Westinghouse I. L. 41-177

INSTALLATION • OPERATION • MAINTENANCE

INSTRUCTIONS TYPE SCC CURRENT COMPARER RELAY

CAUTION: Before putting relay into service, operate the relay to check the electrical connections. Close output switches last when placing relay in service. Open output switches first when removing relay from service.

A PPL ICATION The type SCC relay supervises tripping of the SDG type of ground distance relay where the latter is current compensated for zero sequency mutual impedance.

The SCC relay prevents undesired tripping for close in faults on the mutually coupled parallel line where the compensating current overpowers the effect of the protected line current.

In addition, logic circuitry is utilized to block undesired tripping for reversals in power flow and allows a coordination time for SDG relay to reset. The logic circuitry permits high speed tripping for valid faults in the trip zone.

CONSTRUCTION The type sec relay consists of two input transformers ( TR-1 and Tr-2) , a plug-in type of circuit board assembly and a tapped resistor for changing the d-e rating.

As shown in Fig. 4, the circuit board consists of a current comparer with output terminal, two transistorized NOT circuits, an AND circuit, a time-delay circuit and a voltage regulator.

Voltage clippers are utilized to protect the secondary a-c input circuitry as well as the d-e input and output circuits.

OPERATION The various components are connected as shown in Fig. 3· If sufficient current is applied to Tr-1 and rated D-C supply voltage connected to the circuit board, transistor TI will turn on. Transistor T2 will turn off and a voltage will appear at the output terminal Jabeled CURRENT COMPARER SUPERVISION OUTPUT ( TERMINAL 10 ) . This output can be used to operate other solid state devices such as the type TD-50 time-delay relay or other logic packages which operate circuit breakers.

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If current is also supplied to transformer TR-2 such that the voltage across resistor R2 is greater than that across Rl, then transistor Tl will not turn � on. The SDG input, terminal (3), is usually tied to negative (terminal 8) through a normally conducting transistor. When the SDG output transistor is non-conducting, a voltage of 10 volts or more appears at terminal 3 and diode Dl7 will be backed biased. Since diode DlF is normally back biased, then transistor T4 will conduct and energize the timer. Approximately .025 seconds later, the normal output voltage appearing between tern1inals l and 8 will drop to almost zero.

By decreasing the current through transformer TR-2, the transistor Tl will now turn on. The timer circuit will then reset and approximately .025 seconds later, the voltage will again appear at terminal 1.

As shown in Fig. 1, protected-line current (3Koio) energizes transformer TR-1; one TR-1 output winding feeds the operating circuit, while the second TR-1 output winding connects into the restraint circuit. Mutual compensation current (3diom) energizes transformer TR-2; the output winding feeds the restraint circuit. The restraint voltage VR is proportional to:

VR � (3Koio-3d Iom)

where d = Zorn, the auxiliary CT ratio. Zol ( l)

Zorn • zero-sequence mutual impedance

Zol = zero-sequence self-impedance of the protected line.

The operate and restraint circuits are so proportioned that operation occurs when:

3Koio > g 3Koio-3d Iom

where g = 0.4 � 0.7 (a design constant).

For illustrative purposes, assume g = 0.4 and d = following examples:

Example l

(2)

0.75 in eq. 2 in the

Assume a far-end fault so that 3Koio : 3 Iom. Restraint voltage is proportional to:

0.4 (3Koio-3d Koio) : 0.4 (l-0.75) 3Koio : 0.1 (3Koio) Operate voltage is proportional to 3Koio, so eq. (2) is satisfied and operation occurs with an output appearing at terminal 10.

Example 2 Assume a fault on the adjacent mutually coupled line with 3 Iom : 4 and 3Koio = -1 (flow in non-trip direction). Restraint voltage is proportional to:

0.4 [ -1-0.75 (4) J = 0.4 ( -l-3) = -1.6

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I.L. 41-177

Example 2 ( continued) The magnitude of the restrain voltage exceeds the operating voltage, so no output appears at terminal 10.

