S&C Source-Transfer Controls I For Two-Way Transfer Type AT-2 Catalog Numbers 38881 and 38883 INSTRUCTIONS For Operation and Adjustment 1 INTRODUCTION 1 CAUTION: The equipment covered by this publication must be operated and maintained by qualified persons who are thoroughly trained and who understand any hazards that may be involved. This publication is written only for such qualified persons and is not intended to be a substitute for adequate training and experience in safety procedures for this type of equipment. The instructions herein are for S&C Source-Transfer Controls-Type AT-2, Catalog Numbers 38881 and 38883. For superseded S&C Source-Transfer Controls- Type AT-2, Catalog Numbers 38822 and 38832, refer to S&C Instruction Sheet 514-500. The S&C Source-Transfer Control-Type AT-2 for Two-Way Transfer is designed for use in S&C Metal- Enclosed Switchgear, in conjunction with two S&C inter- rupter switches driven by S&C Switch Operators-Type MS-2 or Type AS-30, to provide for automatic source transfer for common-bus primary-selective systems rated through 34.5 kv. See Figure 1. When so applied, the Type AT-2 control assures a high degree of critical-load service continuity by minimizing interruptions resulting from failure of one source. Ex- cluding the intentional time delay necessary for coordi- nation, transfer is achieved in 10 cycles when Type MS-2 Switch Operators are combined with S&C Mini-Rupter@ Switches-or three seconds when Type AS-30 Switch Operators are combined with S&C Alduti-Rupterm Switches. S&C Source-Transfer Controls-Type AT-2 are de- signed for drawout mounting on telescoping support rails and proportioned to lit within a grounded, steel-enclosed, low-voltage compartment in the switchgear-bay stile- isolated from high voltage and accessible without opening the door of the switchgear bay. See Figure 2. Field pro- grammable operating-mode selector switches and timer- Figure 1. S&C Source-Transfer Control-Type AT-2 for Two-Way Transfer installed in S&C Metal-Enclosed Switchgear in conjunction with two S&C Switch Operators-Type MS-2. Supersedes InstructIon Sheet 514-501 dated 6-21-82 0 1983 INSTRUCTION SHEET 514-501 S&C ELECTRIC COMPANY. Chicago Page 1 of 15 S&C ELECTRIC CANADA LTO . Rexdale August 29,1983
Transcript
S&C Source-Transfer ControlsI
For Two-Way TransferType AT-2 Catalog Numbers 38881 and 38883
INSTRUCTIONSFor Operation and Adjustment
1 INTRODUCTION 1
CAUTION: The equipment covered by this publicationmust be operated and maintained by qualified personswho are thoroughly trained and who understand anyhazards that may be involved. This publication is writtenonly for such qualified persons and is not intended to be asubstitute for adequate training and experience in safetyprocedures for this type of equipment.
The instructions herein are for S&C Source-TransferControls-Type AT-2, Catalog Numbers 38881 and38883. For superseded S&C Source-Transfer Controls-Type AT-2, Catalog Numbers 38822 and 38832, refer toS&C Instruction Sheet 514-500.
The S&C Source-Transfer Control-Type AT-2 forTwo-Way Transfer is designed for use in S&C Metal-Enclosed Switchgear, in conjunction with two S&C inter-rupter switches driven by S&C Switch Operators-TypeMS-2 or Type AS-30, to provide for automatic source
transfer for common-bus primary-selective systems ratedthrough 34.5 kv. See Figure 1.
When so applied, the Type AT-2 control assures a highdegree of critical-load service continuity by minimizinginterruptions resulting from failure of one source. Ex-cluding the intentional time delay necessary for coordi-nation, transfer is achieved in 10 cycles when Type MS-2Switch Operators are combined with S&C Mini-Rupter@Switches-or three seconds when Type AS-30 SwitchOperators are combined with S&C Alduti-RuptermSwitches.
S&C Source-Transfer Controls-Type AT-2 are de-signed for drawout mounting on telescoping support railsand proportioned to lit within a grounded, steel-enclosed,low-voltage compartment in the switchgear-bay stile-isolated from high voltage and accessible without openingthe door of the switchgear bay. See Figure 2. Field pro-grammable operating-mode selector switches and timer-
Figure 1. S&C Source-Transfer Control-Type AT-2 for Two-Way Transfer installed in S&C Metal-Enclosed Switchgear inconjunction with two S&C Switch Operators-Type MS-2.
INSTRUCTION SHEET 514-501S&C ELECTRIC COMPANY. Chicago Page 1 of 15
S&C ELECTRIC CANADA LTO . Rexdale August 29,1983
S&C Source-Transfer ControlsI
For Two-Way TransferType AT-2 Catalog Numbers 38881 and 38883
1 INTRODUCTION I
adjustment dials, as well as test switches, are located at therear of the device. However, they are readily accessiblewhen the device is extended by means of the telescopingsupport rails.
For grounded-system applications from 12 kv through27.6 kv, the three-phase signal-voltage input circuitry forType AT-2 controls typically utilizes, for each source, twoS&C Indoor Voltage Sensors to derive sensing from two ofthe phases, with third-phase sensing-as well as controlvoltage for the automatic source-transfer scheme-de-rived from a voltage transformer. In the typical switchgearassembly, the two S&C Indoor Voltage Sensors for eachsource are incorporated in the S&C interrupter switch,replacing apparatus insulators at the source-side termi-nals; no additional space or mounting provisions arerequired for them. See Figure 5. (For grounded-systemapplications over 27.6 kv, grounded-system applicationsless than 12 kv, and all ungrounded systems, three voltagetransformers are typically used for each source to deriveboth sensing and control-voltage service for the TypeAT-2 controls. In certain applications utilizing single-phase sensing, one voltage transformer is typically used foreach source to derive both sensing and control-voltageservice for the Type AT-2 controls.)
