US2255496A - Control system for circuit breakers - Google Patents

Description

Sept. 9, 1941. B. w. wYMAN CONTROL SYSTEM FOR CIRCUIT BREAKERS Filed Dec. 22, 1959 Y ITM/enter. Bryce W. Wyman, b 1 5i/Waff@ y I-'Is Attorney.

Patented Sept. '9, 1941 CONTROL SYSTEM FOR CIRCUIT BREAKERS Bryce W. Wyman, Upper Darby, Pa., assigner to General Electric Company, a corporation of New York Application December 22, 1939, Serial No. 310,599

(Cl. 17E-375) 7 Claims.

My invention relates to a control system for an electric circuit breaker and more specifically to a control system for a fluid-operated circuit breaker.

Electric circuit breakers have gone through circuit breaker lies in its ability to interrupt a,

circuit at the proper time and in the proper manner. Similarly, the value of a control apparatus lies in'its ability to effect control of the circuit breaker in the manner intended. A great num-l ber of undesirable conditions may occur as a consequence of the control system or apparatus not effecting the desired regulation. I

My control system will be described hereinafter as applied to a new type of circuit breaker of the cross air-blast type which is disclosed and claimed in the joint application of David C. Prince, Williamr K. Rankin, and Wilfred F. Skeats, Serial No. 303,126, filed November 6, 1939, and assigned to the same assignee as the present application. It will be understood, however, that this control system is also applicable to other types of circuit-interrupting apparatus, for example, circuit breakers in which a blast of uid, such as oil, is used to extinguish the arc between the contacts, or in which the contacts are merely separated in oil.

Accordingly, itis an object of my invention to provide a new and improved control system for electric circuit breakers of the fluid-operated type.'

It is another object of my invention to provide a new and improved combined electric and fluid control system for operating an electric circuit breaker.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features ofnovelty which characterize my inventionwill be pointed out with particularity in the claims'annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing, the single ngure of which is a schematic diagram of the control system for an electric circuit breaker embodying my invention..

Referring now to the drawing, I have illustrated my invention as applied to a gas-blast circuit breaker !0 of the cross blast type comprising a stationary contact II and a movable contact i2 arranged to be operated so' as to draw an arc in an arc chute I3. The xed contact II is connected to the line terminal I4 while the movable contact I2 is connected to the line terminal I5. VFixed contact Il is provided with spring pressed contact fingers IIa and longer arcing contact fingers II' while movable contact I 2 is provided with an arcing tip I2' so that, when the contacts separate, an arc therebetween occurs between arcing tips II and I2. Immediately after separation of the contacts, one terminal of the arc is transferred by an air blast through conduit I6 from contact fingers I I' to the contact I I" which is provided with a tip of arc-resistant metal. The air blast from conduit I6 upon opening of the breaker drives the arc into the arc chute I3 against the edges of a plurality lof partitions I1 in the arc chute, which partitions are transverse to the arc gap and the ends of which extend close to the path of movement of the arcing tip I2' of the movable contact I2. The circuit breaker I0 illustrated by way of example in order to describe my control system is not my invention; but is'described and claimed in copending application Serial No. 303,126 referred to above.

In order to operate circuit breaker I 0 automatically by iiuid pressure, I provide a cylinder I8 with a piston I9 connected through a rod 20 to operate a lever 2| secured to the shaft 22. The shaft 22 has attached thereto an arm 23 of insulating material for operating the movable contact I2 of the circuit breaker. Although circuit breaker IIl is described with respect to a single phase, it will, of course, be understood'by those skilled in the art that it may just as well comprise a plurality'of phases, in which case, a plurality of arms 2 3 would be provided for operating the movable contacts I2 of the various phases. The arm 23 is shown provided with a pin 24 operating the member 25 secured to the outer end of movable contact I2. Member 25 is arranged to slide on a pair of rods 26, only one of which is shown in the drawing since the other is obscured from view thereby. It will be apparent that, when the shaft 22 is rotated in a counterclockwise direction, the arm 23 will move the contact I2 to the open position of circuit breaker III and that, when the shaft 22 is rotated in a clockwise direction, the arm 23 will move the contact I2 to the closed position. The member 25 and the rods -26 constitute a kind of crosshead arrangement by which the movable contact is reciprocated.4 The lever 2| mounted on shaftl 22 has an extension 21 only partially shown'which operates the mechanism for controlling the air-blast. valve (not shown) so as to supply a blast of air through Vconduit I6 during the opening and closing operations of the circuit breaker I0. This arrangement is disclosed and claimed in the joint application of Leonard J. Linde and Torild Andersen, Serial No. 310,602, filed December 22, 1939, and assigned to the same assignee as the present application.