CHA RA CTERISTICS With .42 to .48 amperes applied to the 10 input circuit) only and rated d-e voltage connected to the relay, an output voltage will appear at terminals 8 and 10 with terminal 10 positive.

Fig. 5 shows the response limits of the relay for g • 0.4 + .07 over a large range of current when the two input currents are 180° out of phase. The actual relay characteristics will fall somewhere in shaded area.

BURDEN DATA Burden of Operating Circuit ( terminals 4 and 5) at 5 amperes is 0.75 volt-amperes.

Burden of Restraint Circuit (terminals 6 and 7) at 5 amperes is 0.15 volt-amperes.

Continuous rating is 10 amperes.

One second rating is 280 amperes.

Battery Drain at 48 vdc

125 vdc 250 vdc

rated voltage .o48 amperes .039 amperes .034 amperes

No setting required.

is as follows:

S ETT I NGS

INSTALLATION The relayc: should be mounted on swit®board panels or their equi 1alen-:., in a

location free from misture. Mount the relay vertically by means of the four mounting holes on the flange for semi-flush mounting or by means of the rear mounting stud or studs for projection mounting. Either a mounting stud or the mounting screws may be utilized for grounding the relay. The electrical connections may be made directly to the terminals by means of screws for steel-panel mounting or to the terminal studs furnished with the relay for thick panel mounting. The terminal studs may be easily removed or inserted by locking two nuts on the stud and then turning the proper nut with a wrench.

For detailed FT case information, refer to I.L. 41-076.

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ADJUSTMENTS & MAINTENAN CE

The proper adjustments to insure correct operation of the relay have been made at the factory and should not be disturbed after receipt by the customer.

Acceptance Tests

The following check is recommended to insure the relay is operating properly. All checks can best be performed by connecting the relay per the test circuit shown in Fig._ 5.:_ l. MINIMUM OPERATE CURRENT - with switch S2 and S3 open, close switch Sl and adjust R3 until voltmeter V2 shows sudden indication (approximately 20 volts ). The current through ammeter Io should read between 0.42 and 0.48 amperes. The V� voltmeter pointer should have reset when the current is reduced to 0.40 amperes.

2. CURVE CHECK - close switch 83 and set lorn for 50 amperes. With Io adjusted for 40 amperes, the voltmeter v2 should indicate when switch Sl is closed. With Io adjusted for 30 amperes, there should be no voltmeter indication.

3. TRANSIENT BLOCK CHECK - open switches Sl and S2. Voltmeter Vl should not read. When switch S2 is closed, voltmeter Vl will read almost 30 volts. The time it takes voltage Vl to appear should be 20 to 30 milliseconds and can be checked using a oscilloscope. Likewise when switch S2 is opened, the voltage Vl will be removed in .020 to .030 seconds.

Routine Maintenance

All relays should be checked at least once every year or at such time intervals as may be dictated by experience to be suitable to the particular application.

Calibration

Use the following procedure for calibrating the relay if the adjustments have been disturbed. This procedure should not be used until it is apparent that the relay is not operating properly.

l. MINIMUM OPERATE ADJUSTMENT - if resistor R30 (see Fig. ]_) has been disturbed, it may be recalibrated by referring to test circuit shown in Fig. 2. With switches SI and S3 open, close switch SI and adjust R3 for 0.45 amperes.­

Adjust slidewire res.istor R30 until voltmeter V2 suddenly reads (approximately 20 volts ) o Note that the position of R31 is not critical during this adjustment.

2. CURVE ADJUSTMENT - set lorn for 50 amperes and Io for 35 amperes. Alternately adjust slidewire R31 and close switch Sl until voltmeter V2 indicates. Increasing resistor R31 will decrease amount of Io current for a V2 output. Likewise decreasing resistor R31 will increase amount of Io current required for a V2 output.

