas out through the orifice opening 14, associated with an orifice structure 15 movable with the movable contact 5 by a spider member 16. The direction of the flow of gas out through the orifice opening 14 is indicated by the arrows 17.

The casing 3 generally comprises a grounded intermediate metallic supported portion 18 and a pair of coextensive insulating

cylindrical casings

19, 20 as set forth more in detail in the aforesaid patent application. Preferably, the insulating casings 19, 2.0 are composed of a suitable Weather-proof material, such as porcelain. An

outer corrugated surface, comprising a plurality of petticoats 21, may be provided, as well known by those skilled in the art.

The relatively stationary contact 6 is electrically connected to the left-hand line terminal 22, which is preferably connected to a transmission-line connection L The movable contact 5 is electrically connected to a movable guide-rod portion 23 which is guided by stationary fingers, not shown, which are electrically connected to the righthand line-terminal 24. A transmission-line connection L may be connected, by suitable connector means, to the terminal 24, as shown.

From the foregoing description it will be apparent that in the closed-circuit position of the circuit interrupter 1, as shown in FIG. 1, the electrical circuit traversing the same comprises line connection L line-terminal 22, relatively stationary contact 6, movable contact 5, movable guide-rod portion 23, relatively stationary fingers (not shown), line-terminal 24 to line connection L To effect opening and closing relative motion of the drive shaft 7, which extends by way of a sealed connection externally of the pressurized casing structure 3, there is provided an operating mechanism, generally designated by the reference numeral 26. As shown, the operating mechanism 26 is of the pneumatic type, but it could be of the solenoid type, as well understood by those skilled in the art. As shown in PEG. 1, the externally-extending portion 7A of the drive shaft 7 has affixed thereto a crank-arm 27. Pivotally connected, as at 28, to the crankarm 27 is an operating rod 29' connected to a piston 3d at its lower end. The piston 39 moves within a pneumatic cylinder 31 by application of gas pressure, such as air under pressure, applied to its lower surface. Preferably, a source of compressed gas 32 is provided, and the admittance of this compressed gas, such as compressed air, to the region 33 below the piston 3% is controlled by an operating valve 34. The operating valve 34 has a doubleacting valve structure 35 controlled by an armature 36 energized by a closing coil 37. The closing coil 37 is connected by a circuit 38 through the norma1ly-open contacts 39 of a closing relay X. The other side of the normally-open contacts 39 of the relay X is connected, by a connection 419, to a terminal 41. The terminal 41 is connected to a positive source of voltage 42, which is located in proximate relationship to the operating mechanism 26 at the breaker 1. This is contrasted with a positive source of voltage 43, which is remotely located at the station house, which may be at a considerable distance from the circuit breaker 1. The negative points of both

voltage sources

42, 43 are connected to ground, as shown.

As shown in FIG. 1, an accelerating compression spring 45' is provided to bias the drive-shaft 7 in a circuit-opening direction. The circuit interrupter 1 is maintained in a closed position by a latching device 46. The latch 46 may be released by energizing a tripping coil 47, which energizes an armature 4s controlling a release rod 49. Thus, energizing the trip coil 47 results in releasing the latch 46, and permitting the accelerating spring 45 to drive the crank-arm 27 in a clockwise opening direction, as viewed in FIG. 1, separating the movable contact structure 5, 6 and effecting the extinction of the established are by a blast of arc-extinguishing gas out through the orifice opening 14, as indicated by the arrows 17.

In connection with the opening operation it will be observed that the region 33 below the movable piston St? is dumped to atmospheric pressure by the lower valve element 35a, which opens an exhaust opening 56. Energization of the closing coil 37 will reverse the illustrated position of the double-acting valve 35 closing the exhaust port 5t) and opening the inlet port 51 admitting thereby high-pressure gas, such as compressed air, through an inlet pipe 52 and into the region 33 below the piston 30 to drive the same upwardly to the closed position of the breaker 1. The contact structure is maintained in the closed position by the latch rod 49 moving under the latch nose 4-6 to maintain the breaker in the latched closed position.

