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A118. 27» 1945» w.A K. soNNEMANN 2,406,411 UNIVERSAL SEQUENCE‘CURRENT RELAYING MEANS Find am. 21. 1944 a Í if. "? à.; __ ___ 'wf -.._ Q-o Ja ' Í 7) 7M á ¿ML ATTGRNEY Patented Aug. 27, 1946 2,406,411 UNITED STATES PATENT GFFICE 2,406,411 UNIVERSAL SEQUENCE-CURRENT , RELAYING MEANS William K. Sonnemann, Roselle Park, N. J., as sìgnor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsyl vania Application January 21, 1944, Serial No. 519,145 21 Claims. (Cl. 175-294) l 2 My invention relates to protective relaying de vices for detecting faults in polyphase lines such as transmission-lines, and it has particular rela an approximately vconstant magnitude, which contributes considerable to the non-selectivityof the device, when subjected to faults on different phases, as described. This “HCB" relaying-sys tem is described in a Harder Patent 2,183,646 of december 19, 1939, which is assigned to the West inghouse Electric 8a Manufacturing Company, tion to a universal relaying-’element which is re sponsive to phase-sequence' current-components which are compounded in a special way whereby the single relaying element is responsive with fair ly comparable sensitivity to all possible diiferent kinds of fault which may occur in a polyphase It is an object of my present invention to pro vide an improvement over the Harder “HCB” re line, without being affected by which single phase laying system, in which I avoid the utilization of I is faulted to ground or which two of the three phases are involved in a double phase-to-ground ` the vectorial sum of a positive-sequence current component and a zero-sequence current-com fault. In short, my relaying apparatus does not ponent, which could conceivably total zero if the two components happened to be exactly equal to My derived phase-sequence current-responsive 15 each other and exactly 180° out of phase with each quantity may be utilized directly for the energi other. have a “blind spot.” zation of a single relaying-element, or it may be _ utilized in conjunction with piiot wires or other It is an object of my invention to utilize a re sponse to only `the positive-sequence current com form of a communicating-channel for comparing ponent, and to supervise or alter the responsive similarly derived voltages or currents from the 20 ness tolthis component, in, accordance with the two ends of a protected three-phase line-section. magnitude, but not the phase, of the zero-se quence current-component, or the negative-se Heretofore, two diiîerent types of universal se quence-current relaying-devices have been in gen quence current-component, or both the zero-se eral use, and both have been subject to the possi quence and the negative-sequence current-com bility, or the suspected possibility, that they may 25 ponents. In this way, I provide a relay which can have “blind spots,” or conditions of dangerously ~ have the same sensitivity to all different kinds or reduced sensitivity to certain very special fault locations or magnitudes of fault, or any desired relative degrees of sensitivity to different kinds conditions, of one kind or another, depending upon the phase-relationships between the zero of faults, in a relaying system which has no “blind sequence current component and the positive-se 30 spot” and which is not at all affected by the par quence current-component, or between all three ticular phase which happens to be faulted. of the current-components, depending upon which With the foregoing and other objects in view, single phase is faulted in a double phase-to my invention consists in the systems, circuits, ground fault. In one of these previously known combinations, elements, apparatus, and methods, systems, the line-currents from all three of the 35 hereinafter described and claimed, and illustrated line-conductors are combined in a special trans in the accompanying drawing, the single iigure of former which produces a single-phase current which is a diagrammatic view of circuits and ap which is supposed to be more or less reliably re paratus illustrating my invention in a preferred sponsive to any possible kind of fault. form of embodiment. In the other previously known universal-fault 40 In the drawing, I have illustrated the invention current-deriving system, the positive and zero as being applied to the protection or a line-section phase-sequence components of the line-currents l which is a part of a three-phase transmission have been vectorially added, in a phase-sequence system, the protected line-section I being con network known as an “HCB” network, in which it nected between ‘buses 2 and 2’ at two diiîerent sta is believed