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l.L. 41-177 TROUBLE SHOOTING PROCEDURE

Use the following procedure to locate the source of trouble if the type SCC relay is not operating correctly:

1. Check voltages as listed under ELECTRICAL CHECKPOINTS. 2. Inspect all wires and connections. 3· Check resistances as listed on the relay internal schematic .

ELECTRICAL CHECKPOINTS

Connect relay per test circuit of Fig. 2. With rated d-e -voltage applied to relay and switch Sl open and S2 closed} the following voltages should be measured. These measurements are made at the test points as shown on the relay schematic drawing and should be made with a high resistance voltmeter to reduce instrument loading.

Testpoints Reading Circuit board terminal 19 and relay 30 2:. 3 volts

c;erminal 8 Test point TPl and relay terminal 8 16 + 3 volts Test point TP2 and relay terminal 8 less than 0.5 volt Test point TP3 and relay terminal 8 30 2:. 3 volts Test point TP4 and relay terminal 8 30 + 3 volts Test point TP5 and relay terminal 8 0 volts Test point TP6 and relay terminal 8 21 + 3 volts Test point TP7 and relay terminal 8 less than 0.5 volt Relay terminals 1 and 8 30 + 3 volts Relay terminals .10 and 8 less than 0.5 volt

If switch S2 is opened} then the following readings should be present:

Test point TP4 and relay terminal 8 less than 0.5 volt Test point TP5 and relay terminal 8 30 2:. 3 volts Test point TP6 and relay terminal 8 less than 0. 5 volt Test point TP7 and relay terminal 8 .15 + 3 volts Relay terminals 1 and 8 less than 0.5 volt

If switch Sl is closed and 83 opened} and Io adjusted for approximately 1 ampere:

Test point TP8 and slider on resistor R3 approx. 3.0+0.5 volt Test point TPl and relay terminal 8 less than 0�5 volt Test point TP2 and relay terminal 8 22 2:. 3 volts

If Sl and S3 are closed and Io = 0.25 ampere and Iom = 2.0 amperes:

Test point TP8 and slider on resistor R31 approx. 2. 5,:t0. 5 volt

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RENEWAL PA RTS Repair work can be done most satisfactorily at the factory. However, interchangeable parts can be furnished to customers who are equipped for doing repair work. When ordering parts, always give the complete nameplate data.

Symbol

Cl C2 C3 c4 C5 c6 C7

Dl to :o8 D25 to D27 D9 Dll to Dl4,Dl7 to D20 D24 DlO Dl5 D16 D21-D22 D23

R1 R2 R3-R6 R4-Rl8-R22 R5 R8-Rl2-Rl5 -R20-R21-R24 R25-R29 R7 -R9-Rl3-R17-R26-R27 -R28 R32 R11-R14-R16-R19-R33 R23 R30 R31 R34

T1 T2 to T4 - T6 to T8 T5

ELECTRICAL PARTS LIST

Description

Capacitors 2.0 MFD. 200 VDC 1.0 MFD. 50 VDC 0.56 MFD. 50 VDC 1.0, 50 VDC 2.0 MFD 400 VDC 2.0 MFD 200 VDC • 56 MFD 50 VDC

Diodes IN2071 Thyrector DJ459A

Zener .. IN468 Zener - Dt2989B Zener - IN1313A Zener - IN1317 A Zener - IN3036B

Resi5tors J.OK, 3 ntt 15K, 3 watt 499 ohm 1/2 watt 20K, 1/2 watt 350 ohm/2.5K/6.5K, 40 watt 4.99K, 1/2 watt

4.99K, 1/2 watt lOK, 1/2 watt

49.9K, 1/2 watt 30.J..K, 1/2 watt 100 ohm, 1/2 watt 5K, 10 watt lOK, 10 watt Varistor

