US1062812A - Protective device. - Google Patents

Description

n. BASOH. PROTECTIVE DEVICE. APPLICATION FILED 00T.9, 1912.

Patented May 27, 1913.

WItn es s g s 4% w- UNITED STATES PATENT OFFICE.

DAVID BASCH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO 'GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE.

To all whom it may concern Be it known that I, DAVID BASCH, a. citizen of the United States, residing at- Schenec'tady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Protective Devices, of which the following is a specification.

My invention relates to protective devices for electrical apparatus, particularly for transmission systems.

It is common to connect a plurality of feeders to a single set of bus bars, as for example, for supplying the distributing bus bars of a distributing station. Under variousconditions, as in case of accident to one of the feeders, that feeder instead of supplying energy to the shat-ion, may tend to take energy from the station; obviously this is undesirable in most cases. It is, therefore, common to connect reverse energy relays to the various feeders to direct the operation of the switches in such a manner that the switch connecting the feeder in which the direction of flow of energy has reversed is opened on such reversal. The reverse energy relays commonly used, however, tend to operate not only on reverse energy flow but. also on an excessive flow of energy in the proper direction, this often resulting on the short circuiting of one of a plurality of feeders in opening not only the switch in the short circuitcd feeder, but also the switch in some feeder carrying momentarily an unusually heavy current due to the short circuit, but in the proper direction. The supply of energy to the station is thus interrupted. To prevent such action the reverse energy relays are commonly interlocked in such a way that only one relay can operate at a time. The specification of the patent to Ostermann, No. 1,000,934, describes such an interlocking of relays in detail. One result of the interlocking of the relays is that there can be no response to the simultaneous reversal of energy flow on all the feeders to which the relays are connected. Such interlock ing is sutliciently satisfactory in case the feeders are not tied together outside the station, since there is very little chance of independent and simultaneous reversal of energy on two feeders. However, in those cases where the feeders are tied together outside the station, the interlocked relays fail to perform the unctions desired whenever Specification of Letters Patent.

Application filed October 9, 1912.

Patented May 27, 1913. Serial No. 724,730.

will there be a reversal of energy flow on I that feeder at the bus bars, but there may be a reversal of energy flow on the remain- ,der of the feeders at the bus bars also, the

other apparatus, connected to the bus bars pumping back through the bus bars and all the feeders to the tie line and the short cit Cult. The interlocked relays of responding to these simultaneous reversals. Hence the use of the tie lines greatly diminishes the usefulness of the interlocked relays.

To retain the advantages of the interlocked relays in tie line systems, to preserve the continuity of connection of the healthy feeders to the objects of my invention.

I prt fer to carry out my invention by connecting another and independent reverse energy relay to one of the feeders between the tie line and the bus bars for controlling the operation of a switch or switches in the tie line or lines, this in addition to the interlocked relays. Good practice will probably dictate the connection of such a relay toeach of the feeders, any one of these relays being capable of causing the tie line switch or switches to open. Thus on the occurrence of a.reversal of energy flow due. to action on a feeder beyond the tie line point of connection thereto, an independent reverse energy relay immediately acts to open the tie line or lines; once this line, or these lines, are open the interlocked relays may pick out'and disconnect the faulty feeder.

The adcompanying drawing is a single line diagra each of two feeders of an alternating current system connected to a single bus bar, and the necessary switches, relays and connections for carrying out my invention.

The duplication of conductors and parts re-' quired to make a complete and operative system will be understood by those skilled in the art.

For the purposes of this description, I have assumed the condition of a distributing station supplied by two feeders which may or may not have the same source of energy. To the bus bar 1 of ,the distributing staare incapable the bus bars, is one of n showing a single conductor of l tion are connected two feeders and 3, by which energy issupplied thereto. Energy distributed through the feeders 4. I will further assume for the purpose of this description that to one or more of the distributing feeders 4 there is connected an auxiliary source of energy or a means which may return energy 'hrough the bus bars to the supply feeders and 3 under certain conditions, although it is not desired that this be done. The feeders 2 and 3 may supply other distributing stations; for this or other reasons it may be desirable to connect them together outside of the distributing station by means of the tie line 5. This tie line may be located many miles from the distributing station. Switches 6 and 7 are inserted re spectively in the feeders 2 and 3 and a switch 8 in the tie line 5, for the purpose of opening .these feeders and the tie line when desired.

