US1896943A - Selective circuit protecting device - Google Patents

Description

Feb. 7, 1933. R. DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1930 3 Sheets-Sheet l Feb. 7, 1933. DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1930 3 Sheets-Sheet 2 Feb. 7, 1933. R, DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1950 5 Sheets-Sheet 5 F 5.7 I Inventor-.9

E fluhwc m/Zw'am [Zz'oviczi f y Haw WW 'Efibrnqys.

Patented Feb. 7, 1933 PATENT OFFICE ROGER DUBUSC AND AVBAM DAVID ILIOVI CI, 01 PARIS, FRANCE, ASSIGNORS TO COM- PAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL DUSINES A GAZ, OF

MONTROUGE, SEINE, FRANCE, A JOINT STOCK COMPANY OF FRANCE SELECTIVE CIRCUIT PROTECTING DEVICE Application filed April 15, 1930, Serial No. 444,536, and in France April 30, 1929.

Several devices based on the use of the negative or the zero phase sequence components of the currents, voltages or powers have already been proposed for protecting a circuit.

Pilot wires have likewise been used in selective protection systems and in particular the pilot wires have been used as conductors in the auxiliary circuit, the current of which flows through the trip coils of the circuitbreakers or intermediate relays.

The present invention is concerned with devices in which pilot wires for transmitting the current of the auxiliary sources are used in conjunction with devices for obtaining the negative or zero phase sequence components.

By combining the pilot wires with the filter circuits for obtaining the negative or zero phase sequence components, a more accurate and flexible selection is obtained than when the currents or powers of the circuits are used directly; in addition, as only direct current generally flows through the pilot wires, and, moreover, only for the very short length of time necessary for operating the circuitbreakers, it will nearly always be possible to avoid designing special pilot wires, and telephone wires or any other Wires at hand may be used.

, Several embodiments of the invention have been illustrated in the accompanying drawings in which:

Fig. 1 illustrates a protecting device for a plurality of feeders in series.

Fig. 2 shows a protecting device for a circuit comprising feeders in parallel and groups of feeders in series.

Fig. 3 shows a protecting device which differs from that of Fig. '2 in that the negative or zero phase sequence component of the current or power flows in one direction only.

Figs. 4, 5, 6 and 7 illustrate further modifications of devices for protecting electric circuits. y Y

In Fig. 1, B0 BO ,,BO Bog-designate the bus-bars of the power station or of the sub-stations; F F F are three three-phase feeders following one after another; D D D D' D D, the circuit-breakers of said feeders (it has been assumed that there is one circuit-breaker at each end), but certain of the circuit-breakers may be cut out. B B B B B B are the trip coils of the circuit-breakers which may be replaced by auxiliary relays; fp fp fp are pilot wires through which flow the currents produced by the auxiliary sources SA SA SA F is a return wire for the currents of the pilot wires (the wire F may be replaced by the earth) RW RIV RVV are wattmetric relays (responsive to the negative or zero phase sequence components of power) of the doublethrow type. In these relays 0 is the current winding of the relay RVV fed by the secondaries of the three current transformers t mounted in parallel; 6' is the voltage winding of the same relay fed by the three reactance, resistance or capacity windings 7 7 1* The winding 6 receives the earth current (resultant of the currents in the three phases) and 6' a current proportional to the zero phase sequence component of the voltage. The reference characters e e t 1' 7 1" 6 6' t 1' 1" 7" have the same meaning in connection with the relays RVV and Rl/V as the corresponding preceding reference characters.

The wattmetric relays are so arranged that the contact of each relay will close to the left 1 (at 1) when the negative or zero phase sequence component of the power, according to the case in point, in the corresponding feeder is directed towards the right.

In order to make the operation of the device readily understandable, it will be assumed that there is an earth fault at M; it will likewise be assumed that the relays RW RW are earth relays and that there are at least two earths, one at T and the' other at T It is known that the zero phase sequence power component is always directed from the faulty point towards the earths: hence it will have the direction of the arrows f in the feeder F 1 and in that portion of the feeder F which lies to the left of the point M, and the opposite direction (arrows f) to the right of M. The consequence is that the contacts of the relays RW and RW will close to the right (at 2) whereas the contacts of the relays RW and RVV will close to the left '(at 1). It will be readily understood that the circuit of the auxiliary source 8A is closed, which will cause the circuit-breakers B ,]3 to trip, while the circuits of the sources SA and SA will remain open.

