US1333892A - ackerman - Google Patents

Description

P. ACKERMAN.

PARALLEL FEEDER PROTECTION.

' APPLICATION FLLED DEC. 24. I917. 1,333,892. Patented Mar. 16,1920.

3 SHEETS'SHEET I.

five-21702",-

P. ACKERMAN;

PARALLEL FEEDER PROTECTLON.- APPLICATION FILED DEC. 24, 1,91}.

Patented Mar. 16, 1920.

3 SHEETS-SHEET 2.

five/971702",

P. ACKERMAN.

PARALLEL FEEDER PROTECTION.

APPLICATION FILED DEC. 24, I917. 1,333,892. Patented Mar. 16, 1920.

3 SHEETS-SHEET 3- UNITED STATES PATENT OFFICE.

PAUL ACKERMAN, OF TORONTO, ONTARIO, CANADA, ASSIGNOR T0 SEARS B. CONDIT, JR.

PARALLEL-FEEDER PROTECTION.

Specification of Letters Patent. Patented )Iar. 16, 1920.

Application filed December 24, 1917. Serial No. 208,572.

To all whom it may concern:

Be it known that I, PAUL ACKERMAN, a citizen of Switzerland, and a resident of 'loronto, Province of Ontario, and Dominion of Canada, have invented an Improvement in Parallel-Feeder Protection, of which the following is a specification.

My invention relates to electrical distribution systems, and has particular reference to the protectionof parallel feeders ass0- ciated with such systems.

It is common practice in distribution sys tems, where current is to be transmitted from a central power station to a distributing sub-station, to employ a number of parallel feeders extended between the power is ation bus bars and the substation bus bars in order to provide continuity of operation upon the possible failure of one or more of the parallel feeders.

Each of the parallel feeders is preferably normally arranged to have approximately the same operating characteristics; and all ofthe feeders are arranged to carry equal loads. It sometii'nes happens that a fault occurs upon one of the parallel feeders of the system, and in such an event it is therefore desirable that the faulty feeder be isolated from the system without interfering With the distribution of current throughout any of the other feeders of the system; and it is with means to accomplish this result that my invention is concerned.

As previously stated, the feeders are normally adapted to carry equal currents. Upon the occurrence of a fault, such as a short, in any one of the feeders, the current flow in the faulty feeder is increased over that of the remaining parallel feeders, and may become reversed in direction relative to the current flow in the remaining healthy feeders of the system.

Various protective systems have been conceived, i'naking use ofthe relative increase and reversal of current flow. Such a sys I tern, for instance, is disclosed in my Patent- 1,192,724, dated July 25th, 1916.

In the distribution system. illustrated in said patent, any particular parallel feeder controlling circuit is governed by the condition existing in the parallel feeder to be governed, and by the condition of any two other parallel feeders of the system. This system has the disadvantage that if the two parallel feeders associated with the parallel feeder to be protected are removed from the system, the parallel feeder will be protected only against straight overloads, and not against relative reversal of current flow therein. I

It is highly desirable that the removal of one or more parallel feeders from the distribution system should not affect th operation of the protective devices guarding the remaining feeders from the effects of faults developing within the feeders.

An object of my invention is in the provision of protective means for the parallel feeders of a distribution s stem associated with all of the parallel feeders of the system, whereby the relative change of condi tion of any parallel feeder with respect to all of the other parallel feeders, serves to operate to remove the faulty feeder from the system.

By governing any particular feeder by all the other feeders of the system, it may be seen that the removal from the system of any one or more feeders up to a predetermined niunber, does not affectthe complete control and protection of the particular feeder chosen.

The means whereby I accomplish the object of my invention is in the provision of current transformers associated in the line of all the parallel feeders, and so connected with each other and with relays that, upon the normal condition of the system, in which each parallel feeder has the same value of current flowing through it, and the system is balanced; the current transformers, or the effects of the current from the transformer upon the relays will be balanced, and the relays will thereby be unoperated; but upon the development of a fault in any one feeder, resulting in an increased current flow in that feeder or a relative reversal of current flow in that feeder with respect to the remaining feeders; the increased or reversed current flow in the current transformer of the faulty feeder will serve to unbalance the normally balanced protective system in which the relays are included. and serve to operate the relays to selectively cut out the faulty feeder.

