US1533693A - Automatic reclosing circuit-breaker system - Google Patents

Description

April 14, 1925. 1,533,693

E.C.BRHTON AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM ifidmag- 2, 1924 Fig. I.

Fig. 5.

Stub end Fed Multiple Feed Inventor- I Current Load resistance by 4 f,/ A

I Hi8 Attorney.

Ernest, C. Britten,

Patented Apr. 14, 1925.

UNITED STATES 1,533,093 PATENT orrics.

ERNEST G. BBITTOIF, 0F SOHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

AUTOMATIC RECLO SINGCIB/CUIT-BBEAKER SYSTEM.

Application filed Kay 2, 1924. Serial No. 710,673.

To all whom it may comm:

Be it known that I, ERNEST C. BRIT'lON, a citizenof the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Automatic Reclosing Circuit-Breaker Systems, of which the following is a specification.

My invention relates to automatic reclosing circuit breaker systems and particularly to such systems in which a circuit breaker is arranged automatically to connect a source of current to a load circuit as soon as the load is such that the circuit breaker can be reclosed without overloading the' source.

It is well known to those skilled in the art that in systems in which the load circuit is arranged to be supplied with current at a plurality of points, it is necessary to arrange an automatic reclosing system therefor so that it will function properly under two different conditions of the load circuit.

One ofthese conditions, called the stub end feed condition, is when all the circuit breakers connecting other sources to the load circuit are open, and the othencondition, called the multiple feed condition, is when one or more of the other circuit breakers are closed so that the load circuit is energized at substantially normal potential at some-other point.

One object of my invention is to provide an improved automatic reclosing circuit breaker system which will function properly under both of the above mentioned conditions of the load circuit.

Another object of my invention is to provide an improved arrangement for selectively controlling the reclosing of a circuit breaker in accordance with the feed conditions of the load circuit.

In accordance with my invention I provide a low voltage auxiliary source which is arranged to be connected across the load circuit when the circuit breaker opens, and control the reclosing of the circuit breaker in accordance with the current flowing through the auxiliary source.

It will be observed that when the auxiliary source is connected to the load circuit under the stub end feed condition thereof, the current flows from the auxiliary source to the load circuit and this current deside of the load circuit.

creases as the load connected to the load circuit decreases, whereas under the multiple feed condition of the load circuit, the current through the low voltage source increases as the load decreases. I rovide suitable means which operate to e ect the reclosing of the circuit breaker when the current through the auxiliary source decreases below a predetermined value under the stub end feed condition of the load circuit and when the current increases above a predetermined value under the multiple feed condition thereof.

If the polarity of the low voltage auxiliary source is the same as the main source, and the voltage of the auxiliary source is low compared with the voltage of the main sources, the current .through the auxiliary source reverses under the multi 1e feed condition, so that the direction 0 the current through the auxiliary source isan indica tion of the condition of the load circuit. I provide a suitable directional relay which operates in response to the direction of current through to the auxiliary source selectively to control the reclosing of the circuit breaker in accordance with the conditions of the load circuit.

My invention will be better understood from the following description, when taken in connection with the accompanying drawing, and its scope will be'pointed out in the appended claims.

In the accompanying drawing, Fig. 1 shows an automatic reclosing circuit breaker system embodying my invention, Fig. 2 shows a modification of. the system shown in Fig. 1, and Fig. 3 is an explanatory diagram.

Referring to Fig. 1 of the drawing, 1 represents a circuit breaker which is arranged to connect the source of current 2, shown as a direct current generator, to the load circuit 3, which is also arranged to be supplied at other points. As shown, the load circuit is arranged to be supplied by another source 2. In order to simplify the drawing, it is assumed that the ground is one minal of each of the generators 2 and 2 is shown directly connected to ground and the circuit breaker 1 is arranged to connect the other terminal of the generator to the metallic conductor of the load circuit. It is Therefore, one terevident, however, that my invention is neither limited to a grounded system nor to having the circuit breaker 1 control the connection between only one terminal of the generator 2 and the corresponding side of the load circuit 3.

As shown in the drawing, the circuit breaker 1 is a contactor having a coil -l, which, when energized, maintains the circuit breaker in its closed position. However, it is evident that any other type of circuit breaker may be used. The coil 4 is arranged to be connected across any suitable source, such as the generator 2, and the circuit of this coil is arranged to be interrupted by an overload relay 5 which is so connected that it operates when the current supplied by the generator exceeds a predetermined value.