Fig. 2 shows the diagram of the same device as that of Fig. lapplied to the more complex 10 case of a circuit comprising feeders in parallel and groups of feeders in series. In this and in the following figures, in order to avoid overcrowding, the coils of the relays have not been illustrated but they are of course the same as those shown in Fig. 1. v Only one wire of each feeder has been illustrated, and it has been assumed that there are two earths at T and T The feeders F F FQare in parallel; the feeders F and F 2 are'independent; the first is continued by two independent feeders F and F The feeder F is continued by two feeders F and F in parallel. As in Fig. 1, fp fp illustrate pilot wires which transmit the currents of the auxiliary sources SA SA the latter are not placed, as in Fig. 1, in the pilot wires, but inthe wires which connect the points common to they movable contacts of the relays f to the common return wire F; the other refer- 0 ence characters have the same meaning as in Fig. 1;. The advantage of locating the aux- 'iliary sources in the manner shown is that their number is reduced. It will be observed furthermore that only one auxiliary source is used for two sub-stations. Obviously, one source could be used for each station, each source would then only furnish half the voltage to be provided in the case of Fig. 2.

If batteries are used, the number of units 40 for the whole network is the same whether one source per station or one source per two stations be used. It will be observed that there are two circuit-breakers per feeder and two wattmetric relays, save in th case of the feeders F and F' where one circuit-breaker and one relay per feeder has been provided.

For the latter feeder, two relays with one ortwo circuit breakers, or two circuit-breakers with a single relay might have been used. In reality, there is one relay such as RW for two feeders having a common end. 7 The current coil of this relay may be fed with the current of the one feeder or the other; practically, there will be preferably one relay for each end of each feeder, as will be seen in Fig. 7.

To understand the operation of the device, it will be assumed in the first place that a fault occurs at A, then that the fault is at B, finally at O. 1

If the fault be at A, the zero phase sequence power component fiowsin both directions in the feeder F and in one direction only in allthe other feeders. From what has been seen in the case of Fig. 1, the relay IWV will close its contact at 2, while the contact of the relay RW will close at 1. The current from the source SA will pass through the winds ings B and 13" and the oircuit-breakers D and D 2 will trip. On the other hand, in the other feeders, the contacts of the relays corresponding to the same feeder will close to the same side and the circuits of the corresponding pilot wires will remain open. If thefault occur at B, on the feeder F the same conditions will obtain for this feeder as for the feeder F in the preceding case and the two circuit-breakers between which it is confined will trip.

If the fault occur at O, the zero phase sequence power component to the right of G will be nil while'in the portion of the feeder F -situated to the left of C, the power will be directed towards the left and the circuitbreaker D will trip. In the feeder F the zero phase sequence power component will be nilbecause this feeder includes no earth; consequently its relay RW will remain open. Were there an earth at the right endof this feeder, the power flowing through it would go towards the earth and 'wattmetric relay Rl V would deflect to 1 while the pilot wire p 'would always remain open. Similar results would be obtained with negative phase sequence power components, whether'the neutral of thefeeders be insulated or earthed, the fault occurring between two wires in the first case and between twowires or with the earth in the latter case.

Fig. 3 illustrates the circuit arrangement corresponding to the case in which the zero phase sequence current or power component only proceeds in one direction; this would be the case should-only one earthobtain for example at T. In the case of a fault at a point M, the zero phase sequence current component only exists to the leftof M and the zero phase sequence power component proceeds from M to T.