The S&C Indoor Voltage Sensor, which has relay accu-racy over an ambient temperature range of -4O’F to+160°F, has an output voltage that is directly proportionalto line-to-ground voltage. It is a constant-current-outputdevice like a current transformer, and therefore primary
fusing (required by a voltage transformer) is eliminated.However, a secondary burden is required. The burdens forall of the indoor voltage sensors (for both sources) areprovided by voltage-dividing resistors located behind apanel, at the rear of the Type AT-2 control. Mounted onthe face of this panel are fuseholders for the two voltagetransformers’ secondary fuses, as well as fuseholders con-taining solid slugs; these slugs are in the transformer-secondary grounding circuit and allow complete isolationof each voltage transformer when both the fuse and slug forthat transformer are removed. See Figure 4.
Connected across the output of each S&C Indoor Volt-age Sensor is an S&C Voltage Limiter, a protective devicefurnished to prevent damage to the voltage sensor’s trans-former in the event that its secondary circuit is inadvert-ently opened or the burden is removed. See Figure 5.
If the optional overcurrent-lockout feature is included(as signified by the addition of the suffix “-K” to thesource-transfer control catalog number), three-phasecurrent-sensing input for its circuitry is derived from S&CCurrent Sensors. See Figure 5. When installed, these cur-rent sensors are attached to each entrance cable for eachsource. Refer to S&C Instruction Sheet 514-600 forinstructions on installation of S&C Current Sensors. Alsorefer to the wiring diagram. (Certain applications mayutilize three current transformers or a single window-typecurrent transformer. For these special cases, supplementalinstructions will be included with the wiring diagramsfurnished.)
Telescoping Support Rails,top and bottom
Latch holds control inextended position
Figure 2. Drawout position of the Type AT-2 control permits access to the programmmg ana testmg features at rear 01 tne aevlce.,
514-501 INSTRUCTION SHEETPage 2of 15 S&C ELECTRIC COMPANY - Chicago
August 29,1983 S&C ELECTRIC CANAOA LTO - Rexdale
IThis section is presented for familiarization purposes only.Before making any adjustments refer to pages 9 through11, under the heading “Adjustments and Programming.”
FEATURES
On the Front Panel of the Controll Manual/automatic operation selector switch-when in
the manual position, prevents automatic operation andpermits manual operation of the interrupter switchesusing open/close pushbuttons on switch operators.
l Automatic-transfer “ready” indicating lamp-providesstraightforward indication that the source-transfer
control, interrupter switches, and switch operators arein the normal (preprogrammed) positions and ready forautomatic source transfer. (All indicating lamps havepush-to-test feature.)
l Source-voltage indicating lamps.
l Overcurrent-lockout indicating lamp and reset push-button. (Furnished when optional overcurrent-lockoutfeature is included-as signified by the addition of thesuffix “-K” to the catalog number.)
/ ( i n c l u d e d w i t h t h eoptronal overcurrent-lockoutfeature, catalog-numbersuffix “-K”)
Automatic-Transfer“Ready” Indicating Lamp
Figure 3. Front-panel features of the Type AT-2 control.
lNSTRUCTlON SHEET 514m501S&C ELECTRIC COMPANY - Chicago Page 3 of 15
S&C ELECTRIC CANAOA LTO * Rexdale August 29, 1983
SCLC Source-Transfer Controls For Two-way Transfer Type AT-2 I Catalog Numbers 38881 and 38883
FEATURES
At the Rear of the Control Loss-of-source timer-adjustment dials (for preferred and alternate sources)-to adjust delay of transfer initiation to a period (VI to 10 seconds) considered sufficient to establish loss of source as not transient . . . and thus prevent unnecessary switching. Return-of-source timer-adjustment dial-to adjust delay of automatic retransfer to preferred source to a period (E to 15 minutes) considered sufficient to establish that the return of voltage to the preferred source is not temporary. Overcurrent-lockout-reset timer-adjustment dial (fur- nished when the optional overcurrent-lockout feature is included-as signified by the addition of the suffix “-K” to the source-transfer control catalog number). Timer automatically turns off the lockout circuit if, following a momentary overcurrent exceeding 480 amperes, voltage returns and remains for a preset time (1 to 30 seconds), as would occur in the case of a fault cleared by feeder fuses. Operating-mode selector switch for automatic return transfer to preferred source or hold return for manual retransfer a t a convenient time. (In either position ofthe selector switch, an automatic open-transition return will take place if the alternate source fails after the preferred source has returned.) Operating-mode selector switch for open transition return (nonparalleling) or closed transition return (paralleling) on automatic retransfer to preferred source. Pushbutton test switches-to simulate loss of source voltage and (when the overcurrent-lockout feature is included) overcurrent, providing a convenient means for functional testing of the Type AT-2 control and the switch operators.
~~
Open-phase detection on/off selector switch (furnished when the optional open-phase detection feature is included-as signified by the addition of the suffix “-Ll,” “-L3,” or “-L4” to the catalog number). In the offposition, the feature is defeated to allow testing of the Type AT-2 control by means of an external single-phase source. Preferred-source and alternate-source receptacles, for interchangeable plug-in of control cables from source switches-allow field selection of either source as preferred. Voltage sensor signal-voltage test jacks and adjustment screws-permit measurement and concurrent adjust- ment of the signal voltage of each S&C Indoor Voltage Sensor to the level required by the Type AT-2 control, (Included when S&C Voltage Sensors provide voltage sensing.) Voltage-transformer secondary fuses, along with test jacks to permit measurement of each transformer signal voltage.