Transistors 2ll2349 2»697 2Nll32

.6-

Style #

184A662H07 764A278H07 764A278H08 764A278H07 764A278H17 764A278H18 764A278H08

188A342H05 629A806H01 184A855H08

184A639H05 629A798H01 184A639H10 184A639H02 188A302H09

763AJ.26H20 763A126Ho8 836A503Hl9 836A503H56 184A651H01 836A503H42

836A503H42 836A503H49

836A503H65 836A503H60 836A503H03 185A925H07 185A925H05 183Al22H05

762A585H13 184A638Hl8 184A638H20

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A 8 C

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RELAYS

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SHIELDED CONDUCTOR WITH SHIELD GROUNDED AT BOTH ENDS IF EXPOSED

DEVICE CHART DEVICE

DEVICE RELAY NUMBER

6 1 sec

21N so 6-1 94 SRU OR AR

Fig. l External Schematic of the Type SCC Current Comparer Relay with the Type SDG Ground Distance Relay.

TYPE SCC RELAY

NOTE: A C CURRENT CONNECTIONS ARE SHOWN FOR CONDITION OF Io AND I oM 180° OUT OF PHASE.

848A903

Fig. 2 Test Connections for Type SCC Current Comparer Relay

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WITH RELATIVE INSTANTANEOUS POLARITIES AS SHOWN , MAXIMUM RESTRAINT IS PRODUCED

INTERNAL SCHEMATIC

350 2500 6500

837A606

Fig. 4 Internal Schematic Logic Block Dragram of the Type SCC Current Comparer Relay

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3d I OM IN AMPERES

41-1'77

SCALE I

150 SCALE II

848A902

Relay Operation Limits Curve for the Type SCC Current Comparer Relay .

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DIA ... HOLES filR .190-32 MT&·SCIRS

57-D-7902 Fig. 6 Outline and Drilling Plan for the type SCC Current

Comparer Relay.in theFT 31 Case.

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WESTINGHOUSE ELECTRIC CORPORATION RELAY-INSTRUMENT DIVISION NEWARK, N. J.

Printed in U.S.A. www . El

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Westinghouse 1. L. 41-177

INSTALLATION • OPERATION • MAINTENANCE

INSTRUCTIONS TYPE SCC CURRENT COMPARER RELAY

CAUTION: Before putting relay into service, operate the relay to check the electrical connections. Close output switches last when placing relay in service. Open output switches first when removing relay from service.

A P PL I CATION The type SCC relay supervises tripping of the SDG type of ground distance relay where the latter is current compensated for zero sequency mutual impedance.

The sec relay prevents undesired tripping for close in faults on the mutually coupled parallel line where the compensating current overpowers the effect of the protected line current.

In addition, logic circuitry is utilized to block undesired tripping for reversals in power flow and allows a coordination time for SDG relay to reset. The logic circuitry permits high speed tripping for valid faults in the trip zone.

CONS TRUCTION The type sec relay consists of two input transformers (TR-1 and Tr-2) , a plug-in type of circuit board assembly and a tapped resistor for changing the d-e rating.

As shown in Fig. 4, the circuit board consists of a current comparer with output terminal, two transistorized NOT circuits, an AND circuit, a time-delay circuit and a voltage regulator.

Voltage clippers are utilized to protect the secondary a-c input circuitry as well as the d-e input and output circuits.

OPERATION The various components are connected as shown in Fig. 3. If sufficient current is applied to Tr-1 and rated D-G supply voltage connected to the circuit board, transistor TI will turn on. Transistor T2 will turn off and a voltage will appear at the output terminal labeled CURRENT COMPARER SUPERVISION OUTPUT (TERMINAL 10) . This output can be used to operate other solid state devices such as the type TD-50 time-delay relay or other logic packages which operate circuit breakers.

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If current is also supplied to transformer TR-2 such that the voltage across resistor R2 is greater than that across Rl1 then transistor Tl will not turn on. The SDG input, terminal (3) 1 is usually tied to negative (terminal 8) through a normally conducting transistor. When the SDG output transistor is non-conducting, a voltage of 10 volts or more appears at terminal 3 and diode Dl7 will be backed biased. Since diode DlF is normally back biased, then transistor T4 will conduct and energize the timer. Approximately .025 seconds later, the normal output voltage appearing between tern1inals 1 and 8 will drop to almost zero.