that a somewhat better single-phase 45 tions. Since the equipment at each line-terminal relaying quantity is derived, so as to be responsive or station is identical, and symmetrically disposed to any possible kind of fault, but still having a with respect to the center of the protected line certain amount of variation in the responsive section I, I shall largely confine my explanation ness, according to the variations in the phase and descriptionv to the equipment at the terminal angles between the positive and zero phase-se 50 represented by the three-phase bus 2, the corre quence components, which is to say, according to sponding equipment at the other terminal being which phase is faulted, and what kind of fault it distinguished by primed letters or numerals, as in is. This “HCB” relaying system also makes use the case of the bus 2'. ` of a current or voltage-limiting means for pro The equipment at each station, such as the ducing a substantially sinusoidal output-wave of 55 left-hand station, in the illustrated form ‘of em 2,406,411 bodirr'ient ofthe invention, includes a three-phase line-segregating circuit-interrupting means, such energy to the trip-coil TC, through the auxiliary as a circuit-breaker 3, which has an auxiliary make-switch 3a, and a trip-coi1 TC. The equip ment also includes a bank of three-phase line 5 pole circuit-interrupting operation of the break~ breaker-switch 3a, so as Vto produce a three current transformers which supply energy toa The energiz‘ation of the relay., I2, in the illus fforinofembodirhent of '_theïinvention, is phase-s'ëúuéncjeijfn i pri; orl'netwíor ì ‘Shaving output-ltërmhials‘q Ir" er 3, in the illustrated form of embodiment of the invention. " tratie which the?e'f" appears --a 'th’eïsa?neï as described and claimed in the Harder single-phase current or voltage which is selective- _ patent. The relay is provided with a strong op 1y responsive solely to the positive-sequence coin-“ f’ferating-coil O, and a weaker restraining-coil R, ponent of the line-current. Theparticular nete; v_. which isillustrated as being adjustable. Since work 5 which is shown in the figure also-,basa the relay is a polarized relay, the operating and restraining windings O and R must be energized second pair of terminals I2 in which there appears a single-phase current or voltageljwhljch "isz-selec?` '- with/'unidirectional currents, which are illus tively responsive solely to,thejnegative¿sequence` l5” trate'd‘ -as being obtained through rectifier component of the line-current?" The positive-sequence output I1 of the current ' "bridges, or other full-wave rectiñers, B1 and B2, respectively. The bridge B1 which energizes the operatingcoil O'is energized across the terminals of the insulating transformer ID, while the bridge to energize an adjustable saturating transformer 20 B2," which supplies the restraint-winding R, is 6, which produces peaked wave-forms of more or serially connected in series with the lead 8.„ or .til‘essflimitedmagnitude;V the peaks "of which are -betw'een the lead 8 and the insulating'transform responslve phase-sequenceiietWorkf-'S is'futilized,` in the manner described in the Harder patent,A ,I "i removed` .by La». glow-lamp- 'fI ‘0r- I'similar ' Lmeans, er IIJ: 'wherebysla fairly ¿sinusoidal "‘wave‘lrfo'rm’i's ob' The‘system' so far describedv in detailv is the v- tained ‘in ’ the relayingfßcircuit which is- :provided sameras one of the forms of embodiment‘which zrby.-the-"outputlterminals1B fand' 9 lof the device, i-asïexplainedi’ in theV Harder,v patent, except that I are illustrated inthe Harder patent, except that the saturating"transformer- 6 isenergized re utilize Vauresp'onse Ptolemy-‘the - positive-sequence »sponsively to=only`the positive-sequence current, component, 'i rathersthan -a ¿response îto 'both the rather than the vectorial- sum of the positive and 30 >gizing'thesaturating transformerJB. v " y - ¿ ». _ invention; `.the output: of the vsnetwork-term‘in'als `8,.:and `9 v¿isv> applied: to :anzinsulatingï ‘transformer f the;` particular 'pilot-wire" system - 'which' - is illus trated - being of 'the well-'known . current-circulat othempilot-wire systems may-'be- utilized,V as »will ybe understood -iby the `skilled workers'of the' art. v of> faults-on the protected line-section I ,‘ but the >Illnvvhichìfisf connected-‘to oney end of'fa pair of Vpilot-‘wiresdI"which zextend to ysimilar equipment ,« at the far end of the protected line-section I, no fault on the »protected »line-section TI“, although « ' .. There will, of course, be positive-‘sequence com ponents present in'all possible kinds or'degrees - -vfIrrithe‘ß'illustrated?form -of embodiment` of vthe ing.