US2565127A - Protective relay - Google Patents

Description

us- 1951 w. E. GLASSBURN 2,565,127

PROTECTIVE RELAY Filed Feb. 16, 1950 1 I AVAVAL 1 A AVA B Ayl1l c o@ 5 wJ wJ wJ 3o ""1 "1 ""1 WITNESSES: INVENTOR William E. Glossburn.

72w M w Patented Aug. 21, 1951 UNITED STATES PATENT OFFICE PROTECTIVE RELAY William E. Glassburn, Bloomfield, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 16, 1950, Serial No. 144,401

' 12 claims, (01. 175 294) said overcurrent element from producing any torque when the directional-element contact is open.

It is the principal object of my present invention to producean improved high-speed directional overcurrent relay in which the overcurrent element is so controlled by a directional element that the direction of the torque or operatingforce which is produced in the overcurrent element actually reverses, dependentupon the position of the directional-element contact.

The system-conditions under which my new relay-control is needed, and the nature and structural design of my improved relay. will be hereinafter described and claimed, with reference to the accompanying drawing, wherein the single figure is a diagrammatic view of circuits and apparatus illustrative of a suitable form of embodiment of my invention.

In the drawing, I have illustrated my invention as being embodied in a phase-A relay which is used in the protection of a three-phase transmission or distribution line I. The line is connected to a station-bus 2 by means of a circuitbreaker 3 which is provided with an auxiliary breaker-contact 3a and a trip coil TC. Linecurrent for relaying purposes is derived by means of a bank of line-current transformers 4, and line-voltage for relaying purposes is derivedrby means of a bank of potential transformers 5.

My relaying apparatus, as illustrated, comprises a directional element D, which responds to the direction of the line-current I in phase-A of the line I, and an overcurrent element HR which responds to a predetermined magnitude of the line-current I. Both of these relay-elements D and HR are of the product-responsive type, by which I mean the type of relay which develops a torque or operating-force whichis proportional to the product of two single-phase fluxes, multiplied by a function of the phase.- angle or time-phase between them. This prod- 2 net-responsive effect can be produced, either in a difierential type of relay in which either the operating force or the restraining force is responsive to the resultant of two out-of-phase currents or fluxes, as illustrated in the Goldsborough Patent 2,404,955, granted July 30, 1946,, or it. can be produced in a wattmetric type of relay in which the stator-member has two fluxproducing windings for producing two interacting single-phase magnetic fluxes having poles which are displaced spatially relative to each other, and a rotor member which is so disposed as to produce a torque which is proportional to the product of these two single-phase fluxes multiplied by a function of the time-phase between them, an illustrative example of such wattmetric-type relay being shown in the previously mentioned Hoard patent.

In the drawing, the directional element'D is illustrated as having a current-winding II, a voltage-winding l2, and two sets of make-contacts l3 and I4. The current-winding H is shown as being energized by the line-current I, as derived by the line-current transformer 4. The voltage-001112 is ,il1ustrated as being energized from-the, phase AB voltage, as derived by the potentialdtransformers 5, with, a resistance R, in. series with .said voltage-winding l2.

The overcurrent relay HR is illustrated as havingtwo current-responsive windings 2| .and 22,

and a make-contact |5. Some dephasing means should be associated in shunt-circuit relationto one of the windings, such as 22 of the overcurrent element I-1R,,so that the fluxes which are produced, by the two windings 2| and 22 of this relay shall, not both bear the same time-phase relation to the energizing-currents which are su'pplied to said windings,.when said windings are connected together in series with each other. The dephasingr means which I have illustrated for this purpose is a short-circuited lagging-coil 23., In a broader sense, however, such laggingcoil means should be construed as being representative of any. means which causes the two fluxes of the overcurrent relay HR to be dephased with respect to each other when the two currentwinding circuits are connected in series with each other, so that the fluxes are neither in exact phase with each other or in exact phase-position. In theillustrated form of embodiment of my invention, the two, current-coils 2| and 22 of overcurrent element HR. have a common terminal 24, These two current-coils 2| and 22 are pro videdlwithseparate energizing-circuits 3| and 32, respectively, branchingback from said com- 3 mon terminal 24, the other terminals of these two separate energizing-circuits being indicated at 3| and 32, respectively.