In addition to controlling the air-blast valve .in response to certain operating positions of the circuit breaker I3, it is usually necessary to control certain other parts of the system or apparatus in accordance with the breaker position, and, therefore, I provide another lever 28 rigidly attached to shaft 22 for operating by means of operating rod 23 a plurality of switches which will be hereinafter described.

Control of the operation of circuit breaker I3 by fluid-pressure means operating upon piston I9 is obtained through solenoid-operated valve 38 including a two-way valve 3| adapted to interconnect one or the other end of cylinder I8 with a reserve duid-pressure tank 32. Reserve tank 32 is connected to a duid-pressure supply system through a nonreturn valve, not shown, so as to trap sui'iicient fluid, which, for example, may be air, ata suitable pressure to permit at least one operating cycle independent of the main supply. Therefore, if the main air supply should fail for any reason, one operating cycle of circuit breaker I may still be obtained by virtue of the air or other iiuid trapped in reserve tank 32. Reserve tank 32 is provided with a. pressure relay indicated schematically at 34 as comprising a Sylphon bellows 35 connected to reserve tank 32 and operatively connected to a suitable switch 36 cooperating with a plurality of contacts, which will be hereinafter described in greater detail.

'f operated. Seal-in switching means 55 comprises Valve 3| is schematically illustrated as comprising a cylinder 31 including a plurality of annular chambers 38, 33, and 48. Movably mounted within cylinder 31A is valve member 4I provided with an annular groove 42 adapted to connect either annular chamber 33 or 40 with annular chamber 33 when moved to a double-throw bridging member 56 operatively,

connected to the armature 43 of solenoid 46 by means of rod 51, and a plurality of cooperating contacts 58 and 53. In order to obtain proper wiping action of bridging member 56 and cooperating contacts 58 and 53, as well as to cause closure of one of the seal-in switches before operation of valve 3| a pair of springs 60 and ,6i are provided. A manual lever or handle 62 is also operatively connected to the armature 43 of solenoid 46 and also to valve member 4I of valve 3| so that manual operation of the circuit breaker may be obtained in an emergency without using the electrical circuit which will be hereinafter described.

In order to electrically operate solenoid controlled valve 3| and also to control certain other features of my control system, I provide a source of direct-current potential 63. This -source of potential 63 is connected to the solenoid-tripping coil 41 for tripping circuit breaker I3 through a manually operable trip button 64, limit switch 65 operatively connected tot e circuit breaker III vthrough rod 23, and contacts 6 cooperating with switch member 36 of pressure relay 34. A resistance 66' of such magnitude as to allow sufcient current to iiow to enable coils 41 and 48 of solenoid 46 to hold valve 3| in one of its operating positions but not suicient to operate the valve is connected across contacts 66. Connected in parallel with manually operated "trip button 64 is a switch 61 adapted to be operated by a protective relay (not shown) so as to trip circuit breaker I8 upon the occurrence of abnormal current conditions on the power line connected to line terminals I4 and I5. Also connected in parallel through another circuit with manually operable trip" button 64 are seal-in contacts 53 and bridging member 56 by means of which tripping coil 41 of solenoid 46 may remain energized even after the operator releases trip either the left or right, respectively. If movable buttcn 54. Closing con 4g of solenoid 43 is conmember 4I of valve 3I`is movedto the left, a path for the air or fluid from reserve tank 32 to the left side of piston I3 in cylinder I8 is provided through conduit 43, annular chambers 33, 42, and 38, and conduit 44. Such an operating position of the valve would cause piston I3 to move to the right for opening circuit breaker I0.' If valve member 4I is moved to the right, air or uid from reserve tank 32 may pass through con' duit 43, annular chambers 33, 42, and 48, and conduit 45 vinto the right-hand end of cylinder I8 against the right-hand end of piston I3 so as to close circuit breaker I0. Valve 3| is provided with a solenoid 46 having a tripping coil 41, a closing coil 48, and an armature 43. Armature 43 is operatively connected to valve member 4I through rod 58. In order to tend to maintain armature 43 of solenoid 46 and valve member 4| of valve 3l in the intermediate or neutral position, means comprising springs 5I are provided. In order that valve member 4I assumes a proper position so that annular chamber 42 thereof may register properly with annular chambers 38 and 33 or 33 and 43, solenoid 46 is provided with P016 pieces 52 having CODE-Shaped 75 310,602, referred to above is ready for providing So as to prevent pumping or repeated re closing operations of circuit breaker I 8 when it is closed on a short circuit or other abnormal 'current condition in the power line and the operator fails to release close button 68, relay 69 is provided, as mentioned above, including contacts 63a and 63h and winding 63. Contacts 63a are normally closed when circuit breaker I8 is in the open position. However, when circuit breaker I3 has'l-'reached a predeterminedfposition in the 'latter part ofthe closing stroke at which opening of the breaker may be eectively made, that is, when the blastv valve control mechanism disclosed in copending application, Serial No.