- type,fwhìch circulates-current when there is zero- sequence components. 40 lpositive-sequence component cannot, in general, be utilized, alone, as a fault-detector, even with ,the aid of the. so-calle'd constant-magnitude'de vices 6 and 'I,‘ because‘the-magnitude of the pos* itive-sequence componentV of the‘fault-current, -forcsingle -ground-faults, for example, may be considerably less than theïb'alanced power-'cur' vrents of the line underf'normal 'fault-free opera tion.- It is-an essential feature of. my present in vention, therefore, that the sensitivity or >re Any suitablemeans may 'be> utilized for >re sponse-proportionality of the response‘to the pos sponding-:to- thefcurrentpr voltage which ap 45 itive-sequence current-component is increased, »pears inthe'network-terminals 8 and >9, and this or monitored, by the zero-sequence current-com .response may be eithera simple overcurrent or ponent, or by the :negative-sequence current sovervoltage response to thev current or- voltage in . component, or both; , _thep‘terrninals sand 9 alone, orv it maybe a com Referring to` the drawing, it win be noted that ¿parative -response-of any-sort',> which takes into 50 thel sensitivity of the'positive-sequence response .consideration aV comparison Aof the output- of‘the ,is‘reduced by drawing off energy through a vari terminals- ßgand .9 _atene station, .as 4compared 4_able resistoriARxy, which is connected‘across the »with «the output of Vthe 'corresponding-terminals _network-terminals B and 9 through a rectifier «,8’. and 9’ atathe other station,fsaidr` comparison bridge B3, or-other full-wave rectifier, which sup being eiîectedthrough the'fpilot-wires II, or any 55 plies,unidirectional-current energy to -'the posi equivalent-._y communicating-channel means - ex'-- tive andnegative terminals R+ and R-'of the tending from another'line-,terminal » resistor Rxy. 1n general,` it is desirable to sup ¿The particular.. embodiment .of lmyninventio'n press the ripples in »the rectified-current output v which is illustrated in thexdrawing utilizes a. ra circuit of the bridge B3, which may be accom tio-differential protective relay I2, .which is illus' 60 plished by any suitable means, such as a shunt connected capacitor I6. „ , " »trated asffav polarizedmelay havingß’a` polarized movable` armature I3, `the polarization of 4which In the illustrated form of embodiment of my is indicated >bythe letters `N and'S representing inventioml provide an adjustable transformer northand south poles, respectively. Aipolarized I'I, which may or mayl not be saturable, which vform of differential relayA I2 is shown, for the sake >is energized from the residual-currentfcircuit of the fline-current transformers 4, so asfto be re Loffthe greater'sensltivity and-the lower burden sponsive to the zero-sequence current-component, >which.is¿obtainable in thistype of relay, but; the vinventionis obviously not limited to any particu“ and this transformer `I‘I -is utilizedto energize a lartype, of relayufuIny order to prevent the relay rectifier-bridge B4 which also supplies current, .from respondingtoonuicklyso that‘it would re in the samepolarìty as the bridge B'gfto >the ter spond-:to thepulsations-or ripples ofl its’ ener- ' ` minals R+ and R--of the resistor'Rxy,- the same ,gizatiomgitmay be provided» with ’a’lagi-ring' I4, ‘capacitor'lûserving to- absorbv the ripples of the as willv be well understood. AThe movable element I3 of the differential relay IZV-is'iutilizedto con rectified-current output of the’bridge B4. " In the illustrated form of embodiment of my vtrola trip-circuit" I5Y which suppliestripping 7,5 invention, I also provide another adjustable trans 2,406,41; 5 , positive-sequence network-terminals 8 and 49, by former I8, which also Ímay or may not be sat ‘urable,f.which is energized=from the negative-se. >the bridgerBaI-tdbeireduced in proportionto the amount of energy fwhich isfsupplied to the -re quence terminals ‘Iz-of the current-responsive‘se -sistor-'Rxy by the bridge B4, until, inathe limiting -quence-network 5. “The'transforrner lß'energizes 4case,- no energy at all-is Withdrawn from the posi a rectifier-bridge B5, the output-terminals :of which are connected to the resistor-terminals R+ r “tive-sequence network-terminals v8 and;.9_by-the and R+, inthe same polarity as the outputs of The zero-sequence-responsive bridge B4 may be the bridges B3 and.B4.» 