Metal-Enclosed Interrupter Switchgear
Initial publication
Showing changes from Initial revision
to Rev 1
in Metal-Enclosed Interrupter Switchgear.
+---
+title: Metal-Enclosed Interrupter Switchgear
+category: Electrical / Power Distribution Equipment
+description: >
+ When to use: Stand-alone metal-enclosed interrupter switchgear built to IEEE C37.20.3, rated above 1 kV through 38 kV, in which gang-operated load-interrupter switches, with or without power fuses, are the switching and protective devices, furnished as a medium-voltage service entrance, a primary-selective or loop lineup, a feeder lineup, or the primary switching ahead of separately mounted transformers, indoors or outdoors. Covers the arrangement and the automatic source transfer on a two-source lineup, the ratings, the switches and their mechanisms and operators, the power fuses, the key interlocks and grounding switches, the bus and its insulation, arc-resistant construction, the instrument transformers and the metering section, surge arresters, the cable compartments and the space the lineup provides for terminations, the enclosure, identification, factory and field testing, installation, warranty, and spares.
+ Not intended for: the load-interrupter switch furnished as the primary section of a unit substation, close-coupled to the transformer under one manufacturer of record ([[sync/secondary-unit-substations]]); metal-clad circuit breaker switchgear built to IEEE C37.20.2 ([[sync/medium-voltage-switchgear]]); pad-mounted distribution switchgear built to IEEE C37.74 with separable connectors; medium-voltage motor controllers; the transformers the lineup feeds ([[sync/medium-voltage-transformers]]); the medium-voltage cables, their terminations, and the duct bank ([[sync/medium-voltage-cables]], [[sync/underground-ductbank]]); the metal-enclosed bus that connects the lineup to other equipment ([[sync/medium-voltage-bus-duct]]); the concrete pad ([[sync/concrete-pads]]); the substation ground grid; the meters themselves ([[sync/electrical-power-monitoring]]); low-voltage transfer switches ([[sync/automatic-transfer-switches]]); paralleling switchgear ([[sync/generator-paralleling-switchgear]]); and the short-circuit, coordination, and arc-flash studies that establish the ratings and the fuse selections ([[sync/short-circuit-study]], [[sync/protective-coordination-study]], [[sync/arc-flash-study]]).
+---
+
+# Scope {toc}
+
+## Metal-enclosed interrupter switchgear is a lineup of grounded metal sections in which gang-operated load-interrupter switches make and break load current, power fuses in series with the switches clear faults where fuses are furnished, and the bus, the switches, the fuses, the instrument transformers, and the cable terminations are housed behind doors and covers so that no energized part is exposed with the enclosure closed. It is built to IEEE C37.20.3 and stands between the metal-clad circuit breaker switchgear of IEEE C37.20.2 and the pad-mounted switchgear of IEEE C37.74 in cost, in footprint, and in what it can do. {note}
+
+## This standard governs the stand-alone lineup: what the engineer decides when the switchgear is a product of its own rather than a section of something else. A load-interrupter switch that is close-coupled to a transformer under one manufacturer of record is the primary section of a unit substation and is governed by [[sync/secondary-unit-substations]]; a switch lineup that stands apart from the transformers it feeds, connected to them by cable or by metal-enclosed bus, is governed by this standard. {note}
+
+## The following are governed elsewhere and are outside this standard: {note}
+
+- metal-clad switchgear with drawout circuit breakers, under [[sync/medium-voltage-switchgear]], which this standard neither duplicates nor substitutes for where a circuit breaker is what the one-line diagram shows
+- pad-mounted distribution switchgear built to IEEE C37.74, with separable connectors and a tamper-resistant compartmental enclosure, which is not yet owned by a SynC standard
+- medium-voltage motor controllers and starters above 600 V, which are not yet owned by a SynC standard
+- the transformers the lineup feeds, under [[sync/medium-voltage-transformers]]
+- the medium-voltage cables, their terminations and splices, and the duct bank and manholes they run in, under [[sync/medium-voltage-cables]] and [[sync/underground-ductbank]]
+- metal-enclosed bus above 1 kV connecting the lineup to a transformer or to other switchgear, under [[sync/medium-voltage-bus-duct]]
+- the concrete pad as a structure, under [[sync/concrete-pads]]
+- the room that houses an indoor lineup, under [[sync/electrical-rooms]]
+- the substation ground grid and the grounding of systems over 1000 V, which [[sync/grounding-and-bonding]] excludes and which are not yet owned by a SynC standard
+- the meters and the monitoring system the metering section reports to, under [[sync/electrical-power-monitoring]]
+- automatic transfer switches rated 1000 V and below, under [[sync/automatic-transfer-switches]], and paralleling switchgear, under [[sync/generator-paralleling-switchgear]]
+- the short-circuit, coordination, and arc-flash studies, under [[sync/short-circuit-study]], [[sync/protective-coordination-study]], and [[sync/arc-flash-study]]
+- the acceptance test program, the testing organization, and the criteria the field tests are judged against, under [[sync/electrical-acceptance-testing]]
+
+## The lineup shall be furnished as one assembly of matching sections, engineered, manufactured, and tested by one manufacturer, with the bus, the switches, the fuses, and the control wiring installed and connected at the factory.
+
+## The lineup location, its orientation, and the sequence of sections from left to right shall be as indicated on [[drawing: the electrical plans and the switchgear elevation]].
+
+## The Contractor shall coordinate the incoming and outgoing cable terminations, the pad, the room or yard, the grounding, and the serving utility's requirements with the standards named in this section before the lineup is released for manufacture.
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where the contract documents, the serving utility's requirements, the Authority Having Jurisdiction, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| IEEE C37.20.3 | Standard for Metal-Enclosed Interrupter Switchgear (1 kV to 38 kV) |
+| IEEE C37.20.4 | Standard for Indoor AC Switches (1 kV to 38 kV) for Use in Metal-Enclosed Switchgear |
+| IEEE C37.22 | Standard for Preferred Ratings and Related Required Capabilities for Indoor AC Medium-Voltage Switches Used in Metal-Enclosed Switchgear |
+| IEEE C37.57 | Standard for Switchgear: Metal-Enclosed Interrupter Switchgear Assemblies, Conformance Testing |
+| IEEE C37.58 | Standard for Switchgear: Indoor AC Medium-Voltage Switches for Use in Metal-Enclosed Switchgear, Conformance Test Procedures |
+| IEEE C37.20.7 | Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults |
+| IEEE C37.20.2 | Standard for Metal-Clad Switchgear (reference for distinction from metal-enclosed interrupter switchgear) |
+| IEEE C37.74 | Requirements for Subsurface, Vault, and Pad-Mounted Load-Interrupter Switchgear and Fused Load-Interrupter Switchgear (reference for distinction) |
+| IEEE C37.40 | Standard Service Conditions and Definitions for High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories |
+| IEEE C37.41 | Standard Design Tests for High-Voltage (>1000 V) Fuses and Accessories |
+| IEEE C37.46 | Standard for High-Voltage Expulsion and Current-Limiting Type Power Class Fuses and Fuse Disconnecting Switches |
+| IEEE C37.48 | Guide and Tutorial for the Application of High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories |
+| IEEE C37.100.1 | Standard of Common Requirements for High-Voltage Power Switching Devices Rated Above 1000 V |
+| IEEE C37.90 | Standard for Relays and Relay Systems Associated with Electric Power Apparatus |
+| IEEE C57.13 | Standard Requirements for Instrument Transformers |
+| IEEE C62.11 | Standard for Metal-Oxide Surge Arresters for AC Power Circuits (>1 kV) |
+| IEEE C62.22 | Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems |
+| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
+| NEMA SG 5 | Power Switchgear Assemblies |
+| ASTM B187 | Standard Specification for Copper, Bus Bar, Rod, and Shapes and General Purpose Rod, Bar, and Shapes |
+| ASTM B317 | Standard Specification for Aluminum-Alloy Extruded Bar, Rod, Tube, Pipe, Structural Profiles, and Profiles for Electrical Purposes (Bus Conductor) |
+| NFPA 70 | National Electrical Code (Articles 110, 230, 240, 250, and 495; Article 490 in editions before 2023) |
+| NFPA 70E | Standard for Electrical Safety in the Workplace |
+| ANSI/NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 13) |
+| ICC-ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing of Nonstructural Components |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following for review before the lineup is released for manufacture:
+
+- an outline drawing of the lineup showing every section in plan and elevation, the shipping splits, the weight of each shipping section, the lifting and jacking provisions, the anchor pattern, the conduit entry areas, the cable compartment dimensions, and the clearances the manufacturer requires in front of, behind, and above the lineup
+- a one-line diagram of the lineup showing every switch, every fuse, every instrument transformer, every surge arrester, the bus, and the ratings of each
+- a ratings summary stating the rated maximum voltage, the BIL, the main bus continuous current, the continuous current of each switch, the momentary, fault-closing, and short-time ratings, and the fuse interrupting rating, with the basis on which each was established
+- the three-line, schematic, and wiring diagrams of the control, metering, and interlock circuits
+- the transfer scheme sequence of operation and the control logic, where automatic source transfer is selected
+- the key interlock schedule listing every lock, every key, and the sequence each key enforces
+- the manufacturer's certification that the switches, the fuses, and the assembled lineup comply with the referenced standards for the ratings furnished
+- the seismic qualification certificate for the lineup as configured, where seismic qualification is required
+- the nameplate schedule listing the text to appear on the lineup, section, switch, and fuse nameplates
+
+```datasheet
+label: Action Submittal Package
+type: checkbox
+options:
+ - "Lineup outline drawing"
+ - "Lineup one-line diagram"
+ - "Ratings summary"
+ - "Three-line, schematic, and wiring diagrams"
+ - "Transfer scheme sequence of operation and control logic"
+ - "Key interlock schedule"
+ - "Manufacturer's certification of compliance"
+ - "Seismic qualification certificate"
+ - "Nameplate schedule"
+default:
+ - "Lineup outline drawing"
+ - "Lineup one-line diagram"
+ - "Ratings summary"
+ - "Three-line, schematic, and wiring diagrams"
+ - "Key interlock schedule"
+ - "Manufacturer's certification of compliance"
+ - "Nameplate schedule"
+constraint: all_of
+```
+
+### The lineup shall not be released for manufacture until the action submittals covering it have been reviewed and returned.