0 Remote monitoring provisions (furnished when the optional remote indication feature is included-as signi- fied by the addition of the suffix “-Al” to the catalog number). Includes contacts wired, through an output receptacle and plug, to a terminal block for user’s exter- nal connection to remote indicating devices. Isolated contacts are provided for remotely monitoring the pres- ence of preferred- and alternate-source voltage; the posi- tion of the manual/automatic operation selector switch; the status of the automatic-transfer “ready” indicating lamp; and, if applicable, the status of the overcurrent- lockout circuit. (Remote indicating devices and their control power are to be provided by the user.)
51 4.501 INSTRUCTION SHEET Page 4 of 15 S&C ELECTRIC COMPANY. Chicago August 29,1983 S&C ELECTRIC CANADA LTD - Rexdale
Input Receptacle (signal-voltage and control-voltagecircuits)
Fuseholders for voltage-transformer secondaryfuses
Test Jacks for measurementof signal voltage outputsof voltage transformers
Figure 4. Closeup of adjustment, testing, and programming features at rear of the Type Al-2 control. Inset shows alternatearrangement when three voltage transformers are used for each source.
Fuseholders for voltage-transformer groundrng circuit-contam solid slugs
Preferred-Source andAlternate-Source Receptacles-connector plugs areinterchangeable, to allowselection of either sourceas preferred
Pushbutton Test Switches/ to simulate loss of
source voltage
Pushbutton Test Swatchesto simulate overcurrent
- (Included with the optionalovercurrent-lockout feature,catalog-number suffrx“-K”)
Open-Phase DetectionSelector Switch(included with the optionalopen-phase detectionfeature, catalog-numberSUfflX “-Ll.” “-L3,”or “-L4”)
Remote Indication OutputReceptacle (included with theoptional remote indicationfeature, catalog-numbersuffix “-Al”)
INSTRUCTION SHEET 5141501S&C ELECTRIC COMPANY - Chicago Page 5 of 15
S&C ELECTRIC CANAOA LTO . Rexdale August 29, 1983
S&C Source-Transfer ControlsI
For Two-Way TransferType AT-2 Catalog Numbers 38881 and 38883
1 FEATURES 1
S&C Indoor Voltage Sensor, shown with base (ground) end up.
S&C Mini-Rupter Switch
\
S&C Indoor VoltageSensors-used at /
outboard poles toprovide voltage sensingfor two phases
S&C Current Sensors-furnished for attachmentto each entrance cable
N when the optionalovercurrent-lockoutfeature, catalog-numbersuffix “-K,” hasbeen included
Voltage Transformer-provides control voltage andthird-phase voltage sensing
S&C Voltage Limiters (notvisible) connected acrossoutput of each voltage sensor
S&C Current Sensor.
‘...L Threaded Mounting Inserts
(at both ends) are internallyconnected, provide for high-voltage and groundterminations
Figure 5. Entrance bay showing locations of S&C Indoor Voltage Sensors at source slae 01 nml -nuprer owmcn, ano 3&c. mmremSensors.
514m501 INSTRUCTION SHEETPage 6 of 15August 29,1983
S&C ELECTRIC COMPANY- ChicagoS&G ELECTRIC CANADA LTO - Rexdale
I FUNCTIONAL PERFORMANCE
Normal Condition Under normal conditions, with adequate voltage available from both utility sources, the preferred-source interrupter switch is closed and the alternate-source interrupter switch is open with its associated circuit available as a standby. On the front panel of the Type AT-2 control, the operation selector switch is set in the automatic position and both source-voltage indicating lamps-also the automatic-transfer “ready” indicating lamp-are lit. See “Conditions required to light ‘ready’ indicator lamp” listed on the panel and on page 13.
Transfer Induced by Loss of Source Voltage The Type AT-2 control continuously monitors the signal- input voltage levels of each phase of both sources and compares these inputs to a reference level to determine the status of each source. The control will initiate a loss-of- source transfer when both of the following conditions exist: (a) The signal-input voltage from one or more phases of
the source serving the load is reduced below a preset level (normally factory-set at 1.77 volts), for a period of time sufficient to confirm that the condition is not transient;. and The signal-input voltages from all phases of the standby source exceed a preset level (normally factory- set at 2.19 volts)..
rhus, the control will not allow a transfer to an inade- quate source. Also, repeated transfers are precluded in the event that both sources are below the acceptable level. (As a matter of information, the source-voltage indicating lamps maintain full brilliance until a source signal-input voltage is reduced to the preset level-1.77 volts or 2.19 volts, depending on which source is serving the load-at which point the applicable lamp will completely extinguish.)
If transfer to the alternate source occurs, the “ready” indicating lamp will extinguish-signaling that normal conditions no longer exist.
Return Transfer Upon return of the preferred-source voltage for a period of time sufficient to establish that the return is not temporary, automatic retransfer to that source will occur if the operating-mode selector switch at the rear of the control is positioned for automatic return. The retransfer may be
either closed transition or open transition, as pre- established by the positioning of the open-transition- returnlclosed-transition-return operating-mode selector switch. See Figure 4.
With closed transition return, $ the alternate-source inter- rupter switch will open after the preferred-source inter- rupter switch has closed, so there is no interruption of service to the load. On the other hand, with open transition return-which prevents an automatic operation that would parallel the power sources-the alternate-source inter- rupter switch will open prior to closing of the preferred- source interrupter switch . . . xhere is only a momentary interruption of service to the load..
If the operating-mode selector switch is positioned for hold return, retransfer to the preferred source must be accomplished manually-unless the alternate-source volt- age becomes inadequate (and preferred-source voltage is adequate), in which case an automatic open-transition retransfer to the preferred source will take place.