3 . » , Y l v ,v Y In operation, >`during` normar power-transmit 10 ting conditions when there is ‘a balanced three utilized Valone',iwithout the negatiVe-sequence-re =sponsive l'bridge B5, to -monitorffthe Apositive-se queme-'responsive'terminals A8 and 9, soas to »in crease the-sensitivity of. the positive-sequencere phase load on the transmission-line, ‘butv no fault ‘ ' thereon‘, ‘there will`VÃL be no Vzero-seduencercurrent ,-sponse --iniaccordance with .the amount of zero component and 'no negative-sequencer'current seqùence current-'component Which-is present in -the fault-current, up until the point-‘of maximum component, so that the network-'terminals >8 and Y9 will feed a vconsiderable amount of energy into the resistor Rxy, none of this energy going-through - sensitivity» isereached,` when no 4current Vis .with the bridges B4 and B5, which'a'reconnec'ted in such 'polarity that current cannotflow from the resistor-terminals R+ >and R- int() said bridges, - drawn » from ' the' network-terminals 8-.f9 by the >resistor R'Xy. -Since thefzero-sequence current ¿component is not present at all, except .under except for very'small leakage-currents which may _ Afault-conditions, the zero-sequence response can be assumed to be negligible, so far'as our present l» be madelextremely sensitive’vbeing limited»- only by the `necessity rfor~ avoiding a deleterious re considerations -`are concerned." The resistor> Rxy sponse- to the spurious zero-sequence components is chosen so as to’h-'ave' such a'mag'nitucie,` in com which vare sometimes produced by faulty-match parison with ' the serially connected positive-sè ing-#of-V the line-current- transformers `4. :In this quence-circuitimpedances of the network 5--6--1 and the bridge B3, ythat't'he sensitivity' 'of response-wv. manner, thel relay I2> can have a high sensitivity -tov all faults lhaving* any» zero-sequencey current to the positive-sequence currents~ maybe reduced components, so' that the ability of the relay vI2 to to any desired level 'or value. " ' ` ' ’ ‘ respond to ground-faults can be madel to' match `When a- three-phase'fault occurs on- the pro tected line-section, fa very- large positive-sequence 30 its ability Eto respondft'o faults >which’ have no current-component is present inthe line-current,- î izero-se'quence componenti There are -only'two kinds of Afault which have and the sensitivity of responseis adjusted so that no ¿zero-sequence;ïcomponentj namely, asolid the relay I2 will have thedesired amount oïf re three-phase fault 'involving no- ground, in which 'sponsivity to the positive-sequence component 4under this fault-condition. '_ ’ ' 'y ’v » i 'case »the fault-currents are extremely! heavy, and ` the minimum positive-sequence sensitivity is de sirable,'an'd phase-to-phase faults involving only *two vof ‘the 'line-conductors; butv no ground, in :which case the positive-sequence component is 578%’a's great as with a'three-phase'fa'ult, for the saine fault-amperes, which is ystill generally vamply If a single line-to-g'röund fault should occur,>v the positive-sequence component of I the fault ourrent may be so small that the component which appears in the' network-terminals 8-9 may> be no more than is'neces’sary to produce theÍ required responsivity inthe ‘relay ï'I2, even thoughjno ~ energy is withdrawn'from thet'er'rninals 8-y9rbry Íïsuiiicientlto venable the relay >I2 to respond easily the resistor Rxy. This -condition, whereby Vthe network-terminals 8 and 9 lsupply no energy to -the resistor Rxy; or any intermediate condition, of» beingy oVe'rbui‘dened-on’the more severe fault. ' tofboth of these types'of fault, without danger '- It is fp'ossible, however',1 and sometimes desir able', to utilize afnè'gative-sequence monitoring, as in the case of a >double line-to-'grourid fault, instead of, 0r in addition to, the zero-sequence is brought about by the zero-sequence-responsive ' monitoringfwhich'h'a's just -been described. -The ’i negative-sequence response usually entails the use bridge B4, which maintains, across the À'resistor terminalsv R+ and R+, a potential which isy re of a; networkV which imposes amgreater burden sponsive to the magnitude of the zero-sequence 50 normally upon the current-'transformers 4 than component, reduced by the serially connected im the 'network which delivers thefzero-sequence re pedances of the zero-seduence-energized`trans s'ponse,` which do'es‘no't normally entail “any bur former I‘I and bridge B4, withsuiiicient sensitivity "denjbut'` itv hasy 'certain advantages', in that'the of response so that the rectiiied zero-sequence ' negative-sequencel responsive Voltage, put out by the` bridge B4, may be equal to the rectified voltage which ,is put out by the bridge Badwith a reduced current-,flow from the circuit ß-ïjthrough the bridge B3, to the terminals R+ arid R+; th'atfisywitha reduced voltage-drop in' the' eifectiye positive not vrconditions',y when there is no fault- on the >trans mission