+
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following with or before the action submittals:
+
+- the manufacturer's qualification statement required under Quality Assurance
+- the factory test procedure for the lineup, where witnessed testing is selected in the datasheet
+- the field acceptance testing firm's qualification statement and the proposed field test procedure for the lineup
+- the manufacturer's published derating factors applied for ambient temperature and altitude, where either exceeds the usual service conditions of IEEE C37.20.3
+- the serving utility's written acceptance of the metering section, where a utility metering section is selected
+
+```datasheet
+label: Informational Submittal Package
+type: checkbox
+options:
+ - "Manufacturer qualification statement"
+ - "Factory test procedure"
+ - "Field testing firm qualification and test procedure"
+ - "Ambient and altitude derating factors"
+ - "Utility acceptance of the metering section"
+default:
+ - "Manufacturer qualification statement"
+ - "Field testing firm qualification and test procedure"
+constraint: all_of
+```
+
+## Closeout Submittals {toc}
+
+### The Contractor shall submit the following before the lineup is accepted:
+
+- the certified factory test report for the lineup, identified by serial number
+- the field acceptance test report, giving every measured value, the acceptance criterion applied, and the tester's determination
+- the recorded sequence of the transfer scheme as tested, where automatic source transfer is selected
+- record drawings reflecting every field change to the arrangement, the wiring, and the settings
+- the fuse ratings installed at every position and the settings of every relay and transfer control, as left in service
+- the arc-flash incident energy labels installed, with the study revision they were taken from
+- operation and maintenance data covering the switches, the fuses, the operators, the interlocks, and the transfer control
+- the key interlock keys, delivered to the Owner with a signed receipt
+- the warranty certificate identifying the lineup serial number and the warranty commencement date
+- a signed receipt from the Owner for the spare parts delivered
+
+```datasheet
+label: Closeout Submittal Package
+type: checkbox
+options:
+ - "Factory test report"
+ - "Field acceptance test report"
+ - "Transfer scheme as-tested sequence record"
+ - "Record drawings"
+ - "Installed fuse ratings and final settings"
+ - "Arc-flash label record"
+ - "Operation and maintenance data"
+ - "Key interlock keys and receipt"
+ - "Warranty certificate"
+ - "Spare parts receipt"
+default:
+ - "Factory test report"
+ - "Field acceptance test report"
+ - "Record drawings"
+ - "Installed fuse ratings and final settings"
+ - "Operation and maintenance data"
+ - "Key interlock keys and receipt"
+ - "Warranty certificate"
+ - "Spare parts receipt"
+constraint: all_of
+```
+
+# Quality Assurance {toc}
+
+## Manufacturer Qualifications {toc}
+
+### The lineup shall be produced by a manufacturer that has furnished metal-enclosed interrupter switchgear of the voltage class selected for not less than the period indicated in the datasheet.
+
+```datasheet
+label: Manufacturer Production Experience
+type: range
+unit: years
+options:
+ min: 0
+ max: 20
+ setpoints: [0, 3, 5, 10, 20]
+default: 5
+constraint: min
+```
+
+### The manufacturer shall maintain a factory-trained field service organization able to reach the site, and shall state the location of the nearest such office in the qualification statement.
+
+### The switches, the fuses, the bus, and the enclosure shall be furnished by one manufacturer as one assembly, and a switch or a fuse of another make shall be furnished only where the manufacturer of the lineup has tested the combination to the referenced standards and certifies the ratings of the lineup with that device installed.
+
+## Listing and Certification {toc}
+
+### The lineup shall comply with IEEE C37.20.3 and shall bear the manufacturer's certification of compliance, and where a Nationally Recognized Testing Laboratory offers a listing or a certification program for metal-enclosed interrupter switchgear of the rating furnished, the lineup shall carry that listing or certification.
+
+### The switches shall comply with IEEE C37.20.4 and shall be rated in accordance with IEEE C37.22, and the power fuses shall comply with IEEE C37.46 and shall have been design-tested in accordance with IEEE C37.41.
+
+### Where the lineup is service equipment, it shall be marked as suitable for use as service equipment, and the marking shall be accepted by the Authority Having Jurisdiction and the serving utility before the lineup is released for manufacture.
+
+## Field Testing Firm {toc}
+
+### Field acceptance testing of the lineup shall be performed by the firm indicated in the datasheet.
+
+```datasheet
+label: Field Acceptance Testing Firm
+type: radio
+options:
+ - "Independent testing firm accredited to ANSI/NETA ATS"
+ - "Manufacturer's field service organization"
+ - "Installing contractor's own technicians"
+```
+
+### An independent firm has no stake in whether the lineup passes and reports against a published acceptance standard; the manufacturer's organization knows the switches, the operators, and the transfer control best and is already on site for start-up; the installing contractor's own technicians cost least and are available on the installer's schedule. Which of these the Owner wants depends on how the results will be used, and on whether a report from the party who built or installed the equipment would satisfy the Owner's insurer and the Authority Having Jurisdiction. {note}
+
+### The field testing firm shall be qualified in accordance with [[sync/electrical-acceptance-testing]], and its technicians shall hold a current certification for medium-voltage equipment testing from NETA or from the manufacturer of the equipment tested.
+
+# Environmental and Service Conditions {toc}
+
+## Ambient Temperature {toc}
+
+### The lineup shall carry its nameplate ratings at the design ambient temperature of the room indicated in the datasheet.
+
+```datasheet
+label: Indoor Design Ambient Temperature
+type: range
+unit: °C
+options:
+ min: 30
+ max: 50
+ setpoints: [30, 40, 45, 50]
+default: 40
+constraint: min
+```
+
+### The usual service conditions of IEEE C37.20.3 establish the ratings at a 40 °C maximum ambient, so a 40 °C design ambient is the condition at which the nameplate applies without correction; a higher value buys margin for a room whose ventilation cannot hold that ambient with the lineup at design load, at the cost of a larger bus or a larger switch for the same nameplate. {note}
+
+### Where the lineup is installed outdoors and [[parameter: site-ambient-temperature-maximum]] exceeds 40 °C, the manufacturer shall derate the bus, the switches, and the fuses in accordance with the published factors of the referenced standards and shall state the derated ratings in the ratings summary.
+
+### Where the lineup is installed outdoors, the switches, the operators, and the control devices shall be rated to operate at [[parameter: site-ambient-temperature-minimum]], and the manufacturer shall state in the product data any heater or lubricant the operators require to meet that temperature.
+
+## Altitude {toc}
+
+### The lineup shall be derated for [[parameter: altitude]] in accordance with the correction factors of IEEE C37.20.3 where the altitude exceeds the 1000 m usual service condition, for both dielectric strength and continuous current, and the derated ratings shall be stated in the ratings summary.
+
+### Air thins with altitude, which reduces both the dielectric strength of the air clearances the switches and the bus depend on and the convective cooling that sets the continuous current rating, and an air-insulated switch loses dielectric margin at elevation faster than the bus loses current, so the BIL correction is the one that most often changes what is bought. {note}
+
+### Ambient temperature derating and altitude derating shall be applied cumulatively where both conditions apply.
+
+## Condensation Control {toc}
+
+### Where the lineup is installed outdoors or in a space that is not conditioned, a thermostatically controlled space heater shall be furnished in every section, including every cable compartment.