an opening blast of air, its lever. 28 and operating arm 29 move lever 10 pivoted at 1| which strikes articulated lever 12 pivoted at 13 which,

in turn, mechanically causes relay 69 to operate .so as to open contacts 69a and close contacts circuit 63 through close button 66, the ,winding of relay 69, and contacts 69h, whereby contacts 69a remain in their open position even though levers 1D and 12 would allow relay 69 under the inuence of; its biasing spring to assume the position which it would normally take when circuit breaker Hl is in the open position.

It is desirable that the operator may see at a glance the condition of the circuit breaker I6 and associated control`system. Accordingly, I provide limit switch 14 of the double-throw type which is adapted to'close the circuit through signal means 15 or 16, depending upon the operating position of circuit breakerl. For example, signal means 15 may be a green light for indicating that the circuit breaker IU is in the open position while signal means 16 may be a red light for indicating that the circuit breaker is in the closed position. Single-pole singlethrow limit switch 65 is provided in order to eii'ect a positive cut ofi of the tripping circuit at a predetermined point in the opening stroke of circuit breaker Ill. A plurality of signal means 11 and 18 may also be provided to indicate the pressure conditions in reserve tank 32 and one or the other of these signal means may be energized by switch 36 operated through pressure relay 34 and cooperating with contacts 66 or 19. For example, when the pressure in reserve tank 32 is sufiiciently high, Sylphon bellows 35 will cause switch 36 to bridge contacts 66, thereby energizing signal 16 which may, for example, be a green light. Resistance 66 will not allow sufilcient current to iiow through signal means 16 when contacts 66 are opened to operate the signal. If, however, the pressure in tank 32 falls below a predetermined minimum,

Sylphon bellows 35 will contract, allowing switch 36 to bridge contacts 19, thereby closing an electrical circuit through signal means 11 which may, for example, take the form of a red light.

The operation of my control system for a fluidpressure operated circuit breaker will be described first with reference to the closed position of circuit breaker I as shown in the drawing and also with the trip and close buttons 64 and 68, respectively, in the released positions and with the pressure in reserve tank, 32 sufilciently high so that switch 36 associated with pressure relay 34 bridges contacts 66, thereby energizing green light 16 which informs the operator that the huid-pressure is adequate. Since the breaker is in the closed position, limit switch 14 is moved to the right so as to energize red light 16 and so informing the operator. Valve 3| and solenoid 46 have their respective parts, namely valve member 4| and armature 49, in their intermediate or neutral positions by virtue of spring means Hence, the fluid under pressure in tank32 is not in communication with cylinder I6. If it should be desired to 46 moves to the left.

