Figure 1.Type ME electronic recloser control.

Figure 2.Resistor symbol.

These instructions do not claim to cover all details or variations in the equipment, procedure, or process described, nor to provide directionfor meeting every possible contingency during installation, operation, or maintenance. When additional information is desired to satisfy aproblem not covered sufficiently for the user’s purpose, please contact your Cooper Power Systems sales engineer.

May 1985 • Supersedes 1/83

ReclosersService Information

S280-75-46Type ME Electronic Recloser ControlMaintenance - Advanced Circuitry

Applicable to Form 3 and 3AControls

1

CONTENTSIntroduction ....................................... 1Basic Circuit Design ........................ 1Typical Schematic Symbols .............. 1ME Control Circuits ........................... 4

Control Circuitry Analysis ................ 8Potential Battery Circuit .................... 8Closing From Lockout Circuit ............ 8Sensing Circuit .................................. 8Voltage Level Detector Circuit ........... 9Voltage Level Detector andTiming Circuit.................................... 9

Output Board Circuit .........................11Reclose Board Circuit . .....................11Reset Circuit ....................................11

Appendix I .........................................13Schematic Diagram of Form 2 .....14, 15Schematic Diagram of Form 3and RE/WE Recloser .................16, 17

Schematic Diagram of Form 3and Motor operated Recloser .....18, 19

Schematic Diagram of Form 3Aand RE/WE Recloser .................20, 21

Schematic Diagram of Form 3Aand Motor operated Recloser .....22, 23

Appendix II .........................................24List of Electronic Control AccessoryManuals Containing SchematicDiagrams ........................................24

INTRODUCTIONService Information S280-75-46 detailsthe major electronic components and cir-cuits of the Type ME electronic control(figure 1). A general description of thecontrol and its operating principles, aswell as basic inspection, testing, andmaintenance instructions, is found inService Information S280-75-1. In addi-tion, basic maintenance instructions forthe ME control are found in ServiceInformation S280-75-2. Before proceed-ing with this manual, be sure you have athorough understanding of both thesemanuals (S280-75-1 and S280-75-2).

BASIC CIRCUIT DESIGNA detailed study of ME control circuitryrequires a common understanding ofbasic electronic components and simplecircuits that can be built from these com-ponents. Thus, to assure this com-

mon knowledge — simple electroniccomponents will be reviewed, followed bythe study of basic electronic circuitry.

Typical Schematic SymbolsIn the electronic control, the resistor isshown in two forms . . . a rectangularblock or a sawtooth line (figure 2).Resistors are introduced into a circuit toreduce voltage and limit current flow.

The instructions in this manual are not intended as asubstitute for proper training or adequate experience inthe safe operation of the equipment described. Onlycompetent technicians who are familiar with this equip-ment should install, operate, and service it.

A competent technician has these qualifications:

• Is thoroughly familiar with these instructions.

• Is trained in industry-accepted high- and low-voltagesafe operating practices and procedures.

• Is trained and authorized to energize, de-energize,clear, and ground power distribution equipment.

• Is trained in the care and use of protective equip-ment such as flash clothing, safety glasses, faceshield, hard hat, rubber gloves, hotstick, etc.

Following is important safety information. For safe instal-lation and operation of this equipment, be sure to readand understand all cautions and warnings.

Safety InstructionsFollowing are general caution and warning statementsthat apply to this equipment. Additional statements, relat-ed to specific tasks and procedures, are locatedthroughout the manual.

SAFETY INFORMATION

WARNING: This equipment is not intended toprotect human life. Follow all locally approved pro-

cedures and safety practices when installing or operat-ing this equipment. Failure to comply can result indeath, severe personal injury, and equipment damage.

G102.1

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DANGER: Hazardous voltage. Contact withhazardous voltage will cause death or severe

personal injury. Follow all locally approved safety pro-cedures when working around high and low voltagelines and equipment. G103.3

!

WARNING: Before installing, operating, main-taining, or testing this equipment, carefully read

and understand the contents of this manual. Improperoperation, handling or maintenance can result in death,severe personal injury, and equipment damage. G101.0

!

