US1796817A - Automatic reclosing circuit-breaker system - Google Patents

Description

March 17, 1931. w WALTY AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed April 11, 1927 2 Sheets-Sheet 1 Ab E53 a 2 C Z .6 6 6 4 m 1 a J L d J a 7 f 1 1 Z W .Mw 2 A fl yw re w q m 4 a 5 T1 7% KZU W, H K v T C 1 Aw Z March 17, 1931. w, w T 1,796,817

AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed April 11, 1927 2 Sheets-Sheet 2 Patented Mar. 17, 1931 UNITED STATES PATENT OFFICE WERNER WALTY, OF ENNETBADEN, SWITZERLAND, ASSIGNOR TO AKTIENGESELL- SCHAFT BROWN IBOVERI 80 CIE., 0F BADEN, SWITZERLAND, A JOINT-STOCK COM- PANY OF SWITZERLAND AUTOMATIC RECLOSING CIRCUIT-BREAKER SYSTEM Application filed April 11, 1927, Serial No. 182,674, and in Germany April 26, 1926.

This invention relates to automatic reclosing circuit-breaker systems, and it has particular relation to systems wherein circuit breakers that have been tripped are reclosed if the fault that caused the tripping disappears.

Among the objects of the invention is an improved system of the foregoing character wherein a special testing device that is independent of the tripping setting of the circuit breaker is utilized to test the line conditions at intervals after the tripping occurs, and to cause the circuit breaker to be reclosed only if the line conditions meet predetermined requirements independently of the conditions which govern the tripping of the circuit breaker; means for periodically repeating a limited number of times the testing of the circuit and the reclosing operation, and for finally cutting out the reclosure if the system fails to clear within a predetermined period of time; and other features that will best appear from the following description of exemplifications of the invention, reference being had to the accompanying drawings, wherein Fig. 1 is a diagrammatic view of an automatic reclosing circuit-breaker system embodying the invention; and

Fig. 2 is a view similar to Fig. 1 of a modification of the invention.

Various automatic reclosing circuit breakers have been proposed heretofore. In some of the systems, the reclosing arrangement causes the circuit breaker to be periodically reclosed a number of times after it is tripped, irrespective of the conditions of the line, the circuit breaker being finally opened after a number of unsuccessful attempts to reclose.- Such systems have a very serious drawback when used in places where short-circuits are of frequent occurrence, since the circuit breakers are often over loaded, causing unnecessary damage, both to the circuit breaker and to the other appa-' ratus of the systems.

To avoid the foregoing defects a system has been proposed wherein the reclosing of the breaker has been made dependent on the resistance or impedance of the circuit c0utakes place only when the circuit resistance.

has reached a value at which the current that would flow through the breaker when it is closed will not exceed the tripping current for which'it is set. It often happens that the resistance of the circuit controlled by the breaker is sufficiently low to give a current which exceeds the tripping current of the breaker, but which, nevertheless, does not correspond to the short-circuit conditions. Under such circumstances, the circuit breaker of the last-named svstem would not reelose, although this would not be dangerous either for the system or for the circuit breaker. As a matter of fact, it would be desirable to have the circuit breaker reclose in order to cause the current to burn out a faulty point ofthe line that might be the causeof the tripping and thus have the system again restored to normalcy. However, with the foregoing system the only alternatives available are, either to set the tripping current undesirably high, endangering the line, or to accept the drawback mentioned above.

The deficienc of the foregoing systems is still more pronounced in cases where the resistance of the circuit controlled by the breaker changes as the breaker is closed. This occurs, for example, when the load in the circuit consists of a large number of small squirrel cage motors that are not provided with no-voltage release switches.

According to the invention the advantages of the prior-art reclosing systems are retained, while avoiding the foregoing serious drawbacks of the same, by making the reclosure of the circuit breaker dependent on a short-circuit or circuit-resistance testing device that is independent of the tripping setting of the circuit breaker; and so adjusting the device as to cause the breaker to re close though the current through the reclosed circuit breaker would exceed the tripping current, provided that the circuit is not substantially short-circuited, or, in general. the circuit resistance is higher than a predetermined minimum value; this minim m alue b howeve c n d ra y lower than the value which would causethe breaker to trip.