+
+### Where space heaters are furnished, they shall be sized to hold the interior of each section above the dew point at [[parameter: site-ambient-temperature-minimum]], and shall be supplied from a circuit that stays energized with every switch in the lineup open.
+
+### Condensation on the insulators, the fuse mountings, and the cable terminations is the mechanism behind most tracking failures on outdoor and unheated medium-voltage switchgear, and the cable compartment, which is the lowest and coolest space in the section, is where it forms first. {note}
+
+## Seismic Qualification {toc}
+
+### The seismic qualification of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Seismic Qualification
+type: select
+derived: "[[parameter: seismic-design-category]] and the component importance factor ASCE 7 Chapter 13 assigns to the lineup"
+options:
+ - "Not required"
+ - "Anchorage design only per ASCE 7 Chapter 13"
+ - "Shake-table qualification per ICC-ES AC156 with component importance factor 1.0"
+ - "Shake-table qualification per ICC-ES AC156 with component importance factor 1.5"
+default: derived
+```
+
+### Where seismic qualification is required, it shall be performed in accordance with the seismic provisions of [[parameter: adopted-building-code]] and ASCE 7 Chapter 13, and the certificate shall cover the lineup as furnished, including the heaviest arrangement of switches, fuses, and instrument transformers in any section.
+
+### Whether the lineup must be qualified follows from the seismic design category, and whether it must remain operable after the design earthquake, rather than merely stay anchored, follows from the component importance factor; neither is decided within this standard. {note}
+
+# Lineup Arrangement {toc}
+
+## Service Configuration {toc}
+
+### Whether the lineup is the service disconnecting means shall be as indicated in the datasheet.
+
+```datasheet
+label: Service Configuration
+type: radio
+drawing_ref: "the one-line diagram"
+options:
+ - "Lineup is the service disconnecting means for a medium-voltage service"
+ - "Fed from premises medium-voltage distribution downstream of the service"
+default: deferred
+```
+
+### Where the lineup is the service disconnecting means, it shall comply with NFPA 70 Article 230 Part VIII and the article governing equipment over 1000 V, shall carry the available fault current marking NFPA 70 110.24 requires, and shall provide the metering, sealing, and access provisions the serving utility requires.
+
+### The Contractor shall confirm the serving utility's nominal primary voltage, its system grounding, and the available fault current at the point of connection before the lineup is released for manufacture, and shall report any difference from the one-line diagram to the Engineer of Record.
+
+## Switching Arrangement {toc}
+
+### The switching arrangement of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Switching Arrangement
+type: select
+options:
+ - "Single incoming switch with feeder switches on one bus"
+ - "Feeder switches only, fed from upstream equipment with no incoming switch"
+ - "Duplex, two incoming switches on one bus"
+ - "Main-tie-main, two incoming switches and a bus tie switch"
+ - "Loop, two incoming switches with a fused tap to the load"
+```
+
+### A single incoming switch with feeders is the radial lineup of a plant fed from one source, and the loss of the source or the switch drops every feeder. A feeder lineup with no incoming switch depends on the upstream device to isolate the bus and is the arrangement where that device is close, dedicated, and lockable. A duplex lineup puts two incoming switches on one bus so that the bus can be fed from either source, and the transfer is a two-switch operation with one bus; a main-tie-main lineup splits the bus so that each source normally carries its own half and either source can carry both through the tie, at the cost of a third switch and a longer lineup. A loop arrangement passes a primary loop through the lineup with a switch on each leg and a fused tap to the load, so that the load is fed from either direction and a cable fault is isolated by opening the two switches that bound it. {note}
+
+### The number of switch positions, the rating of each, the loads each serves, and the spare and future positions shall be as indicated on [[drawing: the one-line diagram]].
+
+### Where a spare or future position is indicated, the section shall be furnished with the bus, the bus connections, and the barriers for that position, and the switch and the fuses shall be installed where the one-line diagram shows them and omitted where it shows the position as a provision for future equipment.
+
+## Source Transfer Control {toc}
+
+### The control of transfer between the two sources of a duplex or main-tie-main lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Source Transfer Control
+type: radio
+options:
+ - "Manual transfer at the switches"
+ - "Automatic source transfer with motor-operated switches"
+ - "Not applicable, single-source lineup"
+```
+
+### Manual transfer leaves the operator to open the failed source and close the other, which costs an outage lasting as long as it takes someone to reach the lineup and is the arrangement where the loads can tolerate that or where an attendant is always present; automatic transfer senses the loss of a source and performs the same two operations through motor operators in seconds, at the cost of the operators, the control, a control power source that survives the loss of either source, and a scheme that must tell a lost source from a cleared fault before it acts. A switch opens the failed source before the other closes, so the transfer is open-transition by construction, and the decisions left are the delays and the return to normal. {note}
+
+### Where automatic source transfer is selected, the incoming switches and the tie switch shall be furnished with motor operators, and the manual operation of each switch shall remain available with the operator installed.
+
+## Automatic Source Transfer {toc}
+
+### Requirements in this article apply where the datasheet selects automatic source transfer. {note}
+
+### Loss of a source shall be sensed by voltage sensing on each incoming side through voltage transformers or capacitive voltage sensors furnished within the lineup, with a loss-of-source time delay before transfer as indicated in the datasheet.
+
+```datasheet
+label: Transfer Time Delay After Loss of Source
+type: range
+unit: s
+options:
+ min: 0.5
+ max: 30
+ setpoints: [0.5, 1, 2, 3, 5, 10, 15, 30]
+constraint: exact
+```
+
+### The return of the lineup to its normal configuration after the preferred source returns shall be as indicated in the datasheet.
+
+```datasheet
+label: Return to Normal
+type: radio
+options:
+ - "Automatic retransfer after the retransfer time delay"
+ - "Manual retransfer by the operator"
+```
+
+### Where automatic retransfer is selected, retransfer shall be delayed after the preferred source returns for the period indicated in the datasheet, so that an unstable source does not cause repeated transfers.
+
+```datasheet
+label: Retransfer Time Delay After Source Return
+type: range
+unit: s
+options:
+ min: 5
+ max: 600
+ setpoints: [5, 10, 30, 60, 120, 300, 600]
+constraint: exact
+```
+
+### A short transfer delay limits the outage the loads see but transfers on a momentary dip the source would have recovered from; a long one rides through the dip at the cost of a longer outage when the source is really gone, and a motor-heavy plant sets it so that the motors have dropped out before the alternate source is closed onto them. Automatic retransfer returns the lineup to normal unattended and imposes a second outage on the loads when it does, which an operator choosing the moment avoids. {note}
+
+### The scheme shall not transfer where a fuse has operated on the bus side of the incoming switch, where a protective relay furnished in the lineup has detected a fault on the bus, or where the alternate source is itself out of limits, and shall indicate a lockout that requires a manual reset at the lineup.
+
+### Closing the alternate source onto a bus whose fuse cleared a fault puts the second source onto the same fault, so the scheme distinguishes a lost source from a cleared fault before it acts. {note}
+
+### The control power for the transfer scheme and the motor operators shall be as indicated in the datasheet.
+
+```datasheet
+label: Transfer Scheme Control Power
+type: select
+options:
+ - "Control power transformer on each source with automatic throw-over"
+ - "125 V DC station battery"
+ - "Uninterruptible power supply within the lineup"
+```
+
+### Control power transformers on both sources with a throw-over keep the scheme alive as long as either source is present and need no battery, and they leave the scheme dead through the instant both sources are lost; a station battery operates the switches with both sources lost and is what a plant that already keeps one for its relays connects to, with the battery furnished and maintained under [[sync/dc-battery-systems]]; a supply within the lineup gives the scheme its own stored energy without a battery room, at the cost of a battery inside the switchgear that the Owner must replace on its own schedule. {note}
+
+### The transfer scheme controls, including an automatic-manual selector switch, source and switch position indication, a test provision, and the lockout indication, shall be mounted in a low-voltage control compartment isolated from the medium-voltage compartments.
+
+# Electrical Ratings {toc}
+
+## Voltage Class and Insulation Level {toc}
+
+### The voltage class of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Voltage Class
+type: select
+options:
+ - "5 kV class"
+ - "8.25 kV class"
+ - "15 kV class"
+ - "27 kV class"
+ - "38 kV class"
+```
+
+### The voltage class is the rated maximum voltage of IEEE C37.20.3 that the lineup is built to, and it fixes the BIL, the phase spacing, the switch clearances, and the depth of the section: a 5 kV class lineup serves 2.4 kV and 4.16 kV systems, the 8.25 kV class serves 6.9 kV and 7.2 kV systems, the 15 kV class serves every system from 12 kV through 14.4 kV and is the class most of the market is built for, and the 27 kV and 38 kV classes serve 20 kV through 34.5 kV systems at a larger section and a longer fuse. A lineup is sometimes bought one class above its system so that a later conversion of the distribution voltage does not replace it, at the cost of the larger section. {note}
+
+### The nominal system voltage and the system grounding the lineup is applied on shall be as indicated on [[drawing: the one-line diagram]].