As shown in FIG. 1, an anti-pumping relay Y is provided having a coil 53 connected in a circuit $4, which includes a low-pressure cut-off LPC. In addition, the coil 53 for the anti-pump relay Y is connected, by a connection 55, through auxiliary contacts 56 associated with the operating rod 29. The other side of the auxiliary contacts 56 is connected, by a connection 57, to a ground terminal 53. The ground terminal 5% is also connected to one side of normally-open contacts 59 of the relay Y. As shown in FIG. 1, one side of the coil 60 of the closing relay X is connected through normally-closed contacts 6.1 to a terminal 62. The terminal 62 is connected to normally-

open contacts

63, 64 of the X and Y relays. As shown, one side of the closing coil 37 is connected through normally-closed contacts 65 to a ground terminal 66. One side of the tripping coil 47 is connected through auxiliary contact 67 to a ground terminal 68, the latter being connected through normally-open contacts 69 of the closing relay X.

An important feature of the present invention is a provision of a single pressure switch, generally designated by the reference numeral 7t), for sensing the pressure P within the casing 3, and actuating a pair of single-pole single-throw micro-switches, generally designated by the

reference numerals

71 and 72. The

micro-switches

71, 72 may be of the snap-acting type well known in the art, as for example, the type shown in McGall Patent No. 1,- 960,020, issued May 22, 1934. A pair of metallic strips 73, serving as common terminals, may be actuated by plungers '74- to effect contact with normally-closed contacts 76, 7'7, or normally-open contacts '78, '79. The plungers are responsive to an operating rod 80, which, in turn, is responsive to a diaphragm 81 responsive to the pressure P within a container 32 having a pressure connection 83 with the casing structure 3, as shown.

FIG. 2 more clearly shows the general type of pressure switch re, with which the present invention is concerned. With reference to FIG. 2, it will be observed that the pressure switch 7% generally comprises a housing 85 containing a terminal block 3:: and a rotatable actuating plate 87. The actuating plate 87 rotates about a fixed axis 88, and is biased in opposition to the pressure plunger '74 by a helical coil spring 89. A spring adjustment 9%) may be provided for a fine setting of the pressure plate 87 for causing actuation of the micro-switches 71, 72 (only one being observable in FIG. 2).

This general type of pressure switch is supplied by the United Electric Controls Company of W atertown, Massachusetts, and is similar to their type M27CD. This switch is a temperature-compensated pressure switch, measuring the density, but the temperature-compensating bulb is omitted from FIG. 2 of the drawings since it forms no part of the present invention and is merely a compensating device.

With reference to FIG. 1 of the drawings, it will be noted that the first normally-open contact 79 of the microswitch 72 is connected, by a connection 91, to an alarm device 92, comprising one or more alarm elements d3, 94. The other side of the

alarm elements

93, 94 are connected to a terminal 95, which is at the potential of the positive side of the source 43.

A transfer switch 96 is provided having a pair of s ngle-pole single-

throw switch elements

97, 93 the functron of which will be more apparent from the description to be presented hereinafter.

As shown in FIG. 1, a tripping switch CST is provided connected tothe second normally-closed contacts 76 of micro-switch '71 and also to the contacts 97 of the trans fer switch 95. The tripping switch CST has its other side connected to the positive terminal 99 of the remote source of voltage 43.

A closing switch CSC is provided having one side there- .structure 3 to a hazardous value.

ansaese of connected to the positive terminal 99, and having the other side thereof connected by a connection 1% to the normally-open contacts 64 of the anti-pump relay Y and to the auxiliary contacts 161 associated with the operating rod 29 of the operating mechanism 26.

The opening operation of the circuit interrupter 1 will now be described. With the transfer switch 96 in the open position, as shown, tripping of the breaker may be effected by closing the tripping switch CST. This will energize the tripping coil 47 through the second normallyclosed contacts 76 of micro-switch 71. and through the closed auxiliary contacts 67 of the operating mechanism 26. The energization of the tripping coils 47 will cause releasing movement of the latch rod 49 to permit the accelerating spring 45 to move the crank-arm 2 7 in a clockwise direction to effect thereby opening of the breaker in the manner previously described. The region 33 within the pneumatic cylinder 31 will be exhausted at this time, and will, consequently, offer no opposition to the opening movement of piston 30.

