L® CXpri X PT Ratio Fig. 3 Schematic Connections For Mho And Ohm Units or as follows if the...

I N S T R U C T I O N S GEH-1769BSUPERSEDES GEH * 1 7 6 9 A A N D

GE 1 « 2 5 3 6 0 6

Type GCX17!I

I

L O W V O L T A G E S W I T C H G E A R D E P A R T M E N T

ELECTRICGENERAL ®"P H I L A D E L P H I A , P A .

www.nationalswitchgear.com

Courtesy of NationalSwitchgear.com

CONTENTS

PAGEINTRODUCTION

APPLICATIONOPERATING CHARACTERISTICS

Mho UnitOhm UnitVernier Adjustment For Low Tap SettingsOhm Unit Transfer AuxiliaryContact Co"ordination

RATINGSTarget Seal"in Unit

BURDENS

33333555999

RECEIVING, HANDLING AND STORAGE 11DESCRIPTION 11Relays With External Capacitors For 25 Cycles 11INSTALLATION

LOCATIONMOUNTINGCONNECTIONSADJUSTMENTS AND TESTS

Adjustments on Induction UnitsElectrical Check Tests on Induction UnitsINSPECTION

1313131313131518

MAINTENANCEPERIODIC INSPECTIONPERIODIC TESTING . .CONTACT CLEANING .SERVICING

Laboratory Tests ,

181818181919

RENEWAL PARTS 21APPENDIX

CALCULATION OF RELAY SETTINGSRELAY SETTINGS WHEN POTENTIAL IS TAKENFROM LOW SIDE OF POWER TRANSFORMER

2121

24

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DIRECTIONAL DISTANCE (REACTANCE) RELAYSTYPE GCX17

INTRODUCTIONupon the phase angle between this current and thepolarizing voltage. The b a c k p o l e provides therestraining torque.

The Type GCX17 relay is a high-speed direc-tional distance relay intended for the protection oftransmission lines. It contains two basic units, theohm unit and the mho directional unit. The ohmunit operates on reactance and is therefore par -ticularly applicable to short lines b e c a u s e it isunaffected by arc resistance. This relay is usedto p r o t e c t transmission l i n e s, either single orparallel, from p h a s e“to

_phas e, three-phase, or

double-phase-to-ground faults.

In the ohm unit , the front and back poles pro-duce the polarizing flux by means of current coils.The flux in the right hand or current pole is madeto lag its current by about 90 degrees and, in con-junction with the polarizing flux, produces an oper-ating torque. The left hand or potential pole fluxacting in conjunction with the polarizing flux pro-duces a restraining t o r q u e. The potential c o i lproduces a restraining torque only when the voltageon its circuit is leading the polarizing current.MHO UNIT

The mho unit has a circular impedance cha-racteristic that passes through the origin and hasits center on the line of the angle of maximum tor -que (see Fig. 1). The ohmic reach of the mho unitcan be adjusted to a minimum of 2.5 ohms phase-to-neutral. The ohmic reach can be extended byreducing the percentage of the voltage supplied tothe restraint circuit through the E2 taps (see Fig.10). The diameter of the mho unit circular charac-teristic is the ohmic reach of the unit and can bedetermined from the equation:

APPLICATIONFor three-step distance protection of trans-

mission lines, the Type GCX17 relay is used inconjunction with a Type RPM11 timing relay. Fig,16 shows a stepped time-impedance characteristicfor several transmission line sections. The instan-taneous or first zone operates with no intentionaltime delay while the second or intermediate zoneand thethird zone operate through the Type RPM11timing relay. Typical e x t e r n a l connections forsuch a protective system are shown in Fig. 4. The-Type RPM11 timing unit u s e s the power from adischarging s p r i n g which is wTound by a rotarysolenoid. The time is regulated by an inductiondrag element. The device contains two time-delaymomentarily “dosing contacts which close in twoindependently adjustable times. These c o n t a c t sprovide the necessary time delay for the secondand third steps of transmission-line protection.

The Type RPM11 timing unit also contains anauxiliary element (TX) whose contacts control thetiming u n i t rotary solenoid. This auxiliary ele-ment is a telephone-type relay and two of its nor-mally-open contacts in series are used to controlthe solenoid.

Instruction b o o k GEl-25364 gives d e t a i l e dinformation on the Type RPM11 timing relays.

The Type GCX17 relay is also readily appli-cable tothe three step distance protection of trans-mission lines using carrier current relaying.

The average operating times, both w i t h andwithout bus side PT's for the 0.z5 ohm, 0.5 ohmand 1.0 ohm relays are shown in Figs. 18, 19, 20,21, 22 and 24.

250 cos (0 ~ 6)tap setting (%)

where 0 is the angle of maximum torque of the unitand fl is the angle of the line. For an E2 tap settingof 100 per cent, the ohmic reach is 2.5 ohms whenthe angles 0 and 0 are equal.

The primary purpose of the mho unit in theType GCX relay is to provide directional discrimi-nation which is necessary since the ohm unit isinherently nondirectional. The mhounit directionalcharacteristic is such that it will operate correctlyfor b o t h forward and reverse faults at voltagesdown to 2 per cent of rated voltage over a currentrange of 6-60 amperes. A secondary purpose of themho u n i t is to measure fault impedance for thethird zone of protection.

The operating time of the mho unit is a func-tion of fault current, fault impedance, and reach.Operating time characteristics for the mho unit areshown in Fig. 2.OHM UNIT

Ohmic reach at line angle =

The ohm unit is located near the top of the re-lay, directly beneath the ohm unit transfer auxiliary,OX, (see Fig. 7). It is an induction-cup type unitwith one circuit-closing contact. The purpose ofthe ohm unit is to measure the distance to the faultand to close its contacts if the fault is within thezone protected by the relay.

The ohmic reach or zone protected by the ohmunit is adjustable by means of taps on the tap block.

OPERATING CHARACTERISTICSBoth the mho and ohm units are supplied with

current from two phase conductors and the potentialbetween them. The schematic connections for thesetwo units are shown in Fig. 3. The mho unit hasits side poles energized by the potential to producethe polarizing flux. The front pole is energized bycurrent to produce a directional torque dependent

i

These instructions do nof purport to cover all details or variations in equipment nor to provide for every possiblecontingency to be met in connection with installation, operation or maintenance. Should further information be desiredor should particular problems arise which are not covered sufficiently for the purchaser's purposes, the matter should ^be referred to the General Electric Company.

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Directional Distance Relays Type GCX17

( 6 0° L A G G I N G)

X

f l-eeocU"ccr

M H O U N I T - 3 r d

2 0 N E

l

u

O H M U N 1 T 2n d O RI N T E R M E D! A T E

1s t O RUN I TI N S T A N T A N E O U S

ZONE

- R RS H A D E D A R E A S A R ET R I P P I N G A R E A S

- X

Impedance Characteristics Of Ohm And Mho UnitsFi g. I

O P E R A T I N G T I M E G C X1 7 M H O T Y P E S T A R T I N G U N I T W I T H A N D W I T H O U T

V O L T A G E B E F O R E F A U L T.16 0 I

\110 L Ta

0 A S H E D C U R V E S - O P E R A T I N G T I M E W H E N C L O S I N G O N F A U L T W I T H L I N E

S I D E P O T E N T I A L

iS

1 0 %r>

fc: c rO 120 lz io 1

\L Ui/> O

3 loo r.\ O P E R A T I N G T I M E W I T H B U S P O T E N T I A LS O L I D C U R V E S u

X 6 o % \z8 0

u i \X

\6 oF A U L T Zz

% -R E L A Y R E A C H

x4 0U J

CL.O

6 0%20

10%0

60 7 01 0 5 03 020100

C U R R E N T I N A M P S.Fig. 2 Operating Time Characteristic Of Mho Unit

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The tap setting of the two taps marked No.1 deter-mine the instantaneous zone and the tap setting ofthe two taps marked No. 2 determine the interme-diate zone.

2 - M H O U N .'V’YYTYY'*—

rfer1lAi.iroVKANSFOPMC ?

PACK F I f f 5T RsThe tap setting required to protect a zone X

ohms long, where X is the positive-phase-sequence(phase-tcrneutral) reactance expressed in secondaryterms, is determined by the following equation:

(Input tap Setting) (Min. Ohms)

SISOEa F P f l l

tO C A R A C I ( O R F O RM E M O R Y A C T I O NI

J; jjTCO F R O N TOutput Tap Setting =The minimum ohms of the ohm unit can be found onthe relay nameplate. The input tap setting is dis-cussed below. The input tap leads (see Fig.10) arelocated under the hexagonal tapped head screws inthe 90 per cent and 10 per cent tap. In late modelrelays only the lead in the 10 per cent tap may bemoved.

X i SHIM INGV.P H A S E’ W O O I N G F O R~ C U R R E N 1 P O i E.

IIO' REFI -LL.?

O H M U N I T

PHASE' ANGwEAR.'jjSTMF h I a.*—irrJWl

HHA ^ tS K I H I , N GC I R C l l ’T

%Fl?If X is not known it can be calculated as followsif the primary phase-to-neutral reactance (Xprj) isknown:

U airlNJ—O H M I C

A U J U S'M F.N T L.'dH R C N ICT RatioX = Xpri X PT Ratio Fig. 3 Schematic Connections For Mho And Ohm Unitsor as follows if the three-phase (line-to-neutral)

reactance in per cent, X%) is known.10(KV)2 X%

tripping the directional unit must also be closed(See Fig. 4).CT RatioX =

where KV = line“to-iine v o l t a g e in kilovolts andKVA = base upon which X% is given,

VERNIER ADJUSTMENT FOR LOWTAP SETTINGSThe input is usually set at 100 per cent but with

a high secondary reactance, where the No. 1 tapswould be a low percentage, the input may be variedby the vernier method to obtain closer settings.For instance, with a 1.2 ohm l i n e and a 1.0 ohmminimum relay, the input would be 100 and the out-put tap setting would be 100/1.2 or 83.3 which canbe set within 0.4 per cent. But in the case of a 12ohm line the output setting s h o u l d be 100/12 or8.33. The nearest output setting would be 8 whichis 4 per cent off. To correct this, the input can bechanged to 96 in which case the output tap settingshould be 96/12 or 8, w h i c h can be set exactly.Setting the r e l a y t a p s by calculations will giveoperation on the desired ohmic v a l u e s within 4per cent. For closer settings the relay should beset by test under the desired conditions.

XKVA PT RatioThe operating time of the ohm unit is, as with

the mho unit, a function of fault current, fault im-pedance, and r e l a y reach. Time characteristicsare shown in Fig. 5.

On lines which have highly lagging impedancesthere is a small tendency for the ohm unit to over-reach owing to the transient offset of the current.Fig. 6 shows the overreach characteristic of theohm u n i t for maximum transient offset. This ofcourse, assumes the inception of the fault will beat a point, in the voltage cycle where transient offsetis a maximum. From Fig. 6 it is s e e n t h a t theoverreach is not objectionable for most lines.OHM UNIT TRANSFER AUXILIARY

The ohm-unit t r a n s f e r auxiliary, OX, is atelephone-type relay whose coil and contacts areshown in the internal connection diagram of Fig.10.The unit is mounted at the top of the relay and isused tochange thesetting of the ohm unit to providea second step of transmission-line protection. Itsoperation is controlled by the Type RPM timing unitas shown by the external connection diagram of Fig.4. The normally-closed contacts of the transferauxiliary provide the circuit for instantaneous trip-ping used for faults in the first step of line protec-tion. If the fault is beyond the first zone of protec-tion, the transfer auxiliary changes the setting ofthe ohm unit by switching to the No. 2 taps on theautotransformer from which a smaller potential issupplied to the ohm-unit potential restraint wind-ings. This extends the ohmic reach of the ohm unitand enables it to operate for faults in the secondzone of transmission“line protection.CONTACT CO-ORDINATION

Since the mho u n i t is polarized by the faultvoltage, it may reset somewhat slowly when a sec-ond or third zone fault is cleared beyond the pro-tected line section. To prevent incorrect tripping

For a numerical example of the relay settings,together with a discussion of potential t r a n s f o r-mer connections, refer tothe Appendix of this book.