By decreasing the current through transformer TR-2, the transistor Tl will now turn on. The timer circuit will then reset and approximately .025 seconds later, the voltage will again appear at terminal 1. As shown in Fig. 1, protected-line current (3Koio) energizes transformer TR-1; one TR-1 output winding feeds the operating circuit, while the second TR-1 output winding connects into the restraint circuit. Mutual compensation current (3diom) energizes transformer TR-2; the output winding feeds the restraint circuit. The restraint voltage VR is proportional to:

VR Co( (3Koio-3d Iom)

where d .: Zom, the auxiliary CT ratio. Zol (1)

Zom • zero-sequence mutual impedance

Zol = zero-sequence self-impedance of the protected line.

The operate and restraint circuits are so proportioned that operation occurs when:

3Koio > g 3Koio-3d Iom

where g = 0.4 ± 0.7 (a design constant) .

For illustrative purposes, assume g = 0.4 and d = following examples:

Example 1

(2)

0.75 in eq. 2 in the

Assume a far-end fault so that 3Koio - 3 Iom. Restraint voltage is proportional to:

0.4 (3Koio-3d Koio) : 0.4 (1-0.75) 3Koio : 0.1 (3Koio) Operate voltage is proportional to 3Koio, so eq. (2) is satisfied and operation occurs with an output appearing at terminal 10. Example 2 Assume a fault on the adjacent mutually coupled line with 3 Iom : 4 and 3Koio = -1 (flow in non-trip direction). Restraint voltage is proportional to: o.4 [ -1-0.75 (4) J = o.4 ( -1-3) = -1.6

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I.L. 41-177

Example 2 ( continued) The magnitude of the restrain voltage exceeds the operating voltage, so no output appears at terminal 10.

CHA RA CTERISTICS With .42 to .48 amperes applied to the 10 input circuit) only and rated d-e voltage connected to the relay, an output vOltage will appear at terminals 8 and 10 with terminal 10 positive.

Fig. 5 shows the response limite of the relay for g • 0.4 + .07 over a large range of current when the two input currents are 180° out of phase. The actual relay characteristics will fall somewhere in shaded area.

BURDEN DATA Burden of Operating Circuit ( terminals 4 and 5) at 5 amperes is 0.75 volt-amperes.

Burden of Restraint Circuit ( terminals 6 and 7) at 5 amperes is 0.15 volt -amperes.

Continuous rating is 10 amperes.

One second rating is 280 amperes.

Battery Drain at 48 vdc

125 vdc 250 vdc

rated voltage . 048 amperes .039 amperes .034 amperes

No setting required.

is as follows:

S ETT INGS

INSTALLATION The relay'� �::hou.ld be mounted on sw-i"t.�board panels or their equi \a len� in e

location free from misture. Mount the relay vertically by means of the four mounting holes on the flange for semi-flush mounting or by means of the rear mounting stud or studs for projection mounting. Either a mounting stud or the mounting screws may be utilized for grounding the relay. The electrical connections may be made directly to the terminals by means of screws for steel-panel mounting or to the terminal studs furnished with the relay for thick panel mounting. The terminal studs may be easily removed or inserted by locking two nuts on the stud and then turning the proper nut with a wrench.

For detailed FT case information, refer to I.L. 41-076.

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ADJUSTMENTS & MAINTENAN CE

The proper adjustments to insure correct operation of the relay have been made at the factory and should not be disturbed after receipt by the customer.

Acceptance Tests

The following check is recommended to insure the relay is operating properly. All checks can best be performed by connecting the relay per the test circuit shown in Fig •. �

1 . MINllillM OPERATE CURRENT - with switch S2 and S3 open, close switch Sl and adjust R3 until voltmeter V2 shows sudden indication (approximately 20 volts). The current through ammeter Io should read between 0.42 and 0.48 amperes. The V2 voltmeter pointer should have reset when the current is reduced to 0.40 amperes.

