US2561998A

US2561998A - Protective relay system

Info

Publication number: US2561998A
Application number: US62197A
Authority: US
Inventors: William K Sonnemann
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1948-11-26
Filing date: 1948-11-26
Publication date: 1951-07-24
Anticipated expiration: 1968-07-24

Description

y 1951 w. K. SONNEMANN 2,561,998

' PROTECTIVE RELAY SYSTEM Filed Nov. 26, 1948 Fig. I.

Phase A Reloy Unit) Phase 0 Relay Uni! ABC oc Reference Wliuqe |2OVolts 6O Cycles Fig.3.

Close WITNESSES:

INVENTOR William K. Sonnemunn ATTORNEY Patented July 24, 1951 PROTECTIVE RELAY SYSTEM William K. Sonnemann, Rose'llePark, N. J., as-

signor to Westinghouse Electric Corpor-ation, 'East Pittsburgh, Pa, a corporation of Pennsyl- 'vania Application November 26, 1948, Serial .No. 62J97 (o1. its- 294) 12Claims. 1

This invention relates to electrical systems having relays associated therewith, and it has particular reference to electrical systems employing directional protective relays.

In, some .relay units, a relay, which may be termed a primary relay, is employed for controlling the operatiueness .ofanother relay, which maybe termed .a .secondaryflrelay. As a specificexampleofsucha relay unit, reference may be made to a directionalrelay unit which includes a directional relay as the primaryrelay andan overcurrent timing relayas thesecondary relay. Relay units of this type are described in the Relay Handbook and Supplement published in 1931 by the National Electric Light Association, New Yorkcity, pages 1046 to 1051. Therelay unit therein described is known 1 as .the 'Westinghouse type CR directional ,overcurrent relay.

Relay units of thetype discussed inthe preceding paragraph are provided with adjustable time delay. Several relay units may be-employed in an electrical system and may be coordinated to provide different time delays in operation.

In order to facilitatethe application of 'the relay units, itis :desirable;.that-a large range of adjustment be provided. The :range of adjustmentcould be extended by adjusting the "overcurrent timing relay to trip at values of current below the full load value :ofthe associated system. However, in priorart-relay units, suchadjustment could notlbe employed for the reason that therelayunit would trip for conditions under which no tripping-operation would he -desired. I

accordance-with theinvention, the primary relay is restrained from operation until .a conditionarises wherein a tripping :operation is de-. sired. Under such conditions the secondary relay normally isinoperativeand 'canbe adjusted for operation at any desired value of energization. The primary relay may-be restrained'by a-lquantit which decreases or substantially vanishes when a condition arises necessitating a relay operation. .For example, if the relay unit is asso elated witha polyphase system, a voltage maybe selected which decreases orsubstantially vanishes under fault conditions requiring operation of the relay unit. If this voltage is employed for the purpose of restraining the vprimary relay, .the occurrence of a fault requiring relay-operation will result inremoval ofithe restraintand in operation of the primary relay. ,"In'a directional relay of the type describediin the aforesaid handboolathe current winding may be energized not only in accordance with. curf,

rent flowing in "the associated electrical system being protected but also by a'restra'ining current derived from a voltage which decreases or substantially vanishes under conditions necessitating relay operation. Conveniently, one of the currents may .be supplied to the-current winding'of the directionalrel'ay through a transformer. The other current "may be supplied "to the current inding through an energizingwinding which-is inductively coupled to the secondary winding of the transformer. I

It'is,1therefore, an'o'bject-of the 'inventio'nto provide arelay uni-t'havin'g a primary rela and a secondary relay responsive in part to'the pri mary relay wherein the primary relay is restrained "from operation until a condition arises wherein operation of the relayunit is required.

It is a further 'objectof the invention to'provide 'a directional "relay having a voltage winding and a current winding wherein one of'the windings is energized through a transformer and through an auxiliary winding inductively coupled to .the secondary winding, of the transformer.

"It isastill further object of the'invention to provide an electrical system wherein a relayuni't is provided whichin'cludes a relay normally restrained .:from operation by a condition of'the system which decreases or substantially vanishes upon the occurrence of a fault to which the relay unit should respond and which includes a second relay responsive in partto operation of the first relayfor controlling the electrical system.

Other objects of theinvention will be apparent from the'following description taken in conjunction with the accompanying drawinggin which:

Figure .1 is a schematic view of an electrical system embodying the invention; v

Fig. 2 is .a vector diagram showing voltage and current relationships present in the system of Fig. 1;;and

Fig. 3 is apolar diagram showing performance characteristics of a relay employed in thesystem 0f.Fig..1.