The impedance pick-up characteristic of theohm unit is shown in Fig. 1, Since the character-istic is a straight line and parallel to the R axis,the unit responds to a constant component of lineimpedance. This component is the reactance com-ponent. During n o r m a l conditions when l o a d i sb e i n g transmitted over a transmission line, thevoltage and current supplied to the relay presentan impedance which lies rather close to the R axis3ince load will be very near unit power factor ascompared with the reactive KVA which flows duringfault condition. Reference to Fig. 1 indicates thatan impedance near the R axis will lie in an area ofthe ohm unit characteristic where its contact willclose. No harm can result from this since to cause

Hs< 5




PHASESEQUENCE1-2-3m

3=?-l

lGCX-17 ' 5 GCX-19 s:—vE? M RESTR.^To*—2

"iML4| IF3 CONNECT PT'S FOR115 VOLTS PHASE TOPHASE

ficx-ie oox$1-2 *2 iUj C3 UJ prs *1POLAR $3-1£*n c\a > 3AMFASGCX-18 |l-2

Ga-?o *GCX-17 O

GCX-17

*2-3§SAME

g , ASy »1-2OVERCURRENT UN ' T( WEN USE D)

GCX-10CJ

GCX 03-1A-

GCX *1 -7e>ar/CL u

£GCX $2-3 GCX 4*1-2

? 'iO5 OC 0 6 MO \ \ O \

M 9 0 3O— Af o

OCX *>i GCX 42-307s 'lO5 ^vOC

O—^0 6 U M 9

A/—o0

\ o

Ci’S

-3CONNECTION FOR 50 CYCLE AND 60 CYCLE RELAY

CIRCUITBREAKER

2 1AC CIRCUITS

*1-2+-J DC SUPPLY *3-1 *2-31

fY jGCX-ll 11 11*> S.I. A T S. I. AT ?* S. T . A T

RPM-7

OVERCURRENTUNIT( WEN U5ED.K ’'"

':Ip SI cpsi pzsi CONNECTIONS

FOR 250 VOLTAND 40 VOLT RPM11A

INSERT

1 1~r“ u::0

'piM rp M

..I0 w M W0 rJCX-16r.

GCX-3 < f> 3 O “1I1 RPW-20

3 <;i i A16XI XXI XI J(OX ) (OX )( OX)16 r> r 1a RPM-13 -_ X2 L. X2 - X 2

(ox) r ( ox; -r (ox )GCX-l6RPM-1!ip si iisidz si

10 1 r IIJ«I n.L RPM-.U ( r->TX "p TXGCX-2 2 2KTX ±. S pr.s sT r i1K(0 {'•jGCX-4^ RfflA-ieo GCX-12 ( 12 -RPM-2 RFV-’.OTRIP 1ALARM 'RPM-d 6- - - J_ TU*3 "Sox >ox' '- --OX

RPW-19 Cn T? VT3 )nI s 1' RPM-20* -* T j f s- ss :SRPM-12 T RFM-170 RPM-B :o REDLIGHT 6 RPM 5

O15 cS -RPM-3 OGCX-15 6 15' ICONNECTIONS FOR 125 VOl TAND 24 VOLT RPMllA. FOR250 VOLT AND 40 VOLTCONNECTIONS SEE INSERT.

•• TXGCX - TX TX1

0-4 13 TX-2 r\,P. iJ.APP. 0.0.

16 TX • 15 T-O j| A 9~*~ +l-v A-\I*. 24V . A 125V. CONNECTIONS

''•• 40V. A 260V. CONNECTIONSTX SHORTFD THROUGHSTUDS 6 A 6 OR 15 A 16WHEN E’ THER PLUG ISREMOVED.

REM-10 RPM-9 .

I:~Z a

TRIP

I COIL

(-) D-C SUPPLY

T R I P C I R C U . T.SI

"Three Step Distance Protection For A Transmission Line Using Three Type GCX Distance Relays And OneType RPMl lA T iming Relay

Fig. 4

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i' GCX-17 5PHASE

SEQUENCE1-2-3

OR3-2-1

2 “ fa. \OCX-18 O3 CONNECT PT * S FOR

115 VOLTS PHASE TOPHASE —— GCX-19OX< <fl-2 *2a tJ UT

n. nM M RESTR.

GCX-20 7)>POLAR OX COILCOIL >1a ,SAWEASGcx-ie f l-2

GCX-17 Q

OVERCURRENT UNIT(WHEN USED)

ou GCX-18 ;

GCX $.1-2 GCX $3-1Q

T K2 6s 'T\oc o w\—V—VM

\0CL.

V Oo o o 9iGCX 42-3 iC21 EXTGCX $1-2 GCX $1-210l7s 7soc 0 0M 8 M

O V—VGCX $2-3

<>-a o-VGCX ^3-1 96|2-3XXI? ^ C21 EXT!0O7 ^7W=V-4 4-4 7

oof 9 o -1_ C21 EXTt ioGCXCT'SV

CIRCL. ITBREAKER CONNECTrQNS FOR 25 CYCLE RELAY

3 2 1 A-C CIRCUITS

LEGEND

DESCRIPTIONSYMBOLS ON DEVICEAUXILIARY SWITCH ON CIRCUIT BREAKERe

MHO UNIT ( DIRECTIONAL ANO 3RD ZONE)(XXMOHM UNIT (1ST AND 2ND ZONES)GCX001*1 UNIT TRANSFER AUXILIARYOX GCXAUXILIARY CO-ORDINATING ELEMENTS GCX

SEAL-IN UNITGCXS. I.TARGET

TU I PPM TIMING UNITAUXILIARY FOR TIMING UNITTX RFMFHASE9

* = NOT USED IN THIS APPLICATION

DRAWING REFERENCESOUTLINEDEVICE |NT. CONNS.

K-6375826 K-6209276GCXRPM JHJVTnBv K-6209272K-6400680

K-6209272K-6209282RPM 125V A 24V

Fig. Three Step Distance Protection For A Transmission Line Using Three Type GCX Distance Relays And OneType RPMI IA Timing Relay

7

A




T T TT Y P I C A L T I N E-C U R R E N T C H A R A C T E R I S T I C S O F O C X O H M U N I T S F D RF A U L T S O F 1, 5 0 A N D 9 0 P E R C E N T O F R E A C T A N C E S E T T I N G O FU N I T.

140

a 100s(->u1/3

COo

<0Ix

LAO l

u.10 OHM OHM UN IT

Operating Time Characteristics For Ohm Units

*Um

LIME IMPEDANCE ANGLE ( DEGREES)

Over-Reach Characteristic Of Ohm Units

38




BURDENSon s u c h occurrences, an auxiliary co-ordinatingelement (S) is supplied on the GCX relay. This co-ordinating element operates in conjunction with theauxiliary for the timing unit (TX) as shown by theexternal connection d i a g r a m of Fig. 4. The TXcontact opens thefirst zone trip circuit about 0.030second (2 cycles) after the mho unit has operated.To restore first zone tripping for faults near theend of the ohm unit reach, the S contact closes ifthe mho unit remains closed for 0.015 second (1cycle) after the ohm unit has closed. The one cycledelay in clearing first zone faults is only incurredin cases where the trippingtime would normally bethree cycles or more.

The current burdens at 5 amperes for the ohmand mho units are given in Table I.

TABLE I

CURRENT BURDENS PER PHASEUnit Imp. P.F. VAFreq. Amps

60 5 0.32 8.030.62MhoOhm

0.5 or 1.0 ohm)0.25 ohm)

Total Relay(0.5 or 1.0 ohm)(0.25 ohm)

60 0.615 0.74 18.560 0.19 0.58 4.755

60 5 1.06 0.61 26.5RATINGS 0.5160 5 0.61 12.8

The Type GCX17 r e l a y is available for 115volts, 5 amperes rating with d-c control voltage of24/48 or 125/250 volts, d-c. The ohm-unit minimumohmic setting is available in 0.25, 0.5, or 1.0 ohmphase-to“neutral. The m a x i m u m r e l a y reachwould be 10 ohms phase-to-neutral. The mho unitis available in a minimum ohmic setting of 2.5ohms at an angle of maximum torque of 60 degreeslag.

50 0.27 0.62 6.69Mho 5Ohm

(0.5 or 1.0 ohm)(0.25 ohm)


50 0,625 0.61 15.450 0.16 3.965 0.5950 5 0.89 0.61 22.09

10.6550 5 0.43 0.6125Mho 5 0.19 0.62 4.85

Ohm(0.5 or 1.0 ohm)(0.25 ohm)


The contacts of the relay will close and carrymomentarily 30 amperes, d-c. The breaker t r i pcircuit, however, should always be o p e n e d by anauxiliary switch or other suitable means; it cannotbe opened by the tripping relay contacts, or by thecontacts of the units. The combination target andseal-in element has a dual rating of 0.6/2.0 am-peres for 125/250 volt d ~c control circuits. For24/48 volt d-c control circuits, the target and seal-in element has a rating of 2.0 amperes. The lowerd“C control voltage should be connectedto the lowernumbered stud. See Fig. 4.

The tap setting used on the target and seal-inelement is determined by the current drawn by thetrip coil. The 0,6 ampere tap is for use with tripcoils which operate on currents ranging from 0.6to 2.0 amperes at the minimum control voltage,while the 2,0 amperes tap should be used when tripcurrents are greater than 2.0 amperes. It is notgood practice to use the 0.6 ampere tap when thetrip current is greater than 2.0 amperes since the0.6 ohm resistance of the 0.6 ampere tap will causean unnecessarily high voltage drop which will re-duce the voltage at the circuit"breaker trip coil.If the tripping current should exceed 30 amperes itis recommended that an auxiliary tripping relay beused.Amperes to close first contact at 1% voltage

at maximum torqueResistance fault (in phase) ,Reactance (80 to 90 degrees)

TARGET SEAL-IN UNIT

25 5 0,54 0.63 13.525 5 0,22 0.61 5.425 18.30.625 0.73

5 10,2525 0.41 0.61The potential burdens will vary with the tap

settings used for the ohm and mho unit potentialcoils; therefore, potential burdens should be cal-culated from the following formulae. All burdensare at 115 volts.

Ohm Unit:VA = (a + jb) (No. 1 tap/100)2

where (a + jb) varies with frequency rating of therelay and is given in Table II. No.1 tap is the firstzone setting in per cent.

Mho Unit:VA = (E2 tap/100)2 (c + jd) + (e + jf )

where (c + jd) and (e + jf ) vary with the frequencyrating of the relay and are given in Table n. E*tap is the third zone setting in per cent. The term(c + jd) represents the burden of the mho-unit re-straint-coil circuit while the term (e + jf ) repre-sents the burden of the mho-unit polarizing-coilcircuit.