system, but'it >_is present in all possible kinds of fault, including the phase-to-p'hase fault 60 `sequence-circuit impedance _of theelementsñ, .6, ' -I and B3. Therectiñed Voltage of B4 may even be larger than that of Bs, in which case B4 does not feed energy back into theiterminals 8 and 9 through the bridge B3, because the VAp'îolarity of therectiñers of the bridge n, B3 is 4directed "the Ä wrong way for such energy-transfer, and the re current-component 'is present,> at all, ‘under normal _power-transmitting 'as Wella as ‘the single-phase ground-fault, except 'a balancedr three-phase fault. " '- It isf possible, therefore, to utilize a very sensi tive response to _the negative-sequence current vcomponent,- from'the terminals I2, to energize the rectifier-bridge' Bs,` so '_as to" produce‘a rectified voltage, which is applied to the lresistor-terminals R+ and Rl-, which' bears any desired vrelation to the corresponding positive-sequence-responsive sult is Simply that _no’energy is Withdrawn from rectiñed Voltage lof the bridge B3, under lany vde the terminalsY B and 9 by the-bridge B3 under Asuch 70 -s'i'red conditions, Ithe operation being similar to conditions. ._ ` I l ' ` ' 'that which has already been describedinîconnec In either event, the effect of. thezero-sequence- ' l ’ tion "with monitoring by the zero-sequence re energized bridge B4, in parallel to the positive .» As' previously intimated, both of the monitor sequence-energized bridge B3, is to cause the y amount of energy which is withdrawn from the 75 4ing bridges 'B4 and B5 can be utilized together, in 2,406,411 7 8 which case, whichever voltage-response is the greater, will take control, and control the recti and 9. I desire, therefore, that the appended fied voltage which appears across the resistor claims shall be accorded the broadest construc tion consistent with their language and the prior terminals R+ and R-, since no energy can be art. fed back, in the reverse direction, into any one ' I claim as my invention: of the parallel-connected bridges Ba, B4, and B5, 1. In a relaying system for protecting a poly phase line, means for providing a relaying circuit carrying a single-phase electrical quantity which is responsive to the positive-sequence component of the line-current, means for energizing a resis tor from said relaying circuit through a full the output-terminals of which are connected in parallel across the resistor-buses R+> and R-. . It will be observed that, in a way, my present system is an application of the “largest-phase” relaying-system which is shown in the Harder Patent 2,242,950, of May 20, 1941, assigned to the Westinghouse Electric & Manufacturing Com wave rectifier, means vfor deriving another se quence component of the line-current, means f pany. Harder there utilized a similar parallel for energizing the same resistor from said other bridge system for obtaining a response to which 15 sequence component through another full-wave ever phase was the largest, whether the phase-A rectifier in the same polarity as the first-men current, or the phase-B current, or the phase-C tioned energization, and relaying means having current, or the residual current times any desired an energization yfrom said relaying circuit. multiplying-constant. In my present relaying 2. In a relaying system for'protecting a poly system, however, I do not determine the largest phase line, means for providing a relaying circuit carrying a single-phase electrical quantity which is responsive to the positive-sequence component phase, but, in a way, I determine the largest phase-sequence component (with suitable multi plying-factors), comparing the magnitudes, but of the line-current, means for energizing a resis tor from said relaying circuit through a full-wave ponents which are applied to the input-terminals 25 rectifier, means for deriving another sequence of- the several parallel-connected rectifier-bridges component of the line-current, means for ener B3, B4, and B5, or as many of said 'bridges as may gizingthe same resistor from said other sequence be utilized. component through another full-wave rectifler It will be observed that the sensitivity of the in the same polarity- as the first-mentioned ener response to the positive-sequence component, as A30 gization, communicating-channel means adapted monitored by the zero-sequence or the negative to compare said single-phase electrical quantity sequence components, or both, as obtained in my with a quantity similarly provided at another not the phase-relationships, of the several com present system, is not at all affected by the phase point in the line, and relaying means having relationships between alternating currents or energization from both said relaying circuit and voltages which represent these various phase 35 said communicating channel. sequence components. 