In carrying the invention into eflect, means are provided for causing periodical initiation of reclosure of the circuit breaker, each reclosure operation being independently controlled by a testing element that is dependent on the resistance or impedance of the circuit. The testing element makes reclosure impossible if the circuit resistance is below a certain minimum value, corresponding to the short-circuit condition, for instance; but permits reclosure if the circuit resistance is above said value, although below the tripping value of the circuit breaker. The means for periodically initiating the reclosing action, or placing the testing device in condition to reclose the circuit breaker is arranged to act successively at predetermined intervals. In the preferred embodiment of the invention the successive intervals are gradually longer and if no reclosure takes place after a predetermined number of attempts to reclose, the circuit breaker is permanently set open, or the reclosing device cut out.

In other words, the preferred embodiment of the invention combines an arrangement for periodically reclosing a circuit breaker a predetermined number of times with means for determining the resistance condition of 'the circuit prior to each reclosure operation,

making the actual carrying out of the individual reclosing operations dependent on said condition.

A system of such character is shown in the drawings. An electrical supply circuit 1 leading from a generator 2 is arranged to be connected by means of an overload circuit breaker 3 to a load circuit 4 including load devices 5. The "circuit breaker 3 has an overload tripping coil 6 and maybe reclosed by means of a reclosing coil 7 which is arrange d to be energized from an auxiliary supply line 8 by means of an electromagnetically actuated reclosing contactor 9.

The operation of the reclosing contactor is controlled by means of a reclosure control device 12 comprising three controller elements 13, 14, and 15, in the form of disk contactors mounted on a control shaft 16 which is normally held biased to a predetermined position, as by means of a spiral spring 17,

ut which may be rotated by a servo-motor 18, against the action of said spring. In the case shown in the drawing, the motor is arranged to rotate the shaft and disks counterclockwise, the spring returning the disks to the original position in clockwise direction. The motor is arranged to be supplied from the auxiliary line 8, the energizing circuit of the motor including an electromagnetic cut-out relay 19. The motor energizing circuit may be completed either through a pair of auxiliary contacts 20 on the circuit breakor 3, when the circuit breaker is in open position, or through a pair of auxiliary contacts 21 on the reclosing contactor, when said contactor is in closed position.

Controller disk 13 serves to periodically actuate a circuit-testing device 22 for determining the resistance conditions of the circuit and to discriminatively permit or prevent reclosure of the circuit breaker depending on said conditions. Controller disk 14 serves to periodically establish circuit connection, whereby reclosure of the circuit breaker will be effected if the testing device 22 finds the circuit condition such as to permit reclosure. Disk 15 serves to entirely out out the reclosing means of the circuit breaker if a predetermined number of attempts to reclose have failed.

In the exemplification of the drawings the controller is arranged to make four attempts to reclose the circuit breaker, and, if said fourth attempt fails, the circuit breaker is definitely left open. To this end the control disk 13 is provided with four contact segments 31 to 34 co-operating with a stationary contact brush 35 to establish a circuit -for energizing a testing relay 36, said circuit leading from one pole of the auxiliary supplyline 8, through the energizing coil of the testing relay 36, brush 35, and the cooperating disk segment, to a pair of interlocking contacts 37 on the circuit breaker 3, back to the other pole of the auxiliary line. The interlocking contacts 37 like the motor control contacts 20, are closed when the circuit breaker 3 is open, and are open when the circuit breaker closes.