In order to control the reclosing of the circuit breaker 1 in accordance with the load connected to the load circuit when the circuit breaker is open, an auxiliary source of current 6 is arranged to be connected across the load circuit 3 by means of a time relay 7 after the circuit breaker has been open for a suflicient length of time to allow conditions on the load circuit to become stable. The auxiliary source 6 may be either an alternating current or a direct current source of any suitable type but preferably is a direct current source having a very low voltage compared with the normal voltage of the sources 2 and 2'.

In the particular embodiment of my in vention shown in Fig. 1, it is immaterial whether the auxiliary source 6 is connected across the load circuit with the same polarity as the main sources 2 and 2' or with the opposite polarity. As shown, the auxiliary source is so connected that the current supplied thereby to the load circuit flows through the load in the reverse direction from the current supplied by the main sources 2 and 2'.

\Vhen the auxiliary source 6 is connected across the load circuit under the stub end feed condition of the load circuit, that is, when the source 2 is not connected to the load circuit 3, the current supplied by the auxiliary source decreases as the load resistance increases. It may be desirable to have a small resistor 8 in the circuit of the auxiliary source so as to limit the current supplied thereby under short circuit conditions on the load circuit. It is desirable,

however, that this resistor should be of connected across the load circuit under the multiple teed conditions, that is, w hen the source 2 is connected to the load circuit 3,

the current through the auxiliary source increases as the .load resistance lncreases bea cause the load circuit voltage, which is greater than the voltage of the auxiliary source, increases as the load reslstance increases.

resistor, which has a relatively high resistance and which is arranged tobe connected in series with the auxiliary source 6 under the multiple feed condition of the load circuit. Any suitable means may be employed for this purpose. As shown, the resistor 9 is normally short circuited by the contacts 10 of a selective relay 11, the coil of. which is arranged to be connected across the load circuit 3 by the contacts 12 on the circuit breaker 1' when it is open. The selective relay 11 is set to operate in response to such a high voltage that it operates only when the load circuit is energized by a main source.

With the arrangement heretofore described, it will be evident that when the circuit breaker 1 is o-penan-d no other source is connected to the load circuit, the auxiliary source 6 is connected across the load circuit and the current through the auxiliary source decreases with a decrease in load. When, however, some other source is connected to the load circuit, the resistor 9 is connected in series with the auxiliary source 6 andthc current through the auxiliary source 6 and the resistor9 increases as the load decreases. The curves in Fig. 3show how variations in the load change the current, through the auxiliary source under the two conditions of the load circuit for certain values of voltages of the main and auxiliary sources and of current limiting resistors.

In accordance with my invention, I make use of this characteristic of the current through the auxiliary source by providing means which operate to effect the closing of the circuit breaker when the current de creases belowa predetermined value under the stub end .feed condition of the load circuit and when the current increases above a predetermined value under .the multiple feed condition of the load circuit.- .In the arrangement shown in Fig. 1, these results are accomplished by means of a single relay 14, the coil of which is connecteddn'series with the auxiliary source 6. This relay may be designed so that it picks up and drops out at different currents orsubstantially the same current. Byproperly designing the resistor 9, it is possible to have the current through the coil of the relay 14, when the load is the value at which lt'is desired to have the circuit breaker reel-ose, under the multiple feed condition, substantially the 4 coil l.

same value as when the load is the desired value at which it is desired to reclose the circuit breaker under the stub end feed condition of the load circuit.

As shown, the relay 1% picks up under the multiple teed condition when the :urrent through auxiliary source 6 exceeds a predetermined value and by closing its contacts completes the circuit of the closingcoil at 01' the circuit breaker. This circuit also includes contacts 16 or the selective relay 11, which are closed only under the multiple feed condition of the load circuit. Under the stub end feed condition of the load circuit, the relay 1 1 picks up as soon as the relay 7 closes its contacts, since the resistor 9 is short circuited by the contacts 10 of the relay 11 and therefore the auxiliary source 6 is connected directly across the overload or short circuit. When the overload decreases below a predetermined value, the

relay 1 1 drops down and by closing its contacts 12' completes a circuit for the closing This circuit also includes contacts 19 of the relay 11 which are closed under the stub end feed condition. in order that the circuit of the closing coil 4 cannot be completed until after the relay 1 1 has had time to pick up under the stub end feed condition, T provide a time relay 20 which controls contacts 26 in both of the energizing circuits of theclosing coil at so that these circuits cannot be closed until after the auxiliary source 6 has been connected to the load circuit for a certain length of time.