WARNING: Power distribution equipment mustbe properly selected for the intended application.

It must be installed and serviced by competent person-nel who have been trained and understand proper safe-ty procedures. These instructions are written for suchpersonnel and are not a substitute for adequate trainingand experience in safety procedures. Failure to proper-ly select, install, or maintain power distribution equip-ment can result in death, severe personal injury, andequipment damage. G122.2

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SAFETY FOR LIFECooper Power Systems products meet or exceed all applicable industry standards relating to product safety. We activelypromote safe practices in the use and maintenance of our products through our service literature, instructional trainingprograms, and the continuous efforts of all Cooper Power Systems employees involved in product design, manufacture,marketing, and service.

We strongly urge that you always follow all locally approved safety procedures and safety instructions when workingaround high voltage lines and equipment and support our “Safety For Life” mission.

!SAFETYFOR LIFE

!SAFETYFOR LIFE

This manual may contain four types of hazardstatements:

DANGER: Indicates an imminently haz-ardous situation which, if not avoided, will

result in death or serious injury.

WARNING: Indicates a potentially haz-ardous situation which, if not avoided, could

result in death or serious injury.

CAUTION: Indicates a potentially hazardoussituation which, if not avoided, may result in

minor or moderate injury.

CAUTION: Indicates a potentially hazardous situ-ation which, if not avoided, may result in equip-ment damage only.

!

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Hazard Statement Definitions

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Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

Figure 3.Capacitor symbol.

3

The capacitor is shown in schematicform by two plates. one plate is showncurved to distinguish it from contacts (fig-ure 3). Capacitors are introduced into acircuit to oppose changes in voltageand/or store energy in an electrostaticfield.

Figure 6.Diode symbol.

Figure 7.Diode operation.

Figure 10.NPN transistor symbol.

Figure 9.Zener diode operation.

Figure 4.Manual switch symbol.

Figure 5.Mechanical or electrical contact symbol.

Figure 8.Zener diode symbol.

A simple manually operated contactis shown in figure 4 (may be shown witha dotted line if connected in gang withseveral other contacts). Contacts areintroduced into a circuit to allow theopening or closing of a circuit.

Mechanically or electrically operat-ed contacts are shown in a schematic(figure 5) as parallel lines when normallyopen (N.O.)* or as parallel lines with aslash when normally closed (N.C.).These contacts allow for mechanicaland/or electrical coordination and controlof circuit position.

*Normally open contact—contact state with its operating device (coil, spring, etc ) in deenergized position.

The symbol for a diode is shown infigure 6. A diode can be introduced into acircuit to allow current flow in one direc-tion only. The operation of the diode isshown in figure 7. In a circuit consistingof a voltage source, a resistor, and adiode, the current in the circuit is I = E/R(figure 7A). If the diode is inverted(blocking position) as shown by figure7B, the current in the circuit is zero.When current flows through a diode, anearly constant 0.7 volt drop from anodeto cathode is present.

An electronic device used as a voltageregulator is the zener diode. Itsschematic symbol is shown in figure 8.The zener diode is also commonly usedas a voltage reference. In the simple cir-cuit shown in figure 9, the 10-volt zenerdiode will always subtract ten volts fromthe 25-volt source producing a 15-voltoutput. This output voltage is essentiallyindependent of the current to the zenerdiode. The difference between batteryplus and the voltage on the anode of thezener diode will always remain 10 volts.The variations in the tolerance of theresistor and variations in the battery volt-age itself will not affect this constantvalue.

The NPN transistor symbol is shown infigure 10. It has a collector, a base and anemitter. The base is the normal controllingelement for the transistor. A collector mightbe said to collect the current into the tran-sistor. The emitter, which carries currentthat is common to the base and the collec-tor, can be said to emit the current from thetransistor. The transistor’s primary purposein a circuit is to amplify current or switchcurrent on or off.