The testing relay 36, when energized by means of control disk 13, establishes the operating circuit for the testing device 22, said circuit comprising a resistor 38 connected in series with the testing device across the open contacts of the circuit breaker. The testing device 22 is shown in the form of a relay which is actuated by the current flowing through the resistor 38 into the open load circuit 4. By suitably adjusting the relay and the resistor 38, the armature of the testing device may be caused to be picked up and open its contacts, only if the line resistance is less than a certain value, corresponding to a dead short-circuit, for instance, but to remain in its normal released position, as shown in the drawing, if the resistance of the circuit is below said value. This settin of the testing device ma be entirely independent of the setting of the overload tripping coil 6 of the circuit breaker, and, as pointed out above, is preferably so arranged that the armature of the testing device will remain in the released osition under line conditions at which t e overload coil would cause the circuit breaker to be tripped.

The second controller disk 14 is also provided with four contact segments, 41 to 44, arranged similarly to, but angularly somewhat displaced against, the four segments 3l= tos34eofathei first disk l3-,-.- a-.brus-ha45acos.

circuit including a pair 0 contacts 46 whichare closed by the armature of the testing device when the latter l-S-iIL-l-GIGRISGd condition, and opened when said armature islifted.

In the preferred embodiment of the invention the spacings between the contact segments 31 to 34 and 41' to 44 consecutively are progressively greater so thatthe intervals between the successive engagements of brushes 35 and 45 with their respective disk segments is gradually longer, as the disk rotates from position to position against the action of the spring 17. After the shaft has made a full rotation the cut-out contactor disk 15 establishes, by means of a segment 51 and a co-operating brush 52, an energizing circuit for the operating coil of the cut-out relay 19, thereby actuating said relay and causing itto be locked in lifted position by means of a suitable catch 53 on said relay. The actuation of the cut-out relay interrupts the energizing circuit for the reclosing coil 7, and of the other elements of the control mechanism, thus entirely cutting out the automatic reclosing feature of the system. I p

The operation of the system is as follows:

Upon opening of the circuit breaker, as the result of an overload, or the like, the interlocking contacts 20 and 37 are closed. The motor 18 is thereupon energized, turning the control shaft 16 and the controller disks 13 to 15 counter-clockwise in direction of the arrow. As soon as the first segment 31 on the controller disk 13 comes into engagement with the 00-0 crating brush 35, the testing relay-36 pic up, establishing at its contact the testing circuit leading across the terminals of the open circuit breaker, and including the resistor .38 and the testing device 22. g "Depending on the setting of the testing device, it Wlll either pick up or stay in released condition, shown in the drawing, in accordance wlth the resistance of the circuit controlled by the circuit breaker. Assuming that the testing device is set to prevent the closure only if there is a dead-short-cir- =cuit..on' the line, and the current' flowing through the testing device is less than i the value corresponding to such short-circuit condition, the device will remain in released condition, thereby preparing the energizing; circuit for the reclosing contactor 9. .gSoon after. the circuit through disk segment 231 has been established,,segmelitl of the second controller disk 14 comes into engagement with itsco-operating brush 45,

thereby completing the energizing circuit for the-reclosing contactor, 9, the reclosin G contactonr energizes the recloslng coil 7, and

the circuitbreaker is reclosedm': 7

If, however, the line wasdeadlshort-cir;

testing decuited, the current through the vice 22 would. pull up its armature, opening its contacts 46. Accordingly, the subsequent enga'gement of disk segment 41 by the co-operating brush 45, would have no effect on the energization of the reclosing contactor 9, leaving the circuit breaker open condition. The disks would continue to be rotated and the operation would be repeated at the successive segments 32 1:034

and 42 to 44, respectively. If at any subsequent'actuations of the testing device 22 the resistance of the circuit is found tobe greater than the short-circuit resistance, the circuit breaker is reclosed. Otherwise, the circuit breaker -is left open.