Referring to the drawing, Fig. .1 shows an .6160? trical system which includes a circuit Ito'which are connected additional circuits II and III. The

The circuit II includes a circuit interrupter 20' of conventional construction for segregating portions of the circuit. The circuit interrupter includes a trip coil 20T which is effective when energized for tripping the circuit interrupter. The phase conductors of the system are identified by the reference characters A, B and C.

In order to protect the system, a relay device 22 is associated with the system. For energizing the relay device, a voltage bus 24 having phase conductors a, b and c is energized from the circuit I through a voltage transformer 26 having primary and secondary windings connected in star. The neutrals of the star-connected primary and secondary windings are illustrated as grounded. The voltages between the phase conductors a, b and correspond to the voltages between the phase conductors A, B and C but may be reduced or changed in magnitude, if desired, by suitable selection of the ratio of transformation of the transformer 26.

Currents are supplied to the relay device 22 from

current transformers

28A, 28B and 280, which are associated respectively with the phase conductors A, B and C of the circuit 11. These current transformers may be connected in star with their neutral connected to a neutral conductor 28N and to ground. The output currents Ia, Ib and of the three-current transformers correspond respectively to the line currents flowing in the associated conductors A, B and C but may be reduced or changed in magnitude by proper selection of the transformer ratio of the current transformers.

The relay device 22 includes three relay units 30A, 80B and 300, which are associated respectively with the three phases of the associated electrical system. Since these relay units are similar in construction, a discussion of the relay unit 38A suffices for a presentation of the invention.

The relay unit 30A includes a directional relay 32 which has a magnetic structure provided with a voltage pole 34 and two

current poles

36 and 38. The poles are spaced to define an air gap within which an electroconductive disc 40 is positioned for rotation. The voltage pole has a voltage winding 42 surrounding the pole, whereas the

current poles

38 and 38 have

current windings

44 and 48 therearound. \Vhen these windings are suitably energized, a shifting magnetic field may be produced in the air gap for the purpose of rotating the armature or disc 48. Rotation of the disc 40 in one direction closes a pair of contacts 48, whereas rotation of the disc in the opposite direction opens the contacts. The masnetic structure, disc 48 and contacts 48 comprise parts of a translator which is directionally responsive to the energization of the windings.

The relay unit 30A also includes an overcurrent timing relay 50 which includes a magnetic structure similar to that of the directional relay 32. The magnetic structure includes a main pole 52 and two auxiliary poles 54 and 56 which are spaced to define an air gap within which an electroconductive armature or disc 51 is disposed for rotation. The main pole 52 has a main winding 58 therearound through which the overcurrent relay is energized. This winding may have an adjustable number of turns. The auxiliary poles 54 and 56 have windings B8 and 6| therearound, which are connected in series with each other andwith a winding 62 through the contacts 48 of thedirectional relay.

It will be noted that the windings 58 and 62 4 are inductively coupled to each other. Consequently, if the winding 58 is energized by alternating current and if the contacts 48 are closed, the windings BI] and BI are energized from the windin 62.

Inasmuch as the relay .50 is employed for timing purposes, a damping magnet 64 (a fragment of which is shown) is associated with the disc 51 in a conventional manner.

The overcurrent relay is employed for controlling any desired translating device, such as the circuit interrupter 20. The overcurrent relay 5|] has a pair of contacts 68 normally biased open by a spring (not shown) which when closed connect a pair of conductors 88 and 10. When these conductors are connected, they complete a circuit from a suitable source of energy, such as a battery 12 to the trip coil 20T of the circuit interrupter.

By inspection of Fig. 1, it will be observed that the

windings

44, 46 and 58 are connected in series through a conductor 14. The relay unit MA, as thus described, may be exactly similar to the type CR directional overcurrent relay described in the aforesaid handbook. In order to simplify the 11- lustration, certain components, such as connection blocks and the torque compensator, have been omitted. The only change introduced herein is the provision of a terminal binding post Hi which is connected to the conductor 14.

Inasmuch as the relay unit 38A is associated with phase A of the electrical system, the voltage. winding 42 is connected for energization across the conductors a and c of the voltage bus 24 for energization in accordance with the voltage EEC. If prior art practice were to be followed, the

windings

44, 46 and 58 would be energized solely in accordance with the current Ia which represents the current flowing in the conductor A of the system. However, in accordance with the in vention, the directional relay 32 also is energized by a restraining current which opposes operation of the relays.

