Underground Distribution SwitchgearFunctional Specification Guide
Type PST, Automatic Source Transfer Switchgear with iST Control PS285005ENFunctional Specification for 15 kV, 25 kV, or 35 kV Underground Distribution Switchgear with iST Control
1. Scope
1.1.This specification applies to three-phase [Select: Three way, 2 source 1 tap or Four way 2 source 2 tap], 50-60 Hz, fully dead front, self-contained automatic source transfer switchgear; with a main bus rating of 600 amperes continuous current and tap rating of {600 or 200} amperes. Unit is to be of oil insulated design, utilizing vacuum fault interrupters as a switching and interrupting means.
1.2.The unit is to be insulated with [select: E200 less-flammable fluid for operation to minus 30 degrees C, Envirotemp™ FR3™ less-flammable fluid for operation to 0 degrees C (32 degrees F), or mineral oil for operation to minus 30 degrees C] dielectric, contained in a sealed tank design, so operation is unimpaired by flood conditions or contaminated environments (except control). The unit shall utilize vacuum interrupters for all current switching and fault current interruption such that the dielectric media is not consumed or contaminated by normal operations of the interrupters. The unit shall be designed for installation on a concrete or fiberglass pad at ground level.
1.3.The transfer control shall be iST[621, or 921/901] microprocessor based programmable source transfer relay which will allow for event recording, adjustable time delays, and overcurrent protection.
1.4.The switchgear shall use resettable vacuum interrupters with microprocessor based controls for overcurrent and fault circuit protection fuses shall not be used for protection of the taps.
1.5.This specification shall only cover the purchase and shipment of switchgear. The purchaser and/or user shall be responsible for all site-work, electrical connections, programming, and installation.
2. Applicable Standards
2.1. IEEE Std C57.12.28™-2005 standard – Standard for Pad-Mounted Equipment - Enclosure Integrity
2.2. IEEE Std C57.12.29™-2005 standard – IEEE Standard for Pad-Mounted Equipment - Enclosure Integrity for Coastal Environments – applicable when stainless steel construction is specified
2.3. IEEE Std 386™-2006 standard – Standard for Separable Insulated Connector Systems for Power Distribution Systems Above 600 V
2.4. IEEE Std C37.90™-2005 standard – IEEE Standard for Relays and Relay Systems Associated with Electric Power Apparatus
2.5. IEEE Std C37.90.2™-2004 standard – Standard for Withstand Capability of Relay Systems to Radiated Electromagnetic Interference from Transceivers
Type PST, Automatic Source Transfer Switchgear PS285005EN
3. RatingsThe switchgear shall be rated* as follows:
Nominal Voltage Class, kV 15 25 35
Maximum Design Voltage, kV 15.5 27 38
BIL, kV 95 125 150
1-Minute Withstand (60 Hz) Interrupter and Terminators, kV
35 40 50
Continuous Current (max.) A 600 600 600
Interrupting Current (sym/asym) kA 12/20 12/20 12/20
Momentary Current 10 cycles (asym.) kA 12/20 12/20 12/20
1 second. (sym.), kA 12 12 12
Making Current (sym.), kA 12 12 12
Transformer Magnetizing Interrupting Current, A 21 21 21
Cable Charging Interrupting Current,A 15 15 20
Capacitive, A 10 25 40
* Continuous and short-circuit currents may be limited by ratings of selected bushings.
Minimum Full Life Fault Interrupting Duty Cycle
Percent of Interrupting Current Rating Number of Operations
15-20 88
45-55 112
90-100 32
Total 232
3.1.The switchgear shall have an ambient operating temperature range of -30 ºC to +40 ºC.
3.2.Construction
3.2.1. The underground distribution switchgear shall consist of a 2-sided, sealed tank, and with separate front and rear cable compartments. Overall height, width, depth and layout shall conform to the manufacturer’s standard construction practices for the configuration, ratings, and voltage class specified. Standard construction shall be of [select: mild steel with stainless steel hardware or 100% 304L stainless steel].