When the load is again served from the preferred source, the “ready” indicating lamp will light.
Transfer Induced by Open-Phase Condition When the optional open-phase detection feature (catalog- number suffix “-Ll,” “-L3,” or “-,,”) is included, it provides complete protection for all of the loads from any source-side open-phase condition whether caused by utility- line burndown, broken conductors, single-phase switch- ing, equipment malfunctions, or single-phasing :esulting from blown source-side fuses. This unique feature con- tinuously develops and monitors the phasor sum of the line-to-ground voltages to detect any unbalance present as the result of an open-phase condition. By summing phasor voltages, the open-phase detection feature detects all source-side open-phase conditions, even those where back- feed defeats simple voltage-magnitude sensing schemes. If unbalance exceeds a preset reference level, an output signal is produced which initiates automatic transfer to the other source.
As a point of mformatlon, I 77 volts is equlvalent to 85 volts on a 120-volt bass (correspondmg to approxlmately 70.8% of system he-to-ground voltage) and 2.19 volts IS equwalent to 105 volts on a 120-volt h a m (correspondlng to approxmately 87.5% ofsystem he-to-ground voltage)
Not to he used when parallelmg is prevented by electrlcal, mechancal, or key mterlockmg devlces. For Type MS-2 Swltch Operators combined wlth Mm-Rupter Switches,
Rupter Switches: 3 seconds. 10 cycles, for Type AS-30 Swltch Operators comhmed wnh Aldutl-
INSTRUCTION SHEET 51 4-501 S&C ELECTRIC COMPANY. Chicago Page 7 of 15 S&C ELECTRIC CANAOA LTO . Rexdale August 29, 1983
S&C Source-Transfer Controls For Two-way Transfer Type AT12 I Catalog Numbers 38881 and 38883
I FUNCTIONAL PERFORMANCE I
When equipped with the open-phase detection feature, the control will initiate an automatic source transfer -in the manner previously described on page 7 under the heading “Transfer Induced by Loss of Source Voltage”- as a result of either loss of source or source-side open- phasing when both of the following conditions exist: (a) The signal-input voltage from one or more phases of
the source serving the load is reduced below a preset level (normally factory-set at 1.77 volts); or the signal- input phase-voltage unbalance exceeds 15% for a period of time sufficient to confirm that the condition is not transient;. and
(b) The signal-input voltages from all phases of the standby source exceed a preset level (normally factory- set at 2.19 volts); and the signal-input phase-voltage unbalance is less than 15%..
Thus, the control will not allow a transfer to an inadequate source. Also, repeated transfers are precluded in the event that both sources are below the acceptable level. (As a matter of information, the source-voltage indicating lamps maintain full brilliance until a source signal-input voltage is reduced to the preset level- 1.77 volts or 2.19 volts, depending on which source is serving the load-or until the signal-input phase-voltage unbalance exceeds 15%, at which point the applicable lamp will completely extinguish.)
Upon return of the preferred-source phase voltages to their normal, balanced state, retransfer to that source can be accomplished as described on page 7 under “Return Transfer.”
Overcurrent Lockout When the optional overcurrent-lockout feature (catalog- number suffix “-K”) is included, it prevents an automatic transfer operation that would close a source switch into a fault, thereby avoiding further utility system disturbances.
An overcurrent in excess of 480f amperes (detected by a current sensor in any phase of the preferred source-see Figure 5) will set up the lockout circuit in the Type AT-2 control to prevent the alternate-source switch from closing. The overcurrent-lockout indicating lamp will light.
If the overcurrent is due to a fault that is cleared by the source-side protective device, the prolonged loss of source voltage will cause the preferred-source switch to open, and the lockout circuit will prevent the alternate-source switch from closing into the fault. (Conversely, if the load is being served from the alternate source, the above described pre- ferred/alternate functioning will be reversed.) After the fault has been located and repaired, the manual/automatic operation selector switch must first be placed in the manual position and the overcurrent-lockout reset pushbutton pressed to cancel the lockout condition-and to extinguish the overcurrent-lockout indicating lamp. Then, to restore service to the load, the manuaVautomatic operation selec- tor switch must be placed in the automatic position. Immediately, the preferred-source switch will close and the “ready” lamp will light, or, if preferred-source power is not available, the alternate-source switch will close but the “ready” lamp will not 1ight.A
If the overcurrent is due to a fault that is cleared by feeder fuses, no switching will occur since loss of source voltage is not of sufficient duration to initiate opening of the source switch serving the load. In this case, although the fault current initially sets up the lockout circuit to prevent automatic closure of the standby-source switch (and the overcurrent-lockout indicating lamp lights) the subsequent return of normal source voltage after the fault has been cleared (by the feeder fuse) actuates a lockout- reset timer. After a preset period of time (1 to 30 seconds) the lockout circuit will automatically turn off and the Type AT-2 control will restore to its previous “normal” state (and the lockout indicating lamp will extinguish).
9 As a polnt of Informatmn, 1.77 volts IS equ~valent to 85 volts on a 120-volt basls (correspondmg to approxlmately 70.8% of system he-to-ground voltage) and 2.19 volts IS equivalent to 105 volts on a 120-volt basls (correspondmg to approxlmately87.5W ofsystem he-to-groundvoltage). The 15% phase-voltage unbalance IS equivalent to 18 volts on a 120-volt basls.
t Can be factory adjusted from 200 to 700 amperes rms.