I provide an auxiliary current-transformer 33, having a tapped-changing primary winding 33 which is energized by the line-current I in series with the current-winding I I of the directional element D. The transformer 33 is shown as having a separate secondary Winding 34, although an autotransformer could have been used, with the same winding serving as both the primary and the secondary windings. The secondary winding 34 has terminals 3| and 34, and these terminals 3| and 34' serve as thetwo terminals of a single-phase voltage-source which is used to energize the energizing-circuits 3| and 32 of the two current-windings 2| and 22 f theovercurrent element HR. The secondary winding 34 has an intermediate tap 32', so that this secondary winding 34 serves broadly, in efiect, as an impedance-means having the two terminals 3| and 34', and an intermediate tap 32. The supply terminals 34 is connected to the directional-element contact l3, and thence to the common terminal 24 of the two current-coils 2| and 22 of the overcurrent element HR, while the other terminals 3| and 32 of the current-coils 2| and 22, respectively, are connected to the other sourceterminal SI of the secondary winding 34, and to the intermediate secondary tap 32', respectively.

The tripping-circuit is shown as being connected from a positive battery-terminal through the make-contact I5 of the overcurrent element HR, and the make-contact M of the directional element D, and thence to the trip coil TO, the circuit being completed by the auxiliary breaker-contact 3a and the negative battery terminal The polarities of the connections of the overcurrent element HR are such that this element 1 develops a contact-closing torque when the flux produced by the unshaded coil 2| leads theflux produced by the shaded coil 22 by a certain angle such as 45. This condition is produced when both of these coils 2| and 22 are energized in the same polarity, which is the case when the directional-element contact I3 is closed. In such a case, the coil 2| is impressed'wit-h a voltagerfrom 3 to 34, and while the coil 22is impressed with a substantially in-phase, but smaller, voltage from 32' to 34. When the directional-element contact l3'is open, however, the two coils 2| and 22 are connected in series with each other, across the voltage from 3'|"to 32', so that the polarity of the coil 22 is reversed. The impedances of the two coils 2| and '22may conveniently be designed so that they have the same impedance-angles, although this design-condition is not necessary.

As a result of the above-described connections, my overcurrent element HR has a restraining or contact-opening torque, when the directionalelement contact I3 is open, and said overcurrent element has an operating or contact-closing torque when the directionalelement contact I3 is closed. The contact-opening torque of the overcurrent element is in addition to any relaybias which may be provided, for biasing the relay toward its open or non-responsive condition, as indicated at 40. My relay is designed so as to have its negative orcontact-opening torque when the directionalelement contact I3 is open, in order toj avoid a possible erroneous relaying operation on the pro.- tected line I. It will be understood that the di- Iectional element D is more sensitive than the 4 overcurrent element HR, so that the directional element D responds to the direction of the linecurrent I, or to the phase of this line-current with respect to the line-voltage in phase AB, without attempting to discriminate between heavy currents and light currents, or between fault-currents and load-currents. The directional element D thus responds to the direction of the loadcurrents Which-are flowing in the line I when there is no fault-condition. The overcurrent element HR, on the other hand, is designed to pick up, or respond, or close its contact I5, only when the magnitude of the line-current I is sufficient to indicate a fault-condition as distinguished from the maximum load-current which the line carries.

When the line-current I is flowing into the protected line-section away from the stationbus 2, the directional element D responds, and closes its contacts l3 and. Under these conditions, that is, during normal load-conditions, when there is; no fault-on the protected linesection I, but with theload-current-I flowing away from the station-bus 2, as indicated by the current-arrow I,'the directional-element contacts l3 and I4 will both be closed, and the overcurrent element HR will develop a torque in the currentclosing direction, but this torque will not be sufficient to overcome the forceeof the biasing spring 46, so that the overcurrent-element contact l5 remains open. If,now,-an internal fault occurs, that is, a fault having a'current flowing in the tripping direction, the-currentI in the protected line-section reaches a magnitude sufficient to cause the overcurrent element HR to close its contact |5, thus instantly tripping the trip-coil TC, because the directional-element contact |4is already closed, since the line-current immediately preceding the fault was inthe tripping direction.