4-5 TABLE II8-9

4.5-6 POTENTIAL BURDEN CONSTANTSFrequency Rating 60 50 25

Amperes, A ~c or D~c Ohm Restraint a+ jbMho Restraint c+jdMho Polarizing e+jf

23+ j06.3-j7.07.68+ j.945

24.2+jO6 J.l -j6.816.48+jL98

13.9+ jO7.0-j6.62

10.3+jO2.0 A. Tap(0.3 ohms)

0.6 amp tap(0.6 ohms)

FUNCTION

30Carry for tripping dutyCarry continuouslyMin. Target Operating

Current

15 The maximum potential burdens will exist whenboth the No.1 taps and the E* taps are in the 100per cent setting. At 115 volts the maximum po-tential burdens are given in Table III.

4 0.82 0.6

9

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Mg **RELAY

OVER -CURRENTUNIT ( INGCXI 7 BONLY )

G 2 1

C 33TARGETSEAL -INUNIT

TAPPEDAUTO TRANS- OM

FORMER

sr*-o>

OHM UNITTRANSFER‘AUXILIARY

(OX )

u~RIIR21

_ R 2

R

OHMUNIT

oOO

TAPBLOCK S

oo9>

R u.2 3

MHOUNIT

Type 6CXI7 Relay Removed From CaseType GCXI7 Relay Removed From Case(Front View ) ( Back V iew )

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TABLE IDMAXIMUM POTENTIAL BURDENS

P.F, WATTS VAIMPEDANCEFREQ, VOLTS231.0 23575 -t j 0

940 + j 10431692 “ j 208351 + j 56.9

60 115Ohm RestraintMho RestraintMho PolarizingTotal RelayOhm RestraintMho RestraintMho PolarizingTotal RelayOhm RestraintMho RestraintMho PolarizingTotal Relay

9.46.30.6760 1157.6 7.70.9960 115

37.536.80.9860 11524.21.00 24.2547 + j 0

963 + j 10731864 - j 570354 + j 46.3

50 1159.20.67 6.250 1156.80.96 6.550 115

36.8 37.10.9950 11513.91.00 13.9952 + j 0

943 + j 9971285 + j 0

407 + j 86.5

25 1159.66.60.6925 115

10.310.31.025 11531.831.10.9825 115

RECEIVING, HANDLING AND STORAGEpacking the relay in order that none of the partsare injured or the adjustments disturbed.

These relays, when not included as a part ofa control panel will be shipped in cartons designedto protect them against damage. Immediately uponreceipt of a relay, examine it for any damage sus-tained in transit. If i n j u r y or damage resultingfrom rough handling is evident, file a damage claimat o n c e w i t h the transportation c o m p a n y a n dpromptly notify the n e a r e s t G e n e r a l ElectricApparatus Sales Office.

Reasonable c a r e should be exercised in un_

If the relays are not to be installed immedi-ately, they should be stored in their original car -tons in a place that is free from moisture, dust andmetallic chips. Foreign matter collected on theoutside of the case may find its way inside when thecover is removed and cause trouble in the operationof the relay.

DESCRIPTIONThe relay contains three major units; the mho

starting unit, at the bottom, which isdirectional andwhich detects the presence of faults within the zonecovered by the relay; the ohm unit, in the center,which measures the distance to the fault; and theohm unit t r a n s f e r auxiliary, at the top, whichchanges the setting of the ohm unit for the longerdistance for back-up protection.

A combination target and seal-in element isalso mounted at the top of the relay and is connectedin s e r i e s with the tripping circuits. The targetis reset by a button at the bottom of the cover atthe left.

The Type GCX17 relay is of standard construc-tion. Its drawout case has studs at both ends forthe external connections. The electrical connec-tions between the relay units and the case studsare made through stationary molded inner and outerblocks between which nests a removable connectingplug which completes thecircuits. The outer blocksattached to the case have the studs for the externalconnections, and the inner blocks have the terminalsfor the internal connections.

The relay mechanism is mounted in the steelframework called the cradle and is a complete unitwith all leads being terminated at the inner block.This cradle is held firmly in the case with a latchat both topand bottom and by a guide pin at the backof the case. The connecting plug, besides, makingthe electrical connections between the respectiveblocks of the cradle and case, also locks the latchin place. The cover, which is drawn to the case bythumbscrews, holds the connecting plug in place.

To draw out the cradle, the cover must first beremoved. Then the plug can be drawn out. In sodoing, the trip circuit is first opened, then the cur-rent transformer circuits are shorted and finallythe voltage circuits are opened. After the plug hasbeen removed, the latch can be released and thecradle easily drawn out. To replace the cradle, thereverse order is followed.

A separate testing plug can be inserted in placeof the connecting plug to test the relay in place onthe panel either from its own source of current andvoltage, or from other sources. Or, the relay canbe drawn out and replaced by another which hasbeen tested in the laboratory.

The auxiliary co-ordinating e l e m e n t (S), atelephone-type relay, is mounted at the top of therelay on the front right-hand side.

Figs. 7 and 8 show the relay removed from itsdrawout case and the locations of the major andauxiliary units.RELAYS WITH EXTERNAL CAPACITORS FOR 25CYCLES

When external capacitors are furnished withrelays they are identified by means of serial num-bers. The purpose of these numbers is to insurethat e a c h relay, when installed, will be providedwith the same auxiliaries with which it was cali-brated at the factory.

The reason for this precaution is to eliminatethe variation in calibrations of the relays whichwould otherwise result from the variation in elec-trical properties of the auxiliaries.

5 11<




PANEL LOCATIONSEMI-FLUSH SURFACE

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12

PANEL DRILLING FOR SEMI-FLUSHMOUNTING (FRONT VIEW)

Outline And Panel Drilling Dimensions For The Type GCXI 7 RelaysFi g. 9

12



Directional Distance Relays Type GCX17ij? l4 15 if REMOVE THESE JUMPERSI— 4ME* SEPARATE

20 POLAR 1 ZJNG POTWTIAL '

j IS USED.11 13 1715

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Internal Connections For TheFig. IIType GCXI 7A or 8 Relay ( 25 Cycle )

10 Internal Connections For The TypeGCXI7A or B Relay (60 Cycle)

Fig.

INSTALLATIONADJUSTMENTS AND TESTSLOCATION

The location of the relay should be clear anddry, free from dust, excessive heat and vibration,and should be well lighted to facilitate inspectionand testing.

The following adjustments and tests are thosewhich we suggest at the time the relay is first putinto service. The purpose of these tests is to sat-isfy the purchaser that no changes in calibration oradjustments have occurred since the relays left thefactory and to insure that the relay characteristicsare correct for the particular settings and condi-tions under which they will operate in the field. Theelectrical t e s t s in this s e c t i o n m a y a l s o bemade at six month intervals to insure continuedsatisfactory operation of the relays .

ADJUSTMENTS ON INDUCTION UNITS

1. The lead-in spring of the ohm unit shouldbarely hold the contact against the backstops. Thelead“in spring of the mho unit should hold the con-tacts definitely open.

2. See that the cup assembly moves withoutnoticeable friction.

3 . The ohm-unit stationary c o n t a c t and theupper contact of the mho unit should rest againsttheir felt backstops .

4. The mho-unit lower stationary-contact stopshould be slightly behind the upper stationary feltcontact stop.

MOUNTING

The relay should be mounted on a vertical sur-face. The outline and p a n e l drilling dimensionsare shown in Fig. 9.

CONNECTIONSInternal connections for the 50 cycle and 60

cycle relays are shown in Fig. 10. Internal con-nections for the 25 cycle relay are shown in Fig.11. Typical e x t e r n a l connections are s h o w nschematically in Fig. 4. For exact external con-nections reference should be made to the drawingsfor the particular requisitions on which the relayswere furnished.

One of the relay mounting s t u d s or screwsshould be permanently grounded by a conductor notless t h a n No. 12 B &S gage c o p p e r wire, or itsequivalent .

213




115 VOLT SOURCE AT RATED FREQ.+125 OR 250 V. CONTROL

ac TEST BOXo

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STUD CONNS. ( REO)NOTE: OUTER CIRCLESINNER CIRCLES - RELAY CONNS. ( BLACK ) v

t I<9) TEST PLUGl11 113 15 17 19

12 ^ 16 10 20@ ® ®

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CONNECT TO RELAYSTUO 12 WHENTESTING ZONE 2 LCONNECT TO RELAYSTUD 1 WHEN

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l LOWER (13 5 7 9

CONNECT TO RELAY

STUO 3 WHENTESTING ZONE 3

2 4 6 8 10CONNECT

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TESTING ZONE 2.

Fig. 12 Test Connections For The Type GCXI 7 Relays

>-3s<14




5. The mho-unit l o w e r stationary c o n t a c tshould h a v e approximately 1/32 inch wipe. Thecontact gap as measured from the lower stationarycontact should be 0.1 inch.6. The ohm-unit contact gap should be 1/16

oGCX-17*S

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115 VOLTSSYSTEM FREQ.=i-

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RLELECTRICAL CHECK TESTS ON INDUCTIONUNITS10%

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The manner in which reach settings are madefor the ohm and mho unit is briefly discussed inthe introduction of these instructions. Examplesof calculations for t y p i c a l settings are given inthe Appendix. It is the purpose of the electricaltests in this section to check the ohm and mho-unit ohmic pickup at the settings which have beenmade for a particular line section.To eliminate the errorswhich may result frompossible instrument inaccuracies a test circuit hasbeen selected which requires no instruments. Sucha circuit is shown in Fig. 13. In Fig. 13 Rs + jXsis the source impedance, Sp is the fault switch andRL + j XL is the impedance of the line section forwhich the r e l a y is being tested. The autotrans-former, T^ , which is across the fault switch andline impedance is tapped in 10 per cent and 1 percent steps so that the line impedance RL + j XLmay be made to appear to the relay very nearly asthe actual line on which the relay is to be used.This is necessary since it is not feasible toprovidethe portable test reactor, XL, and the test resistorwith enough taps so that the combination may bemade to match any line.For convenience in fieldtesting thefault switchand tapped autotransformer of Fig. 13 have beenarranged in a portable test box, Cat. No. 6052978,which is particularly adapted for testing directionaland distance relays. The box is provided with ter-minals to which the r e l a y current and potentialcircuits as well as the line and source impedancesmay be readily connected. For a complete des-cription of the t e s t b o x t h e u s e r is referred toGEI-8370.

oiU-

Fig. 13 Tes t Circui t

Connected between terminals A and B of thetest box is an auxiliary relay and resistor whichare arranged in such a way that, when the contactsof the ohm and mho units close, sufficient trip cur -rent will be drawn to operate the Type GCX targetseal-in. After the Type GCX seal-in has had anopportunity t o operate, the auxiliary relay opensthe resistor circuit which draws the trip current.Since the seal-in is operated it will be necessaryto open the test-box switch, S3, which opens thed-c supply and allows the seal-in to reset. Thisarrangement eliminates the necessity of providingan indicating lamp and also checks the operation ofthe target seal-in element.Since the relay is to be tested for the ohmicreach that it will have when in service, the valueof XL to select will be the portable test-reactortap nearest above twice the relay phase-to-neutralohmic reach. Explanation of the twice factor is asfollows: The r e l a y as normally connected (Vj -2potential and 11 — 12 c ur r ent) measures positivesequence phase-to-neutral reactance. Foraphase-to-phase fault, the fault current is forced by thephase-to-phase voltage through the impedance ofeach of the involved phases. In the t e s t circuit,the line impedance, ZL , is in effect the sum of theimpedance of each of the p h a s e conductors andmust be so arranged in order to be equivalent tothe actual fault condition. Since the impedance ofeach phase must be used to make up the line im-

pedance in the test circuit its value will be twicethat of the phase-to-neutral relay reach. The percent tap of the test box autotransformer, w h i c hshould cause the ohm unit to just close its contactswith the fault switch closed is given by:

^ (^Relay )

a. Testing the Ohm Unit

To check the calibration of the ohm unit, it iss u g g e s t e d that the portable t e s t box, Cat, No.6052978; portable test reactor, Cat. 6054975; andtest resistor , Cat. 6158546 be arranged with TypeXLA test plugs according to Fig.12. The circuit ofthe test box and connected equipment is similar tothat shown in Fig. 13 except that the source im-pedance, Rg + j Xg is r e p l a c e d with a load boxwhich serves* to give the source voltage drop andto control the level of the fault current.