3.2.2. The liquid filled unit shall have a tamperproof bolted tank cover design, utilizing Buna-N rubber gaskets. The sealed tank (with deadfront terminators installed) shall be capable of withstanding flood immersion while energized, and shall be impervious to contaminants and animals, so as not to compromise the main insulation structure. The main and tap cable compartments shall be located at the front and back of the tank respectively. The main cable compartments shall house source bushings, source switches and transfer control. The tap compartment shall house tap bushings. Recessed lifting provisions for suitable balanced lift shall be provided on the tank ends.
3.2.3. The source compartment shall have a minimum depth of 30". The tap compartment shall have a minimum depth of 16" to provide ease of cable installation and allow for the addition of termination accessories.
3.2.4. Side-hinged cabinet style doors shall be provided. The side-hinged doors shall provide three-point latching and shall not require a center support post. Side-hinged doors shall have a door stay to
Type PST, Automatic Source Transfer Switchgear PS285005EN
manually latch the door in the open position at approximately 120º from the closed position. The right hand door on each side shall be the first opening door and shall be secured with a recessed stainless steel pentahead bolt, with provisions for padlocking. The cabinets shall be equipped with a hinged cabinet top to facilitate entry to the cable compartments; it shall open approximately 60 degrees and have door stays to hold it in the open position. The cabinet top when in the closed position shall interlock with the cabinet doors without additional means required to secure it. Cabinet construction shall meet all NEMA and ANSI security requirements as defined in the IEEE Std C57.12.28™-2005 standard and the construction requirements of the IEEE Std C37.74™-2003 standard.
3.2.5. Units shall be shipped complete with the specified liquid insulation, and relay installed.
The unit shall be equipped with a [select: 1-inch oil-fill plug and a 1-inch drain plug with 3/8” or 1” drain valve with 3/8” sampler]. A single automatic pressure relief valve shall be supplied that is hotstick-operable and located on the source-side front plate above the oil level indicator within the switchgear. The unit shall have sight gages to monitor the dielectric level located on each unit side equipped with an operating handle.
3.2.6. [select: A 1/2-13 UNC stainless steel ground nut shall be provided that is welded to the switchgear tank and mounted beneath each bushing, or, The manufacturer shall provide a factory assembled 1/2-inch diameter copper ground rod in each compartment, for use with user’s grounded clamps, that shall provide a 3 inch clearance from the ground rod to the front plate of the tank to accommodate grounding of the insulated connectors.]
3.2.7. A non-corrosive operating diagram (one-line schematic of the unit) shall be affixed to the inside of the right hand, first opening door, on both sides of the unit, if two (2) sided. A single nameplate shall be provided that is mounted on the source side tank front plate in the upper right hand corner. The nameplate shall contain the following information:
Catalog Number/Model Number Serial Number Nominal voltage class, kV Rated maximum voltage, kV BIL, kV Manufacturing Date: MM/YYYY Rated continuous current, A Rated load interrupting rating, A Momentary current rating, kA asym. Close & latch rating, kA asym. Total weight, lbs. Liquid dielectric volume (gallons)
3.2.8. Three (3) Faulted Circuit Indicator mounting provisions shall be provided in the sills beneath the cabinet doors at the position of each way. The provisions shall include a 1-1/16 diameter hole sized for Eaton’s Cooper Power series S.T.A.R ™. fault indicator small remote display, cover plate, and tamperproof mounting bolts. There shall be provisions for mounting at least one fault indicator for each equipment bushing.
3.2.9. Operations counter shall be provided on source transfer switches
3.2.10. Bushings
Bushings shall be deadfront type for use with separable connectors conforming to IEEE Std 386™-2006 standard and ANSI Standard C119.2. The source ways shall have a continuous current rating of [select: 600 ampere with bushings, or 200 ampere with wells for bushing inserts]. Tap ways shall have a continuous current rating of [select: 600 ampere with bushings, or 200 ampere with wells for bushing inserts.]