' Now, still assumin that the load-current I is flowing in thetripping direction, that is, out into the protected line-section I, let us assume that an external-fault occurs,;which may be on the station-bus 2; or somewhere on the system back a of this station-bus 2, so that the fault-current now reverses and flows back towards the sta tion-bus 2; When such a fault occurs, the overcurrent element HR'will'at first be in an energized condition in which it develops an operating torque, so thatit will start to close its contact l5. The directional element D, atthe same time, will start to open its'contacts l3 and M, which had been closed, because of 'the direction of flow which was assumedfor the load-current immediately p'revious to the fault. A proper coordination of the'contacts can easily be managed, by the 'propersetting of the contact-follow: and travel, so that theidirectional element D will be ableto get its closed contacts l3 and I4 open before, the overcurrent element HR can travel far enough to close its contact l5; thus preventing. tripping, which is thedesired result when the rfault+current is in the non-tripping direction.

Such an,externallfaultfhowever, willhave to be cleared bysomeyother protective relaying de-, vices (notshown) which are designed to respond to faults Occurringwithin the. place where the assumed fault isilocated, andjwhen these other protective relaying devices respond, and cause av circuit interruptin operation somewhere else in response, to the fault, the faultvmight be cleared, while the overcurrent-element contact |5v is-still closed, or,whil e the overcurrent element HR is still drifting, by its own inertia, in the contact-closing direction. As soon as the ex-.

shown in Fig. 3 of the previously mentioned Hoard patent, where the overcurrent element was merely deenergized, not reversed in torque, in response to an opening of the directional contact [3, there was considerable danger that the overcurrent element would continue to drift into its closed-contact position, after the directional contact 13 had initially opened. In my system, however, the opening of the directional contact l3 does not merely deenergize the directional element HR, or kill its contact-closing torque, but it actually reverses the torque of this overcurrent element, so that this reversed torque will act against the inertia which tends to cause said element to continue to move in its contact-closing direction after the directional contact l3 has opened. The result of my reversed torque is thus a great reduction in the possibility of the incorrect tripping which would result if the overcurrent contact 15 should be closed at the in stant when the external fault was cleared by other means (not shown), and when the directional contact I4 should reclose in response to a load-current flowing in the tripping direction.

If the load-current is in the non-tripping direction, that is, out of the protected line-section, and toward the station-bus 2, there will be a proper operation for all faults within the sensitivity of the elements, because the load-current causes the directional contacts l3 and [4 to be open. An internal fault will first cause the directional contacts 13 and I4 to close, after which the overcurrent element HR will develop a torque in the contact-closing position and will close its contact 15, thus producing a tripping operation. If the fault is in the non-tripping direction, the directional contacts 13 and I4 willremain open, the same way they had been in response to the loadcurrent, and the torque of the overcurrent element HR will remain in the contact-opening direction so that the overcurrent contact l5 will not close.

While I have described my invention, and explained its method of design and operation, with reference to but a single form of embodiment, I wish it to be understood that the chosen embodiment is only illustrative, and that my invention is susceptible of various changes by way of the substitution of equivalent parts or the addition or omission of parts and refinements. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. In combination: a single-phase productresponsive relaying element having contactmeans, two flux-producing winding-means for producing two interacting single-phase magnetic fluxes which are so disposed as to produce a force which is proportional to the product of the two single-phase fluxes multiplied by a function of the time-phase between them, and an energizing-circuit for each of said windin -v means, the two energizing-circuits having one terminal in common; in combination with a single-phase voltage-source having two terminals, an impedance-means having two terminals and an intermediate tap, the two terminals of the impedance-means being connected to the two terminals of the voltage-source, means including a circuit-making and -breaking device for causing the common terminal of said two energizingcircuits to .be either connected to one terminal of said impedance-means or disconnected from said impedance-means, and circuit-means for connecting the other terminals of the respective energizing-circuits to the other terminal and the intermediate tap, respectively, of said impedance-means.

2. A high-speed directional overcurrent relay adapted for use on an alternating-current system and characterized by having an overcurrent element as defined in claim 1, and a directional element for responding to the phase of a line:- current with respect to a line-voltage, said directional element being operatively associated with the circuit-making and -breaking device referred to in said claim 1.

3. In combination: a single-phase productresponsive relaying element having contactmeans, and two windings having one terminal in common; in combination with a tapped singlephase energizing-source having two terminals and an intermediate tap, means including a circuit-making'and -breaking device for causing the common terminal of said two windings to be either connected to one terminal of said source or disconnected from said source, and circuitmeans for connecting the other terminals of the respective windings to the other terminal and the intermediate tap, respectively, of said source.