(100)% = X LFor this test the value of RL may be made zerosince the ohm unit responds only to a reactancequantity. The load box however may be adjusted togive a fault current of approximately 10 amperesor whatever fault current is expected during three-phase and/or phase-to-phase fault conditions.

To illustrate the above the 1.0 minimum ohmphase-to-neutral relay, set zone 1 at 86 per c e n tand zone 2 at 58 per cent, used in Example 1 of theAppendix will be used.

Use of the s o u r c e impedance, Rg + j Xgonly required when the relay is being tested foroverreach and contact co-ordination. S u c h testsare not considered necessary at the time of instal-lation or d u r i n g periodic testing. Tests of thisnature are described later in the section on SER-VICING.

, is

115




A check of the ohm unit' s second zone reachmay be made in the same manner except that thetransfer r e l a y, OX, should be energized by con*

necting a jumper between relay studs 3 and 12 andby connecting the negative return lead to relay stud2 rather than stud 1. (See Fig. 12). For polaritytest see Fig. 24.b. Testing The Mho Unit

The mho unit is tested in a manner very simi-lar to the ohm u n i t above, the m a j o r differencebeing in the manner inwhich the test “box autotrans-former per cent tap setting for pickup is deter -mined. This difference results from the fact thatunlike the ohm unit, the impedance pick-up charac-teristic of the mho u n i t on an R-X diagram is acircle passing through the origin. The diameterof the circle which is the relay angle of maximumreach is at an angle of 60 degrees with the R axis.(See Fig. 1).

Since the reactance of the test reactor may bevery accurately determined f r o m its calibrationcurve, it is desirable tocheck relay pickup with thefault reactor alone, due account being taken of theangular difference between the line reactance, XL,and relay angle of maximum reach. As in the caseof the ohm unit, the line reactance, XL , selected,should be the test reactor tap nearest above twicethe mho unit reach with account being taken of thedifference in angle of the test reactor tap impedanceand the relay angle of maximum reach. From Fig.14 it is seen that twice the relay reach at the angleof the test reactor impedance is:

^ zmin ohms= 2 §

E tap set0 is the angle of the test reactor impedance and 6is the relay angle of maximum reach. The test -box autotransformer percent tap for the mho-unitpick up is given by:

^zRelav

REACH AT TESTREACTOR ANGLE

? Z M INE 2 TOP

/>

V CMR coC'J<oCO

=*cn

LL»

Fig. Reach Of Mho Unit At Angle Of Test Reactor

= 2 = 2.3 ohms.Relay

cos (0 - 0) where2zRelay “Therefore use reactor nominal 3.0 ohm tap. As-sume now that the reactor calibration curve hasbeen referredto and that reactance of the 3.0 tap atthe current level to be used is 3.2 ohms. Fromthis and the above, the test-box autotransformerpercent tap at which the ohm-unit c o n t a c t willclose is:

% tap = zL(100)2,3 (100) = 72%% tap = 3.2

To illustrate the above the relay setting in Exampleof the Appendix will again be used. Reference to

the example shows the E^ tap setting to be 61 percent. The minimum ohmic reach of all Type GCX17mho units is 2.5 ohms with the relay angle (0) ofmaximum reach at 60 degrees. In determining thereactor tap setting to use, it may be assumed thatthe angle ( fi ) of the test reactor impedance is 80degrees. From the above twice, the relay reach atthe angle of the test-reactor impedance is:

The ohm u n i t should therefore close its contactwith test-box autotransformer taps set at 72 percent and remain opened with the percent taps at73 per cent.

1

To determine the phase angle of the ohm unit' sreactance characteristic, it is only necessary toobserve the effect of adding resistance in serieswith the line reactance. This is the resistance,RL, which should be noninductive and in magnitude5 to 8 times as l a r g e as the line reactance XL.Either the calibrated test resistor Cat.No.6158546or the tapped fault resistor included in the test boxmay be used as the line resistor, RL. When thepick-up test is made with this line resistance in thecircuit, the load box used as s o u r c e impedanceshould be readjusted such that approximately thesame fault current flows as did in the first test.With the fault switch closed, the ohm unit shouldclose its contacts at the same test-box autotrans-former per cent tap as before. For phase anglemeter readings see Fig. 25.

cos (80-60) - 7.7 ohm2ZRelay 2

Therefore, use the reactor 12 ohm tap. Twice therelay reach at the angle of test reactor impedanceshould be recalculated using the actual angle of thereactor tap impedance rather than the assumed 80degrees. Table IV shows the angles for each of thereactor taps.

S16 <




ZLIS the 60 degree, 30 degree or zero degree im-pedance value taken from the calibrated resistordata sheet and is mho unit restraint tap settingexpressed as a decimal. As in the case of the pre-vious tests, the load box which serves as sourceimpedanceshould be adjusted to allow approximately10 amperes to flow in the fault circuit when thefault switch is closed.

When checking the angle of maximum reach ofthe mho unit as indicated above, there are two fac-tors to keep in mind which affect the accuracy ofthe results. First, when checking the mho unit atangles of more than 30 degrees off the maximumreach position, the error becomes relatively largewith phase angle error . This is apparent from Fig.14 where it is seen, for example,atthe zero-degreeposition that a two or three degree error in phaseangle will cause a considerable apparent error inreach. Secondly, the effect of the control springshould be considered since the mho unit can onlyhave a perfectly circular characteristic when thecontrol-spring torque is negligible. For any nor-mal level of polarizing voltage, the control springmay be neglected but in testing the unit as indicatedabove it may be necessary to reduce the test “boxautotransformer tap setting t o a point where thevoltage supplied to the unit may be relatively low.This reduces the torque level since the polarizingas well as the restraint will be low with the resultbeing that the control-spring torque will no longerbe negligible. The result of the control spring atlow polarizing voltages is to cause the reach of themho unit to be somewhat reduced.

In order to see the affect of the above in theirtrue proportion, it is suggested that reach charac-teristic as determined from testing be plotted onan impedance diagram such as the mho character-istic s h o w n i n Fig. 1. Obviously, the apparenterror in reach resulting from phase angle error atangles well off the maximum -reach position, are ina region where a fault impedance vector will notlie. Concerning the s p r i n g torque e r r o r, it ispointed out that the mho unit is not the measuringunit for primary protection but rather is only a di-rectional unit and, therefore, its directional res-ponse is the m o s t important consideration. Forthe third-zone back-up protection, the mho unit isthe measuring unit , but for the remote faults, thevoltage at the relay is not apt to be low. Further-more the accuracy of a third-zone back-up unit isnot as important as that of a first -zone unit.

In addition to the above tests on the mho unit,it may also be checked for directional action withthe test-box circuit as shown in Fig. 12. The faultresistor, R 2 , may be zero, the test reactor shouldbe set on the 0.5 ohm tap. With the test-box switch,S2, in the trip position, the mho-unit contact shouldremain closed f o r a current range of 6 ~60 ampereswith 2 per cent rated voltage applied. A voltmetershould be used to read the voltage at studs 17-18 ofthe r e l a y. T h e v o l t a g e over the 6-60 ampere-current range is adjustable by means of the test-box autotransformer tap switches. When switch,S2, of the test box is thrown tothe reverse position,the mho unit contacts should remain open for thesame conditions as above described.

TABLE IV

cos 0-60AngleTap

24 0.8830.8910.8990.9060.9210.9340.951

8812 876 863 852 831 81

0.5 78

From the table it is seen that the angle of the im-pedance of the 12 ohm tap is 87 degrees. There-fore:

2ZRelay " 2 261 cos (87-60) = 7.3 ohms

The calibration c u r v e for t h e portable testreactor s h o u l d again be referred to in order todetermine exact reactance of the 12 ohm tap at thecurrent level being used. For the purpose of thisillustration assumethat the reactance is 12.2 ohms.Since the angle of the impedance of the 12 ohm tapis 87 degrees, the impedance of this tap may becalculated as follows:

12.2ZL ~ X^/cos 3 = = 12.22 ohms.9986

From this calculation it is seen that the re-actance and the impedance may be assumed thesame for this particular reactor tap. Actually thedifference need only be taken into account on thereactor 3, 2, 1 and 0.5 ohm taps.

The test“box autotransformer tap setting re-quired to close the mho-unit contacts with the faultswitch closed is:

7 *3% = (100) = 59.7%12.2

If the ohmic p i c k u p of the mho unit checkscorrectly according to the above, the chances arethat the angle of the characteristic is correct. Theangle m a y, however, be very e a s i l y checked byusing the calibrated test resistor in combinationwith various r e a c t o r taps. The calibrated testresistor t a p s are pre-set in such a manner thatwhen used with 12 and 6 ohm taps of the specifiedtest r e a c t o r, impedances at 60 degrees and 30degrees respectively will be available for checkingthe mho-unit reach at the 60 degree and 30 degreepositions. The mho-unit ohmic reach at the zero-degree position may be checked by using the cali-brated test resistor alone as the line impedance.The calibrated test resistor is supplied with a datasheet which gives the exact impedance and anglefor each of the combinations available. The test-box autotransformer per cent tap for pickup at aparticular angle is given by:

2 (2.5) cos (60-a)(E2 tap) ZL

where a is the angle of the test impedance ( Z j J ,% Tap = 100

17




c. Other Check Tests

In addition to the calibration checks for ohmand mho units as described above, it is desirableto make the following additional tests on the relayin general:

1. Use the test circuit as s h o w n in Fig. 12except connect the negative return lead to relaystud 4 rather than 1, 2 or 3 for the zone 1, zone 2or zone 3 tests. Then close the ohm and mho-unitcontacts manually. The target seal-in element ofthe relay should operate. Reference to the TypeGCX internal connection diagram (Fig.10) indicatesthat tripping in this test is through the"SM relaycontact and therefore the test serves as a check onthe operation of thenSn relay.

2. If the relay being tested is a Type GCX17Brelay which includes an overcurrent unit, its pickupmay be checked by adjusting the fault current levelby means of the load box. Calibration points of theovercurrent unit are marked on the relay name-plate. Normally, the overcurrent unit is set at thefactory on its lowest pickup.

The target should reset promptly when the re-set button at the bottom of the cover is operated,with the cover on the relay.

There should be no noticeable mechanical fric-tion in the rotating structure of the units and themoving contacts should return to their backstopswhen the relay is de-energized.

There should be approximately 1/64 inch endplay in the shafts of the rotating structures. Thelower-jewel screw bearing should bescrewed firm-ly into place and the top pivot locked in place by itsset screw.

If there is reason to believe that the jewel iscracked or dirty, the screw assembly may be re-moved from the bottom of the unit and examinedunder a microscope, or the surface of the jewelmay be explored with the point of a fine needle.When replacing the jewel screw, care should betaken to engage the upper pivot in the shaft beforescrewing in the jewel screw.