The PNP transistor (figure 11) differsfrom the NPN transistor where the emitter,rather than emitting current from the tran-sistor, emits current into the transistor.Except for this variation, everything saidabout the NPN transistor applies to thePNP transistor.

NOTE: The input signal at the base for the PNPtransistor is commonly referenced back to bat-tery plus, where the base for the NPN is con-nected to battery minus. This provides extra flex-ibility in designing transistorized circuitry.

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Figure 11.PNP transistor symbol.

Figure 12.Unijunction transistor (UJT) symbol.

Figure 13.Unijunction transistor operation.

Figure 14.Programmable unijunction transistor(PUT) symbol.

Figure 15.Silicon controlled rectifier (SCR) symbol.

Figure 16.Simple NPN transistor circuit.

Figure 17.Saturated NPN transistor circuit.

The unijunction transistor (UJT)(figure 12) is a voltage detecting andswitching element. As its name (uni-junction) implies, it consists of but onejunction, an emitter connected to abase. However, it is still a three-terminaldevice in that the base has two leads:one normally connected to battery plusand one normally connected to batteryminus. This produces a voltage distribu-tion across the semiconducting materialin the unijunction, and the emitter isconnected approximately to the V/2location on the semiconductor (figure13). No current flows between the emit-ter and the semiconducting materialuntil the voltage of the emitter becomesgreater than V/2, or half the battery volt-age. When the emitter turns on, it effec-tively is connected to base 1 by theimpedance of a forward diode. Theimpedance between base 2 and theemitter remains high, in the order ofseveral thousand ohms.

A programmable unijunction tran-sistor (PUT) (figure 14) is similar in func-tion to the unijunction transistor, exceptthe trigger voltage level can be easilyvaried by the use of a simple poten-tiometer, allowing easy calibration of theRC time delay. No current flows betweenthe anode and the cathode until the volt-age at the anode is greater than voltageat the gate (figure 14).

A silicon controlled rectifier (SCR) isa rectifier with a gate to control conduc-tion in the forward direction. The SCRshown in figure 15 is an open circuitbetween the anode and cathode until agate signal is applied. With a proper gatesignal, the SCR will conduct from theanode to the cathode until the anode cur-rent is removed.

ME Control CircuitsThe NPN transistor, in a simple circuit,shows a battery voltage and a base signalin abbreviated form. The transistor isshown in a common emitter configurationin which the emitter completes both thebase circuit and the collector circuit backto battery minus (figure 16).

The voltages in a saturated transistorare noted in figure 17. It takes about 0.7volt to forward bias the base emitter junc-tion to produce a controlling base current.A transistor that is fully on or saturated willhave about 0 3 volts or less from collectorto emitter, with fairly low collector currents.

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Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

5

Figure 18.Current and power gain in NPN tran-sistor circuit.

Figure 19.PNP transistor circuit.

Figure 20.Darlington pair circuit.

Figure 21.Common base NPN transistor circuitwith two power supplies.

Figure 22.Bias circuit.

Figure 23.Conventional RC circuit.

Except that the PNP emitter emits cur-rent into the emitter, everything else saidabout the NPN transistor applies to thePNP transistor. Note this difference inthat the input signal at the base for thePNP transistor is commonly referencedto battery plus (figure 19), where thebase for the NPN is referenced to batteryminus.

Typical currents in a transistor circuitas shown in figure 18 are about 0.1 mil-liamps into the base which will produceabout 5 milliamps in the collector, totallingabout 5.1 milliamps in the emitter. Notethat both the base and collector currentsemit from the emitter. Thus, we see boththe current gain and the power gain of atransistor in operation. The O.1 milliampsin the base produces about fifty times thebase current or 5 milliamps in the collec-tor for a typical gain of 50. The powergain is even more outstanding.

In circuits where collector currents orload currents of 5 milliamps are inade-quate to power succeeding stages, suchas gating high power SCR’s or operatingrelay coils, transistors must be gangedtogether or connected in what is called aDarlington circuit (figure 20). Note thatin this case the 0.1 milliamps enteringtransistor Q1 is amplified to 5.1 milliampsand is fed into the base of transistor Q2.The 5.1 milliamps into the Q2’s base isamplified to about 255 milliamps in itscollector, assuming each transistor has again of 50. The load circuit now has the

sum of the collector current in each tran-sistor. Transistor Q2 will then have thecapability of carrying up to about 250 mA(1/4 ampere).