In lines in which the neutral is earthed, and assuming that there is a contact between two wires at M, similar conditions to the preceding ones for the negative phase sequencecurrent or power component will prevail, if the line be open to the right of the fault, so that 'llO in this portion, there will be neither generators nor receivers (infinite impedance withrespect to the negative phase sequence current component). 7

In Fig. 3, it has been assumedthat the relays are responsive to the zero phase se quence component and that there is a single earth at T. The various reference characters have the same meaning as in Figs. 1 and 2 but the relays RW RW may be Wattmetric or current relays. V

In the former case, they must deflect to the right when the power proceeds to the left. In the latter case, the flow of current through the relay must make'the latter deflect to the each feeder two pilot wires right. It will be observed that the relays are normally closed to the left (at 1) If a fault occur at a point, the current flows through the feeders, or feeder sections lying on the left of the fault (between the faulty point and the earth) and does not flow through the others. Thus, for example, if the fault occur at M, the current only flows in. the relay RIV which deflects to the right and closes the circuit of the windings B B while the other auxiliary circuits remain open. If the fault occur at M onthe feeder F the relays nw RIV deflect to the right, and it will be readily seen that only the circuit of the winding B" is closed.

Figs. 4 and5 show circuit arrangements in which it has been assumed that the negative or zero phase sequence power component may proceed now in one direction, now in the other, now in both simultaneously, this corresponds to the most general case of a network operating under changing working conditions.

The case of a network with earthed neutral in which the position of the earths is variable will be considered.

In the two figures, there are associated with fl fp i F 7 fp fp fp and a return wire F which may be replaced by the earth. In Fig. 4, it is assumed that the coils of the circuit-breakers have a double winding or that the circuitbreakers have two coils. In Fig. 5, the circuit breakers B B have single windings, but intermediate relays A A A A grouped in pairs with their lel are utilized.

In both figures, the reference letters h ve the same meaning as in the preceding figures; in addition, in Fig. 5, A A A r 22 designate the intermediate relays having con tacts C C C C It will be observed moreover that in Fig. 4, there is one auxiliary source for twostations, whereasin Fig. 5 there is one source per station.

The operation of the device is readily understandable. If, in the circuit arrangement of Fig. 4, a fault occur at a. point M, three cases present themselves: 1. If there be only one earth at the left end, the contacts of the relays RIV and RWV will close at 2, whereas the positions of the contacs of the other relays will remain unchanged; it will be seen that in this case, only the circuit of the coils B and B is closed, whereby the circuit-breakers D;. and D will trip; 2. The earth is at the right end; in this case, the current only flows to the right of M and the relays RI and RW', close their contacts to the left; it will be seen that only the circuit of the windings B and B is closed; 3. Earths exist at both ends; in this case, the relays RVV RI RVV and Rid" close their contacts to the right, while the o h-ers close their contacts to the left (here all the relays contacts in paralare assumed to'be wattmetric and to deflect to the left if the power goes to the right) it will be seen that only the circuits of the windings B B and B B are closed; hence the same circuit-breakers as in the preceding cases will trip.

In the case of Fig. 5, the same three cases have to be considered, but here the closing of the circuits fp or fp will cause the current to flow in the windings A A A A of the intermediate relays, thus closing the contacts (1' (3'2 C3, C which will cause the current to pass through the windings B and B If there be only one auxiliary source for all the stations, an additional pilot wire must beused so that the two poles of the source may be ut lized at each station. Fig. 6 illustrates a c rcuit arrangement similar to that of Fig. 4 save that only one auxiliary so'urce SA obtains. The reference letters have the same meaning as in Fig. 4, but there obiains in addition the wire F which in conjunction with the wire F enables the two poles of the source to be used throughout.

In the preceding devices, it has been assumed that each of the wattmef'ric relays save those at the ends, serves to protect two feeders starting from the same bus-bars. Thus, the relay RVV of Fig. 1 serves for the feeders F and F similarly, the relay RIV of F 2 serves for the feeders F and F Th s arrangement which is economical may become faulty and it is preferable that each wattmetric relay should only serve for a given feeder. Moreover, in the more general types of protective devices, such as those corresponding to the circuit arrangements of Figs. 4 and 5, at each feeder end, a single wattmeric relay having a centrally positioned double contact and two auxiliary relays with contacts pressed against their stops may be used instead of two wattmetric relays with contacts pressed against their stops.