All nuts and screws should be tight with parti-cular attention being paid to tap plugs.CAUTION: Examine the tap block with great careto make sure the tap lead terminals do not come incontact with adjacent terminals, tap-hole shoulders,mounting s c r e w heads or other grounded parts.Even on those relays provided with tap lead-sleeveinsulation, it is possible to mechanically puncturethe sleeve insulation by forcing the tap lead termi-nal against some nearby part. The punctured in-sulation may cause a portion of the tapped auto-transformer to be shorted or grounded, the resultfrom this being eventual failure of the transformer.As a good general practice, it is recommended thatthe tap leads be placed horizontally on the tap blockwith the leads coming out rather than in toward therelay.

INSPECTIONBefore placing the relay into service, inspec-

tion of miscellaneous items should be made to in-sure that no change has taken place in mechanicaladjustment during shipment or storage period. Itis suggested that the following items be examined.

The armature and contacts of the target-seal-in element should operate freely by hand.

There should be a tap screw in only one of thetaps above the right-hand stationary contact of thetarget-seal-in element. A spare tap screw is pro-vided in the tap hole above the left-hand stationarycontact which should be used when it is necessaryto change the tap. When it is desirable to changethe target-seal-in tap, the spare tap screw shouldbe i n s e r t e d in t h e n e w tap a n d tightened be-fore the existing tap s c r e w is removed. Thisprocedure will maintain the right-hand stationarycontact position, since it is held fixed only by thetap screw.

The felt gasket on the cover should be secure-ly cemented in order to maintain an effective dustseal.

The contact surfaces should be clean.

MAINTENANCEPERIODIC INSPECTION insert the test plugs in each relay in succession

and observe relay contact operation when the faultswitch is closed. Frequent calibration tests arenot considered necessary since the calibration ofthis relay does not change appreciably with time.If it is found that the relay does not test correctlyaccording to the above, readjustment may be madeaccording to the procedure set forth under SER -VICING in this section.

At six m o n t h intervals an inspection of therelay should be made covering those items listedunder INSPECTION in the preceding INSTALLA-TION section.

PERIODIC TESTINGAt the same time the periodic inspection is

made, the check tests described in the INSTALLA-TION section should be made. These tests may bemade very quickly if the test-box autotransformersettings for e a c h relay terminal are determinedahead of time in which case it is only necessary to

CONTACT CLEANINGSilver c o n t a c t s should never be handled or

touched by b a r e hands because dampness on thehands may cause the formation of silver salts whichhave high resistance.

s18 <

.....




of the ohm unit has been machined to have a flatsurface on one side. By loosening the core posi-tion locknut on the bottom of the unit, the core maybe rotated until the desired position is reached.The usual position for the flat, as assembled by thefactory, is toward the rear left -hand corner of theunit. The exact position for the flat may be de-termined as well as o t h e r adjustments from thefollowing tests:

1. Pickup, Phase Angle, Core Position

Use the test circuit shown in Fig. 12. Adjustthe control spring so that the moving contact justrests against the backstop. With the number 1 tapsin 100 per cent and the fault switch open, loosenthe core locking screw slightly and rotate the coreclockwise (viewed from the top) until the contactsclose. Then rotate the core counterclockwise untilthe moving contact just rests against the backstop.This adjustment tends to compensate for any straytorques which might cause the contacts to close onvoltage alone. Note that it should be unnecessaryto rotate the core more than 30 degrees in eitherdirection.

For fine silver contacts, a flexible burnishingtool should be used. This consists of a flexiblestrip of metal with an etched-roughened surfaceresembling in effect a superfine file. The polish-ing action is so delicate that no scratches are left,yet it will clean off any corrosion thoroughly andrapidly. Its flexibility insures the cleaning of theactual points of contact. Sometimes an ordinaryfile cannot reach the points of contact because ofobstruction offered by some r e l a y part, but theflexible burnisher can be drawn through the con-tacts while t h e y are held together, thus cleaningboth simultaneously and at the c o r r e c t contactpoints.

Knives, files, and abrasive paper or cloth, etc.,produce scratches on fine silver and, of course,the abrasive medium may be left imbedded in thesurface of the silver and prevent subsequent con-tact. A contact cleaned with one of these devicesmay arc and requirecleaning again in perhaps one-tenth of the time taken by a new contact to deterio-rate to the same condition. This is because theminute raised sides of the fine scratches, made incleaning the contact, form tiny arcing points whichmelt, become sticky and get bigger with each con-tact operation; a new contact has a smooth surfaceand there is no place where the current density isgreat enough to melt the silver and roughen the sur-face, thereby starting the process of deterioration.

Before making pickup or phase-angle adjust-ments, the unit should be allowed to heat up forapproximately 15 minutes, energized with voltagealone. Determine the t e s t-b o x autotransformersetting for pickup and the test reactor tap as des-cribed in the section covering installation tests.With the fault switch closed and the source imped-ance (Rs ) setto allow approximately 10 amperes toflow, adjust (R 2i)so that the contacts just close.Then i n s e r t line resistance (R j ) approximatelythree times the line reactance (XL) in the test cir -cuit, readjust the source impedance (Rg )allow 10 amperes to flow, and adjust (RJI )the ohm-unit contacts just close at the same test-box autotransformer tap setting as before. Thisprocedure p r e s e n t s an impedance to the relaywhose angle is approximately 20 degrees. If therelay pickup is the same for the 20 degree imped-ance as it is with reactance alone, the relay angleof maximum reach will be at 90 degrees or the unitwill m e a s u r e reactance alone. The pickup andphase-angle adjustments of the ohm Nunit are to aslight extent interdependent. For this reason it isnecessary to go back and check the pick-up adjust-ment {R21 ) after the phase-angle adjustment (R JM )has been made and alternately set each until eachis correct.

SERVICING

If it is found that the calibrations do not checkduring installation tests or periodic tests, recali-bration should be made by adjusting as necessaryelements normally called factory adjustments. Theadjustments are listed below. These may be locatedfrom Figs. 7 and 8.

to againso that

Rfl - Ohm U n i t Characteristic Phase AngleAdjustment

R21_

Ohm Unit Characteristic Reach Adjust-ment

R ^3 - Mho Unit Characteristic Reach Adjust-ment

R 23 “ M h o U n i t Characteristic Phase AngleAdjustment

Core Adjustments - Stray TorqueTABLE V

CalibrationRange

Clutch AdjustmentMin.OhmsLABORATORY TESTS

Grams Amps with ZeroRestraintShould it ever be necessary to replace an ohm

or mho unit or if the basic factory adjustments havebeen for some reason disturbed, it is advisable tomake the following tests which are of a laboratorynature.

0.25 23-3014-2010-15

5-75 Amps3“60 Amps2-40 Amps

17-2127-3327-33

0.501.00

Table V shows current calibrating ranges forohm u n i t s of different minimum o h m i c ratings.With the test circuit arranged as above, the ohmicpickup may be checked at different current levelsby changing the amount of source impedance (Rg ).

a. Ohm Unit

To compensate for slight manufacturing dis-symmetries, the iron core inside the induction cup

*-5

2 19<




autotransformer setting above that calculated forpickup. One of the ten trials will be near the pointwhere maximum transient offset occurs. The dif -ference between the test-box autotransformer tapsetting required to keep the c o n t a c t s open on atransient basis and the tap setting which will keepthe contacts open on a steady state basis expressedas a percentage of the latter is the per cent tran-sient overreach of the ohm unit.

3 2 1VAR I AC

OJ111 COaCO

V18 CO

LOPHASESHIFTER

C lW oJ-b. Mho Unit

u»

The mho unit in the Type GCX17 relay is pri-marily intended as a directional unit since the ohmunit is inherently nondirectional. It a l s o servesas the third-zone backup distance-measuring ele-ment. The mho unit may be tested using the testcircuit shown in Fig, 15. The correct directionalaction on a mho unit may be adjusted by varyingthe position of the iron core within the inductioncup. Unlike the core of the ohm unit, the mho unitcore is perfectly round. However, it is mounted inthe mho unit in such a way that it may be movedfrom side to side within the structure. Adjustmentis made by first loosening the lamination clampingscrew at the back of the unit one full turn and thenby turning the core-bracket adjusting screw whichis located at lower rear side of the mho unit. Ac-cess to the adjusting screw head is from the right-hand s i d e of the unit. Make sure the laminationclamping screw is tightened one full turn beforemeasuring electrically the correctness of the ad-justment. The directional a c t i o n is checked at ahigh current and low voltage both at the relay angleof maximum reach and at 180 degrees from therelay angle of maximum reach. This simulates afault just off the bus on the protected line and afault on the bus. With the test circuit arranged asshown in Fig. 15, apply 1 per cent rated volts (1.15volts) and 60 amperes at 60 degrees lag. This testis made with the E2 taps in 100 per cent. At the60 degree lag position the mho unit contacts shouldclose. With the phase angle shifted to 240 degreeslag, the contacts should remain open when currentand voltage are applied. By turning the adjustingscrew clockwise a torque will be introduced in thecontact closing direction.

The suggested way of determining the mho unitangle of maximum r e a c h is b y approaching thecharacteristic from either side until the points arefound where the contacts just close. Half way be-tween the two angles where the contacts just closeis the mho-unit angle-of -maximum reach. Thistest may be made by the test circuit shown in Fig.15 with the voltageadjusted to 55 volts and the cur -rent at 15 to 20 amperes. The phase angle of themho unit is adjusted by two resistors designatedR23 one of which is tapped and the other variable.These may be located from Figs. 7 and 8. For the60 degree position of the mho unit characteristicthe tapped resistor is not used. If the relay appli-cation is such that it is desirable to have the mhocharacteristic at a more lagging angle, it may insome instances be necessary to insert a portion ofthe tapped resistor. This is done by moving thebolted connection on R23 fixed from the lower tothe middle tap. The relay is adjusted at the factoryto have a 60 degree lagging characteristic. Note

PHASE ANGLEMETER

THREE PHASESOURCE

Fig. 15 Laboratory Test Connections

The pickup should not vary more than 3 per centabove or below the set value over the calibratingrange. If it is higher at h i g h currents, the coremay be shifted slightly in a counterclockwise di-rection but the pickup and phase-angle adjustmentsshould be repeated if it is necessary to shift thecore. If the pickup is lower than 3 per cent of theset v a l u e a t l o w v a l u e s of current, the controlspring tension may be slightly decreased althoughnot to such an extent that the contacts close whenthe relay is de-energized.

2. Overreach

Overreach is the tendency of a distance relayto operate on an impedance greater than that forwhich it has been set during the transient stage ofthe fault. Reference to Fig. 6 indicates t h a t thepercent overreach varies with fault current mag-nitude and angle of the line impedance. To checkthe overreach of the ohm u n i t, t h e t e s t circuitshown in Fig. 12 may be u s e d except the sourceimpedance which has heretofore been a load boxshould now be a r e a c t o r. This is necessary inorder to obtain the full offset which can be expectedduring f i e l d conditions. The test-box autotrans-former tap setting are determined as before. Thereactor which replaces the load box as the sourceimpedance may be a standard t e s t reactor, Cat.6054975. The a n g l e of the line impedance, Rj XL should be set by v a r y i n g R L , since XL ISfixed on the basis of the relay setting and relayminimum ohmic rating. The angle should be set bymeans of a phase-angle meter and should of coursebe the same as the line angle since that is the con-dition under which the relay will operate. Accord-ingly, the fault current level now adjusted by Xgshould be in the s a m e order of magnitude as themaximum fault current expected. Since maximumoverreach occurs w h e n the inception of the faultis at a point in the voltage cyclewhere the transientoffset is greatest, the fault switch should be closedten successive times in determining the test box

His20 <




that the ohmic reach of the mho unit is not inde-pendent of the phase-angle adjustment. Where thereach is adjusted for 2.5 ohms phase-to-neutral at60 degrees lag, it will be approximately 3.2 ohmsphase-to-neutral at 75 degrees lag.