With a battery voltage of 25 Vdc, atransistor Q2 load, and a RL of 1000Ω(figure 20), the maximum Q2 collectorcurrent will beIQ2 = ECC = 25 = 25 mA.

The collector current to Q2 has been lim-ited by RL, resulting in Q2 saturating (oroperating like an on-off switch).

Another circuit type as shown in figure21 gives an added transistor feature.The NPN transistor is in a commonbase configuration where two separatepower supplies of different polarities arepowering the collector and the emitter. Inthis circuit the collector and the emitterboth are carrying about the same currentas they have in all previous cases. But,the emitter circuit is being driven by a 2-volt source and the collector circuit has a25-volt source. The important feature ofthis circuit is the emitter and collectorcurrents are essentially equal, and thecollector voltage (if above one volt) haslittle or no effect on the collector cur-rents.

This circuit is used in this case totransfer current from a low voltage circuitto a high voltage circuit. In the Type MEelectronic control, the current from theME control input bridge is transferred tothe battery circuit with a common basetransistor.

RL 1000

The Type ME electronic control also usesthe bias circuit shown in figure 22. In thiscircuit, two diodes produce about a -1.4 voltreference which is used to bias the timingplugs. Connected between the two diodesand the 6.8K resistor is a 17V + 1% preci-sion zener diode. This zener diode is usedas a reference voltage for the minimum triplevels and time-current curves of the MEcontrol. As used on the ME control tieboard,this point is called “-17 VOLTS” in that it is17 Vdc less than the voltage at tieboard ter-minal 5B.

The circuit used in the control reclosingand resetting functions has as its time delaya conventional RC circuit (figure 23). Thiscircuit will reproduce an exact voltagecharge characteristic on the capacitor eachtime the switch is closed. If the voltagecharge in the capacitor can be very carefullymeasured, such as noting the exact time thevoltage on the capacitor is equal to sourcevoltage divided by 2, the circuit will accu-rately reproduce a constant timing interval.

Figure 24 shows an RC circuit operatingwith a unijunction transistor. When thevoltage on C becomes equal to V/2, theemitter turns on with very low impedancebetween the emitter and base 1, and C dis-charges through the

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Figure 24.RC circuit with unijunction transistor (UJT).

Figure 25.RC circuit with programmableunijunction transistor (PUT).

Figure 28.RC circuit with PUT and SCR.

Figure 27.RC circuit with UJT and SCR.

Figure 26.Silicon controlled rectifier (SCR) circuit.

resistor connected to base 1—resultingin a small burst of current for a shortduration of time. This current of shortduration and low magnitude is insufficientto operate most relays, but it is of suffi-cient duration to operate static devicessuch as an SCR.

Figure 25 illustrates the pro-grammable unijunction transistor(PUT) in an operational circuit.Potentiometer R sets the trigger voltage(V trigger). As the voltage rises onCapacitor C, the PUT blocks current flowfrom capacitor C until the capacitor volt-age exceeds trigger. The capacitor thendischarges through the PUT and RL,resulting in a brief voltage pulse at Eo.

The SCR (silicon controlled rectifier) isanalogous to a self-latching relay (figure26). Once turned on it remains on untilturned off by an external event. A positivevoltage pulse to the gate causes the SCRto turn on and remain on until the externalturn off switch is opened to stop the cur-rent flow.

In a typical SCR circuit (figure 27), atime delay caused by the RC circuit and avoltage pulse from a unijunction are usedto gate the SCR on.

The SCR will energize a coil, which cancause a mechanism such as a “BlackBox” to operate and open the contact inthe voltage circuit, turning off the SCR.Closing the switch will not turn on theSCR until the RC-UJT-SCR (figure 27) orRC-PUT-SCR (figure. 28) operates a suc-ceeding time.