A One of the condltlons requlred to light the “ready” lamp 1s that the preferred-source swtch be closed and the alternate-source swltch be open
51 4401 INSTRUCTION SHEET Page 8 of 15 S&C ELECTRIC COMPANY Chicago August 29,1983 S&C ELECTRIC CANADA LTD Rexdale
I DIELECTRIC TESTING I The instructions which follow presuppose that the switch- gear assembly has been assembled and installed in accord- ance with the applicable metal-enclosed switchgear draw- ings, instruction sheets, and wiringdiagrams-but that the high-voltage circuits are not connected. Furthermore, the procedures described herein must be performed by quali- fied persons who are thoroughly experienced with this type of equipment.
If it is considered necessary to perform dielectric tests, make certain that the high-voltage circuits are discon- nected. Test for voltage and tag and ground all circuits in accordance with established system-operating safety proce- dures, In addition, remove the primary fuses and discon- nect all secondary connections from all voltage trans- formers, and disconnect all surge arresters. It is recom- mended that voltage-transformer primary fuses not be reinstalled-nor secondary connections of unfused voltage transformers reconnected-until just prior to final energiz- ation of the switchgear for service.
When high-voltage ac dielectric tests are to be per- formed on the switchgear, the following special precau- tionary measures must be taken to prevent damage to the Type AT-2 control and to the voltage sensors. It is recom- mended that these precautions also be followed when per-
forming high-voltage dc dielectric tests, although the application of rated dc dielectric test voltages will not damage the voltage sensors. (In certain instances, there may be additional precautionary measures required, appro- priate for the switchgear involved; in such instances, these additional precautions are listed on one of the wiring dia- grams furnished with the switchgear.) (a) Remove the plug from the input receptacle located at the
rear of the AT-2 control. Transfer the plug to the con- trol’s shorting receptacle. See Figure 4. This procedure short-circuits the secondaries of the voltage sensors and isolates the voltage transformers.
(b) Perform the dielectric tests in accordance with the user’s operating and safety procedures. Test values which apply to S&C Indoor Voltage Sensors are shown in the “Specifications” section on page 15.
(c) When dielectric testing has been completed, transfer the plug from the shorting receptacle back to the input receptacle.
Upon completion of dielectric testing (and prior to final energization of the switchgear), remove all grounds, replace voltage-transformer primary fuses, and reconnect all high-voltage conductors and surge arresters.
I ADJUSTMENTS AND PROGRAMMING I
Preliminary Tryout Before Switch- gear is Energized-Optional Ideally, the operational testing described on pages 12 and 13 should be deferred until after the adjustments and programming have been completed. However, the user may wish to perform a preliminary checkout so as to expedite full service once high voltage is available. For this reason an S&C Test Accessory, Catalog Num- ber TA- 131 6, is offered which permits checkout of the source-transfer operation of the Type AT-2 control, using an external single-phase 120-volt ac source.
If a preliminary checkout is to be performed, special instructions must be followed to ensure correct opera- tion of the Type AT-2 control. These instructions are set forth in S&C Instruction Sheet 514-605, furnished with the S&C Test Accessory. Proceed as directed therein.
Timer adjustments, preferred-source selection, and operating-mode selection can also be completed during the preliminary checkout. However, the voltage-sensor signal adjustments cannot be finalized until high volt- age has been applied to the switchgear.
INSTRUCTION SHEET 51 4.501 S&C ELECTRIC COMPANY. Chlcago Page 9 of 15 S&C ELECTRIC CANADA LTD Rexdale August 29,1983
S&C Source-Transfer Controls For Two-way Transfer Type AT-2 I Catalog Numbers 38881 and 38883
ADJUSTMENTS AND PROGRAMMING
The instructions which follow presuppose that the switch- gear assembly has been assembled and installed in accord- ance with the applicable metal-enclosed switchgear drawings, instruction sheets, and wiring diagrams, and is in all respects ready for operation, with high-voltage circuits energized.@ Furthermore, the procedures de- scribed herein must be performed by qualified persons who are thoroughly experienced with this type of equip- ment.
Before proceeding, place the manual/automatic oper- ation selector switch, located on the front panel of the Type AT-2 control, in the manual position and decouple the switch operators.
Draw out the Type AT-2 control to attain access to the rear of the device.
Timer Adjustments The electronic timers may be set, by means of their adjustment dials, to within _+ 20% of the desired time intervals. For more precise settings, operational timing must be performed (with the manuaVautornatic operation selector switch in the automatic position). The timers will maintain repetitive accuracy of i 3% of their settings.
Loss-of-source timer"62P or 62A: Must be set to initiate opening of source switch only after a time delay sufficient to allow the source breaker to make the desired number of reclosure attempts-verifying that the loss of voltage is not transient. In any case, the time-delay setting must be longer than the longest total clearing time of any of the load-side feeder fuses at the anticipated fault-current levels- including those which could result from transformer secondary- side faults. These timers are factory-set for 2 seconds but are field adjustable from 1/4 to 10 seconds.
Return-of-source timer"2P: Delays automatic retrans- fer to preferred source for a period considered sufficient to establish that return of preferred-source voltage is not temporary. This timer is factory-set for 3 minutes but is field adjustable from 1/2 to 15 minutes.
Overcurrent-lockout reset timer"62LR (furnished when the optional overcurrent-lockout feature is specified): Delays automatic turn off of the lockout circuit (set up by an overcurrent of sufficient magnitude) for a duration sufficient to establish that the return of source voltage is not temporary. (An overcurrent due to a load-side fault that is cleared by feeder fuses would be transient-no switching would occur; the timer would complete its cycle to turn off the lockout circuit. An overcurrent due to a load-side fault not cleared by feeder fuses would result in a prolonged loss of source voltage-the affected source interrupter switch would open and the other source interrupter switch would remain open and locked out . . , the timer would not time out, and lockout would remain in effect). The timer is factory-set for 20 seconds but is field adjustable from 1 to 30 seconds.