The operation of these switches is controlled by means of the trip coils 9, 10 and 11 resp eoti vely, in the ordinary manner. Any source of energy for the trip coils may be provided, and I have illustrated positive and negative bus bars at 12 for this pur-- pose. Connected to each feeder is a current transformer 13 and 14, and connected to thesame respective feeders are the potential transformers 15 and 16. One end'of these potential transformers herein shown 1111' connected, but it will be understood that this unconnected end. in practice may beconnected to another conductor of the same feeder. The manner of connecting potential transformers is well understood by those skilled in the art. These current and potential transformers are for supplying the relays with energy.

17 is a diagrammatical representation of a. common form of two interlockedreverse energy relays. The Walking beam 18 carries at its ends means for closing two sets of corn tacts. These contacts are shown normally open, but either set be closed by means of the arznatures 19. These armatures do not move the walking beam 18 at the beginning of their movement, but are required to travel a certain distance before commi'inicating their movement to the walking beam, which in its turn. must move a certain distance before either set of contacts can be closed. The reason for this action will be explained later. The armature 19 is controlled by two solenoids 20 and 9.1, the solenoid 20 being supplied w h energy by the potential transformer 1:3, and the solenoid 21 by the current transformer 13. These solenoids are so connected to their transformers that when energy is flowing in the feeder in the normal direction, that is, from the feeder to the bus bar 1, these solenoids oppose each other. The scrotal :irn'uuure 15 also controlled by two similar solenoids which are similarly connected to the current and potential transformers 14 and 16 of the feeder 3. Now it will be apparent that so long as energy flows in the normal direction from the feeders to the bus bar, the walking beam 18 will be maintained in such a position that no contacts are closed. Should, however, the energy reverse in one of the feeders 2 or 3, for example, in the feeder 2, the solenoids 20 and 21, instead of opposing each other, will aid each other, the armature in feeder 2 will be attracted upward and the walking beam 18 moved in such a direction about its pivot that one set of contacts will be closed and the circuit completed from the bus bars 12 through the trip coil 9. The switch 6, will therefore open.

In practice it has been found that the ari matures 19 tend to move and close their contacts not only on the occurrence of reverse energy flow but also in case of overload, since in such a case the current solenoid .21 may so overpower the potential coil 20 as to raise the armature 19 and thus produce the same operatimi as on the occurrence of a reversal of energy flow. Supposing the tie line is not used, a short circuit of one of the feeders, as for example. a short-eircuit on the feeder 2, will not only produce a revei'sal of e y n this feeder between the point of short circuit and the bus bar 1, but willalso produce an overload condition on the feeder 3 which supplies the short circuit through the bus bar 1. To provide against a consequent simultaneous action of both armatures 19 and the operation of both switches E- and 7, the two relays at 17 are interlocked mechanically by means of the walking beam 18 which allows the engagement of but one set of contacts at a time. Such an interlocking of relays, the necessity therefor and their operation are more completely described in the United States Patent to Ostermann above referred to. This interlocking of relays is perfectly satisfactory where no tie line used. The use of the tie line 5, however, produces conditions not suitable for the operation of the interlocked relays at 1.7. Suppose now that the tie line 5 is used, and. that a shortcircuit occurs on the feeder 2 at the point 22 beyond the point of connection of the feeder 2 to the tie line Not only does there occur a reversal of energy flow in the feeder 2, energy being,-

supplied from the feeders 4 and the bus bar 1 direct to the feeder 2, but there is also a reversal of energy flow through the portion of the feeder 3 between the'bus bar 1 and the tie line 5, both the bus bar and the main portion of the feeder 3 supplying energy to the short circuit over the tie line. Thus there is a reversal of energy flow through both feeders 2 and 3 simultaneously, tendto the :imultaneous operation of both of the relays at 17 which action, however, is impossible by reason of the interlocking.