46, limit switch 65, and relay pressure switch 34-36, whereupon the armature 49 of solenoid This movement causes seal-in contacts 56 to be engaged by switch 56 'prior to the opening of valve 3| to transfer control away from` the operator. Valve member 4| moves tol the left and, by virtue of the valvepositioning function of cone-shaped cooperating members 53 and 54 of .solenoid 46, annular chamber 39 is connected with annular chamber -36 by means of annular chamber 42 provided in valve member 4|. This connects the iluid or air in reserve tank 32 with the left-hand end of cylinder |6 through conduits 43 and 44, respectively, causing piston I9 to move circuit breaker I6 to the open position. Fluid or air in the righthand end of cylinder I8 is exhausted to atmosphere through conduit 45 via the exposed bore in valve cylinder 31. During this movement, lever 21, only partially shown, causes operation of an air-blast valve, not shown, so as to supply a blast of air through conduit I6 transversally of the arc drawn between movable contact i2 and stationary contact H for extinguishing such arc. At the same time, lever 28 causes limit switch 65 to be opened, effecting a positive cut off of the tripping circuit through tripping coil 41. Limit switch 14 also moves to the left, deenergizing red light 16 and energizing green light 15. Operating levers 10 and 12 are moved by rod 29 so as to allow relay 69 to move to the left, under the influence of a suitable biasing spring, opening contacts 69h and closing contacts 69a. As soon as limit switch 65 has opened deenergizing the tripping circuit, spring means 5| will cause valve member 4I of valve 3|, armature 39 of solenoid 46, and switch member 56 of seal-in switch 55 to assume their intermediate or neutral positions. The same operating cycle described above would occur if protective relay switch 61 had been operated to the closed position because of an abnormal current condition in the power lines interconnected by circuit breaker I0. Similarly, the same operating cycle could be obtained if the operator had manually grasped handle 62 and pulled it to the left, in which case, the electrical circuit would not be used.

Assuming now that the circuit breaker is in the open position after the tripping cycle just described, closing operation of the breaker may be obtained if the operator depresses close button 66, whereby closing coil 46 of solenoid 46 is energized through contacts 69a of relay 69 and pressure relay switch 34--36. This causes armature 49 of solenoid 46 to move to the right carryingwith it bridging member 56 which cooperates with seal-in contacts 59, taking control away from the operator. Further movement of armature 49 to the right so that cone-shaped member 54 engages with cooperating member '53 of pole piece 52 causes valve member 4| to assume a position interconnecting lconduits 43 and 45, whereby piston i9 is moved to the left forcing movable member I2 to the closed circuit position.y Levers 10 and 12 are rotated so as to mechanically move relay 69 to the right, opening contacts 69a and closing contacts 69h. The opening of contacts 69a breaks the circuit through closing coil 48. However, in the event the operator fails to release close button 66, relay 69 is sealed in through contacts 69h by virtue of winding 66 so as to prevent pumptive relay should cause it to trip. Deenergization of closing coil 48 of solenoid 46 allows spring l to cause armature 49 and valve member 4I to assume an intermediate or neutral position. The closing movement oi' circuit breaker i0 closes switch 65 relatively early during the stroke of movable contact l2 so that the control circuit is completed for a tripping operation. It will be understood that, if the pressure in reverse tank 32 should drop so that the circuit through contacts 66 is opened, the trip and close circuits for the breaker are broken. However, at the discretion of the operator, the breaker may'still be operated if suiilcient pressure remains by moving operating handle 62 to the right or to the left, depending upon the particular operation desired. Since the reserve air tank 32 is relatively small, a pressure drop occurs during each operation of the circuit breaker I0. In order to be sure that pressure relay 34 will not, during the operating cycle of the circuit breaker, open the circuit to solenoid.

sistance 68' will allow sufficient current to flow to hold the valve member 4| in position even though contacts 66 open. However, resistance B6 will not allow suilicient current to ow to` operate valve member 4| initially.

Trip-free response of the circuit breaker in my control system is rendered safe in being accompanied' by an eiective air blast through the instantaneous functioning .at the proper moment of mechanically opened contacts 69a of relay 69. As has been set forth above, contacts G9a are not opened until a predetermined position in the latter part of the closing stroke of circuit breaker Il is reached, at which time, the blast valve control mechanism is ready to provide an opening blast of air. Atv this instant, switch 65 has already closed to complete a tripping circuit. In the event that contacts 61 of abnormal current relay, not' shown, are closed, tripping coil 41 of solenoid 48 is energized even though closed coil 48 is still energized, contacts 69u -.having not yet opened. Nevertheless, the lowered reluctance of closing coil 48 of solenoid 46, in view of the energization of tripping coil 41, enables it to resist the counter-attracpion of tripping coil 41 until cut-oil of closing coil 48 occurs through relay contact 69a, deenergizing closing coil 4I. Thus, all the elements for tripfree operation are prepared in advance so that ,the opening of contact 69a alone governs the earliest safe instant at which the movable contact l2 may reverse itself to open the circuit breaker during a trip-free operation.