Figure 28 shows an RC circuit usingthe PUT and SCR. The trigger voltage ofthe PUT can be varied by the voltage setby the potentiometer. After closing the “b”contact, the voltage across capacitor Cincreases from zero at an exponentialrate. When the capacitor

voltage exceeds the potentiometer volt-age setting, the PUT triggers, gating theSCR. The function of the NPN transistoris to completely discharge capacitor Cafter a trigger operation of the PUT.

Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

7

Figure 29.Potential battery charger circuit.

Figure 30.Closing from lockout circuit.

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8

Figure 31.Sensing circuit

CONTROL CIRCUITRYANALYSIS

Potential Battery ChargerShown in figures 29A and 29B are theschematics for the potential battery charg-ers for the Form 3 and Form 3A ME con-trols.

The AC input to the control batterycharging circuit is applied through one ortwo current limiting resistors to the prima-ry side of a 1:1 ratio isolating transformer.The AC output of the transformer is thenapplied to the input of a rectifier bridgeand is converted to DC. This DC signal isfiltered by capacitor C1 and is limited to33 Vdc by zener diode D5. The propercharging rate to the control battery is setby the proper selection of resistancebetween the zener diode and the controlbattery.

Closing From Lockout CircuitFollowing the circuitry of figure 30, when-ever the control battery is plugged in,resistor R13 of the reclose-reset boardcharges capacitor C14 to battery voltage.If the control sequence relay is not in thehome position, the home contact will beclosed. Closing the manual control (PGS)switch will discharge the capacitor C14through R9 into the gate to SCR Q4. Thisgates SCR Q4, which in turn energizesthe sequence relay coil through the clap-per contact, the home contact, and SCRQ4. The relay pulls in and the clapperopens the coil circuit, allowing the coil toadvance the sequence relay wiper con-tacts to the next position. The holding cur-rent resistor R12 prevents SCR Q4 fromswitching off when the clapper contactopens. When the clapper contacts closeagain, the entire process repeats again ata very rapid rate.

This process continues until stopped bythe home contact. The closing of

the recloser is initiated by closing thesequence relay open-at-lockout contact.The reclose operation has beendescribed on page 5, figure 27 and 28,and will be described further on page 10,figure 35.

Sensing CircuitAs illustrated in figure 31, line currentconditions are monitored continuously bya 1000:1 ratio sensing CT located oneach phase of the recloser. A 100Ωshunting resistor is provided to protectthe CT from damage if the control cableis disconnected while primary load cur-rents exist.

The output current from the CT isapplied to the ME control’s matchingtransformer primary windings. The trans-former steps up the voltage and isolatesthe signal from the DC control circuitryand from the other phases, which are notshown in figure 31. The bridge rectifierconverts the transformer secondary volt-age to full wave DC. This output Vdclevel is proportional to the recloser loadcurrent and is used by the ME control todetermine if fault currents exist, and ifso—what magnitude they are for timecurrent curve purposes.

By design of the ME control, the actualcurrent input to the phase matchingtransformers at minimum trip is 100 mil-l iamperes AC for phase and 5 mil-liamperes AC for ground. The minimumtrip resistor diverts a portion of the CToutput current, causing an increase inthe ME control minimum trip level to anylevel desired by selection of the resis-tance of the minimum trip resistor.

Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

9

Figure 32.Voltage level detector circuit.

Voltage Level Detection CircuitAn important part of the next several sec-tions of the control (Phase-Trip No. 1 andNo. 2 boards) as shown in figure 32 is thereference voltage set up on the outputboard and appearing at the terminalmarked “-17 vo LTS” on the tieboard. Thevoltage is 17 volts (+1%) below voltage atterminal 5B. This reference voltageappears on the Phase No. 2 board, andprovides a bias of minus 17 volts at theemitter of Q1 of the Phase Trip No. 2board with respect to terminal 5B.