There are a number of ways in which the current transformers and relays may be connected between the parallel feeders of F or instance, inasmuch as the object of this inventlon is to connect the controlling or protective circuit of any particular feeder wlth all ofthe other parallel feeders,

a possible scheme of connection is to cor.

nect a current transformer in the particular feeder with the current transformer of particular feeder with currenttransformers in the remaining parallel feeders, forming pairs of connected feeders between the particular feeder and all of the remaining feeders. If there are three parallel feeders in the system, numbered respectively 1, 2 and 8, and feeder 1' is the feeder to be protected then there will be aconnectlon between a transformer in line 1 and a transformer in line 2, and a separate connection between a second transformer in line land'a transformer in line 3. v

Relays are associated in the connection between the pairs of transformers; and the connection between the transformers and the relays is such that, in the norn'ially balanced condition of the. circuit, the relays are ineffectively energized; but upon an unbalancing of the particular feeder, with respect to the other feeders with which it is connected, the relayswillbe operated; but both relays are arranged to be so connected as to collectively control the particular parallel feeds-i3. and therefore, both relays must be operated to cutout the particular parallelfeeder from the system. 1 I

While the connection above described illustrates the principle of the system, in that pairs of connections are made between the feeders, and protective relays arranged in said connections, yet itispossible to combine the relays and the current transformers in the feeders to form a certain minimum number, w rich will completely fulfil the requirementsof the obj ect of the inrention.

In practice, there are two general'schemes of connections between the current transformers associated in the parallel feeder circuits and the relays. It is possible to connect the transformers in series with the coils of the relays and employ differential relays, in which condition the magnetic-flu in the relays will normally be bucking each other, andthe relays are thereby normally. ineffectively energized rand it ispossible to'cornect the currenttransformers of the parallel feeder systeni'inseries and connect the coils of the relays, employing this time non-dif- I 'ferential relay 1n shunt across the trans f01;'mers,1 in which connection the relays are normally inefi'ectively energized. Both schemes of COHHQCtIOH are old in the'prior art, and are interchangeably employed where the type of transformer and other associated instruments seems to justify the use of one system ratlierthanthe other.

In the figures, Figure 1 illustrates dia grammatically a protective system showing the general scheme of connection, embodying my invention, associated with three par allel feeders.

Fig. 2 illustrates a protective system for three parallel feeders in which a minimum number of relays and current transformers are used, the relays being connected in series with the transformers.

Fig. 3 illustrates diagrammatically the scheme of connection forjthree parallel feed ers employing series connected current transformers and shunt connected relays. I

Fig. a system of Fig. 3 in which a minimum number of transformers and relays are employed. l

,Fig. illustrates a protective system for four parallel feeders, employing the series scheme of relay connection'and a minimum number of transformersand relays.

6 is a protective system for four parallel feeders, employing the shunt scheme of relay connection and a minimum number of transformers and relays: I I

As shown in F 1, the parallel feeders 10, 11 and 1-2 are connected to the bus bar 1%, which i in represent the sub-station end of the distribution system. Each parallel feederhas a switcn 15, in its circuit which when operated serves to disconnect its particular parallelfeeder from the bus bar ll;

and each'switch has associated with it the" tripping cell 16, which is arranged to be governed by the protective relays to be hereinafter described. I

The control circuit for any parallel feeder is associated with all of the other parallel feeders, and therefore line 10 associated with line 11 and line 12 the condition of said lines'll andl2 being a dition of line 10. Also line 11 isv associated .with line 10 and line 12, in which case the 1 condit on of said lines 10 and 12 form'a pairs of connections which can be made between the current transformers of the parallel feeders.

I In lcurrent transformers '17 are arranged in lin s '10 and ill-{and the current coils or secom; ries thereof are respectively connected to th coils 18 and19 of a diffen' second current trans-Q ential relay 29. A. former 17", in line 10, and current transmeasure of the con- 7 r I tion between the circuits including the switch tripping coils 16 is such that two relays must be simultaneously closed in order to energize the tripping coils of the switch of a particular feeder, in order that said feeder may be removed from the system.

In the normal operation of the system, the coils 18 and 19 0f the differential relays 20, 21 and '22, in the pairs of connections between the feeders of the system, are equally and oppositely energized, and consequently all of the relays are in a non-operative position.

Upon the occurrence of a fault in feeder 10, for instance, the resulting increase or reversal of current flow in the transformers 17 and 17 connected in said feeder, relatively 1 to the current flow in the transformers in the remaining parallel feeders of the system,

them to actcumulatively to cause the simultaneous operation of said relays" to close the contacts 23, which completes the oper atin g circuit for the tripping coil 16 and the switch of the feeder 10 thereby operates to disconnect said feeder from the bus bar 14.

