US1677328A - Automatic reclosing circuit interrupter - Google Patents

Description

July 17, 1928. 1,677,328

C. A. BUTCHER AUTOMATIC RECLOSING CIRCUIT INTERRUPTER Filed April 25. 1921 l as WITNESSES: F 3. INVENTOR ZJJWM l7 Cfmr'les/lfiufcher:

AIZTORNEY Patented July 17, 192

" UN TATES ATENT QFF'ICE.

cmmis a. BUTCHER, onmsr rnrcrsiaunqn, PENNSYLVANIA, QASS'IGNOR' :ro wnsrmenousn nnncrnrc & manurac'ruame conr'AnY, acoaroRA'rIoN or ammr- SYLVANIA,

- AU-romnrm ancnosrim cmcurr mrmmor'rna A Application filed 4 m '25,

. My. invention relates to circuit interrupters and particularly 'to' automat c clrcplt interrupters.

One object of my invention is to provide a circuit vinterrupter that shall be automatically openedupon the occurrence of a short-circuit on a circuit to be protected thereby, and that shall be reclosed when the short circuit is cleared or removed to render the protected circuit ,normal.

Another object of my "invention isto provide a circuit interrupter for a system, of the above indicated character, that shall be reclosed when the-short-c'ircuit conditions are cleared and when the efiective' connected load is at 'or below a predetermined value.

- A further object ofmy invention is to provide an -interrupter,.of the above-indicated character, that shall be simple and economical inits construction and reliable in its operation. Y Q In systems heretofore employed for. controlling'trolley-feeder conductors, large re.-

sistors having'large current-carrying capace ity have been required. In such systems, upon the occurrence of-an extremely heavy overload or short-circuit, the interrupter was opened to permit the insertion of a resistor or resistors of relatively lowresistance and having a relatively large current-carrying capacity to limit the current that, might 4 traverse the feeder conductor to a safe value. When the resistors were traversed by such A current for a predetermined interval of time and heated to a predetermined unsafe temperature, the feeder circuit was entirelydisconnected from the source ofenergy until the faultmightbe clearedand the resistors cooled. I i.

In Itie prior art, circuit breaker systems have resistor in series with a cont-rolling winding when the circuit interrupter is-openedif The current to the load circuit and fault traverse the resistor. and the "control winding and maintain an auxiliary reclosing circuitopen,

until the current traversing the resistordi-- minishes to a predetermined value. The control "winding is "then deenergizedjto a sufiicient degree to permit the auxiliary reclosing-circuitto be reestablished and the interrupters-reclosed.

Since the-winding in such cases is traven provided which insert a limiting .1921. Serial Ho. 464,2 68.

ersed by the load and "circuit current under abnormal conditions,'it had to bemade of large conductor of low resistance, and could not be made as sensitiye as a potential winding which canbe madeofa small conductor of high resistance.

By inserting the resistor directly inthe circuit, when the interrupter is opened and utilizing the potential thereacross, which can be measured by a sensitive voltage coil, a greater sensitivity maybe obtained to con.- 'trol therecl'osing of'the interrupter. I In- 'practijcing my'invention, I provide means that'areenergized only upon the occurrence-ot "a "sho'rt-cir'cuit upon the feeder circuit'to o'pen'the interrupter to permitthe efi'ective insertion of areslstor of relatively high resistance between the source of energy and the feeder-conductor circuit. Upon the clearance of the'short-circuit and upon the increase of'gthe effective-load resistance to or above'a' predetermined value, the interrupter is reclosed to shunt the limiting resis- 'tor; Since "the opening of the interrupter may be eifected' onlyby such currents as might result a from short-circuit; conditions, the interrupter,""whe-n reclosed to connect a load of relatively low resistance to the main circuit, is not-immediately reopened because of the sudden rush. of -current.

Figure lof the-accompanying drawings is a diagrammatic view of; anelectrical circuit including an "interrupter and a control system embodying my invention; and

Fig.2 is a'diagrammatic view of a similar circuit including a modified controlling de- V1ce Referring to Fig. 1, a source 1 of directcurrent electromotive iorce provides energy .for a supply circuit 2 "from which energy is supplied tofa" feeder circuit 3 through a circuit interrupter 4.