As illustrated in figures 31 and 32, thevariable output voltage level is determinedby the recloser load current. This variablevoltage level is applied to the emitter-basejunction of transistor Q1 and resistor R4 ofthe Phase Trip No. 1 board. Per figure 32,a nearly identical collector current will flowthrough precision resistors R6, R8, andR9. The voltage drop across these threeresistors is therefore proportional to therecloser primary line current. (A simpleversion of this circuit can be seen in figure21.)

Zener diodes D4 and D5 on the outputboard, along with transistor Q1 of thePhase Trip No. 2 board, functions as anelectronic voltmeter which monitors thevoltage across resistors R6, R8, and R9.

When the recloser’s primary load

current is sufficient in magnitude tocause 17.7 peak Vdc to appear acrossresistors R6, R8, and R9, transistor Q1of the Phase Trip No. 2 board will beturned on. Transistor Q1 then turns onthe Darlington transistor pair Q2 and Q3.Transistor Q3 is turned on and driveninto saturation, lowering the voltage atthe anode of D4 very close to zero. Thus,for any positive voltage on the cathode ofD4, D4 is reversed biased and effectivelyan opened circuit.

Voltage Level Detector andTiming CircuitReferencing figure 33, the emitter of Q4(similar to the emitter of Q1 on thePhase Trip No. 1 board) connects to thenegative side of the input bridges. Theoutput voltage of the input bridge causesa current to flow through the base emit-ter of transistor Q4 and resistors R6 andR7. And, providing the collector voltageof Q4 is not zero, the collector currentwill be virtually equal to the emitter cur-rent. The collector current will then bevirtually independent of the collector volt-age and proportional to the recloser linecurrent which produced the voltageacross the output of the rectifier bridge.

At line currents below minimum trip,Q3 is turned off (no base current and no

collector emitter current); R5 (1000Ω ) thenlooks like a short circuit to transistor Q4.The normal or less than pickup currentthrough D4 is less than 100 microamps, andsince one side of R5 is connected to batteryplus, the voltage at the cathode of D4 isalso near battery plus.

At line currents above minimum trip, Q3 issaturated, back biasing D4 so it is effective-ly an open circuit. The collector current ofQ4 is then supplied by the timing plugcapacitors, causing the capacitors to chargeunder fault conditions. When the voltage atterminal 2 of the timing plug is charged to avoltage of about 7 Vdc (or 17.7 Vdc lowerthan tieboard terminal 5B), the emitter baseof Q1 of the output board (figures 33 and34) is forward biased, initiating operation ofthe output board.

If at any time during a timing operation,the line current drops below pickup level,Q3 switches off, and pin 3 of the timing plugis driven back to battery plus by resistor R5,resetting the capacitors in the timing plug.NOTE: The selected timing plug can be disabledby removing battery plus from its pin 4 connec-tion. Thus, by switching between two timingplugs, the control can switch from fast to slowtime-current curves during a sequence to lockoutunder fault conditions.

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Figure 33.Voltage level detector and timing circuit.

Figure 34.Output board circuit.

Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

Figure 35.Reclose board circut

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Output Board CircuitsWhen the timing plug causes Q1 of theoutput board (figure 34) to turn on, a tripoperation will take place. Q1 drives theDarlington transistor amplifier pair Q2 andQ3 which in turn gates the trip SCR Q4.The collectors of Q2 and Q3 are suppliedfrom the anode circuit of Q4. When Q4turns on, its anode voltage switches tobattery minus. With battery minus at thispoint, there is no positive voltage at thecollectors of Q2 and Q3. This turns off Q2and Q3, removing the gate signal fromSCR Q4.

The trip SCR Q4 of the output boardstarts a trip operation when turned on.(The contacts shown between C and D inthe Q4 anode circuit are in the recloser).Resistor R8 is a very high value, whichwill not allow the SCR to hold on after atrip operation.

While the trip SCR is on, the sequencerelay coil, the counter, and the trip coil areenergized. The “CD” contacts open whenthe recloser’s main contacts open. Thiscauses the sequence relay, the counter,and the trip coil to be deenergized. Thesequence relay contacts then advance onthe de-energization of the relay coil.