Type PST, Automatic Source Transfer Switchgear PS285005EN
[select: Six hundred (600) ampere bushings, or The two-hundred (200) ampere wells] shall be horizontally configured at 24 inches above the pad and accept molded, separable deadfront connectors. Bushings shall be mounted with minimum spacing of 8.0-inches between centerlines, except that the between the C-phase bushings which may be a minimum of 5.0-inches between centerlines. A standoff bracket or parking stand shall be supplied for each bushing and shall be mounted horizontally adjacent to each bushing on a 4.0-inch centerline from the bushing centerline. The standard phasing of the bushings from left to right shall follow the sequence ABC-CBA. Each bushing shall have identification affixed to the front plate identifying its source or tap designation, as shown on the one-line operating diagram, and its phase identification.
Where 35 kV rated switchgear with 200 amp sources or taps are specified, [select: Eaton’s Cooper Power series one-piece, loadbreak, large interface, integral bushings shall be supplied, or, bushing wells shall be supplied for use with small interface, user furnished, inserts.]
3.2.11. Source Switches
3.2.11.1. [Model 6] Source Switches shall utilize vacuum interruption only, such that the dielectric media is never contaminated by switching arc products. The source switches shall incorporate vacuum fault interrupters that shall provide both the source switching and tap fault interrupting functions. Switches shall be three-phase gang-operated vacuum switches. The switches shall incorporate Flux Shift Trippers to initiate tripping, and solenoids to initiate closing of the switches in response to signals from the transfer control. The maximum opening time after issuance of an Open or Trip signal shall be 2 cycles. The maximum close time after issuance of a Close signal shall be 5.5 cycles. As a safety precaution, the interrupter shall incorporate a trip-free mechanism to prevent the possibility of holding the interrupter closed under a faulted condition. The mechanism and the vacuum interrupters employed shall be capable of interrupting the rated continuous current [select: 600 amperes, or 200 amperes] and fault currents up 12,000 RMS amperes symmetrical.
[Model 9] Source Switches shall utilize vacuum interruption only, such that the dielectric media is never contaminated by switching arc products. The source switches shall incorporate vacuum fault interrupters that shall provide source switching. Switches shall be three-phase gang-operated vacuum switches. The switches shall incorporate Flux Shift Trippers to initiate tripping, and solenoids to initiate closing of the switches in response to signals from the transfer control. The maximum opening time after issuance of an Open or Trip signal shall be 2 cycles. The maximum close time after issuance of a Close signal shall be 5.5 cycles. As a safety precaution, the interrupter shall incorporate a trip-free mechanism to prevent the possibility of holding the interrupter closed under a faulted condition. The mechanism and the vacuum interrupters employed shall be capable of interrupting the rated continuous current [select: 600 amperes, or 200 amperes] and fault currents up 12,000 RMS amperes symmetrical.
3.2.11.2. The switches shall incorporate spring-charged operating mechanisms that are motor-driven. Both opening springs and closing springs shall be charged by a 120 Vac motor that shall run automatically after each opening operation. Sufficient energy shall be stored within the springs to allow a manual Close/Open operation upon loss of ac supply voltage. The springs must be fully charged before the switch can be closed. A manual spring charging handle shall be provided in the event that voltage is not available for motor operation and the springs are in an uncharged state. The manual operating handle for each switch shall be provided on the tank frontplate and shall allow manual trip and manual close of the switch and shall be pad-lockable in the Trip position
3.2.11.3. A spring Charged/Discharged indicator shall be visible through a viewing port located on the source side tank frontplate.
Type PST, Automatic Source Transfer Switchgear PS285005EN
3.2.12.1. The switchgear shall incorporate two vacuum fault interrupters (VFI) for tap overcurrent protection. The device shall interrupt all fault currents up to the rated maximum. The VFI shall be manually resettable, with no consumable parts (i.e. fuses). The maximum interrupting time from issuance of a trip signal from the electronic control shall be 2 cycles.
3.2.12.2. To provide maximum safety to the operator, the VFI shall incorporate a trip-free mechanism to prevent the possibility of holding the interrupter closed under a faulted condition.