' The interrupter 4 comprises a main switch 5, an auxiliaryswitchz6and an operating coil 7 that-serves to'closeboth switches, when energized; =The circuit of the .coil 74s completed through a switch 8 0i" "a" relay 9 and a switch'10 of a relay= 11.

The relay 9 comprlse's the switch 8 and an operating'coil 12. The relay11-comprises the switch 10, a floating lever arm '13 and two controlling coilsl t and 15, respectively. that control the switch .10. throughithe lever arm 13. The circuit of the operating coil 12 of the relay 9 includes the switch 10 and a resistor 16. i

v A current transformer 17 and two relays 18 and 19, respectively, areemployed to ef- -fect the actuation of the interrupter 4 to. open the main switch 5 upon the occurrence of a short-circuit on the feeder circuit- 3.

.The relay 18 comprises a switch 20 "and an actuating coil 21. The relay 19 comprises a switch 22 and an actuating coil 23.

Upon the occurrence of a short-circuit that serves to efi'ect the opening of the interrupter -4, a resistor 24, that is connected across the terminals of the switch 5, is inserted between the supply circuit 2 and the .ffeeder circuit 3 to limit the current that may traverse the latter circuit. -The actuating coil 14 of the relay 11 is connected across the terminals of the resistor 24.

.. While conditions are normal in the syscircuit 3, and consequently, the primary winding of the current transformer 17 suffices to quickly energize the winding of the relay 21 to effect the closing of the switch 20.. -Upon the closing of the switch 20, a circuit is completed through the auxiliary switch 6, the switch 20 and the coil 23 of the relay 19 that permits the energization of that coil to close the switch 22. The switch 22, when closed, completes a holding circuit for the coil 23 through the auxiliary switch 6" until the interrupter 4 opens.

The moving members of the relays 18 and 19 are relatively lightin weight and rela tively sensitive. mentarily closed, short-circuits the operating coil 12 of the relay 9. The immediate closing of the switch 22 thereupon serves to maintain the short-circuit about the coil 12 of the relay 9, and the switch 8 is permitted to open. A 1

Upon the opening of the'switch 8 of the relay 9, the interrupter 4 is also permitted to open, and the main switch 5 and the auxil-- iary switch '6 are opened. The opening of- .the auxiliary switch 6 de-en'ergizes the coil 23 of the relay 19 to. permit the switch 22 to open.

Upon the opening of the switch 5, the re sistor 24, which, for example, may have a resistance of ohms, is inserted 'into the feeder circuit to limit the current that may The switch 20, when mo-' traverse the same to a maximum of 10 am-. -.peres, assuming that the voltage of the C11- cuit 2 is normally 600 volts. When the shortcircuit conditions in the feeder. circuit 3 are cleared and the effective load resistance con-- nected thereto equals or exceeds 0.6 of an ohm, the maximum current thatunjay trav erse the interrupter. is 9.9 an'iperes.

Assuming short-circuit conditions on the circuit 3, the full voltage of the. circuit 2,.

normally 600 volts, will be consumed in the resistor 24 and, consequently, the corresponding potential difference thereacross will be effective in energizing the coil 14 of the relay 11. Since the winding 15 is correspondingly energized by a potential difference'of 600 volts, the relay 11 is maintained in a balanced position at whichposition the switch 10 is maintained open.

However, when the short-circuit is cleared and the resistance of the connecting load increases toor above 0.6 of an ol'nn, the potential difference across the terminals of the resistor 24 is 594.volts.

between the potentials applied to the two coils 14 and his thus 6 volts. Since the re lay 11 may be arranged to obtain'a sensitivity of 1%, the difference in the degree of energization between the two coils 14 and 15, effected by the difference of 6 volts, will suflice to effect the closing of the switch 10. I V

. The closing of the switch 10 immediately completes the circuit of the operating coil 12 of the relay-.9. whereupon the switch 8 is closed. The closing of the switch 8 completes the. circuit of the operating coil 7 of the interrupter 4, and the main switch is thereupon reclosed.