To effect the closing operation of the interrupter, it is merely necessary to press the closing button CSC. This will energize the closing relay X through the now normally-closed contacts 101, through the low-pressure cutout contacts LPC, through the normally-closed contacts 61 of relay Y and the first normally-closed contacts 77 of micro-switch 72 to the negative side of source 43. The closing of the closing relay X will eifect closing of the contacts 39 thereof and this will energize the closing coil 37 of the double-valve device 35. Opening of the inlet port 51 and closing of the exhaust port 50 will pressurize the region 33 below piston 30 and effect upward driving movement thereof which will correspondingly effect counterclockwise rotation of the crank-arm 27 and closing of the circuit interrupter 1. The latching device 46 will latch the breaker in the closed position, as shown in FIG. 1 of the drawings.

It will be apparent that if the pressure conditions P within the casing structure 3 drop to a dangerous or hazardous value, then the pressure connection 83 of the pressure switch 70 will reflect this low pressure value and cause lowering of the actuating plunger 74 of

microswitches

71, 72 to effect closing of the second and first normally

open contacts

78, 79 respectively, and opening of the companion second and

first contacts

76, 77 respectively. This will prevent energization of the closing relay X and will sound the alarm device 92. In addition, the opening of the contact 76 of micro-switch 71 will open the tripping circuit to the tripping coil 4-7 by Way of the tripping button CST, so that it will be impossible for a Serviceman to close the tripping button CST and thereby energize the tripping coil 47 to trip the breaker open, if it has previously been closed.

For certain applications it may be desirable to trip the breaker open when the pressure P decreases in the casing To perform this function, the transfer switch 96 may be closed. Assuming that the transfer switch 96 is closed, the closure of second normally-open contact 78 of micro-"switch 71 upon a lowering pressure P will energize the tripping coil 47 through the now closed contacts 98 of the transfer switch 96. As a result, automatic tripping of the breaker 1 will ensue upon such a lowering of the pressure P. The customer then will have this option by closing the transfer switch 96 or leaving it open according to his desires.

From the foregoing it will be apparent that all three of the functions, namely energizing the alarm circuit, opening the closing control circuit and opening the tripping circuit would normally take place at the same pressure. However, the supplier for this type of switch ,states that it is possible to provide independent pressure control for each single-pole single-throw switch without increasing the cost. Using such an arrangement,

namely having micro-switch 72 operate prior to microswitch 71, this will enable the alarm circuit to function,

say at 5 p.s.i. above the minimum operating pressure for tripping, which would probably be desirable to most customers.

Again using the differential pressure setting between the micro-switches 7'1, 72 and assuming that customers insist on low-pressure cutout for the closing control functioning at minimum operating pressure, instead of at the alarm pressure, this may be accomplished by adding an inexpensive protective relay 102 instead of providing another expensive pressure switch. Such an arrangement is illustrated in FIG. 3 of the drawings, which is to be considered in conjunction with FIG. 1 thereof. Here again, the micro-switch 72 is set to function at substantially 5 p.s.i. above the operation of micro-switch 71. Upon a lowering of pressure P, the micro-switch 72 will operate first. This will operate the alarm devices 92 upon closure of the contact 79 of micro-switch 72. At a 5 psi. lower pressure than occurred to effect operation of the micro-switch 72, the micro-switch 71 will function to energize the coil 108 of protective relay 102 and effect closure of the contacts 109 and opening of the normally-closed contacts 110, 111. Thus, the closing of the normally-open contacts 79 of micro-switch 72 at the higher pressure will result in immediate actuation of the alarm circuits including

alarm elements

93, 94. This will give the station attendant warning that a lowering of pressure within the interrupting unit 1 is present.

At 5 pounds per square inch lower pressure than the pressure condition which caused micro-switch 72 to function, micro-switch '71 will close the contacts 78 thereof resulting in energization of the auxiliary relay 102. This will do two things. First, it will open up the closing circuit to the X relay. Secondly, it will open up the tripping circuit to the trip coil 47.