3.2.12.3. The VFI shall act as a three-phase gang operated fault interrupter. The trip mechanisms for each phase shall be mechanically linked and the electronic control shall be set so that an overcurrent condition on any one phase simultaneously trips all three phases. The VFI shall be provided with a single operating handle for manual opening, reset and closing. The operating handle shall be mounted on the frontplate of the tank in the tap compartment and shall have three distinct operating positions corresponding to whether the vacuum fault interrupter is open, closed, or tripped. A pointer attached to the handle along with a decal shall be provided for ready identification of the handle position. The handle shall be designed for operation with a lineman’s hotstick and have a push to close / pull to open / pull to reset operation requiring no more than 75 lbs. of force at the handle and 60 degrees of movement for complete operation. When the vacuum fault interrupter is tripped the operating handle shall drop to an intermediate position between its closed and open positions, to indicate that it is tripped. The operating handle assembly shall include provisions to padlock the handle in the Open position. [add option if required: An operations counter shall be supplied that is externally mounted on the frontplate of the switchgear and mechanically linked to the vacuum fault interrupter operating handle.]
4. iST Relay and Control
4.1.An iST relay shall be provided for the purpose of providing source transfer control of the [PST-6 or PST-9] switchgear. In addition, overcurrent protection and metering shall be provided for the loads. The relay shall be programmable via RS-232 interface with a laptop computer, or programmable via the relay front plate.
4.2. [Model-6] the iST-621 relay provides source transfer control of the 2 sources, and OC protection and metering for the single feeder.
4.3. [Model-9] Two iST relays shall be used:
The iST-921 shall provide source transfer control of the two sources, and overcurrent protection and metering for tap 1.
The iST-901 shall provide overcurrent protection and metering for tap 2 and shall be capable of providing a fault block signal to iST-921 control with over-current pickup.
4.4.Source Transfer operation
4.4.1. Source Transfer operation shall be enabled when the following conditions are true: Non-Volatile mode Manual / Automatic is in Automatic Fault Block is disabled, or Fault Block is enabled and no OC elements are picked up
4.4.2. The iST shall initiate a transfer from one source to the other source when one or more of the enabled Transfer Parameters asserts(indicating an unhealthy source)and the Alternate Source meets all of the enabled Restoration Parameters (indicating a healthy source).
4.4.3. The operating sequence shall be:
The switch of the unhealthy source opens. If the alternate source is a utility and meets all enabled Source Restoration parameters, closing
of the alternate source switch will assert immediately.
4.4.4. If the alternate source is a generator, the Generator Power-up Contact Output will assert. Closing of the alternate source switch will occur when the generator meets all enabled Source Restoration parameters.
Type PST, Automatic Source Transfer Switchgear PS285005EN
4.4.5. In the event of a dual source outage (both sources are unhealthy),a user defined setting shall be available which will allow the user to select whether both switches shall open, or if the current switch state at the time of the outage shall be maintained . If open both is selected, the closed source switch will open. The switch of the first available healthy source shall close.
4.4.6. Restoration of normal power sequence of operation shall be dependent on the user selectable Preferred Source and Restoration Mode settings. The available options shall be:Preferred Source
Five Preferred Source settings shall be available:1) Source 1 preferred; normal restoration
o Restoration back to source 1 will occur after all enabled restoration parameters are met and the Time Delay has expired. The iST shall remain in automatic mode.
2) Source 1 preferred; hold on alternateo No restoration, Source 2 will remain closed; the iST is switched to manual mode
and no further transfers will occur until automatic mode is re-enabled.3) Source 2 preferred; normal restoration
o Restoration back to source 2 will occur after all enabled restoration parameters are met and the Time Delay has expired. The iST shall remain in automatic mode.
4) Source 2 preferred; hold on alternateo No restoration, Source 1 will remain closed; control switched to manual mode
and no further transfers will occur until automatic mode is re-enabled.5) No source preference
o Transfer between Sources 1 and 2 will occur when the closed source is unhealthy. The iST shall remain in automatic mode
Restoration ModeRestoration Mode for Preferred Source options 1, & 3 shall occur in a user defined parallel or non-parallel mode:1) If non-parallel restoration is selected: the alternate source will open, then the
preferred source will close after a customer settable time delay.2) If parallel restoration is selected: the alternate source will remain closed, the
preferred source will close when the user defined sync check parameters are met, then the alternate source will open.