The operation of the system shown in Fig. 1 is as follows: When the circuit breaker 1 is closed and the load is normal, the circuit breaker 1 is held in its closed position by the energization of the closing coil 4:. This circuit is from the ungrounded terminal of the generator 2 through the contacts 21 of the overload relay 5, coil 1 of the circuit breaker 1, auxiliary contact 22 on the circuit breaker 1 to ground. Under these conditions the automatic reclosing apparatus occupies the position shown.

When an overload occurs, which is suliicient to cause the overload relay 5 to open its contacts 21, the coil 1 is deenergized and the circuit breaker 1 opens. The closing of the auxiliary contacts 12 on the circuit breaker, when the circuit breaker opens, connects the selective relay 11 across the load circuit 3, and the closing of the auxiliary contacts 23 connects the time relay 7 across the generator 2.

It the source 2 is disconnected from the load circuit when the circuit breaker 1 opens, the voltage across the load circuit becomes substantially zero so that the relay 11 remains in the position shown. if, however, the source 2 is connected across the load circuit, there is still a voltage across the load circuit after the circuit breaker opens and relay 11 is designed SO as to pick up under such conditions. 2

First it will be assumed that the soul-(e 2' is not connected to the load circuit after the circuit breaker 1 opens. When the time relay 7 closes its contacts 2 1 and 25, the closing of the contacts 2 1 connects the auxiliarysource 6, the resistor 8, and the coil of the relay 1a in series across the load circuit. 1t will be observed that the resistor 9 is short circuited by the contacts 10 unde. the stub end feed condition. 11? the overload is still connected to the load circuit when the contacts 24 are closed, the current through the relay 141 is sufficient to cause the relay to pick up and close its contacts 15, but the closing of these contacts does not complete the circuit or the. coil 1 becauseit is open at the contact 16 of the relay 11 and also at contacts 2t? of the time relay 20.

The closing oi the auxiliary contacts 25 of the relay 7 completes the circuit of the time relay 20. This circuit is from the ungrounded terminal of the generator 2, throughthe auxiliary contacts 23 of the circuit breaker 1, contacts 25 of the time relay 7, coil of the time relay 20 to ground. The purpose oi the time relay 20 is to allow sutiicient time for the relays 11 and 14 to operate in accordance with the load condition before the circuit "for the coil 4 can be closed.

As the overload decreases, the amount of current supplied by the auxiliary source (5 decreases, and, when this current decreases below a predetermined value, the relay 14 drops down and closes its contacts 17 to c01n-= plete an energizing circuit for the coil 4. This circuit is from the ungrounded terminal of the generator 2 through the contacts 21 of the overload relay 5, which are closed after the circuit breaker 1 opens, coil 4: of the circuit breaker 1, contacts 26 of the time relay 20, contacts 17 of the relay 1 1, contacts 19 of the selective relay .11 to ground. When the'circuit breaker closes, the closing of the auxiliary contacts 22 thereof completes the heretofore described circuit for the coil 4 to. maintain the circuit breaker in its closed position, and the opening of the auxiliary contacts '23 deenergizes the re lays 7 and 20 to cause the rest of the reclosing apparatus to return to its normal position.

It the source 2 is connected to the load circuit when the circuit breaker 1 opens, the relay 11 is sutficiently energized to open its contacts 10 and 19 and to close its contacts 16. Therefore, when the relay T subsequent- 1y closes its contacts 24, the auxiliary source 6, the resistors 8 and 9, and the relay 14: are connected in series across the load circuit 3. The resistance of the resistor 9 is such that so long as the overload connected to the load circuit exceeds a predetermined amount, sufficient current does not flow through the relay 14 to cause it to pick up. When, however, the overload decreases so that the current; through the relay 14 exceeds a predetermined value, the relay 14: picks up and closes its contacts 15, thereby completing an energizing circuit for the closing coil This circuit is from the ungroundcd terminal of the generator 2, contacts 21 of the overload relay 5, closing coil 4 of the circuit breaker 1, contacts 26 of the'time relay 20, contacts 15 of the relay 14, contacts 16 of the relay 11 to ground.

The closing of the circuit breaker 1 effects the decnergization of the relays 7, 11 and 20 which disconnect the auxiliary source 6 from the load circuit and causes the automatic rel-losing apparat-usto be restored to its normal position.