2. CURVE CHECK - close switch 83 and set Iom for 50 amperes. With Io adjusted for 40 amperes, the voltmeter v2 should indicate when switch Sl is closed. With Io adjusted for 30 amperes, there should be no voltmeter indication.

3. TRANSIENT BLOCK CHECK - open switches Sl and S2. Voltmeter Vl should not read. When switch S2 is closed, voltmeter Vl will read almost 30 volts. The time it takes voltage Vl to appear should be 20 to 30 milliseconds and can be checked using a oscilloscope. Like-vrise when switch S2 is opened, the voltage Vl will be removed in .020 to .030 seconds.

Routine Maintenance

All relays should be checked at least once every year or at such time intervals as may be dictated by experience to be suitable to the particular application.

Calibration

Use the following procedure for calibrating the relay if the adjustments have been disturbed. This procedure should not be used until it is apparent that the relay is not operating properly.

l. MINIMUM OPERATE ADJUSTMENT - if resistor R30 (see Fig. 3) has been disturbed, it may be recalibrated by referring to test circuit shown in Fig. g. With switches SI and S3 open, close switch SI and adjust R3 for 0.45 amperes. Adjust slidewire res.istor R30 until voltmeter V2 suddenly reads (approximately 20 volts)o Note that the position of R3l is not critical during this adjustment.

2. CURVE ADJUSTMENT - set Iom for 50 amperes and Io for 35 amperes. Alternately adjust slidewire R3l and close switch Sl until voltmeter V2 indicates. Increasing resistor R3l will decrease amount of Io current for a V2 output. Likewise decreasing resistor R3l will increase amount of Io current required for a V2 output.

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l.L. 41-177 TROUBLE SHOOTING PROCEDURE

Use the following procedure to locate the source of trouble if the type SCC relay is not operating correctly:

l. Check voltages as listed under ELECTRICAL CHECKPOINTS. 2. Inspect all wires and connections. 3. Check resistances as listed on the relay internal schematic.

ELECTRICAL CHECKPOINTS

Connect relay per test circuit of Fig. 2. With rated d-e voltage applied to relay and switch Sl open and S2 closed} the following voltages should be measured. These measurements are made at the test points as shown on the relay schematic drawing and should be made with a high resistance voltmeter to reduce instrument loading.

Testpoint'=> Reading Circuit board terminal 19 and relay 30 .:!::. 3 volts

"Lerminal 8 Test point TPl and relay terminal 8 16 .:!::. 3 volts Test point TP2 and relay terminal 8 less than 0.5 volt Test point TP3 and relay terminal 8 30 .:!::. 3 volts Test point TP4 and relay terminal 8 30 + 3 volts Tes t point TP5 and relay terminal 8 0 volts Test point TP6 and relay terminal 8 21 + 3 volts Test point TP7 and relay terminal 8 less than 0.5 volt Relay terminals 1 and 8 30 + 3 volts Relay terminals .10 and 8 less than 0.5 volt

If switch S2 is opened} then the following readings should be present:

Test point TP4 and relay terminal 8 less than 0.5 volt Test point TP5 and relay terminal 8 30 .:!::. 3 volts Test point TP6 and relay terminal 8 less than 0. 5 volt Test point TP7 and relay terminal 8 .15 + 3 volts Relay terminals 1 and 8 less than 0.5 volt

If switch Sl is closed and S3 opened} and Io adjusted for approximately 1 ampere:

Test point TP8 and slider on resistor R3 approx. 3.0+0.5 volt Test point TPl and relay terminal 8 less than 0�5 volt Test point TP2 and relay terminal 8 �2 .:!::. 3 volts

If Sl and S3 are closed and Io = 0.25 ampere and lorn = 2.0 amperes:

Test point TP8 and slider on resistor R31 approx. 2. 5.:!:,0·5 volt

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RENEWAL PARTS � Repair work can be done most satisfactorily at the factory. However, interchangeable parts can be furnished to customers who are equipped for doing repair work. When ordering parts, always give the complete nameplate data.