Preferred-Source Selection Either source may be selected as preferred by plugging the appropriate connecting plugs into the respective preferred- source and alternate-source receptacles on the side of the Type AT-2 control. See Figure 4. The preselected timing and automatic functions of the control are otherwise unaffected by interchanging the above cables.
Operating-Mode Selection Place the automatic-returdhold-return and open-trans- ition-returdclosed-transition-return* selector switches in the respective positions required to provide for re- transfer to the preferred source in the manner desired. The selector switches are locking-lever toggle type-lift (pull) to operate.
fIJ Upon mitlal energlzatlon, the source-voltage Indicating lamps may not light untll the voltage-sensor slgnal voltages are adjusted. See page 11 Also, check functionmg of any lamp not llghted by pushing on 1t5 len,.
* Closed-transition-return I S not to he used when parallelmg is prevented hg electrcal, mechanical, or key Interlocking devices
51 4m501 INSTRUCTION SHEET Page 10 of 15 S&C ELECTRIC COMPANY. Chicago August 29,1983 S&C ELECTRIC CANADA LTD . Rexdale
ADJUSTMENTS AND PROGRAMMING
Voltage-Sensor Signal Adjustments The S&C Indoor Voltage Sensor is a constant-current- output device, like a current transformer, and requires a secondary burden. Resistive burdens for all of the voltage sensors are located behind a panel at the rear of the Type AT-2 control. See Figure 4. Each voltage-sensor burden consists of a fixed resistor in series with a variable resistor (the voltage-sensor signal adjustment screw) to form, in effect, a voltage divider. A 2.5-volt (nominal) signal is developed across the adjustable segment of the burden to provide the sensing input for two of the phases of each source. Also behind the panel are nonadjustable voltage- dividing resistors connected across the secondary of each voltage transformer and which are similarly segmented to provide a 2.5-volt (nominal) signal for third-phase sensing of each s0urce.A
On the face of this panel are the fuseholders for the two voltage-transformer secondary fuses and slugs. In addi- tion, test jacks, for measurement of the signal voltages of the voltage transformers and S&C Indoor Voltage Sensors, and adjustment screws, for precise setting of the voltage sensor signal-voltage outputs, are provided on the face of the panel. The signal-voltage outputs of the two S&C Voltage Sensors on each source can be measured and adjusted to match the signal-voltage output of the associ- ated voltage transformer.
For each source, adjust the voltage-sensor output volt- ages as follows, using a voltmeter having a minimum input impedance of 5000 ohms per volt. (It is assumed that the phase-to-ground voltages of the source circuits are normal.)
1. Place the manual/automatic operation selector switch, located on the front panel of the Type AT-2 control in
the manual position (to prevent unexpected transfer operation while performing the following adjustments).
2. Insert the meter’s test probes into the test jacks at the voltage-transformer secondary-fuse location, on the panel at the rear of the Type AT-2 control. Measure and record the magnitude of the transformer output voltage.
3. For each voltage sensor, in turn, insert the meter’s test probes into the appropriate test jacks. Loosen the lock- ing nut on the voltage sensor signal adjustment screw and use a screwdriver to adjust the magnitude of the voltage sensor output to match that of the associated voltage transformer. Then tighten the locking nut fin- gertight. CAUTION: Overtightening of the locking nut can affect the setting. Recheck the output voltage. Note: As a matter of information, S&C Indoor Voltage
Sensors have an inherent phase shift between input and output voltages which results in the phase-to-phase output voltage differing from the normal 4.33 volts (fl X 2.5). The phase shift between input and output is 79 degrees nominal for 14.4-kv voltage sensors, and 84 degrees nomi- nal for 25-kv voltage sensors. When the optional open- phase detection feature is included (as signified by the addition of the suffix “-Ll,” “-L3,” or “-L4” to the source-transfer control catalog number), it incorporates a circuit which compensates for this condition by phase- shifting the outputs of the associated voltage transformers accordingly.
I Not applicable if three voltage transformers are used for each source to derive both sensing and control-voltage service
A In addmon to the 2.5-volt signal produced by means of the voltage- dlwding resistors, the full 120-volt output of each voltage transformer IS uthzed for the sw~tchgear control circu~ts.
INSTRUCTION SHEET 51 4m501 S&C ELECTRIC COMPANY. Chicago Page 11 of 15 S&C ELECTRIC GANAOA IT0 - Rexdale August 29,1983
s&c Source-Transfer Controls For Two-way Transfer Type AT-2 I Catalog Numbers 38881 and 38883
[OPERATIONAL TESTING (EXERCISING)
CAUTION: Make sure, before performing any switch-operator operations, that all switchgear- compartment doors are closed and securely latched. An interlock between the interrupter switch and its compartment door is furnished when Type MS-2 Switch Operators are utilized, and prevents switch operation when the door is open (or not securely latched)-therefore, an attempted operation of the interrupter switch under this condition will cause the switch operator to stall.
Since S&C Switch Operators-Type MS-2 and Type AS-30 may be conveniently decoupled from the associated S&C interrupter switches, checkout of the functional per- formance (e.g., operating sequence and timing) of the Type AT-2 control-and the switch operators-may be accomplished at any convenient time, without requiring an interruption of service. Refer to “Timer Adjustments” on page 10.
Before proceeding, make sure that the switch operators are decoupled from their interrupter switches (unless tem- porary service interruptions are permissible) and that the manual/automatic operation selector switch on the front panel of the Type AT-2 control is in the automatic position. hTote, however, that the control ulill not function automati- cally ifone switch operator is coupled and the other switch operator is decoupled.