The energization of the

windings

44, 48 and 58 conveniently may be obtained through an auxiliary unit 18A. Similarly, units 183 and 180 are provided for the relay unit 303 and the relay unit 300 respectively.

The

windings

44 and 46 are connected in series across the terminals of the secondary winding of a transformer 80. This transformer may have separate primary and second windings, as in the conventional two-winding transformer. In the embodiment of Fig. 1 an autotransformer is em ployed. The circuit may be traced from the winding 44 through the winding 48, the conductor 14, the terminal binding post 18, a conductor 82, the secondary winding of the transformer 8|] and a conductor 84 to the winding 44.

The primary winding of the transformer is energized from the current transformer 28A through one of a plurality of

taps

80D, 80E, 80F and 80G on the primary winding. The energizing circuit for the primary winding of the transformer may be traced from the current trans former 28A through a conductor 86, a terminal block 81 through which the conductor 88 may be connected to any of the taps on the primary winding of the transformer, the selected portion of the primary winding, the conductor 82, the terminal winding post 16, the winding 58 of the overcurrent relay and the conductor 28N to the remaining terminal of the secondary winding of the current transformer 28A. Consequently, the primary winding of the transformer and the menace winding 58 of the overcurrent relay are-energized in accordance with the currentIu. This current flowing through the primary winding of the transformer produces a our-rent KIa. in the secondary winding and the latter currentKIa flows through-the windings 44 and 4 B of the directional relay.

It =wi1lbe recalled that a restraining current is Supplied to the directional relay. This current is sufiicient to provide the desired restraint during normal operation of the associatedelec'trical system. When a fault occurs for which the relay unit 30A should operate, the restraining current should decrease or substantially vanish.

The "phase A relay unit is intended to operate for a line fault involvlngthe phases A and B of "the associated electrical system, for a. ground fault involving phases A and B-of the associated electrical system and for a three-phase fault. For any of these fault conditions, the 'voltage'b'etween'the phase conductors A'and B is substantially reduced. Consequently, the voltage Em may "be employed for producing thedesiredre- Straintfor the directional relay. This voltage is employed for energizing a winding 8B which is inductively coupled to the secondary winding of the transformer 80. Consequently, the secondary'winding of" the transformer also serves as the secondary winding of a two-winding transformer Whereinthe winding68 is the primary winding.

The energization of the winding is effected through a suitable impedance 90. This "impedance may be selected to produce the desired phase relationship between the voltage Eba and the currentsuppliedto the windingBB. For the'purposes of illustration, it is assumed that thei'impedance 90 includes an inductive reactancerepresented by a coil 90D and a resistance represented by "a resistor 90F connected in series. The entire energizing-circuit'for the winding .88 may be traced from the conductor a of the voltage bus 24 through a conductor 92, the winding 88, the impedance 90 and aconductorlll to the conductor b of the voltage bus 24.

The operation of the relay unit 30A maybe understood more clearly from a study of the vector diagram illustrated in Fig. 2. Conventional counterclockwise rotation of the vectors is assumed. The three voltages Eat, Elia, Ecb of the voltage bus 24 are shown in Fig. 2. It will be recalled that the voltage Eba isemployed "for energizing the winding 88 to induce in the secondary winding of the transformer 80 a voltagewhich produces the current Ie. The impedance 90 is selected to provide a phase displacement between the current Ie and the associated voltage "Eta which brings the current substantially into phase opposition with the voltage Eat. Inasmuch as the voltage Etc is employed for energizingthe voltage winding 42 of the directional relay, the "current Ie in flowing through the windings "4i and 46 "cooperates with the energization of the voltage winding to urge the disc 40 in a contact opening direction. Therefore, the current'le is arestrainingcurrentwhich opposes operation of the v directional relay. It will be recalled that this currentdecreases to a small value when a'fault occurs for'which operation of the relay unit 30A is desired. v

The three currents Ia, Ib and Ic'fllSO are illustrated "in Fig. '2. The current Iaenergizesthe wlnding58' of the overcurrent relay. In'a'ddition, this current in flowing through the-primary'windlng'of the transformer "80 induces an the secondary winding *of the transformer a current Kit lit is illustrated .by'a vectorTB B.

8 r whereinik represents-thetransformer ratio "oiithe transformer. The resultant current passing throug'nthe windings ll 1 and 46 of the directional relay then is representedby the'current Ir "which is the vectorsumpfthe currents Ie'and Kls.