F g. 7 illustrates a circuit arrangement similar to that of Fig. 5 in which the feeders are protected independently of one another with wattmetric and auxiliary relays.

In this figure, D D illustrate the cir (nit-breakers mounted in the feeders F F F 3 B B the coils of the circuit-breakers: fp fp the pilot wires, FF the common return wire or the earth; RWV RIV wattmetric relays with two contacts 1 and 9.; RA RA HA auxiliary relays. The relays HA HA RA have their contacts thrown over against the lefthand stops and deflect to the right when current flows, while therelays RA RA RA have their contacts thrown over against the righthand stops and deflect to the left when current flows through their windings.

The relays RW RW close the contact 1 when the zero or negative phase sequence powercomponent is directed tothe of operation of the device is f is directed to the left in the feeder F and in of a plurality'of the portion of the feeder F lying to the left of M, while no power passes to the right of M. The relaysRW and RW close their contacts 2, so that the contacts of the auxiliary relays RA and HA move over to 2 and the pilot wires fp and fp remain open. Similarly, the pilot wires fp and fp remain open because the relays RW and RW do not act. On the other hand, the relay RN' deflecting to the right closes the contact of vR-A at 2, whereby the circuit of the pilot wire fp is closed and current passes through the windings B and B thus causing the circuit-breakers D and D to trip.

It will be seen similarly that if the earth is at T it is the pilot wire fp which is closed; if the two earths T and T exist simultanenously, the two pilot wires fp and In the various devices indicates, the relays may be instantaneous. However, in practice it will be preferable slightly to retard certain of the relays so as to avoid untimely operation. 7

If watmetric or curren relays are used alone, they will be slightly retarded. When using auxiliary relays, only the latter might be retarded. In all the devices, the windings B B 13 may be windings of intermediate or auxiliary relays acting on the windings of the circuit-breakers.

We claim: Y

1. In a selective protective system for an alternating current network, the combination relays, means for rendering said relays responsive to the negative or zero symmetrical phase sequence component of the power or current of said network, a plurality of circuit-breakers mounted in said alternating current network and including trip coils, auxiliary sources of current, a plurality of auxiliary relays, pilot wires adapted to convey current from said auxiliary sources both to said trip coils and to said auxiliary relays, and two sets of switch means operated by said'iirst mentioned relays and said auxiliary relays respectively for closing circuits for said auxiliary relays and trip coils respectively through said pilot wires.

2. In a selective protective system for an alternating current network, the comblnationof a plurality of relays, means for rendering said relays responsive to the negative Let a fault occur current, a plurality of auxiliary relays, two

pilot wires for each feeder adapted to convey current from said auxiliary source both to said trip coils and to said auxiliary relays, V

and two sets of switch means operated by said first mentioned relays and said auxiliary relays respectively for closing circuits for said auxiliary relays and trip coils respectively through said pilot wires. 1 Y

3. In a selective protective system for an alternating current net-work, including a plurality of feeders, the combination of a plurality of relays, one at each end of each feeder, means for rendering said relays responsive to the negative or zero phase sequence component of the current flowing in each feeder, or of the'tension between two feeders, a plurality of circuit breakers mounted in said alternating current net-work and including trip coils, auxiliary sources of current, a pilot wire for each feeder adapted to convey the current of said auxiliary source to said tripcoils, and means controlled by said relays for making or-breaking the circuits of said trip coils through said auxiliary sources depending onthe direction of the phase sequence component of thecurrent or tension influencing the relays.

a. In a selective protective system for an alternating current net-work, including a plurality of feeders, the combination of a plurality of relays, one at each end of each feeder, means for rendering said relays responsive to the negative or zero phase sequence component of the current flowing in each feeder, or of the tension between two feeders, auxiliary sources of current, a plurality of circuit breakers mounted in said alternating current net-work and including trip coils, pilot wires connecting said trip coils to said auxiliary current sources and two-way acting contact makers operated by said relays respectively in one direction or the other depending on the direction of the symmetrical phase sequence componentof the current or tension influencing said relays, for making or breaking the circuits of said trip coils through said auxiliary sources.

' ROGER DUBUSC.

AVRAM DAVID ILIOVIOI.

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