'I'his is particularly true 3'. In a relaying system for protecting a poly when some sort of ripple-suppressor, such as the capacitor I6 or any equivalent device, is utilized for substantially suppressing or withdrawing the ripples from the rectified-voltage outputs of the 40 various parallel-connected bridges B3, B4, and B5. In this manner, I obtain,.in a single device, a response with any desired uniformity of sensitiv ity, to all kinds of faults, without any “blind spots” and without being affected by which phase the fault is on. ' It will be understood that the magnitude-con trol elements 6 and 1, which were carried over from the Harder “HCB" system, may, or may not, be utilized. 'I'his feature is useful in reducing the effect of differences in the severity of the fault, particularly the severity of a three-phase fault, but my explanation of the invention has been given on the basis of properly increasing the sensitivity of the positive-sequence response in accordance with the monitoring zero-sequence or negative-sequence components, or both, without reference to the presence or absence of the mag phase line, means for deriving the positive-se quence component of the line-current, magni tude-limiting means for providing a relaying cir cuit having a single-phase electrical quantity which is responsive to said positive-sequence com ponent, means for energizing a resistor from said relaying circuit through a full-wave rectifier, means for deriving another sequence component 45 of the line-current, means for energizing the same resistor from said other sequence component through another full-wave rectifier in the same polarity as the first-mentioned energization, and relaying means having an energization from said relaying circuit. 4. In a relaying system for protecting a poly phase line, means for deriving the positive-se quence component of the line-current, magni tude-limiting means for providing a relaying cir cuit having a single-phase electrical quantity which is responsive to said positive-sequence component, means for energizing a resistor from said relaying circuit through a full-wave rectifier, means for deriving another sequence component of the line-current, means for energizing the same resistor from said other sequence component through another full-wave rectifier in the same lpolarity as the first-mentioned energization, com municating-channel means adapted to compare said single-phase electrical quantity with a quan tity similarly provided at another point in the nitude-limiting feature 6--1. It will be under stood that, even when the magnitude-limiting feature 6--1 is utilizedl my monitoring-combina tion may be effective, even at voltages before the saturating effect of the transformer 6 begins to be felt, so that the output-circuit B--S may be monitored, even though the positive-sequence component is not large enough to saturate the transformer 6. line, and relaying means having energization It will further be observed that, while I have from both said relaying circuit and `said com illustrated a particular kind of pilot-wire system, municating channel. and a particular kind of differential relay I2, my 70 5, The invention as defined in claim 1, char invention is not limited to either one of these acterized by said other sequence component being details, as it is applicable, generally, to any device the zero-sequence component. which may be connected in any manner whatso ever, so as to be energized, at least in part, in response to the monitored network-terminals 8 6. The invention as defined in claim 2, char acterized by said other sequence component being the zero-sequence component. 2,406,411 7. The invention as deñned in claim 3, charac terized by said other sequence component being the zero-sequence component. 8. The invention as defined in claim 4, charac terized by said other sequence component being the zero-sequence component. 9. The invention as defined in claim 1, charac terized by said other sequence component being the negative-sequence component. l0. The invention as deñned in claim 2, char acterized by said other sequence component be ing the negative-sequence component. 11. The invention as deñned in claim 3, char acterized by said other sequence component be 19. In a relaying system for protecting a poly phase liney phase-sequence means for developing a single-phase control-voltage in a relay-circuit in response to a phase-sequence function of the line-current at the relaying station, fault-detector means for selectively responding to line-current conditions other than balanced positive-sequence currents at the relaying station, means for utiliz ing said fault-detector means for at times in creasing the response-proportionality of said single-phase control-voltage which is developed in ing the negative-sequence component. 