The reach of the mho unit is adjusted by R13which may be located in Fig. 8. With the test cir -cuit as shown in Fig. 15, set the phase angle of 60degrees lag and the voltage at 55 volts. The mho-unit contacts should close when the current is in-creased to 11.0 amperes. After the pickup of themho unit has been set, it is desirable to again checkits directional action and angle of maximum reach.

with the fault switch open. The line impedance, RL+ j Xj_, should be slightly greater than that of theprotected section and should be selected such thatthe impedance presented to the relay by virtue ofthe test-box autotransformer tap setting w i l l bedone so, with the tap settings as high as possible.This will make the potential on the relay beforethe fault switch is closed nearly 115 volts, which isof course a normal operating condition. The sourceimpedance s h o u l d be made up of reactance as inthe case of the ohm-unit overreach test and againshould be of such magnitude that maximum antici-pated-fault current will flow when the fault switchis closed. The ohm and mho unit settings are thosewhich will be used in s e r v i c e. For successiveclosures of the fault switch with the d

_c circuits

energized, the seal-in unit should not set up if co-ordination is satisfactory.d. Clutch Adjustment - Ohm and Mho Units

To improve contact action, ohm and mho unitsare provided with friction clutches which slip whenthe contacts areclosed with high torqueand preventcontact bounce. The tension on the clutch spring,which is concentric with the shaft, may be variedby loosening the set screw in the clutch spring col-lar which may then be rotated to increase or de-crease the clutch spring tension. Clutch settingsfor ohm units are given in both grams and amperesat zero restraint in Table V. The mho-unit clutchs h o u l d slip w i t h approximately 50 grams forcea p p l i e d. This corresponds to approximately 30amperes at the angle of maximum reach and tapsettings at zero per cent.

c. Ohm and Mho Unit Contact Co-ordination

In the section headed OPERATING CHARAC-TERISTICS, theMS" relay was described as the co-ordinating element which prevents tripping if themho and ohm unit contacts were closed at the sametime a f t e r an external fault is cleared. For thereverse situation i.e., where the ohm unit is closedon load and a fault occurs just beyond the protectedsection, no auxiliary element is required to obtainsatisfactory co-ordination. The contact co-ordina-tion for this condition may be checked by arrangingthe test circuit as shown in Fig. 12 except that aresistor and capacitor series connected should beplaced across the fault s w i t c h. T h e capacitorshould be of such magnitude that it cancels the in-ductive reactance of the line impedance. The re-sistor should allow approximately 4.5 amps to flow

RENEWAL PARTSIt is recommended that sufficient quantities of

renewal parts be c a r r i e d in stock to enable theprompt replacement of any that are worn, broken,or damaged.

When ordering r e n e w a l parts, address the

nearest Sales Office of the General Electric Com-pany, specifying thequantity required and describingthe parts by catalogue numbers as shown in RenewalParts Bulletin No. GEF-2508.

APPENDIXCALCULATION OF RELAY

SETTINGSKV = line-to-line voltage in kilovoltsX% ~ phase“to-neutral line reactance in per -

centKVA = KVA base upon which X% is given.2. Calculate the secondary phase-to-neutral

reactance

Following is a discussion of and examples ofcalculations of r e l a y settings. Factors affectingrelay settings such as infeed and potential trans-former connections will be considered.

Proceed as follows in determining relay set-tings: CT ratioxsec Xpri PT ratio

1. C a l c u l a t e the primary phase-to-neutralreactance in ohms of the line to be protected fromthe formula 3. The instantaneous zone (zone 1) is set by

the two tap leads on the tap block marked No.1 andusually c o v e r s 80 per cent to 90 per cent of theline section. If it is assumed that 90 per cent ofthe line section is to be covered, the No. 1 tap set-ting is given by:

10KV2 X%xpri “ KVAwhere Xprj = primary phase-to -neutral reactance

in ohms.2

21<




R O U G H L I M I T S F O R Z O N E B2Z O N E 1 - I N S T A N T A N E O U SZ O N E 2 - I N T E R M E O I A T EZ O N E 3 - F I N A L B A C K-U P Z O N E

I Ik a*1i <0I a

CDI CO

I Z O N E CDZ O N E A 3 IS T N BS T N AoiZ O N E B 2Z O N E A2 14-tfZ O N E Z O N E C x ' |Z O N E B^ D-D! FO--DD-D I I

Fig. 16 Zone Setting Diagram, 2nd And 3rd Zone Reach

(input tap) X min better understand t h e s e drops, we must picturecurrent IA at station A and current IQ, infeed atstation B. Now if we imagine a fault somewherebetween stations B and C we can set up an equationto show what the relay sees at station A.

IA - Current at station A.ZA - Impedance of line A.IB = Current infeed at station B.

No. 1 Tap = .90 X 1where No. 1 tap = Number 1 tap setting in percent

Input tap = Input tap setting in percent^min = Minimum p h a s e-to-neutral re-

actance reach of the r e l a y thevalue of which is g i v e n on therelay nameplate.

= Phase“to“neutral secondary re*

actance of the first line section.XlZ'Q = Impedance from station B to fault .

IAz A + ( JA + !B) zB4. The tap settings for the second zone (No. 2)and the third zone (E 2) depend upon system con*

figuration and the amount of infeed fault currentsupplied from the bus at the end of first line sec*

tion.

Relay sees = lAZ A + Z B + l B 2 B

l AReferring to Fig. 16, the second z o n e of the

relay at A must reach beyond B and yet must notreach far enough to overlap the second zone of therelay at B. Similarly, the third zone of the relay*

at A should not overlap the third zone of the relayat B and yet should not overlap the third zone ofthe relay at B and yet should reach beyond station

As we can see, the relay will see the true im-pedance ZA and Z B but will be falsely misled byIB ZR. This is the section t h a t has to be takenIA

into consideration when settings are made . It hasbeen shown that the impedance of the section be -yond B as it appears to the back-up elements at Ais increased by the ratio of fault current in thesecond section to the fault c u r r e n t in the firstsection.

C.

The second zone should reach to cover the last10 percent of z o n e one to provide back-up pro-tection. Thus, with the first zone of the followingsection set to cover 90 percent of its section,ideally this zone 2 setting could be fixed at 80 per -cent of the section. This can be regarded as theupper limit for zone 2. The lower limit for zone 2is around 20 percent of the second section whichassumes that the third zone setting for the pre-ceding station can be set to fall within this 20 per -cent.

However, the primary functions of zone 2 is toobtain end-zone protection for the remainder of theline section protected by zone 1. Unless this is atapped line with infeed from the tap, there shouldbe no necessity for considering infeed for end-zoneprotection.

As a rough guide in determining back-up set -tings, set zone 2 to cover 50 per cent of the adja-cent line s e c t i o n under conditions of maximuminfeed. Set zone 3 ten per cent beyond the end ofthe adjacent section.

The phas,e“to~neutral secondary reactance ofzone 2 is calculated in the same m a n n e r as forzone 1. Assuming reach is to be 50 per cent intothe second section the No. 2 tap setting can be cal-culated from

The major factor which determines the accu-racy with which the zone 2 and zone 3 can be set isthe determination of infeed current from the busesat the ends of the protected-line sections. For ex-ample, in Fig . 16 current infeed at stations B andC cause voltage drops in the line between theirrespective buses and the fault. These drops causethe elements at A to underreach for faults in thebackup zones unless the infeed currents are takeninto consideration when the settings are made . To

(input tap) Xmin= Xj + 0.50 K2 X2No. 2 tap

*-9s<22




Y 10 KV2 X%KVA

where No. 2 tap = Number 2 tap setting in per centInput Tap = Input tap setting per cent^min = Minimum p ha s e-to“neutral re-

actance reach of the relay- Phase-to“neutral secondary re“

actance of the first line section= ratio of fault current in second

section to the f a u l t current inthe first section for a fault 50per cent into the second section- Phase“to“neutral secondary re-actance of thesecond line section

10 (154 j2 X 6 = 28.5 ohms 0“N50,000Xl= 28.5 x 60v CT ratio

pri PT ratio

It will be assumed that no current is fed into thesecond s e c t i o n at the intervening station, (i. e.*2 = K 3 =1)‘

K2 = 1.3 ohms.X 1340sec

*2

The third zone is protected by the mho unitw h i c h as seen f r o m Fig, 1 is responsive to animpedance at an a n g l e. This is unlike the ohmunit which is responsive to reactance alone. Sincethe reach of the mho unit varies with the angle ofthe f a u l t impedance the determination of the E2tap setting which controls the mho unit reach musttake into account the difference between the angleof the fault impedance and the angle of maximumreach of the mho unit. The a n g l e of maximumreach of the mho unit, as set at the factory, is 60degrees lag and the minimum p h a s e-t o neutralohmic reach is 2.5 ohms. Impedance rather thanreactance alone are used in calculating the reachrequired for the third zone. The impedance of thesections to be protected is determined in a mannersimilar to the determination for zones 1 and 2 ex-cept that impedance rather than reactance quantitiesare used.

Use a relay with 1.0 ohm minimum phase-to-neutral reach and set zone 1 to cover 90 per centof the protected section,

100 x 1.0No. 1 tap =per cent tap should be used.

= 85.5 per cent so that the 860.9 x 1.3

The second or intermediate time zone is usu “

ally set to cover about one“half of the next section.The reactance of the second section is 10 per centor 10/6 x 1.3 = 2.17 ohms secondary.

100 x 1.01.3 + (0.5) 2.17 ~ 2.38

100 - 42.0%No. 2 Tap =

Zone 2 taps should therefore be set on 42 per cent,covering the protected section and approximately50 per cent of the next adjacent section. The timesetting s h o u l d be the tripping time of the nextbreaker plus say 10 cycles margin.

Assuming the reach of the third-zone elementis to be 10 per cent beyond the end of the secondsection, the E2 tap setting may be calculated from

(Input Tap) 2,5 cos (0 ~6Q)U (Z1 V K3 Z2 )E2 tap =

To set the third zone of protection, the linecharacteristic angle m u s t be known. These aredetermined from the impedances of thetwo sectionsto be protected.

where - E tap setting in per cent= Input tap setting in per cent= Angle of protected l i n e imped-

ance= Phase-to-neutral secondary im-

pedance of the first line section= Phase-to-neutral secondary im-

pedance= Ratio of fault current in second

line section to fault current firstline section for a fault of the endof the second line section.

E tapInput tapP

1st section 1.61 + j 6% = 6.22% at 75 degrees lag2nd section 2.68 - j 10% -10.35% at 75 degrees lagZ1

Z2 The total impedance for the two sections is 16.6 at75 degrees lag. The primary impedance in ohms*3

(10) 1542 (16.6) - 78.8 ohms at 75°Z - =pri 50,000

Example 1 The secondary impedance in ohms is

As an example let us consider a 154 KV line with1.61 + j 6 per cent impedance on a 50,000 KVA baseand an adjoining section of 2.68 + j 10 per cent im-pedance with 300/5 CT' s.

60= 78.8 = 3.53 ohms at 75 degreeszsec “ 1340

The third zone is set by the E2 tap settings andis 10 per cent greater than the first and secondline sections.

E2 tap set =

The E2 taps should therefore be set on 62 per cent.