liurthcrmorc. provided these rchiys were not ilitcrhx l ed, they would ho incapable of picking out the faulty feeder and their failure to do so would result in opening both switches t3 and T and a cessztiion of supply of energy I to the hiss hm '1. How to cnt rcly disconnect a fault t'ce or from the nus bar 1 and still maintain lhc cunncclion of the hcalthy feeder nr fecders thereto in order to continue the supply of L1 'rgy to the 1 eirihuling station, I hare pr ideal the swi h 8 in the tie line and the epcndent relay 23. This re lay in \i-onncctcd to th urrent mid lfl'ilitlilill transformers 13 and 13 of the tecdcr 2, This relay similar to each of the rel: ys at l l7, but is cntirely independent of over other i relay and is free in net and close its contacts 1 under the action el 1 y lcnoids unhindered by the action of any other relay; The closing of the contacts of this ruin), it will he seen, fluflipltftrs a circuit. from the supply buses. l2 through the trip C(Jll ll, resulting l in the opening of the switch and the cut Now suppose a short l ting of the ticv line 5. circuit occurs, for example at the point l on the feeder 2, the switch 8 in the tic linc I) g being closed, as it will he in normal operzv l tion of the system. On thc Occurrence of the l short circuit, each relay at 1? is prevented 1 from closing its contacts by the other, as 1 before. The relay 23, however, is true to i opera) on the reversal of energy tlow, and i does operatmoptiiing the switch 8. The tie l line 5 now being cut, the energy in the feeder 3 must resume its normal direction, that is, t0 the bus bar 1, supplying energy to the 1 short circuitv 22 only through this bus bur. The right hand armature 19 is now free from the, ell act of a rcvcrst; energy flow and hence ceases to oppose, at lmnt with the smile force, the closing of LUl'll'iif'ifl by the left hand urinaturc 19 which is Ail. effected by a reverse cncrgy riow. This resulis in the closing of the propcr pair of contacts and the opening of ihe switch 6. It will he apparent that the. relay 23 will operate not only in the case of revcrse energy tlo'w due to an action on the: {coder 2, but that it will also Operate on rcverse'cncrgy flow due to an action on the fncdcr 3, since, before pointed out, a rsrcrsal of energy flow occurs on both feeders; between the bus bars and the tie line connections on an action on either feeder beyond the point of connection to the tie line. However, as the cpening in. the tie line 8 is essential to the operation of the protoctivo system, good practice may prescribe l the addition of another independent reverse energy relay 24 connected to the feeder 3. The closing of the contacts of either of these E independent reverse energy relays 23, 24 will result in the opening of the switch 8. It will be apparent that a reverse cner y flow due to an action on one of the fee ers between the point of connection to the tie line and point of connection to the bus bar 1, will result in the opening of the propelfeedcr switch 6 or 7, and also the opening of the tie line switch 8. Thus any action at any point on any feeder producing a reversal of energy causes thc complete segregation of thc faulty feeder from the rest of the system.

What I claim as new and dsireto secure by Letters Patent of the limited States, is

l. The combination with a receiving station, two feeders connected thereto, a tie line 1 connecting together the feeders, a switch for disconnecting each feeder from the station and a switch for opening the tie line, of

in 11115 for operating said switches including a, trip coil for each switch, a source. of energy for said trip coils, a reverse energy relay connected to each feeder the two relays being inczwahle of operating simultaneously, each relay controll ng the supply of energy to the trip coil of the switch of the feeder to which it eonnectcd, and another reverse encrgy relay connected to one of the feeders and controlling the supply of energy to the trip, mil of the switch of thc tic line.

ilfliho con'ibinzition with a receiving stalion, two feeders rmineeted thereto, a tie line connecting together the feders, a switch for disconnecting each feeder from the station and a switch fur opening the tie line, of means for operating saidswitches includ ing it trip (oil for each swiich, a source of energy for said trip coils, ll reverse energy relay connected to each l'eedci the two relays 10$ being incapable of operating himultnncously, each relay controlling the supply of energy to the trip coil of the switch of the feedcr to which it is connected, and another re verse current relay connected to each of said feeders, each of said last mentiuncti relays controlling the supply of energy to the trip coil hf the switch of the tie line.

In witness whereof, l lltlit" hyreunto set my hand this 8th day of ()ctober, 1912.

' DAVID BASCH.

\Vitnesses BENJAWIN B. HULL, HELEN ()nronn.

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