ELECTRICAL PARTS LIST

Symbol Description Style #

Capacitors l84A662H07 Cl 2.0 MFD. 200 VDC

C2 1.0 MFD. 50 VDC 764A278H07 C3 0.56 MFD. 50 VDC 764A278H08 c4 1.0, 50 VDC 764A278H07 C5 2.0 MFD 400 VDC 764A278Hl7 c6 2.0 MFD 200 VDC 764A278Hl8 C7 .56 MFD 50 VDC 764A278H08

Diodes Dl to D8 D25 to D27 IN207l l88A342H05 D9 Thyrector 629A806H01 Dll to Dl4,Dl7 DJ459A 184A855H08 to D20 D24 """'"'!· DlO Zener .. IN468 l84A639H05 Dl5 Zener .. IN2989B 629A798H01 Dl6 Zener .. IN1313A l84A639Hl0 D21-D22 Zener - INl317A l84A639H02 D23 Zener - IN3036B 188A302H09

Resistors Rl 10K, 3 watt 763A126H20 R2 15K, 3 watt 763Al26H08 R3-R6 499 ohm 1/2 watt 836A503Hl9 R4-Rl8-R22 20K, 1/2 watt 836A503H56 R5 350 ohm/2.5K/6.5K, 40 watt 184A651H01 R8-Rl2-Rl5 -R20- 4.99K, 1/2 watt 836A503H42 R21-R24 R25-R29 4.99K, 1/2 watt 836A503H42 R7 -R9-Rl3-Rl7- lOK, 1/2 watt 836A503H49 R26-R27 -R28 R32 49.9K, 1/2 watt 836A503H65 Rll-Rl4-Rl6-Rl9-R33 30.1K, 1/2 watt 836A503H60 R23 100 ohm, 1/2 watt 836A503H03 R30 5K, 10 watt 185A925H07 R31 lOK, 10 watt 185A925H05 R34 Varistor 183Al22H05

Transistors Tl 2)12349 762A585Hl3 T2 to T4 - T6 to T8 2»697 184A638IU8 T5 2Nll32 184A638H20

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A B C

A B C

'----:,? PHASE

RELAYS

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NEG. SHIELDED CONDUCTOR WITH SHIELD GROUNDED AT BOTH ENDS IF EXPOSED

DEVICE CHART DEVICE

DEVICE RELAY NUMBER

6 1 sec A B C 21N SDG-1

94 S R U OR AR

Fig. l External Schematic of the Type SCC Current Comparer Relay with the Type SDG Ground Distance Relay.

TYPE SCC RELAY

N OTE: AC CURRE N T CONNECTION S ARE SHOWN FOR CONDITION OF Io AND I oM 180° OUT OF PHASE.

848A903

Fig. 2 Test Connections for Type SCC Current Comparer Relay

671B232

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WITH RELATIVE INSTANTANEOUS POLARITIES AS SHOWN , MAXIMUM RESTRAINT IS PRODUCED

I�TERNAL SCHEMATIC

6500

837A606

Fig. 4 Internal Schematic Logic Block Dragram of the Type SCC Current Comparer Relay

9

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150 SCALE n

848A902

Relay Operation Limits Curve for the Type SCC Current Comparer Relay.

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PML OIILLIH 011 CUlWT fiH '*KTIOI Jmi. (FIMT YliW)

DfA,q HOLES FilR • 190-32 MTG·SCIPS

57-D-7902 Fig. 6 Outline and Drilling Plan for the type SCC Current

Comparer Relay.in theFT 31 Case.

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WESTINGHOUSE ELECTRIC CORPORATION RELAY-INSTRUMENT DIVISION NEWARK, N. J.

Printed in U.S.A. www . El

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