300_ = 6Q/1oCT ratio =100 (2.5) cos (75-60) = 62.1%1.1 (3.53)

PT ratio = 154 000 = 1340/1110

23




RELAY SETTINGS WHENPOTENTIAL IS TAKEN FROM LOWSIDE OF POWER TRANSFORMER

Transformer Reactance:10 (154)2 5%

40,000Overall PT ratio;

- 29.6 ohms

When a l i n e is terminated in a transformerand nosource of potential for line relaying is avail-able on the line side, it is necessary to use lowside potential and take into a c c o u n t the powertransformer ratio, the phase shift which occurs ina delta“wye power transformer and the impedanceof the transformer itself. The 30 degree phaseshift in the delta-wye power transformer may becompensated for by s e l e c t i n g phase-to-neutralrather than phase-to-phase voltage from the sec-ondary of the wye-wye connected potential trans-former or by using an auxiliary wye-delta potentialtransformer. The latter method is preferred sincethe phase-to-neutral voltage of the former methodis affected by ground faults on the low voltage sys-tem. When the auxiliary potential transformer isrequired, Cat. YT1557M may be used. Using lowside potential means the relay will see the trans-former reactance as a part of the protected sec-tion. Since the relay first zone is to be set to cover80-90 per cent of the protected section which in-cludes the transformer, it will cover a relativelysmall section of the line if the transformer react-ance is high compared to the l i n e reactance. Ifinstantaneous tripping is required over a greaterportion of the line section than can be covered bythe Type GCX relay, some form of pilot relayingnot using the distance principle should be investi-gated. When the potential transformer ratio hasbeen properly selected from the application stand-point, the overall PT ratio may be considered as:

154.000TT5 =

CT Ratio:

= 30/1Secondary Reactances:

/130 '\\jM6J ~Xj = 57.0 1.27 ohms

f 30 \X2 = 47.5 = 1.06 ohms

X- (w) = 0.66 ohmsTSecondary Reactances and Impedances:Assume transformer has 85 degree phase angle.Rl , Xt _i tan J5 tan 70

Zi 0.46 + j 1.27 = 1.35 ohms at 70°

1.27 = 0.46,

1.06X 2R2 ~ tan p ~ tan 70 ~ °-38’Z2 = 0.38 + j 1.06 = 1.13 ohms at 70°

XTrans _ 0-^tan 85*2* Trans= + j 0.66 = 0.66 ohms at 85°

Zone 1 Setting Assuming 90 Per cent Coverage andOne Ohm Relay

High side line-to-line voltagerelay voltage (115)

Example 2

Consider a 154 KV l i n e w i t h two adjoiningsections of 12 per cent and 10 per cent reactancerespectively on a 50,000 KVA base. Line anglesare 70 degrees. A power transformer at the endfor which relay settings are being determined is13,8 KV delta connected oil the low side and 154KV wye connected on the high side. CT's on theline side are connected in wye and have a ratio of150/5. Three PT' s connected wye-wye on low sideof the power transformer have PT ratios of 120/1.An auxiliary potential transformer connected fora rating of 115 volts wye primary to115 volts deltasecondary. The power transformer has 5 per centreactance on a 40,000 KVA base. Assume that fora fault in the middle of the second section K2 = 1.7and for a fault at the end of the adjacent sectionthat K3 = 1.5.

The relay settings are determined as follows:Line Reactances:

1»

= .058,RTrans “

tan jS

100 x 1No.1 tap = = 57%(1.27 + .66) .90Zone 2 Setting Assuming 50 Per cent Coverage ofAdjacent Section

100 X 1No.2 tap = = 35%(1.27 + .66) + 0.5 x 1.7 x 1.06Zone 3 Setting

Zl + ^Trans = 0.518 + j 1.93

K3 Z2 = 1.5 (0.38 + j 1.06) =0.57 + i 1.591.088 + j 3.52

„2 _ 1 0 0 x 2,5 cos (73-60)E tap " 1.1 x 3.69

10 (154)2 1250,000

10 (154)2 1050,060

= 3 ,69 ohms at 73°= 57.0 ohms1st Section

2nd Section - 47.5 ohms - 60%

5s24<




There are occasions when the backup cannotbe satisfactorily o b t a i n e d with the t h r e e zonemethod as outlined above. This can occur when alarge generating station feeds power to an inter*

mediate point in a line.In Fig. 17 for a fault as shown, if breaker 2

fails to operate, normally breaker 1 would operateon backup. If , however, the generators at A supplya large amount of current to the fault there maybe many times as much current in line 2 as in line1. To provide backup, the relay at B would requirea third z o n e setting correspondingly large com-pared with the first z o n e setting. Such settingswill make the relay susceptible to power swings.

A solution is to use an auxiliary timing unitin conjunction with the tripping circuits for the linebreakers at the station A. If these breakers failto open in a definite time after their trip coils havebeen energized, the timing unit operates an aux-iliary relay to trip all the breakers connected tothe bus.

STATION A

GOSTATION B

CM O—Q2

<o *-o-p04 F A U L TCDCO ©Or-. cnu-

Fig. 17 Zone Se t t ing, Ef fec t ive Of In f ie ld

minimum reach of the mho unit is 2.5 ohms. Itwill be necessary to g r a d e the time settings toobtain selectivity.

Where a protected l i n e terminates in a busfrom which a number of lines are radiating it iscommon to set the backup s t e p s for the longestline. This will result in overreaching on backupfor faults in the shorter lines. Selectivity maybeobtained by grading the time settings.In short line sections it maybe difficult to pre-

vent the third zones from overlapping, since the

i 25




16

14

12

00

CO<CCQ 0010

-1=O oroCOI*<0OCOCO

UJ

8o>-oz

UJ2

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cQ;UJ 40-o

901

2501 & 701

01 A 251

00 10 20 30 40 50 60 70 80 90 100

FAULT CURRENT AMPS

Fig. 18 Average Operating Time Curves ( With Bus Side PT' s) For Type GCX17 0.25 Ohm Relay

S26




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o

h~< gor vUJQ_O

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010 20 30 40 50 60

FAULT CURRENT AMPS70 80 90 10C0

Average Operating Time Curves ( Zero Voltage Before Fault ) For Type GCXI 7 0- 25 Ohm RelayFig. 19

*-a

27




o>•<CM

3

oCM

C7I

100 20 30 40 u.5 0 60 807 0 9 0 100F A U L T C U R R E N T A M P S .

Fig. 20 Average Operating Time Curves ( With Bus Side PT’ s) For OCX 17 0.5 Ohm Relay

16

1 42in a>•<.CM

3iO 12<LCO

2CM10o

CD

U.UJ8

oz 6h~<tCt

4UJQ-O

2

030 40 50 60

F A U L T C H P P F W T A M P*80 90 10020 70100

Fig. 21 Average Operating Time Curves ( Zero Voltage Before Fault ) For GCXI 7 0.5 Ohm Relay

s28 <




16

14

12

zj-(£>05

- 10CMO

<cCDCsl I

CM 4— -2cnO<X>— 8LU5

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6 5 VOLT<ccnLLJ ( RESISTIVE)Q-O

4

2

0200 10 30 40 50 60

FAULT CURRENT AMPS70 80 90 100

Fig. 22 Average Operating Time Curves ( Zero Voltage Before Fault ) For GCX17 1.0 Ohm Relay

Hj

229




c c1 7 B O T H N E O N L MPS S H O U L D

G L O W W H E N E 2 T A P L E A D S1 8 A R E C O N N E C T E D I N T O T H E T A P

B L O C K .f A P O L A R I T Y T E S T. B O T H U N I T S O P E N .1 9 W H E N R E L A Y E N G E R G I Z E D .

S E T T I N G S O F 1 0 0 %.

I r-

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TAPB O T H U N I T SC L O S E T H E I R C O N T A C T S W H E N2 0 O N E N O . t A N D O N E E 2 T A P

L E A D S A R E R E M O V E D .R E S I S T O R5l E

76 . 8 -T L81 0

1 1 5 VR A T E D

F R E Q U E N C Y

A . P O L A R I T Y T E S T

Fig. 23 Average Operating Time Curves ( With Bus Side PT' s ) For GCXI 7 1.0 Ohm Relay

7

6

£ 501<toVI

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70to 400 20 30 50 60

FAULT CURRENT WPS.Fig. 2Y Polarity Test Connections For GCXI 7 Relay

30




STATIONRELAYS & ,BREAKER BUS1© © © Y X

11 13 19 K W OR .KVARFLOW "OUT"% (a> 0

o6 +6 i

6±TEST PLUG ( TOP ) SOURCEE

INSERT TES1PLUG IN GCX

D RELAY

•oA C RESISTOR< —r115 V

B ZT-f++ o' 6PHASE

ANGLEMETER

E Io<Dcn PHASE ANGLE METER

READS ZERO DEGREESFOR ABOVE CONNECTIONS

<lf- ©© ©rO

l 5 7 9LO 2 4 6© © ©

10OJ

NOTE: ADD JUMPER C TO D WHEN PHASE ANGLEMETER IS CONNECTED TO A & B OR VICE VERSATO AVOID OPEN CIRCUIT ING CT ’S

cfi

LL.

TEST PLUG (BOTTOM) METER READING WITH PROPEREXTERNAL CONNECTIONSPHASE SEQUENCE 1-2-3

POWER FACTORANGLE ( DEG.. LEAD )

270- 315-180- 225-135-0 -45 45-9 C 9 0-13 S 315225 270180 3 6 0KW 0UT>K V A R

K W I N> K V A R >K V A R O U TO U T K W I N

150- 195-K V A R 1M >KW I N>K W I N K V A R

K V A R > K V A R > K W O U T >K V A R

K W & K V A R D I R E C T I O N SWITH RESPECT TO THE BUS IN OUT

KW OUT240-

JJl OUTKW OUTLit60- 105- 285-330- 15-tr> X TO A Y TO B 150 33015 60 105 195 240 285o

210-120- 255- 300-30- 75- 165- 345-X TO C Y TO Dc_> 120 210 255 300165 345 3075LU5= PHASE SEQUENCE 1-3-2o

300-o 210- 255- 345-30- 75- 120- 165-X TO A Y TO B 255120 165 300 345210 7575>-c 240- 285-60- 150- 195-330- 15- 105-X TO C Y TO DLLJ 33028560 24015 105 150 195o c

THE ABOVE RANGES OF PHASE ANGLE METER READINGS ARE THE ANGLES BYWHICH THE CURRENT LEADS THE VOLTAGE WITH THE DESCRIBED CONDIT IONSOF POWER ( KW ) AND REACTIVE POWER ( KVAR ) FLOW WITH THE STATION BUSCONSIDERED AS THE REFERENCE IN ALL CASES.CAUTION: MAKE CORRECTIONS FOR METER ERRORS ON LOW CURRENTS, INHERENTIN SOME PHASE-ANGLE METERS.

Fig. 25 Connections And Reading For Phase Angle Test

>-5s< 31



GENERAL ELECTRIC SALES OFFICES GEZ- 2 SOOKREADY TO ASSIST YOU . . . When You Have Electrical Problem! . . . Need Further Information . . . Require Ordering Instructions

tOUISIANA OHIOSALES OFFICE CODE KEY* Industrial Equipment (including Agent ond

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1 720 Murray $t,633 Oak Villa Blvd.

422 Seventh St.837 Gravitr St.206 Beck Bldg.

500 Natchitoches St.

t*

t I* t

MAINEt Augusta

Bangor 04402152 State St.