3) Restoration does not occur for Preferred Source options 2, 4,& 5.
4.5.The relay will allow for user programmable Source Transfer Settings
Five selections for preferred source, described above Selection of Alternate Source: Utility or generator Fault block: Enable or Disable Restoration Mode: Non-parallel or parallel Dual-Source Outage: Maintain Closed or Open Both
4.6.User defined Source Health Settings
4.6.1. Transfer parameters – any combination shall be selectable. The source shall be determined to be unhealthy if any of the enabled parameters are met. Each parameter shall have a programmable time delay. Two levels of undervoltage: 27-1 & 27-2 One level of positive sequence undervoltage: 27P Two levels of underfrequency: 81U1 & 81U2 Two levels of overfrequency: 81O1 & 81O2
Type PST, Automatic Source Transfer Switchgear PS285005EN
4.6.2. Restoration parameters– any combination shall be selectable. The source shall be determined to be healthy if all enabled parameters are met. Each parameter shall have a programmable time delay. One level of minimum phase-ground voltage: 59 One level of minimum positive sequence voltage: 59P One level of minimum source frequency: 81U One level of maximum source frequency: 81O
4.7.User selectable and programmable Sync Check Settings
4.7.1. Sync check shall be active if parallel restoration is selected. The sync check algorithm will compare positive sequence voltage magnitude, angle, frequency, and slip to determine synchronism. The following settings shall be available to provide user programmable tolerances. Maximum delta voltage angle Maximum delta voltage magnitude Minimum time for phasors to meet Maximum delta voltage angle and Maximum delta voltage
angle Delta frequency limit Mechanism closing delay Sync. close attempt window which shall be the maximum time in which the iST will attempt a
synchronous close. Failure to sync within this time will assert a fail to sync signal. An option to allow non-parallel restoration shall be provided if a Failure to Sync occurs during a
parallel restoration. The time window to attempt a synchronous close shall be adjustable from 10 to 300 seconds.
4.7.2. In the event the iST is to operate with a standby generator, the following user programmable features shall be included when preferred source option 1 or 3 is selected.- Generator power up time (Assertion time of the generator power up contact)- Generator power down time (Assertion time of the generator power down contact)- Generator standby time (how long to keep the generator running after the preferred source is
restored and the switch is closed)
4.7.3. The generator source switch will close after the generator meets all of the enabled Source Restoration parameter settings. One or more of the following elements shall be programmable:- Minimum Phase-ground voltage- Minimum positive sequence voltage- Minimum frequency- Maximum frequency
4.7.4. Restoration from the generator back to the preferred source shall be made after the preferred source meets all of the enabled Source Restoration parameters. The user shall have the option for restoration to be parallel with sync check or non-parallel.
- Non- Parallel restoration sequence: After the preferred source is “healthy”, the generator switch opens, then the preferred source switch closes after a customer programmable time delay.
- Parallel restoration sequence: The preferred source switch will close when it is in sync with the generator, then the generator source switch will open.
4.7.5. The generator power down contact will close after the user defined generator standby timer expires
Type PST, Automatic Source Transfer Switchgear PS285005EN
When the relay is set in Automatic Mode Source Transfer operation is enabled. All front panel and SCADA switching of sources shall be blocked.
When the relay is set in Manual Mode, Source Transfer operation shall be disabled. Front panel and SCADA operation of the source switches shall be enabled.
Manual mode operation shall be supervised by the User defined Restoration Mode settings such that; when restoration mode is set to Non-parallel Mode, only one source may be closed. If one source is closed, manual closing of the second source is blocked.
When restoration mode is set to Parallel Mode, if one source is closed, manual closing of the second source is permitted, supervised by the sync check algorithm and settings as described above.
When the source transfer mode is switched from Manual to Automatic Mode, the iST shall configure the sources per the Preferred Source and Restoration Mode settings. (example: if Automatic Mode is enabled with Source 2 closed and the Preferred Source setting is Source 1, the iST will initiate restoration to Source 1 if it is healthy.)
4.9.Fault Block settings – Model-6 with iST-6214.9.1. The relay will be provided with a fault block feature which will operate in such a manner that:
4.9.2. If Fault Block is disabled, source transfer operation remains in automatic mode, regardless of the status of the OC elements.