As a point of information, when operational testing is performed with the switch operators decoupled, the “ready” indicating lamp will not function. (See “Condi- tions required to light ‘ready’ indicator lamp” on page 13.)
Loss-of-Source Testing Pushbutton test switches, for simulating loss of voltage on either the preferred or alternate source, are provided on the panel at the rear of the Type AT-2 control.
Simulate a loss of source voltage by depressing the preferred-source test pushbutton and holding it in that position long enough for the 62P timer to complete its preset cycle (% to 10 seconds) and initiate transfer. Then release the pushbutton, simulating a return of source voltage.
If the automatic-returdhold-return selector switch is programmed for automatic return, retransfer to the pre- ferred source will take place automatically after a time period equal to the setting of the 2P return-of-source timer. Retransfer will be closed transition or open transition as determined by the position of the open-transition- return/closed-transition-return selector switch.
On the other hand, if the automatic-returdhold-return selector switch is programmed for hold return (for manual return at a convenient time), no automatic retransfer will occur unless the alternate-source test pushbutton is then depressed and held in that position long enough for the 62A timer to complete its cycle (Vi to 10 seconds), in which case an automatic open-transition retransfer to the pre- ferred source will take place. Otherwise, a manual re- transfer to the preferred source may be accomplished in either of two ways: (1) Place the manual/automatic operation selector switch
on the front panel of the Type AT-2 control in the manual position to prevent automatic operation. Each associated interrupter switch+ may then be indi- vidually opened and closed to accomplish the retrans- fer (in any sequences) by means of the appropriate “Open” or “Close” pushbutton located on the Type MS-2 or Type AS-30 Switch Operator. Then place the manuaVautomatic operation selector switch in the automatic position.
(2) Temporarily place the automatic-returdhold-return selector switch on the panel at the rear of the control in its automutic return position. After retransfer to the preferred source has occurred, the automatic-return/ hold-return selector switch may again be placed in the hold return position.
Overcurrent Lockout Testing If the optional overcurrent-lockout feature is furnished, pushbutton test switches for simulation of overcurrent conditions are provided on the panel at the rear of the Type AT-2 control, These pushbuttons-one for the preferred source and one for the alternate source-are positioned directly below the corresponding loss-of-source test push- buttons. To simulate an overcurrent, momenlarily depress, then release the appropriate pushbutton. This will “set up” the lockout circuit, as indicated by illumination of the overcurrent-lockout indicating lamp on the front panel of the control. To simulate lockout, momentarily depress, then release the appropriate simulate-overcurrent push- button and, at the same time, depress and hold the associated simulate-loss-of-source pushbutton. (This will simulate a fault that is cleared by the source-side protective device.) If the simulate-loss-of-source pushbutton is held in the depressed position long enough for the associated
Although the term “mterrupter switch” IS used in referrmg to opening and closmg operations, actually, If the switch operators are in the decoupled
closed posmons condmon, only the operators w~ll move to their switch-open and switch-
a Except operatlons which would connect sources In parallel, when parallel- mg IS prevented by elrctrlcal, mechanical, or key mterlocktng devices.
51 4-501 INSTRUCTION SHEET Page 12 of 15 S&C ELECTRIC COMPANY. Chlcago August 29,1983 S&C ELECTRIC CANADA LTD Rexdale
OPERATIONAL TESTING (EXERCISING)
62P or 62A loss-of-source timer to complete its cycle, the interrupter switch+ serving the load will open-and the other interrupter switch will remain open and locked out.
To cancel the lockout condition, place the manual/auto- matic operation selector switch in the manual position and press the overcurrent-lockout reset pushbutton located on the front panel of the control. The overcurrent-lockout indicating lamp will extinguish. Then restore service by pressing the “Close” pushbutton on the preferred-source switch operator (or alternate-source switch operator if preferred-source voltage is not available). Alternately, fol- lowing cancellation of the lockout condition, service can be restored by placing the manual/automatic operation selec- tor switch in the automatic position. Immediately, the preferred-source interrupter switch will close (or the alternate-source interrupter switch will close if preferred- source voltage is not available).
On the other hand, if only the simulate-overcurrent pushbutton is momentarily depressed (simulating a fault that is cleared by feeder fuses), no interrupter-switch
action will occur. The momentary overcurrent will initially set up the lockout circuit and light the overcurrent- lockout indicating lamp on the front panel of the Type AT-2 control. However, the continuity of source voltage will start the 62LR overcurrent-lockout reset timer which, after a preset time delay, will automatically turn off the lockout circuit, extinguishing the overcurrent-lockout indicating lamp.
If any of the procedures described on pages 10 through 13-under the headings “Adjustments and Programming” and “Operational Testing (Exercising)”-were accom- plished using the S&C Test Accessory and a single-phase source (see box on page 9), restore the Type AT-2 control to its normal condition as directed in S&C Instruction Sheet 514-605.
Although the term “interrupter switch” IS used In referrmg to opening and closlng operatlons, actually, if the switch operators are ~n the decoupled conditlon, only the operators will move to thelr switch-open and swltch- closed positions.
Before Walking Away . . . So that the AT-2 control is ready for automatic opera- tion, make sure that the selector switches on the rear of the device are correctly positioned. Also make sure that the “ready” lamp is lit. See “Conditions required to light ‘ready’ indicator lamp,” as listed on the front panel of the control and at the right.
Then replace and padlock the protective steel covers (if furnished) over the Type AT-2 control and the switch operators.