+
+### The BIL of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Basic Impulse Insulation Level
+type: range
+unit: kV
+derived: "the voltage class, per the insulation level table of IEEE C37.20.3, corrected for [[parameter: altitude]] where the altitude exceeds the usual service condition"
+options:
+ min: 60
+ max: 150
+ setpoints: [60, 95, 110, 125, 150]
+default: derived
+constraint: min
+```
+
+### The BIL is assigned by IEEE C37.20.3 to each rated maximum voltage, so the field records a consequence of the voltage class rather than a preference, and the one case that changes it is an altitude above the usual service condition, where the manufacturer either applies the correction factor to the clearances or furnishes the next higher class. {note}
+
+### The system frequency shall be as indicated in the datasheet.
+
+```datasheet
+label: System Frequency
+type: radio
+options:
+ - "60 Hz"
+ - "50 Hz"
+default: "60 Hz"
+```
+
+## Continuous Current {toc}
+
+### The main bus continuous current rating shall be as indicated in the datasheet.
+
+```datasheet
+label: Main Bus Continuous Current
+type: range
+unit: A
+drawing_ref: "the one-line diagram"
+options:
+ min: 600
+ max: 3000
+ setpoints: [600, 1200, 2000, 3000]
+default: deferred
+constraint: min
+```
+
+### Each switch shall be rated for not less than the continuous current shown at its position on the one-line diagram, and the incoming switches and the tie switch of a two-source lineup shall each be rated to carry the combined load of both sources.
+
+### Where power fuses are furnished, the continuous current rating of the fuse mounting and of the fuse unit shall be not less than the continuous current of the position, and the fuse unit shall be applied within the continuous current limit IEEE C37.48 assigns to its type and its enclosure.
+
+### The bus is sized once for the lineup, and the switches are sized by position, so a 1200 A bus with 600 A feeder switches is the usual lineup and a 600 A bus feeding 600 A switches is the small one; a two-source lineup carries the whole plant through one incoming switch when the other source is lost, which is why the incoming and tie switches are rated for both halves. {note}
+
+## Short-Circuit Ratings {toc}
+
+### The short-circuit rating of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Short-Circuit Rating
+type: range
+unit: kA
+derived: "the available symmetrical fault current at the lineup established by the short-circuit study, with the momentary, fault-closing, and short-time ratings of the switches and the bus each not less than the corresponding duty"
+options:
+ min: 12.5
+ max: 63
+ setpoints: [12.5, 16, 20, 25, 31.5, 40, 50, 63]
+default: derived
+constraint: min
+```
+
+### A load-interrupter switch can make and carry a fault but not break one: it carries a momentary rating for the first cycles of a fault, a fault-closing rating for the case where it is closed onto one, and a short-time rating for the time the fuse or the upstream device takes to clear, and it carries no interrupting rating at all. The fuses interrupt, or the upstream device does where the switch is unfused, and the lineup is rated for the duty the study establishes rather than for a preference. {note}
+
+### The bus and every bus connection shall be braced for the momentary current corresponding to the short-circuit rating, and the bus bracing shall have been verified by design tests under IEEE C37.20.3 on a bus of the same construction, spacing, and support.
+
+### Where power fuses are furnished, the fuse interrupting rating shall be not less than the short-circuit rating at the rated maximum voltage, and where the fuses are current-limiting the switch and the bus may be applied at the let-through current the fuses establish only where the manufacturer has tested the combination and certifies it.
+
+### Where an incoming switch is unfused, the short-time rating of the switch and the bus shall be not less than the short-circuit rating for the clearing time of the upstream device shown on the one-line diagram, and the Contractor shall report a clearing time longer than the rated short-time duration to the Engineer of Record before the lineup is released for manufacture.
+
+# Load-Interrupter Switches {toc}
+
+## Switch Type {toc}
+
+### The load-interrupter switch type shall be as indicated in the datasheet.
+
+```datasheet
+label: Load-Interrupter Switch Type
+type: select
+options:
+ - "Air load-interrupter switch"
+ - "SF6-insulated load-interrupter switch"
+ - "Vacuum load-interrupter switch with air-insulated isolating disconnect"
+```
+
+### An air switch interrupts in air through arc chutes, gives a visible open gap that an operator can see through the viewing window, and is the switch most of the market is built around, with a contact life set by the number of load interruptions and an arc that the chutes must contain. An SF6 switch interrupts in a sealed gas tank, has a smaller footprint at the higher voltage classes and a contact life well beyond an air switch, and depends on the gas pressure, which the lineup monitors, and SF6 is a greenhouse gas whose handling and reporting some jurisdictions regulate. A vacuum switch interrupts in a sealed bottle with the longest contact life of the three and no arc in air, and because a vacuum bottle gives no visible gap it is furnished with an air-insulated disconnect in series so that the isolation can be seen, at the cost of a second device in each position. {note}
+
+### Each switch shall be a three-pole, two-position, gang-operated switch complying with IEEE C37.20.4, rated for the rated maximum voltage, the continuous current of its position, and the momentary, fault-closing, and short-time duty established under Electrical Ratings.
+
+### Each switch shall be furnished with a quick-make, quick-break stored-energy operating mechanism whose closing and opening speeds are independent of the speed of the operator.
+
+### A switch closed slowly onto a fault welds, and a switch opened slowly under load draws an arc the chutes were not designed for; the stored-energy mechanism charges a spring through the handle stroke and releases it at the end, so the blade speed is the spring's and not the operator's. {note}
+
+### An SF6 switch shall be furnished with a gas density monitor with alarm and lockout contacts wired to the control compartment, and a vacuum switch shall be furnished with a means to verify the vacuum integrity of each bottle without removing the switch from the section.
+
+## Switch Position Indication and Viewing Windows {toc}
+
+### Each switch shall be furnished with a viewing window in the compartment door through which the position of every blade, or of every pole of the isolating disconnect, can be verified with the door closed.
+
+### Each switch shall carry mechanical open and closed position indication at the operating handle, driven by the switch shaft and not by the mechanism.
+
+### A window shows the blade and the indicator shows the shaft, and the two agree except on the day a linkage has broken, which is the day the window is what keeps an operator from racking into a closed switch. {note}
+
+### Each switch position shall be furnished with capacitive voltage indicators on the load side of the switch, visible with the door closed.
+
+## Switch Operation and Locking {toc}
+
+### The operating handle of each switch shall be lockable in the open and closed positions and shall accept not fewer than three padlocks in the open position.
+
+### The switch compartment door shall be interlocked so that it cannot be opened with the switch closed and the switch cannot be closed with the door open, with a tool-operable defeat for authorized testing.
+
+### The motor operators furnished in the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Motor Operators
+type: select
+options:
+ - "Manual operation at every switch"
+ - "Motor operators on the incoming and tie switches"
+ - "Motor operators on every switch"
+```
+
+### A motor operator lets a switch be opened or closed from outside the arc-flash boundary, from a remote station, or by a transfer scheme, and it costs an operator, a control circuit, and a control power source for each; a plant that operates its feeders rarely motorizes only the source switches a transfer scheme needs, and a plant whose feeders are switched often, or whose incident energy at the lineup is high, motorizes every switch so that no operator stands at the door to switch. {note}
+
+### Where a motor operator is furnished, the switch shall be manually operable with the operator installed, the manual operation shall be blocked while the operator is in motion, and a local-remote selector at the switch shall disable remote operation while the switch is being operated by hand.
+
+## Grounding Switches {toc}
+
+### Grounding switches in the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Grounding Switches
+type: radio
+options:
+ - "No grounding switches"
+ - "Grounding switch on each incoming cable compartment"
+ - "Grounding switch on the load side of every switch position"
+```
+
+### A grounding switch grounds a de-energized circuit before work begins and depends on an interlock to keep it off an energized one; a switch on each incoming compartment grounds the cable from the source, which is the cable an operator cannot otherwise isolate from the lineup, and a switch on every position grounds each feeder cable as well, at a cost per position, which suits a plant whose feeders are worked often. A lineup with no grounding switch is grounded with portable grounds through the grounding provisions this standard requires in every cable compartment. {note}
+
+### Each grounding switch shall be a three-pole, gang-operated switch rated for the fault-closing duty of the lineup, interlocked so that it cannot be closed unless the associated switch is open and locked, and so that the associated switch cannot be closed while the grounding switch is closed.
+
+### A grounding switch rated only to carry the fault current is closed onto a circuit that someone has forgotten to de-energize, which is why its fault-closing rating is the rating that matters. {note}
+
+## Switch Accessories {toc}
+
+### Each switch position shall be furnished with the accessories indicated in the datasheet.