4.9.3. If Fault Block is enabled, source transfer operations are blocked while any OC element is picked up. For a temporary fault that does not result in an OC trip, automatic operations are unblocked
when the OC element drops out. For a fault that results in an OC trip, a trip command is asserted for both sources and automatic
operations are blocked until the iST is manually reset.
4.10.Fault Block settings – Model-9 with iST-921 and iST-9014.10.1. The relay will be provided with a fault block feature which will operate in such a manner that:
4.10.2. If Fault Block is disabled, source transfer operation remains in automatic mode, regardless of the status of the OC elements.
4.10.3. If Fault Block is enabled, source transfer operations are blocked while an internal OC element is picked up or the OC pickup contact input from the iST-901 is closed.
For a temporary fault that does not result in an OC trip, automatic operations are unblocked when the OC element drops out.
For a fault on feeder #1 that results in an OC trip, the iST-921 will issue a trip command to feeder #1. Automatic operations are unblocked when the OC element drops out.
For a fault on feeder #2, the iST-901 will trip feeder #2. The fault block contact output will open when the fault is cleared. Automatic operations of the iST-921 are unblocked when the CO opens.
4.11.Overcurrent controls4.11.1. The relay shall be provided with tap overcurrent protection which is user programmable and
shall include: Individual Settings for phase and ground overcurrent and fault protection The relay shall be supplied with the following user selectable TCC curves:
o IEEEo IECo Eaton’s Cooper Power series Tri-Phase and TPG curves
Type PST, Automatic Source Transfer Switchgear PS285005EN
TF K F H
o Eaton’s Cooper Power series recloser curves (curves 106-165)
4.12.Cold Load Pickup Settings4.12.1. The relay shall be provided with tap cold load pickup settings which are user programmable
and shall include: Individual settings for phase and ground Curves:
o IEEEo IECo Eaton’s Cooper Power series Tri-Phase and TPG curves
EF TF K F H
o Eaton’s Cooper Power series recloser curves (curves 106-165)
4.13.Additional Features:
Sequence of Event recorder with capacity to store the most recent 250 events in non-volatile memory. Oscillography for fault analysis. The oscillography shall be 20 cycles long with capacity for storing the
most recent 10 events. Programmable Data Profiler to record any combination of the available metering data. Metering – instantaneous current, voltage, power factor, power, energy, demand, and harmonics
(requires PTs, available liquid insulated only) Available communications protocols shall include DNP3 via serial and TCP/IP, and Modbus via serial. Graphical programming environment for custom logic and communication point maps. Virtual Test Set for testing relay settings without the need for an external test set. Twenty-five front panel LED target to indicate relay status.
4.14.Overcurrent sensing shall be accomplished with an electronic trip control that shall be Eaton’s Cooper Power series iST control.
4.15.The control shall use internally mounted 1000:1 bushing current transformers (CTs) to sense line current, and be powered from the B phase of the internally mounted voltage sensing PTs. The control shall be self-contained and includes the following:
4.15.1. No minimum load requirement shall be necessary to meet the specified time-current characteristics.
4.15.2. The control shall have a minimum operating temperature range of -30 ºC with no more than a ±5% variation in time-current response characteristics from its response at +25 ºC.
4.16.The standard control shall provide minimum phase overcurrent trip settings that are field programmable from 25 amps to 600 amps. Trip settings may be changed while the switchgear is energized (so service is not interrupted
4.17.The control shall provide ganged tripping of the vacuum fault interrupters on each phase of the protected tap. This shall be a standard feature and shall be selectable via a switch located on the control circuit board.
Type PST, Automatic Source Transfer Switchgear PS285005EN
4.18.The control and its enclosure shall be mounted on the inside of the cabinet door of the source compartment. The control enclosures shall be [Select option: mild steel or stainless steel (as specified for the unit)] and vented in design to prevent trapping of moisture within the control. The control enclosures shall have internal thermostatically controlled 120 Vac heaters to prevent condensation in the enclosure.