In case the circuit breaker is reclosed, Say, at the first position of the control segments, and the overload is so far reduced as to fail to trip the breaker, the motor'18 becomes deenergized, and the control shaft 16 is returned to the zero position by the spring 17 However, if the overload ersists, the circuit breaker will be trippe soon after it is reclosed; During the short time while the circuit breaker remains closed, its interlocking contacts are open; but the motor is arranged to continue the rotation of the con-v troller shaft 16 for a short while after reclosure of the circuit breaker. This is effected by the auxiliary motor control contacts 21 on reclosing contactor 9, the latter contactor being suitabl delayed in its return to the released posltion, as by means of a dashpot 10, or the like. As soon as the circuit breaker reopens, the motor energizing circuit is again reestablished at the interlocking contacts 20 of the circuit breaker, and the shaft continuesto rotate to the next reclosing position. If the overload persists, the sequence of operation is repeated at each of the further segments on the controller shaft disks, in amanner analogous to the operation when a dead short-circuit continues to persist on the line. v

.A'ftera repeated number of attempts to reelose, or unsuccessful reclosures, the. disk operating coil of the cut-out relay 19, pulling up the relayand locking it in openposition. This deenergizes'the circuits forrthe motor 18 and the otheru'eclosing apparatus, I

cutting out further reclosure operations,

The spring 17 brings the apparatus back: to

its initial position, but no" fnrthcraction will take place until after the cut-out relay has been unlocked, either by hand or through suitable remote control means.

In the modification shown in Fig. 2 the testing device comprises, in addition to a coil or element actuated by a current flowing through the series resistance 38 connected across the terminals of the circuit breaker, a differentially acting coil which is traversed by a current proportional to the line voltage. A much better determination of the resistance conditions of the line may thus be obtained, the remainder of 'the circuit organization being unchanged. The invention is susceptible of many other modifications that will be obvious to those skilled in the art, such as the substitution of other testing devices, switching devices, relays, circuit connections, or combinations thereof, for those shown in the drawing.

I claim:

1. In a reclosing circuit-breaker system, the combination with a supply circuit, a load circuit, a circuit breaker connecting said cir cuits, and means for tripping said circuit breaker in response to predetermined operating conditions, of testing means actuated by the tripping of said circuit breaker to ascertain the existence of predetermined operating conditions, means for reclosing said circuit-breaker in response to predetermined action of said testing means, and means for rendering said testing means efit'ective 'periodically with respect to said reclosing means.

,2. In a reclosing circuit-breaker system, the combination with a supply circuit, a load circuit, a circuit breaker connecting said circuits, and means for tripping said circuit breaker in response to predetermined operating conditions, of testing means actuated by the tripping of said circuit- I by the tripping of said circuit breaker to ascertain the, existence of predetermined operating conditions, means responsive to predetermined action of said testing means for reclosing said circuit breaker, means for periodically repeating the operation of said testing means, and means for cutting out said reclosing operations in response to a predetermined repeated number of operations of said testing means.

means for perio ically actuating said re-.

closing device, the operation of said reclosing divice being responsive to predetermined action of said testing device.

5. In a system of the character described,

an electrical suppl line, a feeder line, means,

operable to provi e for connection and disconnection of said lines with res ect to each other, electro-responsive means or efiectm connecting operation of said first-name means, means providing a control circuit for said electro-responsive means, switch means forming part of said control circuit and being operable to render the same efiective with respect to said means, means operable to rovide for repeated operation of said swltch means and means responsive to an abnormal condition in one of said lines when the same are disconnected and forming part of said control circuit and being operable upon existence of such condition to render said control circuit non-efiective with respect to said electro-responsive means.

6. In a system of the character described, an electrical supply line, a feeder line, means operable to rovide for connection and disconnection 0 said lines with respect to each other, electro-responsive means for efli'ecting ,connecting operation of said firstnamed means, means providing a control circuit for said electro-responsive means, switch means forming part of said circuit and being operable to render the same effective with respect to said electro-responsive means, means responsive to an abnormal condition in said s m when said lines are disconnected and orming part of said control circuit and being operable u n existence of such condition to render sa d control circuit non-efiective with respect to said electro-responsive means, switch means operable to provide for operative association of said last-named means with said system, and means operable to provide for repeated operation of said first and second-named switch means with the operations of said second-named switch means receding the respective operations of said first-named switch means.

In testimony whereof I have hereunto subscribed my name this fist day of March, A. D. 1927, at Zurich Switzerland.

WERNER WALTY.

electr'o-responsive.

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