If the utility customer desires an automatic tripping of the circuit interrupter 1 at the lower pressure setting which caused micro-switch 71 to operate, the transfer switch 96A may be closed and this will result in tripping the tripping device 47. More specifically, the automatic tripping circuit for the tripping solenoid 47 comprises ground terminal 68, auxiliary contacts 67 of mechanism 26, tripping coil 47, terminal 166, contacts1tl9 of Z relay (which are now closed) closed contacts 98 of trans-fer switch 96A, to positive terminal 95. Thus, an automatic tripping of the circuit breaker 1 will take place at the lower pressure. As mentioned, the conditions set up in FIG. 3 are for the purpose of enabling a utility customer to open up the closing circuit only at the lower pressure and not at the higher pressure, as was the condition which existed in the FIG. 1 control diagram.

It will be noted that in FIG. 1, with the transfer switch 96 closed the normally open contact 78 of micro-switch '71, when closed by low-pressure conditions would have to carry the current suffieient to energize the tripping coil 47. This current is appreciable. In case the

contacts

73, 78 of microswitch 7 1 of the pressure switch of FIG. 1 are not capable of having capacity to close the tripping circuit to the tripping coil 47 an auxiliary protective relay 86, as shown in FIG. 4 may be employed.

With reference to FIG. 4, it will be noted that the pressure-control circuit is in many respects similar to that of FIG. 1. However, upon a drop of pressure within the casing 3 of the circuit interrupter .1, this drop of pressure will be reflected .Within a container 81 to cause a closing of the contacts 73, 117. This will energize the coil 118 of the SG protective relay. The closing circuit for the coil 118 of the SG relay includes connection 119 to the negative terminal 58 and through connection 126 to the positive terminal 41. Closure of the SG relay will effect closing of the contacts 121 and 122 with a consequent opening of the contacts 123. With the transfer switch 963 in the open position, as shown in FIG. 4, closing of the SG relay upon a drop of pressure will open up the tripping circuit 124 to the tripping switch CST. This will prevent tripping the breaker open upon such a drop of pressure.

Actuation of the pressure switch 125 causing separation of the contacts '73, 126 will open up the closing circuit 127 to the X relay, preventing thereby closing of the breaker 1 upon a drop of pressure.

Should it be desired toeffect an automatic tripping of the breaker it open in the event of a drop of pressure, then the transfer switch 963 will be closed. In such an eventuality, it will be noted that closing of the contacts 73, 117 of the pressure switch 125 upon a drop of pressure will energize the coil 47 of the latch release 48 to effect opening of the breaker 1 by a circuit which includes connection 127, contacts 122 of S6 relay (now closed) contacts 128 of transfer switch 963 and COEI1C tion 12%) to the positive terminal 4 1.

From the foregoing, it will be apparent that there has been provided an improved pressure control circuit for controlling the proper operation of the breaker 1 by utilization of only a

single pressure switch

70, 125 for obtaining many control functions. The three functions enumerated above, namely energizing an alarm circuit, opening the closing control circuit of the operating mechanism, and opening the tripping circuit, or automatically tripping the breaker open, has been provided by a single pressure switch. There results considerable simplification and cost saving. In addition, by minimizing the number of parts employed, the number of component parts which may individually cause trouble has been diminished.

Although there has been illustrated and described specific structures and control circuits therefor, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art Without departing from the spirit and scope of the invention.

I claim as my invention:

1. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas Within said casing and having independent dual contact structure actuated thereby, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, said independent dual contact structure associated with said single pressure switch having normally closed contacts in series with the circuit for said closing relay under normal pressurized condition of said casing, said independent dual contact structure in ad dition having normally closed contacts in series with said tripping coil, said pressure switch functioning to open both said pairs of normally-closed contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said independent dual normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter.

2. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas within said casing and having independent dual contact structure actuated thereby, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, said independent dual contact structure associated with said single pressure switch having first normally closed contacts in series with the circuit for said closing relay under normal pressurized condition of said casing, said independent dual contact structure in addition having second normally closed contacts in series with said tripping coil, an alarm circuit including an alarm element, normally open contacts associated with said first normally-closed contact structure for sounding an alarm upon drop of pressure within said casing, aid pressure switch functioning to open both first and second normallyclosed contacts and close said normally open contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter and also actuate said alarm element.

3. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas within said casing and having independent dual contact structure actuated thereby, said dual contact structure including two pairs of first and second normallyclosed contacts actuated at different pressure settings of the pressure switch, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, the first normally closed contacts opened at the higher pressure setting upon dropping pressure being in series with the circuit for said closing relay, the other second normally closed pair of contacts opened at the lower pressure setting upon dropping pressure being in series with said tripping coil, said pressure switch functioning to open both first and second normally closed contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will first open said first normally-closed contacts in series with the closing relay to prevent closing and upon a further drop of pressure the other second pair of contacts will open to prevent tripping of the gas-type circuit interrupter.

4. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas within said casing and having independent dual contact structure actuated thereby, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, said independent dual contact structure associated with said single pressure switch having first normally closed contacts in series with the circuit for said closing relay under normal pressurized condition of said casing, said dual contact structure in addition having second normally closed contacts in series with said tripping coil, an alarm circuit including an alarm element, normally open contacts associated with said first normallyclosed contact structure for sounding an alarm upon drop of pressure within said casing, said pressure switch functioning to open both first and second normally-closed contacts and close said normally open contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said first and second normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter, and said normally open contacts of the pressure switch closing at a higher differential pressure setting than said second normally closed contacts associated with the tripping circuit.

5. The combination in a gas-type circuit interrupter of a housing containing an arc-extinguishing gas under pressure, a movable contact separable from a relatively stationary contact to establish an arc within said gas under pressure, a single pressure switch having a sensing gas connection with said housing for sensing the pressure conditions therein, the pressure switch having an independent pair of single-pole double-throw micro-switches actuated thereby, an operating mechanism for operating the movable contact including a closing coil and a tripping coil, a closing relay for energizing said closing coil, a first normally closed contact of one of the micro-switches being in series with said closing relay, a second normally closed contact of the other micro-switch being in series with the circuit of the tripping coil, said pressure switch functionin g to open both said pairs of normally-closed contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter.

6. The combination in a gas-type circuit interrupter of a housing containing an arc-extinguishing gas under pressure, a movable contact separable from a relatively stationary contact to establish an are within said gas under pressure, a single pressure switch having a sensing gas connection with said housing for sensing the pressure conditions therein, the pressure switch having an independent pair of single-pole double-throw micro-switches actuated thereby, an operating mechanism for operating the movable contact including a closing coil and a tripping coil, a closing relay for energizing said closing coil, 21 first normally closed contact of one of the micro-switches being in series with said closing relay, a second normally closed contact of the other micro-switch being in series with the circuit of the tripping coil, said pressure switch functioning to open both said pairs of normally-closed contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter, means providing an alarm circuit, and a normally open contact associated with the first normally-closed contact of the first said micro-switch being in series with said alarm circuit for sounding an alarm upon a drop of housing pressure.

7. The combination in a gas-type circuit interrupter of a housing containing an arc-extinguishing gas under pressure, a movable contact separable from a relatively stationary contact to establish an are within said gas under pressure, a single pressure switch having a sensing gas con nection with said housing for sensing the pressure conditions therein, the pressure switch having an independent pair of single-pole double-throw micro-switches actuated thereby, an operating mechanism for operating the movable contact including a closing coil and a tripping coil, a closing relay for energizing said closing coil, a first normally closed contact of one of the micro-switches being in series with said closing relay, a second normally closed contact of the other micro-switch being in series with the circuit of the tripping coil, said pressure switch functioning to open both said pairs of normally-closed contacts upon a hazardous drop of pressure, whereby a drop of pressure within said casing to a dangerous state will open said first and second normally closed contacts to prevent closing and tripping of the gas-type circuit interrupter, means providing an alarm circuit, a normally open contact associated with the first normally-closed contact of the first said micro-switch being in series with said alarm circuit for sounding an alarm upon a drop of housing pressure, and means for actuating the two micro-switches at different pressure settings.

8. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas within said casing and having contact structure actuated thereby, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, said contact structure associated with said single pressure switch having first and second independent normally open contacts, a protective relay energized by closure of said second normally open contacts, said protective relay when deenergized having normally closed contacts in series with said closing coil, an alarm circuit connected in series with said first pair of normally open contacts, said pressure switch functioning to close both pairs of normally-open contacts upon a hazardous drop of pressure, the first and second pair of normally open contacts having different pressure responses, whereby the alarm circuit will be energized prior to an opening of the closing circuit upon dropping pressure.

9. A gas-type circuit interrupter including a casing filled with an arc-extinguishing gas, a pair of separable contacts disposed within said casing in the ambient of said enclosed gas, the interrupting integrity of the gas-type circuit interrupter being dependent upon the pressure of said enclosed gas, a single pressure switch responsive to the pressure of the gas within said casing and having contact structure actuated thereby, an operating mechanism for operating said separable contacts, circuit means for said operating mechanism including a closing coil and a tripping coil, a closing relay for energizing said closing coil, said contact structure associated with said single pressure switch having normally closed contacts in series with the circuit for said closing relay under normal pressurized condition of said casing, said contact structure in addition having normally open contacts, a protective relay for energizing said tripping coil, said normally open contacts being connected to energize said protective relay, said pressure switch functioning to open the normally-closed contacts and to close the normally-open contacts upon a hazardous drop of pressure, whereby actuation of the pressure switch upon a drop of easing pressure will open the circuit to the closing coil and energize the protective relay to trip the circuit interrupter open.

References Cited by the Examiner UNITED STATES PATENTS 2,766,404 10/56 Ashenden 31722 2,911,492 11/59 Beatty 200-148 X 2,937,320 5/60 Easley 3 l722 SAMUEL BERNSTEIN, Primary Examiner.

Claims

1. A GAS-TYPE CIRCUIT INTERRUPTER INCLUDING A CASING FILLED WITH AN ARC-EXTINGUISHING GAS, A PAIR OF SEPARABLE CONTACTS DISPOSED WITHIN SAID CASING IN THE AMBIENT OF SAID ENCLOSED GAS, THE INTERRUPTING INTEGRITY OF THE GAS-TYPE CIRCUIT INTERRUPTER BEING DEPENDENT UPON THE PRESSURE OF SAID ENCLOSED GAS, A SINGLE PRESSURE SWITCH RESPONSIVE TO THE PRESSURE OF THE GAS WITHIN SAID CASING AND HAVING INDEPENDENT DUAL CONTACT STRUCTURE ACTUATED THEREBY, AN OPERATING MECHANISM FOR OPERATING SAID SEPARABLE CONTACTS, CIRCUIT MEANS FOR SAID OPERATING MECHANISM INCLUDING A CLOSING COIL AND A TRIPPING COIL, A CLOSING RELAY FOR ENERGIZING SAID CLOSING COIL, SAID INDEPENDENT DUAL CONTACT STRUCTURE ASSOCIATED WITH SAID SINGLE PRESSURE SWITCH HAVING NORMALLY CLOSED CONTACTS IN SERIES WITH THE CIRCUIT FOR SAID CLOSING RELAY UNDER NORMAL PRESSURIZED CONDITION OF SAID CASING, SAID INDEPENDENT DUAL CONTACT STRUCTURE IN ADDITION HAVING NORMALLY CLOSED CONTACTS IN SERIES WITH SAID TRIPPING COIL, SAID PRESSURE SWITCH FUNCTIONING TO OPEN BOTH SAID PAIRS OF NORMALLY-CLOSED CONTACTS UPON A HAZARDOUS DROP OF PRESSURE, WHEREBY A DROP OF PRESSURE WITHIN SAID CASING TO A DANGEROUS STATE WILL OPEN SAID INDEPENDENT DUAL NORMALLY CLOSED CONTACTS TO PREVENT CLOSING AND TRIPPING OF THE GAS-TYPE CIRCUIT INTERRUPTER.