\Vhen the switch 5 is closed and the resistance of the connected load is 0.6of an ohm,

1000 amperes will immediately traverse the circuit. However, since tlns value of cur,- rent is far below such value as might be caused toitraversc the circuit by short-circuit conditions, the current transformer 17 is not sufiiciently energized to effect the actuation of the relays18 and 19.

The difference If, however. the magnetic circuit of the current transformer 17should not be magnetized, the sudden rush of'current of such value might be sufficient to actuate the relays 18 and 19 toefl'ect the opening of the main interrupter. Upon the occurrence of such opening, "however, the. magnetic circuit would be so magnetized and. relatively so saturated that the consequent rush of curreng upon the next reclosing would not again b sufficient to'effect the operation of the relays 18- and 19;

The feeder circuit- 3 may be connected directly, through a series of sections connected N by sectionalizing switches, to a distant source of energy; but t 4, upon the occurrence of short-circuit and 'the reclosing, upon the clearance of the e opening of the interrupter short-circuit, at a predetermined value of load resistance, will be efiected irrespective of whether potential is applied to the circuit 3 from an exterior source. 7

The operation of the system illustrated in Fig. 2 is similar to that described in connection with the system illustrated in Fig. 1

- with the exception of the relay 25 which 7 more, the coil 27 is sufiiciently energized to maintain the switch open. When the po tential difference across the terminals of the resistor decreases to a value below 594: volts by reason of an increase of the load resistthe accompanying drawings, will thus dis connect a load circuit from a supply circuit upon the occurrence of short-circuit conditions in the load circuit and will immediately reconnect the load circuit when the short-circuit conditions are. cleared and the connecting load of the load circuit is at or above a predetermined value.

My invention is not limited to-t-he specific devices illustrated or to the specific arrangement of those devices, since modifications may be made therein within 'the'spirit and scope of the invention, as set forth in the appended claims.

I claim as my invention 1. An automatically reclosing circuitinterrupting device comprising means for connecting twoeircuit conductors, an operating coil therefor, a switch in circuit with the coil, and means for controlling the switch comprising a resistor connected directly across the terminals of the interrupting device and means responsive tov the potential difference thereacross when the switch is open.

2. An automatically reclosing' interrupting device comprising means for connecting two circuit conductors. and operating coil therefor, a switch in circuit' with the coil, and means for controlling the switch comprising a resistor connected directly across the terminalsof the interrupting device, means responsive to the potential circuitdifference thereacross when the switch is open and means for controlling the effectiveness of such potential difference.

3. In an electric system,.tl1ecombination with a supply circuit, a load circuit and a circuit interrupter therebetween, of a current-limiting resistor connected in parallelrelation to the circuit interrupter, means for opening the circuit interrupter in response to predetermined abnormal conditions in the load circuit, and means for reclosing the circuit interrupter when the resistance of the load circuit equals or exceeds a predetermined value, comprising a closing coil for the circuit interrupter, a switch for controlling the energization of the closing coil,

and two opposed coils for controlling the operation of the switch, one of said coils being connected in parallel relation to the supply circuit and. the other ofsaid coils being connected in parallel relation to the 1 current-limiting resistor.

4. In an electric system, the combination with-a supply circuit, a load circuitand a circuit-interrupter therebetween, of a current-limiting resistor connected in parallel relation to the circuit-interrupter, means for openinethe circuit interrupter in response to predetermined abnormal conditions in the load circuit, and means for reclosing the circuit interrupter when the resistance of the load circuit equals or exceeds a predetermined'value. comprising a closing coil for the circuit-interrupter, a switch. for controlling the energization of the closing coil, and two coils for controlling the operation of the switch, one of said coils being so disposed as to beresponsive to the potential across the supply circuit and to tend to close the switch. and the other of said coils being so disposed as to be responsive to the potential across the current-limiting resistor and to tend to open the switch.

5. 'In an electric system, the combination with a supply circuit, a load circuit and an interrupter therehetween, of means 'for open- CHARLES A. BUTCHER.

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