In the event the “CD” contacts openbefore the sequence relay has pulled infar enough to advance its contacts on de-energization, a “7B-10B” contact bypassis provided. This circuit (5A, sequencerelay coil, 7B clapper contacts, 10B, D10and Q4 of the output board) bypasses the“CD” contacts and provides a separate

circuit to ensure proper operation of thesequence relay.Reclose Board CircuitAfter a trip operation, figure 35 shows the“b” contact (between control cable termi-nals A-F) in the recloser closed, startinga reclosing operation. With “b” closed,battery plus is applied to the sequencerelay 11 B terminal. These wiper contactsselect the proper reclosing delay plug(R1, R2, or R3). This resistor with C4 onthe reclose reset board forms an RC tim-ing circuit. When capacitor C4 charges toabout 15 volts, the PUT Q1 breaks over,and the capacitor energy dumps throughthe PUT Q1 and transistor Q5, gating theSCR Q2. This causes the SCR to con-duct, energizing the close coil throughthe fuse. When the recloser closes, the“b” contact opens — turning off thereclose circuits.NOTE: In the event the recloser cannot close,the control fuse will blow in about 5 seconds.This removes the high current drain of therotary solenoid, protecting the control battery.It also protects the closing coil in the recloserfrom damage if line voltage is too low to causeproper closure.

Reset CircuitTo cause reset of the control to the homeposition after clearing of temporary faults, areset circuit is provided (see figure 36). Theenergy to operate the reset time-delaycomes from terminal 5B of the sequencerelay. When the wiper connected to 5B is inthe second, third, or fourth position (8B, 4A,or 3A), then terminal Z of the diode boardhas battery plus to it providing positive biasto the reset PUT Q3.

Since battery power to the reset delayplug must come from the recloser”C-D” con-tact, automatic reset can only occur whenthe recloser is closed. The signal from the“C-D” contact causes the R-C timing circuit,consisting of the reset delay plug, andcapacitors C7, C8 and C9, to trigger thereset PUT Q3. The PUT then gates thereset SCR Q4. The sequence relay is thenenergized by the sequence relay coil, thesequence relay clapper contact, diode D3,the sequence relay home contact, and theSCR Q4. The coil armature then pulls in,opening the clapper contact. The armaturereturns to normal, advancing the sequencerelay wiper contacts, simultaneously reclos-ing the clapper contacts. Resistor R12 pro-vides holding current to the SCR, and thecycle continues until the home contact shutsoff power to the reset SCR Q4.

If a fault should occur during the resettime delay, the two diodes marked D3 andD4 discharge the reset timing capacitorsthrough the minimum trip transistors Q3 ofthe phase and/or ground trip No. 2 boards.This circuitry then only allows automaticreset when the recloser is closed, and nofault exists on either phase or ground sens-ing of the control.

The above circuitry applies to the Form3A control and any Form 2 or Form 3 con-trol equipped with the KA304ME Reset AfterSuccessful Reclose Accessory.

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Figure 36.Reset Circuit.

Type ME Electronic Recloser Control Maintenance - Advanced Circuitry

APPENDIX I

Figure 37a and 37b Schematic Diagram of Form 2 ..14, 15Figure 38a and 38b Schematic Diagram of Form 3

and RE/WE Recloser .............................................16, 17Figure 39a and 39b Schematic Diagram of form 3

and Motor Operated Recloser................................18, 19Figure 40a and 40b Schematic Diagram of Form 3A

and RE/WE Recloser .............................................20, 21Figure 41a and 41b Schematic Diagram of Form 3A

and Motor Operated Recloser................................22, 23

S280-75-46!SAFETYFOR LIFE

This manual S280-75-46 has three parts:S280-75-46A ......................................pages 1-12S280-75-46B ......................................pages 13 - 19S280-75-46C ......................................pages 20 - 24For the remaining pages of this manual (pages 13 - 19) refer to S280-75-46B, (pages20 - 24) refer to S280-75-46C.

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