4.19.The ground trip sensing portion of the control shall be capable of being de-activated
4.20.The control shall provide fuse protection on all potential inputs. The fuses shall be easily removable, to simulate a loss of phase during testing, and shall provide easy visual identification if the fuse is blown.
4.21.The source transfer control shall be mounted within the source side cable entrance compartment on the cabinet door.
5. Finish Performance Requirements
5.1.Unless otherwise specified, the switchgear shall be constructed of mild steel with stainless steel details and painted green conforming to Munsell 7GY 3.29/1.5. The coating system employed shall meet or exceed IEEE Std C57.12.28™-2005 standard coating system requirements for underground distribution equipment, including the following performance tests:
1500-hour 5% salt spray corrosion test per ASTM B117 / D1654 1000-hour humidity test per ASTM D2247 / D1654 500-hour ultraviolet accelerated weathering test per ASTM G53 / D523 Direct impact test with 160 in. lb. falling dart per ASTM D2794 Tabor abrasion test 3,000 cycles per ASTM D4060 Crosshatch adhesion per ASTM D3359
5.2. [select (additionally): for stainless steel ], The switchgear and its compartments shall be constructed of 100% 304L stainless steel painted green conforming to Munsell 7GY 3.29/1.5. The coating system employed shall meet or exceed IEEE Std C57.12.29™-2005 standard coating system requirements for underground distribution equipment in coastal environments,]
6. [select: Optional Features]
6.1.Auxiliary Switches
6.1.1.When specified, the source vacuum switches, and/or/or both VFIs, shall be provided with two stage “a” and two “b” auxiliary switches for the purpose of remote indication of status. The auxiliary switches shall be linked to the movable contact rod of the vacuum switch/VFI and shall be internally pre-wired to a MIL C-5015 style circular power connector receptacle, mounted on the front plate. The receptacle shall be provided with a mating plug for user’s cable termination. These auxiliary switches shall be rated for 15 amps @ 120 Vac / 1 amp @ 125 Vdc.
6.2.Motor Operator Mounting Provisions (Model 9 only) 6.2.1. When specified, the VFI taps shall be provided with mounting provisions for future
addition of motor operators. The provisions shall include auxiliary switches with one “a” and one “b” contact, mounting studs for motor operator mounting brackets, switch operating handles with provision for attachment to motor operators, studs and channels for routing cable connections to the future motor operator control, stud mounting provisions on the inside of one of the cabinet doors (standard location) for the future motor control, and a minimum of a 30-inch deep cabinet that shall have side-hinged doors. A semaphore shall be provided to indicate whether the VFI is open or closed.
6.3.Motor Operators (model 9 only) 6.3.1. When specified, DC motor operators, with control shall be supplied for the VFI taps. The
unit shall include all standard motor operator mounting provisions specified above. The motor operators shall utilize 24 Vdc motor actuators to open and close the respective switch or VFI. The
Type PST, Automatic Source Transfer Switchgear PS285005EN
time required to open or close a switch or VFI shall be approximately 8 seconds. The motor control shall be equipped with a 2.5 amp-hour sealed lead acid gel-cell battery to supply energy to activate the motor operators and control functions. Battery charge shall be maintained by a temperature/voltage regulated charger within the motor control that shall be capable of fully re-charging a low battery within 24 hours.
The motor control shall utilize a user supplied 120 Vac two-wire grounded supply. [optional: The control shall also have provisions for accepting a second, alternate 120 Vac supply and shall provide a transfer relay to transfer to the alternate supply if the primary 120 Vac supply is lost.] If an internal potential transformer for power supply to the motor control has been specified (see below), the unit shall be provided with all necessary wiring factory installed.
The motor control shall include the following features:
The motor control shall be capable of operating up to six motor actuators, one at a time. A local selector switch shall be provided on the control panel to select the motor actuator that is to be operated.
Open, Close, and Stop pushbuttons shall be provided for operation of the selected motor actuator.
Open and Closed indicating lights shall be provided to indicate status of the selected switch or VFI. These status lights shall use auxiliary switch inputs from the source vacuum switch or VFI to determine open or closed status.