+
+```datasheet
+label: Switch Accessories
+type: checkbox
+options:
+ - "Blown-fuse trip of the switch on a fused position"
+ - "Shunt trip of the switch from an external device"
+ - "Remote open and closed position indication contacts"
+ - "Infrared inspection windows at the switch and fuse connections"
+ - "Mimic bus on the front of each section"
+ - "Provision for a portable ground on the load side of each switch"
+default:
+ - "Remote open and closed position indication contacts"
+ - "Provision for a portable ground on the load side of each switch"
+constraint: all_of
+```
+
+### A blown-fuse trip opens the switch when one fuse operates, so that a transformer or a motor downstream does not run single-phased on the remaining two, which is the condition that overheats both; a shunt trip lets a transformer protective device or a remote station remove the feeder from the system, and it is available only on a switch with a stored-energy trip; position contacts tell a supervisory system what the lineup is doing; infrared windows let the connections be scanned under load with the doors closed; a mimic bus keeps an operator oriented at a long lineup. {note}
+
+# Power Fuses {toc}
+
+## Fused and Unfused Positions {toc}
+
+### Feeder switch positions shall be fused or unfused as indicated in the datasheet.
+
+```datasheet
+label: Feeder Switch Fusing
+type: radio
+options:
+ - "Fused"
+ - "Unfused"
+```
+
+### Incoming and tie switch positions shall be fused or unfused as indicated in the datasheet.
+
+```datasheet
+label: Incoming and Tie Switch Fusing
+type: radio
+options:
+ - "Fused"
+ - "Unfused"
+ - "Not applicable, no incoming or tie switch"
+```
+
+### A fused position clears a fault on its own cable or transformer at the lineup, with a fuse that is replaced rather than reset, and a fused feeder is what makes a switch lineup a protective device rather than a switching point; an unfused position leaves protection to the device upstream and is the arrangement where that device is dedicated and close, where the position feeds another lineup that carries its own protection, or where the position is an incoming switch under a utility's or a circuit breaker's protection. A fused incoming switch protects the bus and clears a bus fault at the lineup, and it costs a fuse large enough to carry the whole bus load, which at the higher bus ratings is at or beyond the largest fuse the class offers. {note}
+
+### Where a feeder position is unfused, the overcurrent protection of the circuit it feeds shall be provided by the device shown on [[drawing: the one-line diagram]], and the switch shall be interlocked with that device so that the switch cannot be opened or closed with the device closed, unless the switch is rated for the load-break duty and the Engineer of Record accepts live switching in writing.
+
+## Fuse Type {toc}
+
+### Where power fuses are furnished, the fuse type shall be as indicated in the datasheet.
+
+```datasheet
+label: Power Fuse Type
+type: select
+options:
+ - "Current-limiting power fuses"
+ - "Solid-material boric-acid power fuses"
+ - "Expulsion power fuses"
+ - "Not applicable, unfused lineup"
+```
+
+### A current-limiting fuse clears a high-magnitude fault within the first half cycle and limits the peak current the bus, the switch, and the downstream equipment see, which is what lets a lineup be applied where the available fault current exceeds the switch's momentary rating, and it vents no gas, so it is applied indoors without provision for discharge, at the cost of a fuse that cannot interrupt a low overcurrent and must be backed by the switch or by a second element for that range. A solid-material boric-acid fuse clears every current from its minimum melting current through its interrupting rating in one element, with a time-current characteristic that coordinates readily with a transformer's inrush and damage curve, and it discharges gas and water vapor when it operates, which an indoor installation handles with a muffler or an exhaust provision and which sets the fuse's interrupting rating below a current-limiting fuse of the same class. An expulsion fuse clears by expelling the arc products through a tube, costs least, and is applied where the discharge can be directed safely and the interrupting duty is within its rating, which is more often the case outdoors and at the lower classes. {note}
+
+### Power fuses shall comply with IEEE C37.46 and shall be applied in accordance with IEEE C37.48 for the fuse type, the enclosure, the ambient, and the continuous current of the position.
+
+### Where a fuse type that discharges on operation is furnished indoors, each fuse shall be furnished with a muffler or an exhaust control device, and the section shall have been design-tested with that device installed.
+
+## Fuse Ratings and Mountings {toc}
+
+### The ampere rating and the speed or time-current characteristic of the fuse at every position shall be those established under [[sync/protective-coordination-study]], and the Contractor shall not install a fuse element of a rating or characteristic other than the one the study establishes.
+
+### Fuse mountings shall be of the disconnect type, de-energized and isolated on both sides with the associated switch open, and accessible for replacement from the front of the section with the door open and without reaching past an energized part.
+
+### Fuse mountings shall accept the full range of fuse ratings available in the class selected, so that a fuse change made under a revised coordination study does not require a change to the mounting.
+
+### Each fuse shall carry a blown-fuse indicator visible with the door closed.
+
+### Where a blown-fuse trip of the switch is selected under Switch Accessories, the fuse mountings shall be furnished with the striker or the trip actuator the fuse type provides, and the trip shall operate on the opening of any one fuse.
+
+### Fuse pullers or the handling tool the fuse type requires shall be furnished with the lineup, one set per lineup, and stored in a holder inside the lineup.
+
+# Key Interlocks {toc}
+
+## The key interlocks furnished in the lineup shall be as indicated in the datasheet, and every key interlock shall be listed in the key interlock schedule submitted under Action Submittals.
+
+```datasheet
+label: Key Interlocks
+type: checkbox
+options:
+ - "Two-of-three interlock between the two incoming switches and the tie switch"
+ - "Incoming switches interlocked so that both cannot be closed at once on a duplex lineup"
+ - "Grounding switch interlocked with its associated switch"
+ - "Incoming cable compartment door interlocked with the upstream device locked open"
+ - "Feeder switch interlocked with the downstream transformer secondary main device"
+ - "Feeder switch interlocked with the downstream device it is unfused behind"
+ - "Fuse compartment access interlocked with the switch open and locked"
+constraint: all_of
+```
+
+## A key interlock enforces a sequence with a physical key that cannot be in two locks at once, which no loss of control power or wiring error defeats, and it governs the manual operation of a switch whether or not a motor operator is also furnished. The two-of-three and the duplex interlocks keep two sources off one bus; the grounding switch interlock keeps the ground off an energized circuit; the cable compartment and fuse compartment interlocks keep a door closed until the circuit behind it is dead; the downstream interlocks keep a switch from being opened under a load it cannot break or closed onto a secondary whose main is still closed. Which of these a lineup needs follows from the arrangement, the fusing, and what is connected to each position, so the field asserts no default. {note}
+
+## Where automatic source transfer is selected, every key interlock on a motor-operated switch shall be wired so that the position of the key interlock is read by the transfer scheme and a switch whose interlock is engaged is not commanded.
+
+## Key interlocks shall be of the same manufacturer and keying system throughout the lineup and throughout the equipment interlocked with it, and the Contractor shall coordinate the keying with the equipment at the other end of every interlock before the lineup is released for manufacture.
+
+## One key shall be furnished for each lock, no duplicate key shall be furnished except where the schedule shows a key held in a key exchange unit, and the keys shall be delivered to the Owner under Closeout Submittals.
+
+## A duplicate key defeats the interlock on the day it is used, which is why every key is accounted for in the schedule and the keys are counted into the Owner's hands. {note}
+
+# Bus {toc}
+
+## Bus Material {toc}
+
+### The main bus and the connections from the bus to the switches and the fuse mountings shall be of the material indicated in the datasheet.
+
+```datasheet
+label: Bus Material
+type: radio
+options:
+ - "Copper"
+ - "Aluminum"
+```
+
+### Copper bus carries more current per unit cross-section, which gives a smaller bus for the same rating, has the lower contact resistance at a bolted joint, and costs more; aluminum bus is lighter and less expensive for the same rating and depends on the plating and the joint hardware to hold its resistance through thermal cycling. Neither is distinctly the norm across projects, so the field asserts no default. {note}
+
+### Where copper is selected, the bus shall be copper bus bar conforming to ASTM B187 with a conductivity of not less than 98% IACS.
+
+### Where aluminum is selected, the bus shall be an aluminum alloy bus conductor conforming to ASTM B317 with a conductivity of not less than 55% IACS, and shall be plated over the full length of every bar.
+
+### Every bolted bus joint shall be plated at the contact surfaces, and every joint between an aluminum bar and a copper bar, terminal, or lug shall be made through a plated contact surface listed for the combination.
+
+## Bus Insulation {toc}
+
+### The main bus insulation shall be as indicated in the datasheet.