As long "as i the .eurrentlehas a value sufficient to prevent operation of the directional relay '32, the'contacts "of the'directional relay are held open to maintain the overcurrentrelay so in an inoperativecondition. For this reason, the overcurrentrelay may be adjusted-to-operate for a current corresponding to a value less than full load current of the associated system without fearo'f anlncorrect operation 'of the overcurrent relay While the system is in normal "operating condition. When "a fault occurs for which "the relay unit can should operate, the :current Is decreases to a value sufllciently small to permit operation of the directional relay '32. Theresulting closureofthecontacts!!! thenpla'cesthe 'overcurrent relay "in operating condition, and the 'overcurrent "relay operates with the-proper *time delay" to close its contacts 86.

The "directional relay operates only if the energy fiow'ing in theassociated system is in" the proper direction. For example, it may be connectedto close its contacts only for the direction of energy flow represented by the arrow 96.

It willloe recalled that several taps are providedon theprimary winding of the transformer '80. These taps "control the sensitivity of the directional ireiay. For example, if the current Iaiis "inphase wlththevoltage EM (this'corresponds "to *a 30 "lagging "power factor), the tap BUD'may the so selected that five ampere's flowing therethrough 'su'mc'es Ito "neutralize the restraining current It. Any'increase in the "current 1! above five amperes'would result inoperation of the "directional relay. "Similarly, the tap E may be so selected that under the assumed con ditions "I M; amperes "flowing through the primary winding ofthetransformer neutralizes the effect of the .reStrairiing current Ie in the directional relay. As "further examples, the taps 80F "and BUG, respectively, may require 10 and '1'2 amperes to neutralizethe restraining currentiIe.

The characteristics or the relay unit 30A'are illustrated in Fig.'.3 by means of a conventional polar diagram. In this diagram the circles rep resent values of current, whereas the radial lines represent phase angle. The reference voltage employed for energizing the voltage winding n The curve'99D represents a conventional characteristic curve of the type CR. relay described in the aforesaid handbook. .Current vectors terminating above thiscurved'esult-inclosure of the contacts of the directional relay. fIl'iecon-tacts remain open for current vectors which fall below the curve 89D. ThB'CUIWWSsQQE, k991 98G and 99H represent the characteristics of :the directional relay, respectlvely, for the Etaps -80D,-BOE,-80F and MG. It will be observed that the change in shapeof the characteristic curve is so :small as to be virtually negli ible 1 for all relay applications.

in operation, the relay system is connected "as illustrated linil'i'g. 1. The conductor 86 then is connected tothe proper taponthe primarywindsing of the transformer 80'to provid'e the desired relay :sensitlvity. .Asa result Of this connection, the overcurrent timingrelay 50irnay be adjusted to respond to any :desired value "of "current, even though current'corresponds 'to a value below the run :load :current "of the associated 7 1 system. A [greatly increased range oftiming adjustmentthus isavailable. a I a a .Although the inventionhasbeen described with reference to certain specific. embodiments thereof, numerous. modifications falling within the spirit and scope of the invention, are possible. 1 1 claim'as my invention: L 1-. Inzan electrical relay. device, a directional relay having first and, second windings arranged for independent energizations, a first source of energy for energizing the first winding,asecond sourceof energy for energizing the first winding, athird source of energy for energizing the second winding, and a translator. having a. predetermined directional response to only a predetermined direction of energization of the first and second windings, the second source being connected to the first winding to cooperate with said energization of the second windingtooppose said directional response of the translator. 2. In an electrical relay device,,a directional relay having first and second windings arranged for independent energizations, a first source of energy for energizing the first windin a second source of energy for energizing the first winding, one-of the sources comprising. a transformer, and the othergof the sources being connected to its associatedwinding through the secondary winding of the transformer, a third source of energy for energizing the second winding, and a translator having a predetermined directional response only to a predetermined direction of energization of the first and second windings, the .secondsource being connected to. energize the first winding to cooperate with said energization .ofthe second winding to oppose said directional response of the translator. 3 3. In an electrical relay device, a directional relay having first and second windings arranged for independent energizations, a first alternating source of energy for energizing the first winding, a second alternating source of energy for energizing the first winding, one of the sources comprising a transformer having an adjustable'primary winding and the other of the sources including a winding inductively coupled to the secondary winding of the transformer, a third source of alternating energy for energizing the second winding, and a translator having a predetermined directional response to a predetermined direction of energization of the first and second windings, the second alternating source being, connected to energize the first winding in a direction cooperating with said energization of the second winding to oppose said directional response of the translator. ,4. In a 'relay device,a directional relay having current and voltage windings, a normally inoperative protective relay, conditioning means res'ponsive to operation of the directional relay for conditioning the protective relay for operation, connections connecting the current winding and the protective relay for energization in'accordance with a first quantity, and connectionsfor energizing the current winding in accordance with a second quantity, the'connections being poled to cause the two energizations of the current winding operating in conjunction with the voltage winding when energized to act in opposition on the conditioning means. ,w 5. Inan electrical relay device, an over-current relayhaving windings normally ineffectively conne'ctedfor operation, a directional relay having avoltage winding and a current winding, and eflectuating means responsive touoperation of the directional relay for connecting the windings of the overcurrent relay for operation, a transformer having a secondary winding connected for energizing the current winding, said transformer hav ing a primary winding coupled-to the secondary winding for supplying energy thereto,.and a winding inductively coupled to the secondary winding of the transformer to form therewith a two-winding transformer for additionally energizing the current winding.