In the modification of Fig. 1 shown in Fig. 2, the auxiliary source 6 is arranged so that it is connected to the load circuit with the same polarity as the main sources 2 and 2. Therefore, under the stub end feed condition of the load circuit, the current flows from the auxiliary source 6 to the load circuit, and under the multiple feed condition thereof, the current flows in the opposite direction through the auxiliary source because the voltage across the load circuit is higher than the voltage of the auxiliary source. This reversal of current is used in the arrangement shown in Fig. 2 as a means for causing the selective relay 11 to operate under multiple feed conditons of the load circuit. The relay 11, instead of being connected across the load circuit as shown in Fig. 1, is arranged to be connected to the generator 2 by the auxiliary contacts 23 on the circuit breaker 1 when it is open. The circuit of the relay 11 also includes contacts and 31 of a polarized relay 32 which is connected in the circuit: of the auxiliary source 6 so that it operates in response to the direction of flow ofcurrent through the auxiliary source 6. The polarized relay 32 may be of any suitable type and is arranged so that the contacts 30 and 31 are closed only when reverse current flows through the auxiliary source, that is, under the multiple feed condition of the load circuit. Therefore, the selective relay 11 is only energized to open its contacts 10 and 19 and close its contacts 16 under the multiple feed condition of the load circuit.

As shown in the drawing, the polarized relay 32 has a polarizing winding 33 which is connected across the auxiliary source 6 by the auxiliary contacts 34 on the. circuit breaker when it is open and an operating winding 35 which is connected in series with the auxiliary source and the load clrcuit so that the direction of current through the winding 35 varies with the direction of the current through the auxiliary source.

In Fig. 2 the relay 14 of Fig. 1 is replaced by two relays 14 and 14", both of which are arranged tobe connected in serics with the auxiliary source across the load circuit by the time relay 7 The same functions are performed by these two relays as are performed by the single relay 1% in Fig. 1. The relay 14 operates under the multiple feed condition of the load circuit to close the contacts 15 and complete the energizing circuit for the coil 4 of the circuit breaker through the contacts 16 of the selective relay 11 when the current through the auxiliary source exceeds a predetermined value. The relay 14" operates under the stub end feed condition of the load circuit to close the contacts 17' and complete the ener izing circuit for the coil 4 of the circuit breaker through the contacts 19 of the relay 11 when the current through the auxiliary source decreases below a predetermined value. One advantage in using the two relays l4 and 149 instead of a single relay is that entirely different values of current may be used to control the re-, closing of the circuit breaker under the two different conditions of the load circuit.

It is believed that detailed description of the operation of the modification shown in Fig. 2 is unnecessary as it is the same as the arrangement shown in Fig. 1 except for the changes heretofore mentioned. If the load is above a predetermined value when the circuit breaker opens under the stub end feed condition of the load circuit, the relay 14* opens its contacts 17 as soon as the auxiliary source 6 is connected to the load circuit by the time relay 7 after the circuit breaker opens, and maintains its conta-cts 17 open until the load resistance decreases below a predetermined value. The closing of these contacts 17 after the time relay 2O closes its contacts 26 completes the circuit of the coil 4 of the circuit breaker to close the circuit breaker.

lVhen the circuit breaker opens under the multiple feed condition of the load circuit, the polarized relay 32 operates to complete the circuit of the selective relay 11 when the time relay 7 connects the auxiliary source 6 to the load circuit. As soon as the voltage across the load circuit reaches a predetermined value, indicating that the overload has disappeared, the relay 14 closes its contacts 15 and completes the circuit of the coil 4 of the circuit breaker to close the circuit breaker.

WVhile I have, in accordance with the pat-- ent statutes, shown and described my invention as applied to a. particular system and a modification thereof'and as embodying various devices diagrammatically indicated, changes and modifications will be 0blflO vious-to those skilled in the art and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope'of my invention.

lVhat I claim as new and desire to secure load circuit when said circuit breaker is open, and means for reclosing said circuit breaker when the current through said auxiliary source decreases below a predetermined value under the stub end teed condition of said load circuit and increases above a predetermined value under the multiple feed condition of: said load circuit.

2. ln an automatic reciosing circuit breaker system wherein a circuit breaker is arranged to connect source of current to a load circuit under stub end and multiple feed conditions thereof, the combination of a low voltage auxiliary source or" current arranged to be connected across said load circuit when said circuit breaker is open, current limiting means, means operative under multiple feed conditions of said load circuit for connecting said current limiting means in series with said auxiliary source and load circuit, and reclosing means for said circuit breaker controlled by the current through said auxiliary source.