+
+```datasheet
+label: Main Bus Insulation
+type: radio
+options:
+ - "Insulated bus"
+ - "Bare bus"
+```
+
+### IEEE C37.20.3 does not require the main bus of interrupter switchgear to be insulated, which is one of the differences between it and metal-clad switchgear. A bare bus is the construction most lineups are built with and depends on the air clearances the voltage class sets; an insulated bus adds a flame-retardant insulation over the bars and boots over the joints, which lowers the chance that a dropped tool or an animal starts a phase-to-phase fault and raises the chance that an internal arc stays phase-to-ground until it is cleared, at the cost of the insulation and a bus whose joints must be unbooted for inspection. {note}
+
+### Where insulated bus is selected, the insulation shall be a flame-retardant, track-resistant material applied to the full length of every bar, every joint shall be covered with a removable boot, and the insulation system shall have been tested on the bus construction furnished.
+
+## Bus Supports and Ground Bus {toc}
+
+### The bus shall be supported on insulators of a track-resistant material, braced for the momentary current established under Electrical Ratings, and arranged so that the bus passes from section to section without a splice inside a switch or fuse compartment.
+
+### A copper ground bus of not less than 1/4 in. by 2 in. shall run the full length of the lineup, bonded to every section, to every switch frame, to every instrument transformer case, and to every cable shield ground, with a ground connection terminal at each end of the lineup sized for the grounding electrode conductor shown on the grounding plan.
+
+### Each cable compartment shall be furnished with a ground terminal on the ground bus sized for a portable grounding set.
+
+### Barriers between the bus compartment and the switch and cable compartments shall be grounded metal or an insulating material the manufacturer has tested as part of the section, arranged so that a switch or a fuse can be worked on with the bus energized once the switch is open and the compartment is isolated.
+
+# Arc-Resistant Construction {toc}
+
+## The arc-resistant construction of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Arc-Resistant Construction
+type: select
+options:
+ - "Not arc-resistant"
+ - "Type 2 accessibility per IEEE C37.20.7"
+ - "Type 2B accessibility per IEEE C37.20.7"
+```
+
+## Arc-resistant construction directs the products of an internal arcing fault away from the front, sides, and rear of the lineup through a plenum, and Type 2B keeps that protection with the low-voltage control compartment door open. On a medium-voltage lineup the incident energy is high enough that arc-resistant construction, motor operators, or both are often what brings the labeled personal protective equipment category to a workable level, and the construction adds a plenum, reinforced doors, and pressure-relief flaps that raise the height and the cost of the lineup and that must discharge somewhere the room can accept. A lineup without arc-resistant construction depends on remote operation and on the arc-flash study's boundaries for the same protection. {note}
+
+## Where arc-resistant construction is selected, the lineup shall have been tested to IEEE C37.20.7 in the configuration furnished, including the switch type, the fuse type, and the cable compartments, and the exhaust plenum and its discharge location shall be shown on the shop drawings and coordinated with [[sync/electrical-rooms]].
+
+## Arc-resistant construction does not lower the incident energy at a section whose door is open, and a fuse being replaced with the door open is the operation the construction does not protect. {note}
+
+# Instrument Transformers and Metering Section {toc}
+
+## Metering Section {toc}
+
+### The metering section of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Metering Section
+type: select
+options:
+ - "No metering section"
+ - "Utility revenue metering section built to the serving utility's requirements"
+ - "Owner's metering section with current and voltage transformers"
+ - "Utility revenue metering section and Owner's metering section"
+```
+
+### A utility revenue metering section is furnished where the service point is at medium voltage and the utility bills on the primary side; it is built to the utility's metering requirements, which fix the compartment, the instrument transformers, and the sealing, and it must be accepted by the utility before the lineup is drawn. An Owner's metering section serves a campus or a plant that allocates energy by feeder or by source, and it is built to the Owner's monitoring standard rather than the utility's; a lineup that is both a service entrance and a plant distribution point often carries one of each. A metering section cannot be added to a lineup in the field, so an omitted metering decision is discovered when the meter will not fit. {note}
+
+### Where a utility revenue metering section is furnished, it shall be a separate section with its own door, sealing provisions, and instrument transformer mounting as the serving utility requires, and the Contractor shall obtain the utility's written acceptance of the section before the lineup is released for manufacture.
+
+### Where an Owner's metering section is furnished, the meter and its communications shall comply with [[sync/electrical-power-monitoring]], and the meter shall be mounted in the low-voltage compartment of the section by the manufacturer.
+
+## Instrument Transformers {toc}
+
+### Current transformers and voltage transformers shall comply with IEEE C57.13, shall be rated for the voltage class and the BIL of the lineup, and shall be of the metering accuracy class the meter they serve requires at the burden connected.
+
+### Voltage transformers shall be furnished with current-limiting primary fuses, mounted on a drawout carriage or behind a door interlocked with the primary fuses so that the transformer is disconnected from the bus before it is accessible, and the secondary shall be fused and grounded at one point only.
+
+### Current transformer secondary circuits shall be wired to shorting-type terminal blocks in the low-voltage compartment and grounded at one point only, and no current transformer secondary shall be left open with the primary energized.
+
+### Where protective relays are furnished in the lineup, they shall comply with IEEE C37.90, shall be mounted in the low-voltage control compartment, and shall be set from the coordination study performed under [[sync/protective-coordination-study]].
+
+# Surge Arresters {toc}
+
+## The surge arresters furnished in the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Surge Arrester Class
+type: select
+options:
+ - "No surge arresters in the lineup"
+ - "Distribution-class metal-oxide arresters"
+ - "Intermediate-class metal-oxide arresters"
+ - "Station-class metal-oxide arresters"
+```
+
+## Distribution-class arresters carry the lowest energy rating and the highest discharge voltage of the three classes and are the smallest and least costly; intermediate-class and station-class arresters lower the discharge voltage and raise the energy capability, which buys protective margin where the lineup is fed from an overhead line exposed to lightning or where a vacuum switch's transients reach a transformer winding through a short cable. A lineup fed by a long underground cable from switchgear that carries its own arresters is often furnished without arresters, since the cable's surge impedance attenuates what arrives and the arresters at the transformer, furnished under [[sync/medium-voltage-transformers]], protect the winding. {note}
+
+## Where arresters are furnished, they shall be metal-oxide arresters complying with IEEE C62.11, applied in accordance with IEEE C62.22, mounted in the incoming cable compartments on the line side of the incoming switches, and rated as indicated in the datasheet.
+
+```datasheet
+label: Arrester Duty-Cycle Voltage Rating
+type: range
+unit: kV
+derived: "the nominal system voltage and the system grounding shown on the one-line diagram, applied per IEEE C62.22 so that the maximum continuous operating voltage of the arrester is not less than the maximum line-to-ground voltage the system can sustain"
+options:
+ min: 3
+ max: 36
+ setpoints: [3, 6, 9, 10, 12, 15, 18, 21, 24, 27, 30, 36]
+default: derived
+constraint: exact
+```
+
+## An arrester on a solidly grounded system is rated for the line-to-ground voltage; an arrester on a delta, ungrounded, or impedance-grounded system must hold the full line-to-line voltage during a ground fault on the other phases, so its rating rises accordingly, and an under-rated arrester on such a system fails during the first sustained ground fault. {note}
+
+## Arrester ground leads shall be as short and as straight as the compartment allows and shall be bonded to the ground bus, and the arresters shall be mounted so that they can be disconnected and tested with the cable compartment de-energized.
+
+# Cable Compartments and Terminations {toc}
+
+## Cable Compartment Space and Supports {toc}
+
+### Each cable compartment shall be sized to receive the number and size of cables as indicated on [[drawing: the one-line diagram and the conduit and cable schedule]], with space to make up a termination on each cable without bending the cable below its minimum radius, and with the terminations themselves complying with [[sync/medium-voltage-cables]].
+
+### Each cable compartment shall be furnished with cable supports, a termination support bracket, a ground terminal for the cable shields, and a barrier between the cable compartment and the switch and fuse compartment, and the compartment shall be accessible from the front or from the rear as indicated on the outline drawing.
+
+### A cable compartment that is too shallow for the termination kit is discovered after the lineup is set and the cable is pulled, when neither can be changed, which is why the cable count and size are coordinated into the compartment before the lineup is drawn. {note}
+
+### Where the lineup is connected to a transformer or to other switchgear by metal-enclosed bus, the bus shall comply with [[sync/medium-voltage-bus-duct]], and the lineup shall furnish the flanged bus entry, the bus connection within the section, and the barriers that keep the bus compartment closed.
+
+## Cable Entry {toc}
+
+### Cable and conduit entry to the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Cable Entry
+type: radio
+drawing_ref: "the electrical plans and the switchgear elevation"
+options:
+ - "Bottom entry"
+ - "Top entry"
+ - "Top and bottom entry"
+default: deferred
+```
+
+### Conduit shall enter only through the areas designated on the outline drawing, and no raceway shall enter a bus compartment or a switch compartment.
+
+# Enclosure {toc}
+
+## Enclosure Type and Housing {toc}
+
+### The enclosure of the lineup shall be as indicated in the datasheet.