Opening and closing indicating lights shall be provided to verify that the selected motor actuator is in process of opening or closing a switch. A lamp test pushbutton shall be provided to confirm that indicating lights are functional
A Power On/Off toggle switch shall be provided that shall disconnect the dc voltage supply from the control and any selected motor actuators and shall function as a dc circuit breaker to interrupt the dc supply in the event of a short circuit or overload.
An indicator shall be provided to verify that 120 Vac power is present and that the battery charging circuit is providing a charging voltage to the battery. A battery test pushbutton shall be supplied with test points to apply a voltmeter for testing the condition of the battery.
A Local/Remote toggle switch shall be provided. In the Local position, the switch shall allow operation of the motor actuators by the pushbuttons on the control panel only and shall not allow remote or SCADA operation. In the Remote position, the switch shall only respond to the remote or SCADA operation of the motor actuators.
The control shall include a terminal strip for connection to SCADA or remote control equipment. The terminal strip shall have connections for selecting a motor actuator with a maintained dry contact input, reading the Open/Closed status of the associated switch or VFI, initiating a Open or Close operation via a momentary dry contact, and reading the Opening/Closing status of the motor actuator as it performs the required operation.
[select: The control shall also include provisions to add a had-held extended control accessory and an interconnecting cable (length to be specified, maximum is 200 ft.). This accessory shall provide the same motor selection and operating pushbuttons as the main control that is mounted with the switchgear so as to temporarily allow operation of the motor actuators from a more remote and convenient location.]
An electrical interlock shall exist to coordinate the operation of any motor controlled switch with any separately specified visible break switch.
[select: Optional provisions, such as an internal potential transformer (to 25 kV) for power supply to the motor control, shall be supplied only when specified as a requirement for a liquid-insulated unit.]
A semaphore shall be provided to indicate whether the VFI is open or closed.
Type PST, Automatic Source Transfer Switchgear PS285005EN
Certified design test data shall be furnished upon request. The test data shall bear the seal of a Registered Professional Engineer and shall be available for the following:
7.1.Coatings per [select: IEEE Std C57.12.28™-2005 or IEEE Std C57.12.29™-2005 standard.]
8. Production Testing –
The unit shall be subjected to the following production tests:
8.1.Continuity test to assure correct internal connections.
8.2.Hi-pot test to determine dielectric strength of the unit.
8.3.Pressure test to assure tank is completely sealed.
8.4.Electrical TCC trip test.
9. Submittals
9.1. The manufacturer shall furnish a detailed list of ratings and accessories and set of drawings defined as follows [select optional: drawings for approval] :
Detailed front elevation. Single Line Base Plan Schematics
9.2. The manufacturer shall furnish instruction manuals covering the installation of the switchgear and the operation of its various components.
10. Quality Assurance10.1.The manufacturer shall be a company specializing in medium voltage underground distribution switchgear
with at least fifteen years of documented experience.
10.2.Equipment shall be built in accordance with the industry standards for medium voltage equipment.
10.3.The manufacturer shall be registered and certified as ISO 9001 compliant by a recognized international and independent body.
11. Warranty
The underground distribution switchgear shall be provided with a one-year warranty in-service/18 months maximum from date of shipment.
Type PST, Automatic Source Transfer Switchgear PS285005EN
APPENDIX A: MODELS AND WAYS
These notes are for the user of this specification guide and are not intended to be a part of the specification.
Definitions:
WAY - A “way” is defined as a connection from the exterior (either a source or a tap) to the interior switchgear bus that may be a direct electrical connection or a connection via switch or a vacuum fault interrupter. The total number of “ways” is the sum of all sources and taps. An internal bus tie switch is not a way.
MODEL or MODEL NUMBER – A shorthand method to describe a bus arrangement that includes sources, taps and tie switches that further defines the presence of switches, VFIs, and direct connections to the bus. This allows one to describe bus common arrangements without creating or transmitting drawings. Typical model number arrangements follow; these may be modified to accommodate any possible arrangement of the circuit elements.
INSERT A MODEL DIAGRAM INTO THE SPECIFICATION FROM THIS LIST OR CREATE A SKETCH (maximum of 3 ways, total):