The closing of contacts 24 of the relays and 21,upon theoperation of said relays to isolate the feeder 10 from the system does not operate to complete the circuit for the tripping coil for any other feeder switch,

inasmuch as both of the separate trip coil circuits, controlled by the contacts 24; of the relays 20 and 21, are also governed by the relay 22 connected between the two normal or healthy feeders 11 and 12, and which is thereby unaffected by the faulty condition of the feeder 10.

If the fault occurs in feeder 11 instead of in feeder 10, then the relays 20 and 22,, connected in the connections between parallel feeders 11 and 10, and 11 and 12 respectively, operate to close contacts 2& of the relay 20, and 23 of relay22, to coninnctively control the operation of the trip coil for tl e switch in feeder 11, to isolate said feeder from the bus bar 14;.

The trip coil circuits for the switches in the remaining and healthy feeders 10 and 12 will be maintained openat the contacts controlled by relay .21 which is unaffected by the condi the fault in e or M.

The ion of he protective system to isolate the feeder 12 from the distribution ce of a fault in of current flow caused by connecticn with feeders 10 illustrates a simplified arrangein the protective circuits of Fig. 1, embodying the scheme of pairs of connections between the p .llel feeders, in which the feeders 10, 11 12 have but the current tran (-1'111" z' associated therewith, which tram rs are independently con nected with a three differential relays 20, and 22. In the connection shown, cur rent transformer 17 in line 10 is connected to the coils 18 of relays 20 and 21. Transformer 17 in ine 11 is connected to the coil 18 of din erential relay and the coil 19 of relay 20. Transform 17 of line 12 is connected to the coil '19 of relay 22 and the coil 19 of relay Considering feeder 10, the two relays 20 and 21 are adapted for its protcction, and are c orerned by t the feeder 11. the r'r-nsftu'n er of which is Connected to the coil 19 of relay and hy feeder 12 the transformer of 1 ch is connected tothe coil 19 of relay :1. The other pairs connections between the 1GJ"211111l feeders are v connected to the coils of the dif 12- ea "*lijttl COllClltlUll l. p ticularl'v to feeder cm the energization botl in both relays 20 and 21 will the relays will there fore n r t to close the contacts 23 and I f acted as in Fig. 1, to tie tripping circuits or the switches 15 in. the feeders Unon the occurrence of a faultin feed r 10 which results in an overload or a 'ent flow therein relative to the coils 18 of the rebecoine energized in greater proportion than the coils 19 of said relays, ch are connected respectively to the trans in feeders 11 and 12 and which are normally energized or in which, t 1 s there is no relative reversal of cur e l and thereby both relays will be i-nltaneously operated to complete the connection, through con-c s of the relays, with the trippi coil 16 to cause the opening of the s\ -ch 15 in the feeder 10, to thereby isolate the feeder from the circuit. Upon a fault occurring in any other feeder, the same condition of affairs will he set up, and the proper relays will be effectively energized to remove the faulty feeder from the system.

formers of the pairs of parallel feeders are connected in series and the relays are con nected 1n shunt across the connections between the pairs of current transformers.

. that in Fig. 3 there is a series connection of current coils, and shunt connection of relays. As here shown in Fig. 3, the current trans former 17 in feeder 10 is connected in series 'with the transformer 17 of feeder 11. A second transformer 17 in feeder 10 is connected in series with-a transformer 17 in feeder 12, thereby connecting line 10 with all of the other feeders of the system. -A transformer 17 in feeder 11 is connected in series with a transformer 17 in feeder 12, and feeds 11. is thereby connected witlrall of the other feeders in the system, and line 12 is also connected wit-hall the other feeders in the system.

Relays 25, 26 and 27 are connected respectiyely in shunt across the connections between the. transformers connecting feeder 10 with 11, 10 with 12 and 11 with 12. In

I the normal and balanced condition of the feeders there is no voltage'drop across the relay coils; and consequently, the relays are not operated. .Howeyer, 7 upon .an occurrence of a fault 111'f6QCl6l.10, for instance, the current in transformers l4 and 17 in said feeder will become greater than the [current in transformer 17; of feeder 11 and in the transformer 17. of line 12; andtherefore the relays and 26 will become effectively energized and operate to close the 7 contacts 23 controlled by said relays to energize the tripping coil 16, and cause the isolation of the faultyfeeder 10 from the system. other feeder will cause pair of relays to be operated in a similarmanner to remove the faulty feeder from the system.