... 77 Central St.ALABAMABirmingham 35205Mobile 36602

2151 Highland Ave.704 Government St.

* t* OKLAHOMAMARYLAND

* f t Boltimore 21201...Hagerstown

MASSACHUSETTS•t \ § Boston 02117Springfield 01103Worcester 01605

Oklahoma City 73102....119 N. Robinson Ave.Tulsa 74M4 .Columbia Bldg., 2651 E. 21st St.

tARIZONA* t t Phoenix 85012 .* f Tucson 85716ARKANSAS

111 Park Ave.49 East Franklin St. t3550 N. Central Ave.

....tSI S. Tucson Blvd. tOREGON• t Eugene 97401...* } Medford

1 t Portland 97210

1170 Pearl St.. .. . 107 E. Main St.2929 N.W. 29th Ave.

31 St. James Ave.... .. 1 2 0 Maple St.

288 Grove St.North Little Rock 72204 1900 E. Washington

P. O. Box 1033* *Pine Buff\CALIFORNIA ENNSYLVANIA

Allentown 16102Erie 16501Johnstown

§ Philadelphia 19102Pittsburgh 15222 ....

MICHIGAN* f \ Detroit 48207 ...

Flint 48503* | Grand Rapids 6

Jackson 49201KalamazooLansing 48933Saginaw 46607

Fresno 93728Los Angeles 90054

t § Los Angeles 90005Oakland 94612Redwood City 94063Sacramento 95816.San Bernardino

1532 N. West Ave.212 N. Vignes St.

3325 Wilshire Blvd.409 Thirteenth St.55 Veterans Blvd.

2407 ”J‘* S».

t ... 732 North I6fh St.1001 State St.

041 Oak St.3 Penn Center Plaza

700 Antoinette St.316‘A W. Court St.

... 2821 Madison Ave., S.E.120 W. Michigan Ave.

927 S. Burdick St.501 Bank of Lansing Bldg.

.1006 Second National Bank Bldg.

* ttIt* 1 t*

The Oliver Bldg., Mellon Sq.§ Pittsburgh 15228 733 Washington Rd.» York 17403 56 N. Harrison St.

* t* tt*337 N. Riverside Ave., Rialto, Cal.

2560 First Ave.235 Montgomery St.

2155 So. First St.• t $ So" Diego 92103* i| § San Francisco 94106

San Jose 95112OUTH CAROLINAt Columbia 29201MINNESOTA»

Duluth 55802Fergus FallsMinneapolis 55402.

1010 Fidelity Bldg.Norby Bldg., Room 4

12 S. Sixth St.301 Palmette Stote Life Bldq.

Greenville 29602 . 106 W. Washington St.' tCOLORADO•M § Denver 80206CONNECTICUT* t \

t201 University Blvd. * t *MISSISSIPPIt Gulfport 39502

* t Jackson 39201

TENNESSEE* f $ § Chattanooga 37402 ...

Kingsport 37662...Knoxville 37921Memphis 38104Nashville 37203

§ Ook Ridge

B32 Georgia Ave.322 Commerce St.

1301 Hannah Ave., N.W.1420 Untan Ave.

1717 W. End Bldg.253 Main St.. East

764 Asylum Ave.129 Church Sf.Hartford 06105

New Hoven 06510 P.O. Box 33203 W. Capitol St.• t tDISTRICT OF COLUMBIA

* f § Washington 20005FLORIDA

tMISSOURI t777—14th St., N.W.Joplin 64802Kansas City 64105.St. Louis 63101

.... 212«/, W. Fifth 5t.106 W. Fourteenth $t.

816 Olive St.* i* 15 Cocoa Beach 32931 (Cape Canaveral Office)

1325 N. Atlantic Ave.250 Bird Road

25 S.E. Second Ave.1901 Hill St.

First Bank Bldg.2106 South Lois Ave.

TEXAS* t Abilene 79601 442 Cedar St.Amarillo 79101 303 Polk St.Beaumont 77704 1305 Colder Ave.Corpus Christi 78401 ... 205 N. ChaparralDallas 75222 8101 Stemmons FreewayEl Paso 79901 215 N. Stanton St.Fort Worth 76102 408 W. Seventh St.

$ § Houston 77027 4219 Richmond Ave.Lubbock 79404 . 3302 Avenue “A"Midland 228 Wilkerson-Foster Bldg.San Antonio 7B2Q4 419 S. Main Ave.

* t Coral Gobies 33146 ....Miami 33131.

Jacksonville 32202 . .,Pensacola 32503 .

* t * Tampa 33609GEORGIA* t I Atlanta 30309

MaconSavannah 31405

MONTANAt Billings 59101Butte 59701

* t .... 303 N. Broadway103 N. Wyoming St.* t * tt INEBRASKA•t Omaha 66102 409 $. Seventeenth St.

NEVADAI860 Peachtree Rd., N.W.682 Cherry St.

5002 Paulsen St.a Las Vegas

NEW HAMPSHIREManchester 03104

1711 $. Bfh St.t* ttIDAHO 1662 Elm St.t UTAH

* t § Salt Lake City 84H0 200 S. Main St.VERMONT

* t Boise 63706 1524 Idaho SI.NEW JERSEY* t t East Orange 07017.

ILLINOIS* f t |Chicago 60680 .

Peoria 61611Rockford 61106Springfield 62701

26 Washington St.840 S. Canal St.. 2000 N.E. Perry Ave.4223 East State $t.

607 E. Adams St.Rutlandt 38'/2 Center St.* t NEW MEXICO

VIRGINIAAlbuquerque 87108.* \ 120 Madeira Dr., N.E.t § Newport News 23601NEW YORK* j $ Albany 12201 ...

t Binghamton 13902.* f I Buffalo 14202•t § New York 10022•1 t Rochester 14604

Syracuse 13201Utica I

t Waverly

P.O. Box 1036, 311 Main St,5001 W. Broad $t.

920 S. Jefferson St.INDIANA

6 Colvin Ave.19 Chenango St.

625 Delaware Ave.570 Lexington Ave.

East Ave.3532 James St.1001 Broad St... P.O. Box 308

• f Richmond 23230Roanoke 24005

* t Evansville 47714Fort Wayne 46807Indianapolis 42607South Bend 46601

.. 2709 Washington Ave.3606 S. Calhoun St.

3750 N. Meridian St.430 N. Michigan St.

* t* 1* t WASHINGTON

Pasco* t * § Seattle 98104....* f Spokane 99220...WEST VIRGINIA

BluefieldCharleston 25328...306 MacCorkle Ave.. S.E.

* t Fairmont 26555Wheeling

* t 824 W. Lewis St.710 Second Ave.

East 1805 Trent Ave.89IOWA

* t Cedar Rapids 52401* ( } Davenport 52805

* t210 Second St., S.E.1039 State St., Bettendorf, Iowa

Des Moines 50310 .3839 Merle Hay Rd.Sioux City 51101

*

704 Blond St.NORTH CAROLINA* f f Charlotte 28202

GreensboroRaleigh 27602

NORTH DAKOTABismarck 58501Fargo 58101

* tt 520 Fierce St. 129 W. Trade St.

. 801 Summit Ave,16 W. Martip St.

310 Jacobs Bldg.40 Fourteenth St.KANSAS

* tWichita 67211* t 820 E. Indianapolis Ave. WISCONSIN* t § Appleton

Madison 53703• t * Milwaukee 53233HAWAII: American Factors, Ltd., P.O. Box 3230, Honolulu 9680!

KENTUCKY* f Lexington 40508* t \ Louisville 40218

510 W. College Ave..340 W. Washington Ave.

940 W. St. Paul Ave.628 E. Main St.

2300 Meadow Dr.CANADA: Canadian General Electric Company, Ltd., Toronto

t 418 Rosser Ave.802 S. Park Drive

t*

* GENERAL ELECTRIC SERVICE SHOPSWHEN YOU NEED SERVICE . . . These G-E service shops will repoir, recondi-tion, ond rebuild your electric apparatus. The facilities are available day andnight, seven days a week, for work in the shops or on your premises. Latestfactory methods and genuine G-E renewal parts are used to maintain peakALABAMA

performance of your equipment. For full information about these services,contact your nearest service shop or sales office.•Denotes Aircraft Service Shops

P.O. Box 4198, 2128 Eakin Rd.405 Deorborn Ave.

272 E. Indianola Ave.

KENTUCKYLouisville 40209 3900 Crittenden Drive Toledo 43605

Youngstown 44507Birmingham 35211, P.O. Box 3687

7 — 18th $ '.» S.W LOUISIANAARIZONA OREGONNew Orleans 70117 2815 N. Robertson St.(Phoenix) Glendale 4911 West Colter S Portland 97210 2727 N.W. 29th Ave.MARYLANDCALIFORNIAPENNSYLVANIA

Allentown 18103 668 E. Highland St.Johnstown 841 Ook St.Philadelphia 19124 1040 E. Erie Ave.(Pittsburgh) Homestead 15230.... .Box 308. RD I, Buttermilk Hollow Rd.York 17403 54 N. Harrison St.

Baltimore 21230. 920 E. Fort Ave.Los Angeles 90001*(Los Angeles) Ontario

. 6900 Stanford AveMASSACHUSETTS

(Boston) Medford 02155Ontario International Airpor. 3400 Wood S99 North 17th S1098 Harrison S

Oakland 94608Sacramento 95814San Francisco 94103

3960 Mystic Valley ParkwayMICHIGAN

Detroit 48202 5950 Third St.COLORADOTEXASMINNESOTADenver 80205

^CONNECTICUT3353 Larimer S

Corpus ChristiDallas 75235Houston 77020..Midland

MS Waco St.3202 Manor Way

...5534 Harvey Wilson Drive704 S. Johnston St.

Minneapolis 55430 2025—49th Ave., N.( Southington) Plantsville 370 Atwater S MISSOURIFLORIDA Kansas City 64120 3525 Gardner Ave.

St. Louis 63110Jacksonville 32203 1115 East Road UTAHP.O. Box 2932, 2020 W. Beaver Si 1062 E. 28th S

P.O. Bo* 1245

NEW YORK Salt Lake City 84104 301 $. 7th West St.(Miami) HialeahTampa 33601 Albany 12205

Buffalo 14211•(New York) Linden, N. J... 1097 Central Ave.

318 Urban St. VIRGINIARichmond 23224Roanoke ...

P.O. Box 1327, M 5 Albermorle Ave., S.E.1403 Ingram Ave.GEORGIA

A.... -(Atlanta) Chomblee 1611 W. Elisabeth Ave.5035 Peachtree Industrial Blvd (New York) North Bergen, N. JILLINOIS WASHINGTONSeattle 98134•Seattle 98108....Spokane 99206

WEST VIRGINIACharleston 28..

6001 Tonnelle Ave.Schenectady ( Instrumentation Service} 12305

I River RoadChicago 60632

Ft. Wayne 46803Indianapolis 22

(Davenport) Bettendorf 1025 State S

4360 W. 47th St 3422 First A.«., S.220 Dawson St.

E. 4323 Mission St.INDIANA

1731 Edsail Ave1740 W. Vermont 5

NORTH CAROLINACharlotte 28208 2328 Thrift RoadIOWA 306 MacCorkle Ave.OHIO

Cincinnati 45202. 444 W. Third St.•Cincinnati 45232 260 W. Mitchell Are.Cleveland 44125Columbus 43223

WISCONSINKANSAS Appleton 54910 Midway Industrial AreaP-O. Box 83, County Trunk P- J 940 W. St. Paul Ave.

•(Strothur) Arkansas City 4477 East 49th St.G.E. Co., P.O. Box 797 Milwaukee 38162 - 6 4 GENERAL ELECTRIC COMPANY, PHILADELPHIA , PA.

HAND B O O K REFERENCE 7 2 t 6

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L® CXpri X PT Ratio Fig. 3 Schematic Connections For Mho And Ohm Units or as follows if the...

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Transcript of L® CXpri X PT Ratio Fig. 3 Schematic Connections For Mho And Ohm Units or as follows if the...