While I have shown and described a particular embodimentof my invention as applied to a control system for an electric circuit breaker schematically shown, it will be obvious to those skilled in the art that various changes and modications may be made without departing from my'invention in its broader aspects and I, therefore, aim in the appended claims to cover all such changes and modiilcations as i'all within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of vthe United Statesis: l.

l. In a control system for a Enid-operated cir- 'cuit breaker, operating means for said circuit breaker including a valve arranged to be supplied with uid under pressure' for controlling the opening and closing movements of said circuit breaker, a solenoid having its armature connected to operate said valve, means normally tending to hold said valve and armature in a neutral or intermediate position, an electric circuit for selectively energizing said solenoid to operate said valve including a trip and close button, and means mechanically operated by closure of said circuit breaker for preventing repeated closing operations of said circuit breaker when the operator does not release the close button in the event that said circuit breaker fails to remain closed.

2. In an electropneumatic control system for a circuit breaker, the combination of pneumatic means for operating said circuit breaker including an air storage tank for trapping suilicient air for one operating cycle of said breaker, a valve arranged to interconnect said pneumatic means and said storage tank to obtain closing and tripping operations of said circuit breaker, solenoid means including closing and tripping coils and an armature operatively connected to said valve, an electric circuit for selectively energizing said closing and tripping coils, spring means` normally tending to hold said valve and solenoid in the neutral position, and a relay mechanicallyoperated in one direction by said breaker including a winding associated with said electric circuit for preventing repeated closure operations of said breaker in the event the circuit breaker is closed on a short-circuit current condition.

3. A control system including a circuit breaker, a valve arranged to be supplied with gas under pressure for operating said circuit breaker, an actuating means associated. with said valve including a solenoid having its armature connected to said valve, said solenoid including tripping and closing coils, an electric circuit including manually operable means associated with said tripping and closing coils for remotely controlling said valve to control-said circuit breaker, means responsive to the pressure of the gas supply determining the control of said manually operable means over said actuating means, a sealin switchoperatively connected to said solenoid armature for taking control away from said manually operable means, and a switch mechanically operated by movement of said circuit breaker including a winding connected in said electric circuit for preventing pumping of said circuit breaker when closed on an abnormal current condition.

4. A control system including aI circuit breaker, a valve arranged to be supplied with gas under pressure for controlling said circuit breaker, an actuating means associated with said valve including a solenoid having its armature connected to said valve, said solenoid including tripping and closing coils, an-electric circuit including manually operable means associated with said tripping and closing coils for remotely con'- trolling said valve to control said circuit breaker, means responsive to the pressure of the gas supply determining the control of said manually operable means over said actuating means, and means for preventing said means responsive to the pressure of the gas supply from interfering after an operation oi said circuit breaker has begun.

5. In a control system for a circuit breaker of the duid-operated type, a valve arranged to be supplied with fluid under pressure for controlling said circuit breaker, an actuating means associated with said valve including a solenoid having its amature connected to said valve, said solenoid including tripping and )closing coils, an

electric circuit including manually operable means Aassociated with said tripping and'c1osl ing coils for controlling said valve, means responsive to the uid pressure supply for maintaining said manually operable means ineffective in the event said iluid pressure falls below a predetermined value, and means for maintaining said means responsive to said duid pressure supply inefl'ective after an operation of said circuit breaker has begun.

6. In a control system for a circuit breaker of the duid-operated type, a valve arranged to be supplied with gas under pressure for controlling said circuit breaker, an actuating means associated with said valve including a solenoid having its armature connected to said valve, said solenoid including tripping and closing coils, an electric circuit including manually operable means associated with said tripping and closing coils for controlling said valve, a pressure relay including a plurality of'contacts i'or preventing the operation of said circuit breaker when said gas under pressure for operating said circuit breaker falls below a predetermined value, and a resistance connected across said contacts so that the operation of said circuit breaker may be completed once it has started even through the pressure of said gas falls below said predetermined value during said operation.V

7. In a control system for a fluid-operated circuit breaker, uid-operated means for causing opening and closing movements of said circuit breaker, a solenoid operatively connected to a valve for controlling said last-mentioned means, an electric circuit for selectively energizing said solenoid including manually operable tripping and closing means, and means mechanically operated by closure of said circuit breaker for preventing pumping thereof when said manually operable closing means is held in its controlling position after closure oi' said circuit breaker which fails to remain closed.

BRYCE W. WYMAN. n

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