+
+```datasheet
+label: Enclosure Type
+type: select
+options:
+ - "Indoor, Type 1"
+ - "Outdoor, Type 3R non-walk-in"
+ - "Outdoor, Type 3R walk-in aisle"
+```
+
+### A plant service entrance stands outdoors in a yard as often as it stands in a room, so the field asserts no default. An indoor lineup is the Type 1 construction built for a dry electrical room; a non-walk-in outdoor housing is the smaller and lighter outdoor structure, with its working space on the pad in front of it and every switch operated in the weather; a walk-in housing puts the working space in front of the switches inside a weatherproof aisle so that a switch can be operated and a fuse replaced in any weather, at the cost of a larger and heavier structure. {note}
+
+### An outdoor enclosure shall be Type 3R at minimum under NEMA 250, with rain hoods over ventilation openings, a drip shield over each door, drain provisions in each section, and doors that can be opened with the padlocks in place.
+
+### Where the lineup is installed within reach of salt air, chemical fallout, or de-icing spray, the enclosure shall be Type 3RX or shall be of a corrosion-resistant construction the manufacturer certifies as equivalent, and the hardware shall be stainless steel.
+
+### Where a walk-in housing is furnished, the aisle shall provide the working space NFPA 70 110.34 requires in front of every switch, and the housing shall have lighting, a convenience receptacle, and a door openable from inside without a key at each end of the aisle.
+
+### Where the lineup is installed indoors in an unconditioned space subject to dust or dripping liquid, the enclosure shall be furnished with gasketed doors and covers in addition to the Type 1 construction.
+
+## Enclosure Construction and Finish {toc}
+
+### Each section shall be a self-supporting, grounded steel structure with a bolted or welded frame, with doors on hinges that allow the door to be removed, and with every door, cover, and barrier interlocked or tool-removable as this standard requires for the compartment it closes.
+
+### Sections shall match in height and depth and shall present one continuous front, and shipping splits shall be at section boundaries with the bus connection made up through removable covers.
+
+### The painted steel finish shall be the manufacturer's standard powder coat or liquid finish over a phosphate pretreatment, and the manufacturer shall state the finish system and its dry film thickness in the product data.
+
+### The finish color shall be as indicated in the datasheet.
+
+```datasheet
+label: Finish Color
+type: select
+options:
+ - "ANSI 61 light gray"
+ - "ANSI 49 medium gray"
+ - "ANSI 70 sky gray"
+ - "Custom color matched to a sample furnished by the Owner"
+default: "ANSI 61 light gray"
+```
+
+### ANSI 61 is the color the sections are stocked and painted in and the one every other lineup in a medium-voltage room is likely to match; a medium or sky gray is chosen to match existing equipment; a custom color is matched where the Owner's standard requires it, at a cost in lead time. {note}
+
+# Identification {toc}
+
+## Nameplates shall be furnished on the lineup, on each section, on each switch, and on each fuse mounting, and shall comply with [[sync/equipment-labeling]] for material, lettering, and attachment.
+
+## The lineup nameplate shall state the lineup designation, the rated maximum voltage, the BIL, the main bus continuous current, the short-circuit rating, the fuse type and interrupting rating, the source that feeds each incoming switch, and the manufacturer.
+
+## Each switch nameplate shall state the position designation, the circuit served, the continuous current, the momentary and fault-closing ratings, and the fuse rating installed where the position is fused, and each fuse mounting shall carry a label stating the fuse rating and characteristic the coordination study establishes for that position.
+
+## A fuse mounting labeled with its study rating is what keeps the next operator from ending an outage with the fuse that was on the shelf, which is the substitution that defeats the coordination and the current limitation the downstream equipment depends on. {note}
+
+## Arc-flash incident energy labels shall be applied to each section in accordance with NFPA 70 110.16 and NFPA 70E, with the values taken from the study performed under [[sync/arc-flash-study]].
+
+## The available fault current and the date it was calculated shall be marked on the lineup in accordance with NFPA 70 110.24 where the lineup is service equipment.
+
+## Where automatic source transfer is selected, the control compartment shall carry a permanently mounted sequence-of-operation placard and a placard stating the position of the automatic-manual selector in which the lineup is normally left.
+
+# Testing {toc}
+
+## Factory Tests {toc}
+
+### The lineup shall have been design-tested in accordance with IEEE C37.20.3, and the switches in accordance with IEEE C37.20.4, on a construction of the same design, rating, and voltage class as furnished, and the manufacturer's certification of compliance shall identify the design tests relied on.
+
+### Each lineup shall receive the production tests IEEE C37.20.3 requires, including the power-frequency withstand test of the primary circuits, the dielectric test of the control and secondary circuits, the mechanical operation of every switch and every interlock, the grounding of instrument transformer cases and secondary circuits, and the electrical operation and control wiring checks, with a certified report for each lineup.
+
+### In addition to the production tests, the manufacturer shall perform a functional test of the transfer scheme through every sequence, including transfer, retransfer, lockout on a simulated blown fuse, and loss of control power, with the switches operated, where automatic source transfer is selected.
+
+### Factory acceptance test witnessing shall be as indicated in the datasheet.
+
+```datasheet
+label: Factory Acceptance Test Witnessing
+type: radio
+options:
+ - "Witnessed by the Owner's representative"
+ - "Unwitnessed with a certified test report"
+```
+
+### Where witnessed testing is indicated, the manufacturer shall give the Owner not less than two weeks notice of test readiness, and the test procedure shall have been submitted and returned before the test date.
+
+### A witnessed test lets the Owner see every switch operate, every interlock hold, and the transfer scheme run before the lineup ships, and it commits a representative to a trip to the factory; a certified report records the same tests without the trip, and leaves any discrepancy to be found at field acceptance testing instead. {note}
+
+## Field Acceptance Tests {toc}
+
+### Field acceptance tests shall be performed on the lineup after installation is complete, after every cable has been terminated, and before the lineup is energized, in accordance with ANSI/NETA ATS and [[sync/electrical-acceptance-testing]], and shall include the tests indicated in the datasheet.
+
+```datasheet
+label: Field Acceptance Tests
+type: checkbox
+options:
+ - "Visual and mechanical inspection of the assembly per ANSI/NETA ATS 7.1, including anchorage, nameplates, clearances, barriers, shipping brace removal, and door and compartment interlocks"
+ - "Bolted connection torque verification or contact resistance across every bus joint and termination per ANSI/NETA ATS 7.1"
+ - "Insulation resistance of each phase of the bus and of each switch, phase-to-phase and phase-to-ground, per ANSI/NETA ATS 7.1 and the switch section of 7.5 for the switch type furnished"
+ - "Dielectric withstand test of the bus and the switches with the cables disconnected, per ANSI/NETA ATS 7.1"
+ - "Contact resistance across each switch pole per ANSI/NETA ATS 7.5.1.2, 7.5.3, or 7.5.4 for the switch type furnished"
+ - "Mechanical operation of every switch through open and close, by hand and by motor operator where furnished, per ANSI/NETA ATS 7.5"
+ - "Verification of the fuse rating and characteristic at every position against the coordination study, and fuse resistance per ANSI/NETA ATS 7.5.1.2"
+ - "Functional test of every key interlock in every combination of switch positions"
+ - "Functional test of every grounding switch interlock"
+ - "Gas density monitor and lockout verification on SF6 switches per ANSI/NETA ATS 7.5.4"
+ - "Vacuum integrity test of each vacuum switch per ANSI/NETA ATS 7.5.3"
+ - "Current and voltage transformer ratio, polarity, and secondary grounding verification per ANSI/NETA ATS 7.10"
+ - "Metering verification against the instrument transformer circuits per ANSI/NETA ATS 7.11"
+ - "Surge arrester insulation resistance and ground connection verification per ANSI/NETA ATS 7.19.2"
+ - "Functional test of the automatic source transfer scheme through every sequence with the switches operated, and relay settings verification per ANSI/NETA ATS 7.9 where relays are furnished"
+ - "Phasing verification at every incoming and outgoing termination"
+default:
+ - "Visual and mechanical inspection of the assembly per ANSI/NETA ATS 7.1, including anchorage, nameplates, clearances, barriers, shipping brace removal, and door and compartment interlocks"
+ - "Bolted connection torque verification or contact resistance across every bus joint and termination per ANSI/NETA ATS 7.1"
+ - "Insulation resistance of each phase of the bus and of each switch, phase-to-phase and phase-to-ground, per ANSI/NETA ATS 7.1 and the switch section of 7.5 for the switch type furnished"
+ - "Contact resistance across each switch pole per ANSI/NETA ATS 7.5.1.2, 7.5.3, or 7.5.4 for the switch type furnished"
+ - "Mechanical operation of every switch through open and close, by hand and by motor operator where furnished, per ANSI/NETA ATS 7.5"
+ - "Verification of the fuse rating and characteristic at every position against the coordination study, and fuse resistance per ANSI/NETA ATS 7.5.1.2"
+ - "Functional test of every key interlock in every combination of switch positions"
+ - "Functional test of every grounding switch interlock"
+ - "Current and voltage transformer ratio, polarity, and secondary grounding verification per ANSI/NETA ATS 7.10"
+ - "Phasing verification at every incoming and outgoing termination"
+constraint: all_of
+```
+
+### Insulation resistance shall be measured for one minute at the test voltage ANSI/NETA ATS assigns to the voltage class, with the cables disconnected and the voltage transformers withdrawn, and a reading below the minimum ANSI/NETA ATS Table 100.1 states for the voltage class shall be investigated before the lineup is energized.