- In Fig. 4: isshown a simplified scheme of connections of the protective system of Fig. 3, the'operation of which is exactly similar to the operation of the system shown in Fig. As here shown, the current transformers 17 1n the parallel feeders 10, 11 and 1.2 are connected in series with'each other.

The relays 25, 26 and-Q27 are connected in,

, shunt across, the three transformers 17 in the feedercircuits, and, here shown, re lays 25 and 26, in series, are connected across transformer 17 in line 10; relays and 27, in series, are connected across the transformer 17 in line 11; and relays 26 and 27 are connected inserie's across the current coil 17 'in'line 12. It is seen that with this scheme of connection, any particular feeder is connected with all the other feeders...

7 Two relays must be operated to control the controlling circuit for'any particular feeders to be Tie occurrence of a fault in any feeder system In the operation of the system shown in Fig. at, in the normal and balanced condition of the feeders, there is an equal current flow in each of the current transformers in the feeders; and, consequently, the relays 25, 26 and 27, connected across these transformers will not be operated, due to the absenceof a differ ence of potential at the points to which the relaysare connected. If, however, a fault develops in feeder 10, for instance, the current in the transformer 17 in said feeder to operate said switch to isolate the feeder from the system; Upon the occurrence-of a fault 1n any other feeder of the system said feeder Wlll be cut out of the systen'l in a manner similar to that described in regard to feeder 10. v x V Fig. 5 shows a simplified scheme of-conuections for a protectiy'e' systemrinvolying' four parallel feeders, in which the current transformers are connected in series with the relays governing .the tripping circuits. The relays in this case are "differential relays. 7 f

Inasmuch as there are four parallel ployed V r relays, which represents the number of pairs of connections which may be made,

protected, there must bejemand which is the n'iinimunr number of 're- 7 lays that may be employed to completely protect a system comprising four feeders, and which is connected between the parallel feeders of the system in accordance with 7 he invention Considering the case of any one feeder, there are three remaining feeders to the system, and there must of necessity be'three relays, each of which respec-:

parallel feeders in which the series connection of current coils and-the shunt connectlon of relays is. employed. "Inasmuch as there are three combinations of one line,

considering any particular parallel feeder against the remaining three feeders, it follows that there must be provision for three taps of three relays corresponding to one line. WVith one transformer per line, there is available but two such taps, and it thereforenecessary to employ at least two transforn'iers for each line in order to provide the requisite number of taps to properly connect the three relays required to completely protect the line in question.

As here shown, feeders 10, 11 and 12 have each a transformer 17, which are connected in series. A second transformer 17 in feeder 10 is separately connected in series with a second current transformer 17 in feeder 12, and with atransformer 17 in feeder 13. A second transformer 17' in line 11 is connected in series with a transformer 17 in feeder 13, which connection is independent from the two previous sets of transformer connections. Relays 28, 29 and 31 are connected to points between the transformers 17 in feeders 10, 11 and 12.

Relays 30 and 33 are connected across the connections between transformers 17" and 17 in feeders 10, 12 and 13 respectively, and

relay 32 is connected across the connections between the current coils 17 in feeders 11 and 13.

By the arrangement of transformers and relays shown, any particular feeder is connected with all the remaining feeders, and the operation of three relays serves to control the controlling or tripping circuit for the switch of the particular feeders chosen.

In the operation of the protective system illustrated, in the normal condition of equal current flow in all of the current transformers in the parallel feeders, there is no potential difference between the points between the transformers to which the relays are connected, and consequently the relays are not operated. Upon the occurrence of a fault, say in feeder 10, a potential difference is set up across the transformer 17 in said feeder, and relays 28 and 29 are energized, and operate to close the contacts :23 and 24 controlled thereby. The operation of said relays alone does not, however. suflice to cause the'energization of the tripping coil 16 of the switch 15 of. the feeder 10.

Due to the fault, the potential across transformer 17 in feeder 1.0, which transformer is connected with transformers 17 and 17' respectively in feeders 12 and 1", serves to energize relay 30, and the operation of said relay 30 serves to complete the tripping circuit and cause the isolation of the faulty feeder 10 from the system.

No other tripping circuits will be affected inasmuch as other relays, arranged to be nnoperated upon the occurrence of a fault in feeder 10, must also be operated to control the tripping circuits for the other feeders.

A similar operation of the proper relays occur upon the occurrence of a fault in any other feeder of the system.

As a general proposition, it may b stat d that with n feeders, the total number of relays to adequately protect all the feeders is and the number of relays that must be simultaneously operated to selectively remove any faulty feeder from the system is o1/1. If there are six feeders to be protected, for instance, then the total, number of relays to adequately protect all of the feeders is relays, and the number of relays that must be simultaneously operated to remove a feeder from the system is one less than the total number of feeders in the system; or five relays.