4. A high-speed directional overcurrent relay adapted for use on an alternating-current system and characterized by having an overcurrent element as defined in claim 3, and a directional element for responding to the phase of a linecurrent with respect to a line-voltage, said directional element being operatively associated with the circuit-making and -breaking device referred to in said claim 3.

5. In combination: a single-phase productresponsive relaying element having contactmeans, two flux-producing winding-means for producing two interacting single-phase magnetic fluxes which are so disposed as to produce a force which is proportional to the product of the two single-phase fluxes multiplied by a function of the time-phase between them, and an energizing-circuit for each of said windingmeans, the two energizing-circuits having one terminal in common, said winding-means and their respective energizing-circuits being so related that the time-phase between the flux produced by one winding-means and the current carried by its energizing-circuit is different from the time-phase between the flux produced by the other winding-means and the current carried by its energizing-circuit; in combination with a single-phase voltage-source having two terminals, an impedance-means having two terminals and an intermediate tap, the two terminals of the impedance-means being connected to the two terminals of the voltage-source, means including a circuit-making and -breaking device for connecting the common terminal of said two energizing-circuits to one terminal of said impedance-means, and circuit-means for conn'ecting the other terminals of: therespective energizing-circuits to :the other terminal and the intermediate tap, respectively, of saidflimpedance-means. 7 6. A high-speed directional overcurrent relay adapted for useon an alternating-current system and characterized by having an overcurrent element as defined in claim 5, and .a directional element for responding to the phase ofa linecurrent with respect to a line-voltage, said. directional. element being operatively. associated with the. circuit-making and breaking device referred to insaid claim 5.

7. In combination:' a singlesphase product-responsive relaying element having contact-means, two windings vhaving one terminal in common, and dephasing means associated with at least one of said windings; in combination with a tapped single-phase energizing-source'having two terminals and an intermediate tap, means including a circuit-making and -breaking device for connecting the common terminal of said two windings to one terminal of said source, and circuitmeans for connecting the other terminals of the respective windings to the other terminal and the intermediate tap, respectively, of said source.

8. A high-speed. directional overcurrent relay adapted for use on an alternating-current system and characterizedby having an overcurrent ele ment as defined in claim 7, and a directional element for responding to the phase of a line-current with respect to a line-voltage, said directional element being operatively associate-d with the circuit-making and -breaking device referred to in said claim '7.

9.- In combination: a single-phase product-responsive relaying element having contact-means, two windings having one terminal in common, and dephasing means associated in shunt-circuit relation to at least one of said windings; in comminal of said two windings to one terminal of said source, and circuit-means for connecting the other terminals of the respective windings to the other terminal and the intermediate tap, respectively, of said source.

g ment for responding to the phase of a line-current with: respect to a line voltage, said directional element being operatively associated with the cir- 'cu'itsmaking' and -'breal ing device referred to in said .claim 9.

11..1A directional overcurrent relay adapted fornuse on an alternating-current system and characterized by having a directional elementfor responding to the phase of a line-current with respect to a line-voltage, an overcurrent element having two windings in such operative relation-to each other that the overcurrent element develops acontact-opening force or a contact-closing force dependent upon the relative directions of the currents traversing said windings, and means under the control of said directional element for causing the two windings of said overcurrent element to be energized in one phase-relation when the directional element. is in one position, and for causing said two windings of the overcurrent element to be energized in-a 10. A high-speed directional overcurrent relay adapted for use on'an alternating-current system and characterized by having an overcurrent element as'defined in claim 9, and a directional elesubstantially different phase-relation when said directional element is in its other position.

12. A directional overcurrent relay adapted for use on analternating-current system and characterized by having a directional element for responding to the phase of a line-current with respect to a line-voltage, an overcurrent element having two windings in such operative relation to. each other that the overcurrent element develops a contact-opening force or a contact-closing force dependent upon the relative directions of thev currents traversing said windings, and means under the control of said directional element for causing the two windings of said overcurrent element to be energized in substantially the same polarity when the directional element is in one position, and for causing said two windings of the overcurrent element to be energized in the opposite polarity, one with respect to the other, when said directional element is in its other position.

WILLIAM E. GLASSBURN.

REFERENCES CITED The following references are of record'in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,379,905 Hoard July 10, 1945 I 2,432,328 Morris Dec. 9, 1947

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