3. In an automatic reclosing circuit breaker system wherein a circuit breaker is arranged to connect a source of current to a load circuit under stub end and multiple feed conditions thereof, the combination of a low voltage auxiliary source of current arranged to be connected'across said load circuit when said circuit breaker is open, current limiting means, means operative under the multiple feed condition of said load circuit for connecting said current limiting means in series with said auxiliary source and load circuit, and means for reclosing said circuit breaker when the current through said auxiliary source decreases below a predetermined value under the stub end feed condition of said load circuit and increases above a predetermined value under the multiple feed condition of said load circuit.

4. in an automatic reclosingcircuit breaker system wherein a circuit breaker is arranged to connect a main source of current to a load circuit under, stub end and .multiple feed conditions thereof, the comcircuit breaker is open so as to supply reverse current to said load circuit under the stub end feed condition of said load circuit, reclosingmeans for said circuit breaker arranged to close said circuit breaker in response to predetermined conditions of the load circuit under stub end feed and multiple feed conditions thereof, and means controlled by the direction of flow of current through said auxiliary source for selectively controlling the operation of said reclosing means in accordance with the feed conditions of the load circuit.

-5. In an automatic; reclosing circuit breaker system wherein a circuit breaker is arranged to connect a main source of current to a load circuit under stub end and multiple feed conditions thereof, the combination of an auxiliary source of current of relatively low voltage arranged to be connected across .said'load circuit when said circuit breaker is open so as to supply reverse current to said load circuit under the stub end feed condition of said load circuit reclosing; means operative to effect the closing of said circuit breaker when the current through said auxiliary source decreases below a predetermined value under the stub end feed condition of said load circuit and increases above a predetermined value under themultiple feed condition of said load circuit, and means operative in response to the direction of current through said auxiliary source for selectively controlling said reclosing means.

6. In an automatic reclosing circuit breaker system wherein a circuitbreaker is arranged to connect a mainsource of current to a load circuit under stub end and multiple teed conditions thereof, the combination of a low voltage auxiliary source of current ar ranged to be connected to said load circuit when said circuit breaker opens, electroresponsive closing means for effecting the closing of said circuit breaker, two energizing circuits for said closing means, current responsive means arranged to effect the completion of one of said energizing circuits when the current in the circuit of said auxiliary source exceeds a' predetermined value, and a second current responsive means arranged to effect the completion of the other one or said energizing circuits when the current through said source decreases below a predetermined value.

7. In an automatic rcclosing circuit'breaker system wherein a circuit breaker is arranged to connect a main source of current to a load circuit under stub end and multiple feed conditions thereof, the combination of a low voltage auxiliary source of current arranged to be connected to said load circuit when said circuit breaker opens, electrore' sponsi-ve closing means for efiecting the dos ing of said circuit breaker, two energizing llllh circuits for said closing means, current responsive means arranged to effect the completion of one of sald energizlng circuits when the current in the circuit of said auxiliary source exceeds a predetermined value, a second current responsive means arranged to effect the completion of the other one of said energizing circuits when the current through said source decreases below a predetermined value, and means operative in accordance with the feed conditions of said load circuit for selectively controlling said energizing circuits.

8. In an automatic reclosing circuit breaker system wherein a circuit breaker is arranged to connect a main source of current to a load circuit under stub end and multiple feed conditions thereof, the combination of a low voltage auxiliary source of current arranged to be connected to said load circuit when said circuit breaker opens, so as to supply reverse current to said load circuit under the stub end feed condition of the load circuit, electroresponsive closing means for effecting the closing of said circuit breaker, two energizing circuits for closing means, current responsive means connected in the circuit of said auxiliary source arranged to complete one of said energizing circuits when the current in the circuit of said auxiliary source exceeds a predeterminedvvalue, a second current responsive means connected in the circuit of said auxiliary source arranged to complete the other one of said energizing circuits when the current through said source decreases below a predetermined value, current limiting means arranged to be connected in series with said auxiliary source, and means operative in response to across the load circuit when the circuit breaker opens so as to supply reverse current to said load circuit under the stub end feed condition thereof, electroresponsive closing means for efi'ecting the closlng of said circuit breaker, two energizing circuits for said closin means, current responsive means arrange to effect the completion of one of said energizing circuits when the current through said auxiliary source exceeds a predetermined value, current responsive means arranged to eifect the completion of the other one of said energizing circuits when the current through said auxiliary source decreases below a predetermined value, a polarized relay operative in response to the direction of flow of current through said auxiliary source selectively to control said energizing circuits in accordance with the feed condition of said load circuit, and means for preventing either one of said energizing circuits being completed until after the auxiliary source has been connected to the load circuit for a certain length of time.

In witness whereof, I have hereunto set my hand this 1st day of May 1924.

ERNEST G. BRITTON.

Images