12. The invention as defined in claim 4, char acterized by said other sequence component be ing the negative-sequence component. 13. The invention as deiined in claim 1, char acterized by said relaying system having two such said relay-circuit in response to said phase-se other-sequence deriving-means and energizing quence function of the line-current at the relay ing station, and relaying means having an ener means, one involving the zero-sequence compo nent and the other involving the negative-se gization from said relay-circuit. 20. In a relaying system for protecting a poly phase line, phase-sequence means for developing a single-phase control-voltage in a relay-circuit quence component of the line-current, 14. The invention as deñned in claim 2, char acterized by said relaying system having two such other-sequence deriving-means and energizing in response to a phase-sequence function of the means, one involving the zero-sequence com line-current at the relaying station, fault-de ponent and the other involving the negative-se quence component of the line-current. 15. The invention as defined in claim 3, char tector means for selectively responding to line current conditions other than balanced positive sequence currents at the relaying station, means for utilizing said fault-detector means for at acterized by said relaying System having two such other-sequence deriving-means and energizing times increasing the response-proportionality of said single-phase control-voltage which is devel means, one involving the zero-sequence compo` nent and the other involving the negative-se oped in said relay-circuit in response to said quence component of the line-current. phase-sequence function of the line-current at the relaying station, communicating-channel means for comparing the single-phase control voltage of said relay-circuit with the control-volt 16. The invention as defined in claim 4, char acterized by said relaying system having two such other-sequence deriving-means and energizing means. one involving the zero-sequence compo nent and the other involving the negative-se quence component of the line-current. 17. In a relaying system for protecting a poly phase line, phase-sequence means for developing two diiïerent single-phase control-voltages, in two different relay-circuits, in response to two diiîer ent phase-sequence functions of the line-current at the relaying station, relaying means having an 10 control-voltage of a relay-circuit similarly pró vided at another point in the line, relaying means having energization from both said communicat ing-channel and said relay-circuit at said relay ing station, a direct-current load-device, and two separate rectifier-means for respectively energiz ing said direct-current load-device from said two relay-circuits at the relaying station. age of a relay-circuit similarly provided at an other point in the line, and relaying means hav ing energization from both said communicating channel and said relay-circuit at said relaying station. 45 energization from one of said relay-circuits, a di rect-current load-device, and two separate rec tiñer-means for respectively energizing said di- ì 21. Multi-responsive fault-detector means, adapted to be responsive to a plurality of diñîerent kinds and phases of ground- and phase-faults on a three-phase line, comprising current-responsive voltage-developing means operative to develop a voltage which is responsive, to a function of the rect-current load-device from said two relay-cir cuits at the relaying station. 18. In a relaying system for protecting a poly three-phase line-current, means responsive to said developed voltage, ground-fault detector means for selectively responding to ground-fault phase line, phase-sequence means for developing two different single-phase control-voltages, in two different relay-circuits, in response to two differ ent phase-sequence functions of the line-current at the relaying station, communication-channel means for` comparing the single-phase control rent-responsive voltage-developing means, and voltage of one of said two relay-circuits with the line-conditions more sensitively than said cur means controlled by said ground-fault detector means for making said current-responsive volt age-developing means respond more sensitively to said function of the three-phase line-current. WILLIAM K. SONNEMANN.