In the cases above cited, a single phase line is illustrated. If a three phase line, or any multi-phase line is employed, the number of relays must be duplicated for each phase. The diagrams represent one end of the feeder system, which may be the end connected with the sub station bus bars. The other end of the feeder may be provided with exactly the same equipment of relays, to isolate the faulty feeder from the system at that end. The total. number of relays in any system will always correspond to the total possible number of pairs of con nections between feeders, and the total num ber of relays in series to trip one switch to isolate the corresponding feeder from the system will be equal to the total number of pairs of connections between one feeder and the remaining parallel feeders.

In the lines above described, it has been assumed that the feeders have approxi mately the same characteristics. If one or more of the feeders are of different characteristics, then the windings of the relays, or the transformers, associated with such feeders is so arranged as to compensate for such difference.

I claim:

1. In an electrical distribution system comprising a plurality of parallel feeders connected through switches with buses, connections between any particular feeder and all other feeders in the system, a relay in each connection, a tripping circuit for each feeder, each relay arranged to govern a plurality of tripping circuits, and means to cause the relays in the connections between a particular feeder and all other feeders to operate to selectively and conjointly control the tripping circuit for the particular feeder to isolate said feeder from the bus upon the occurrence of an abnormal current condition in said feeder.

2. In an electrical distribution system comprising a plurality of parallel feeders connected through switches with buses, in-

nected hrough switches with buses, connec tions between the'feeders to form a combinatlon of pans of connected feeders between any particular feeder and all other feeders of the system, a relay in the connection between each pair of connected feeders, a tripping circuit for each feeder,

means to cause each relayto control a plu V rality of tripping circuits, and means to cause the relays in a particular combination to operate to conjointly control a particular tripping circuit upon the occurrence'of an abnormal current condition in the corre sponding feeder to thereby isolate said feeder from the bus. I i

4:. In an electrical distribution system comprising plurality of parallel feeders connected through switches with buses, inductive connections between thefeeders to form a combination of pairs of connected feedersbetween any particular feeder and all other feeders of the system, a relay in the connection between each pair of con nected feeders, atripping' circuit for each feeder, means to cause each relay to control a plurality of tripping circuits, and means to cause the relays in a particular combination to operate to congointly control. a particular tripping circuit upon the occurrence of an abnormal'current condition in the corresponding feeder to thereby isolate said feeder from the bus. V

5. In an electr cal distribution system comprising a plurality of parallel feeders connected through switches with buses, induct-ire connections between the feeders to form a combination of pairs of connected feeders between any particular feeder and all other feeders of the system, a relay in the connection between each pair of connected feeders, tripping circuit for each feeder, means to cause each relay to control two tripping circuits, and means to select for operation certain relays to conjointly control the tripping circuit of particular feeder to isolate said feeders from the bus upon the 00- I currencc of an abnormal current condition in said feeder.

6. In an electrical distribution system p Z a comprising a plurality of parallel feeders connected through switches with buses, inductive connections between the feeders to form a combination of pairs of connected feeders between any particular feeder and all other feeders of the system, a relay in the connection between each pair of connected feeders, mon to a plurality of such combinations, a tripping circuit for each feeder, the relays included in a particular combination operable to conjointly control the tripping cir- 'transformer-sin said feeders, connections between the secondaries of said transformers to form 'a combination of pairs of inductively connected feeders between a particular feeder and all other feeders of the system a relay in the connection between each pair of connected feeders, thenumber of relays being one less than the number of possible combinations, certain of said relays forming a part of more than onecombinm tion, a tripping circuit for each feeder, the relays of a particular combination arranged to control the feeder circuit of the feeder forming the combination with all other feeders, and means to cause the relays of the particular combination to operate to certain of said relays being com i conjointly control the particular} feeder to disconnect it from the bus upon the occurrence of'an abnormal current condition in said feeder. e

8. In an electrical distributionsystem comprising a plurality of parallel feeders connected through switches with buses, transformers in said feeders'tripping' circuits for said feeders, plurality of relays each arranged to control two tripping circuits, two or more relays arranged to coin trol each tripping circuit, and connections between said transformers, and relays to select certain of said'relays for operation to conjointly control the tripping circuit for a particular feederto isolate said feeder from the bus upon the occurrence of an abnormal H. B. DAVIS,

Gannrrwccn.

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