6. In an electrical relay device, an overcurrent timing relay having windings normally ineffectively connected for operation, a directional relay having a voltage winding and a current winding, and efiectuating means responsive to operation of the directional relay for connecting the windings of the overcurrent relay for operation, an autotransformer having a secondary winding connected for energizing the current winding in accordance with energization of the primary winding of the autotransformer, a winding in ductively coupled to the secondary winding of the autotransformer to form a two-winding transformer for additionally energizing the current winding, said autotransformer having an adjustable winding, and connections for energizing the overcurrent relay in accordance with the energization of the primary winding of the autotransformer.

'7. In an electrical system, an electrical main circuit, a first relay connected to the circuit for response to a first predetermined fault condition of the circuit, a second relay, connections established in response to operation of the first relay for effectively connecting the second relay for response to a second condition of the circuit, connections establishing a local circuit responsive to a condition of the main circuit which substantially disappears upon occurrence of the predetermined fault condition on the main circuit for energizing the first relay to restrain operation of the first relay, and a translating device responsive to the second relay.

8. In an electrical system, an electrical polyphase circuit, a directional relay including a winding, connections energizing the relay including said winding from the circuit in accordance with a first phase voltage and a current of the circuit for response in accordance with the directionof energy flow in the circuit, and connections energizing said winding of the rela in accordance with a second phase voltage of the circuit for restraining operation of the relay, the second circuit phase voltage decreasing to a substantially greater extent than the first circuit phase voltage under a predetermined fault condition for which operation of the relay is desired, an overcurrent relay, connections completed in response to operation of the directional relay for energizing the overcurrent relay for operation in accordance with the current flowing in the circuit, and a translating device responsive to operation of the overcurrent relay.

9. In an electrical relay device, a directional relay having a voltage winding and a current winding, and an armature element responsive to a function of the product of the energizations of the voltage winding and the current winding, a current autotransformer having a secondary connected to supply first energy to the current winding, said autotransformer having primary terminals suitable for connection to a first source of electrical energy, and an auxiliary winding coupled to the secondary winding to constitute therewith a two-winding transformer, whereby second energy may be supplied through the twowinding transformer to the current winding from a second source of electrical energy independent accordance with a first voltage of the polyphase alternating-current circuit, and connections for energizing the auxiliary winding in accordance with a second voltage of the polyphase alternating-current circuit which decreases upon occurrence of a predetermined fault condition for which the relay device is to operate, said connections including impedance producing phase relations between thetwo energizations of the current winding respectively and the energization of the voltage winding which produce opposite forces acting between the armature element and the relay windings.

12. The combination claimed in claim 11 in combination with an overcurrent relay, and connections completed by operation of the directional relay for operatively energizing the overcurrent relay in accordance with the current supplied to the primary terminals.

WILLIAM K. SONNEMANN.

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

UNITED STATES PATENTS Number Name Date 1,765,395 Bauch June 24, 1930 1,792,271 Breisky et al Feb. 10, 1931 2,024,706 Smith Dec. 17, 1935 2,053,416 Bostwick Sept. 8, 1936 2,131,608 Warrington Sept. 27, 1938 2,352,985 Warrington July 4, 1944 2,380,164 Goldsborough July 10, 1945 2,432,328 Morris Dec. 9, 1947