Note: A lighted “ready” lamp indicates that the sta- tus of associated components is normal, but an absence of illumination does not necessarily mean that the con- trol is inoperative. For example, when transfer to the alternate source occurs, the lamp extinguishes, but the control is ready for any subsequent programmed auto- matic operation required by a change in source condi- tions. Likewise, if the entrance-bay switch operators are decoupled, the “ready” lamp is extinguished but the control is fully operative. Of course, the control will not operate if, for example: the manual/automatic opera- tion selector switch is in the manual position; the con-
nector plugs are not inserted; the associated switch- compartment doors are not closed; or an overcurrent- lockout condition exists-as indicated by illumination of the overcurrent-lockout indicating lamp.
in on position. 10. Overcurrent-lockout indicator reset (if furnished).
I
INSTRUCTION SHEET 51 4m501 S&C ELECTRIC COMPANY. Chicago Page 13 of 15 S&C ELECTRIC CANADA LTD R e x d a l e August 29,1983
S&C Source-Transfer Controls For Two-way Transfer Type AT-2 I Catalog Numbers 38881 and 38883
I MAINTENANCE I
No routine maintenance is recommended for the S&C Occasionally, check functioning of the overcurrent- Source-Transfer Control-Type AT-2 other than an lockout indicating lamp, as well as any other indicating occasional exercising-in the manner described on pages lamp not lighted, by pushing on its lens. These lamps have 12 and 13-about once per year to verify that it and its a life expectancy of two years under continuous operation. associated switch operators are operational. Experience has shown that, if any lamp fails, all lamps
should be replaced.
I SPECIFICATIONS I S&C Source-Transfer Control- Type AT-2 Control Circuit Voltage, Nominal.. ........................... 120 v ac Voltage, Operating Range. . . . . . . . . . . . . . . .80 to 140 v ac Current.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 milliamperes Fuse Rating.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FNM-5 Operating Temperature Range Ambient Adjacent to Device . . . . . . . . . -40°F to +160°F Signal-Input Circuits Voltage Input, Nominal .................... .2.5 v rms Current Input (primary of current sensor)
62A and 62P ....................... 1/4 to 10 seconds 2 P . ................................ to 15 minutes 62LR (optional) ..................... 1 to 30 seconds
Interrupting . . . . . . . . . . . 10 amperes, 120 v ac, 80% P.F. Indicating Lamps Chicago Miniature Lamp Works
Sylvania or General Electric Catalog Number .......................... CM-382
Catalog Number ............................... 382
* Equivalent to 85 volts on a 120-volt basis. A Not field adlustable
Equivalent to 105 volts on a 120-volt basis
Sensed at the primary of the S&C Current Sensors.
t Allowing for variances ~n mounting position of the current sensor, cable slze, manufacturlng tolerance, and operatmg temperatures.
@ Equivalent to 18 volts on a 120-volt basis.
i For 50-hertz applications, refer to the nearest S&C Sales Office
51 4=501 INSTRUCTION SHEET Page 14 of 15 S&C ELECTRIC COMPANY. Chicago August 29,1983 S&C ELECTRIC CANADA LTD + Aexdale
t SPECIFICATIONS 1 Optional Features Optional features which have been included in the S&C Source-Transfer Control-Type AT-2 are signifiea by the addition of one or more suffixes to the catalog number of the control, as indicated in the following table:
Source-Transfer For
Catalog Number Control
Overcurrent-Lockout Feature-Includes adlustable-delay, automatic-reset tlmer, lockout-lndlcatlng lamp, and manual-reset pushbutton
Open-Phase Detection Feature-develops and monltors the phasor sum of the line-to-ground voltages to lnltlate source transfer when source-slde open-phase condltlon occurs-even If the open phase IS backfed by connected loads, such as motors, etc
absence of preferred- and alternate-source voltage, the operatlng mode for the source-transfer Remote lndlcatlon Feature-Includes provwons to permlt remote monltorlng of the presence or
control ( I e , automatic or manual), and the status of the “ready” lndlcator Thls optlonal feature also Includes provlslons to permlt remote lndlcatlon of overcurrent lockout [where applicable)
38881 and 38883
3888 1
38883
38881 and 38883
System
Number
Control Kvl
Catalog Nominal
Transfer Rating’ ”,”,“,“p,:
4 t h r o u g h 34 5 I -K 4through I -L1
34 5
“ 12 through
through 27 6 I -L4
4 through -Al 34 5 I I
SBC Indoor Voltage Sensors For the convenience of users who normally perform electrical tests on system components, appropriate with- stand test values are given in the table below:
INDOOR VOLTAGE SENSOR RATINGS AND INSULATION TEST VALUES Rating, Kv
Catalog Number Applied Line-to-Ground System Withstand, Kv
Nom. M-Hertr, Rms@ I Dc@@ I Impulse (BIL) Max Nom. Max I I I I
81602R2-A 25 81603R2-A
8 3 17.0 14 4 14.4 29
@ Ac w~thstand tests madeon thlsequipment after shipment by S&Cshould be conducted at no more than 0 75 times the values shown. When making ac tests, the time duratlon for appllcation of the test voltage should be llmlted to less than IO seconds
@ The column headed “Dc” IS glven as a reference only for those making dc
equivalent to the correspondmg power-frequency wlthstand test values tests and represents values believed to be approprlate and approximately
9.8 16 7
95 50 36 125 70 60
specified for components of thls voltage class. The presence of this column in no way Implies any requirement for a dc withstand test on these components
@ Dc withstand tests made onthis equipment after shipment by S&Cshould be conducted at no more than 0 75 times the values shown. When making dc tests, the test voltage should be raised in dlscrete steps-one minute per step.
INSTRUCTION SHEET 51 4-501 S&C ELECTRIC COMPANY Chicago Page 15 of 15 S&C ELECTRIC CANADA LTD . R e x d a l e August 29,1983