+
+### Where a dielectric withstand test is selected, it shall be performed at a direct-current or power-frequency voltage not exceeding 75% of the power-frequency withstand voltage IEEE C37.20.3 assigns to the rated maximum voltage, held for one minute per phase to ground with the other phases grounded, with the cables disconnected and the instrument and control circuits isolated.
+
+### A dielectric withstand test stresses the bus and the switch insulation at a voltage above operating voltage and below the factory test voltage, so that a cracked insulator, a foreign object, or a clearance lost in field assembly breaks down under test rather than in service; the 75% ceiling exists because the factory test has already been applied once and insulation is not meant to see that voltage twice, and the cables are disconnected because their own withstand test is a different test at a different voltage under [[sync/medium-voltage-cables]]. {note}
+
+### A switch pole whose contact resistance exceeds the manufacturer's published value, or exceeds the lowest pole of the same switch by more than 50%, shall be reported, corrected, and retested before the lineup is energized.
+
+### A lineup that fails a field acceptance test shall not be energized, the Contractor shall report the failure to the Engineer of Record within one working day with the measured values, and the cost of the correction and of every repeated test shall be borne by the Contractor.
+
+### No section shall be energized until the field acceptance tests covering it have passed, the fuses of the study rating have been verified in every position, and the arc-flash labels have been installed.
+
+## Start-Up and Initial In-Service Inspection {toc}
+
+### Manufacturer start-up shall be provided where indicated in the datasheet.
+
+```datasheet
+label: Manufacturer Start-Up
+type: radio
+options:
+ - "Manufacturer's field service present at energization and start-up"
+ - "Not required"
+```
+
+### The lineup shall be energized from the source side with every feeder switch open, held for not less than one hour while the bus, the switches, and the cable compartments are observed, and then loaded one feeder at a time.
+
+### Infrared thermographic inspection shall be as indicated in the datasheet.
+
+```datasheet
+label: Infrared Thermographic Inspection
+type: select
+options:
+ - "Not required"
+ - "One inspection within 90 days of energization"
+ - "One inspection within 90 days of energization and a second at eleven months"
+```
+
+### Where infrared inspection is indicated, it shall be performed with the lineup carrying not less than 40 percent of its main bus rating, shall scan every bus joint, every switch, every fuse mounting, and every termination through the inspection windows furnished or with the doors open under the safe work practices of NFPA 70E, and every connection showing a rise of more than 10 °C above a comparable connection under the same load shall be reported and corrected.
+
+### A fuse clip that holds its fuse short of full contact and a switch blade that seats short of full pressure run hotter than their neighbors from the first day of load, and the only test that finds either with the lineup in service is a scan under load; a second inspection near the end of the first year finds the connection that loosened through the first full cycle of seasonal load, which the first inspection cannot see, and it costs a second visit under load and a warranty claim filed before the warranty ends. {note}
+
+# Installation {toc}
+
+## Room, Yard, and Working Space {toc}
+
+### An indoor lineup shall be installed in a room complying with [[sync/electrical-rooms]] and with NFPA 70 110.31 for equipment over 1000 V, and the room ventilation shall carry away the losses of the lineup at the indoor design ambient temperature selected in the datasheet.
+
+### Working space in front of, behind, and beside the lineup where it is accessible there shall comply with NFPA 70 110.34, and the clearance the manufacturer requires to open every door fully, to withdraw a voltage transformer carriage, and to replace a fuse shall be maintained in addition.
+
+### Where the lineup is installed outdoors in a dedicated yard, the fence, the gate, and the warning signs shall comply with NFPA 70 110.31, and the yard grounding grid shall be as indicated on [[drawing: the yard grounding plan]].
+
+### The design of a substation ground grid for step and touch potential is not owned by any standard in this library and is carried on the grounding plan by the Engineer of Record; this standard furnishes the ground bus and the terminals the grid is bonded to and nothing more. {note}
+
+### Working space shall not be used for storage at any time.
+
+## Foundation and Anchorage {toc}
+
+### The lineup shall be set on a concrete pad constructed under [[sync/concrete-pads]], of the height indicated in the datasheet, extending not less than 3 in. beyond the lineup base on every side.
+
+```datasheet
+label: Housekeeping Pad Height
+type: range
+unit: in.
+options:
+ min: 0
+ max: 6
+ setpoints: [0, 3, 4, 6]
+default: 4
+constraint: exact
+```
+
+### A pad keeps the base of the lineup above a wet floor and gives the anchors something to bite into that is not the slab's reinforcing; a pad height of zero is the direct-to-slab installation used where the floor is a structural slab designed for the anchors, and an outdoor lineup stands on a pad whose height the site grading sets. {note}
+
+### The pad shall be level across its full length so that the sections align at the bus splices without shimming beyond the manufacturer's stated limit.
+
+### The lineup shall be anchored to the pad as indicated on [[drawing: the seismic anchorage details]], using the anchor type, size, and embedment stated there, and where seismic qualification is required the anchorage shall be that on which the qualification depends.
+
+### The Contractor shall confirm the pad dimensions, the conduit stub-up locations, the anchor locations, and the weight of each shipping section against the reviewed shop drawings before the pad is placed, and shall report a discrepancy to the Engineer of Record before concrete is placed.
+
+## Setting and Field Connections {toc}
+
+### Shipping sections shall be set, aligned, and bolted together in accordance with the manufacturer's instructions, and the bus splice at each shipping split shall be made up with the manufacturer's hardware torqued to the manufacturer's values with a calibrated tool.
+
+### Every shipping brace, block, and desiccant shall be removed from every section before the lineup is energized, and their removal shall be recorded on the field test report.
+
+### The medium-voltage cables and their terminations shall comply with [[sync/medium-voltage-cables]], the duct bank with [[sync/underground-ductbank]], and the raceways above grade with [[sync/raceways-and-conduit]].
+
+### The ground bus shall be bonded at each end of the lineup to the grounding electrode system or the yard ground grid as indicated on [[drawing: the grounding plan]], and every cable shield shall be bonded to the ground bus in the compartment where the cable terminates.
+
+### Every field termination shall be torqued to the manufacturer's published value with a calibrated tool, and the torque values applied shall be recorded in the field test report.
+
+### The fuses of the rating and characteristic established under [[sync/protective-coordination-study]] shall be installed at every position, and the relay and transfer control settings from that study shall be applied, before the lineup is energized.
+
+# Delivery, Storage, and Handling {toc}
+
+## The lineup shall be shipped in the largest sections that the route from the delivery point to the final location will pass, and the Contractor shall verify door, corridor, and crane dimensions along that route before the shipping splits are fixed on the shop drawings.
+
+## Each shipping section shall be lifted only at the lifting provisions the manufacturer furnishes, kept upright, and not dragged, rolled on its base, or set on an unlevel surface.
+
+## Power fuses shall be shipped separately from the lineup in their original packaging, and shall be installed in the mountings only after the lineup is set and the field acceptance tests of the bus have passed.
+
+## The sections shall be stored indoors in a clean, dry location protected from construction dust and water until they are set, except that an outdoor lineup may be stored on its pad with its doors closed, its ventilation openings covered, and its space heaters energized.
+
+## Where a section must be stored for more than 30 days or in a space that is not conditioned, its space heaters shall be connected to a temporary supply and energized for the duration of storage.
+
+## A section that has been wetted in transit or in storage shall be dried, inspected by the manufacturer's field service organization, and released in writing before it is energized.
+
+# Warranty {toc}
+
+## The manufacturer shall warrant the lineup, including every switch, every fuse mounting, every operator, every interlock, and every factory-installed device, against defects in materials and workmanship for the period indicated in the datasheet.
+
+```datasheet
+label: Warranty Period
+type: range
+unit: years
+options:
+ min: 1
+ max: 5
+ setpoints: [1, 2, 3, 5]
+default: 1
+constraint: min
+```
+
+## The warranty period shall commence on the date indicated in the datasheet.
+
+```datasheet
+label: Warranty Commencement
+type: select
+options:
+ - "Date of substantial completion"
+ - "Date of energization"
+ - "Date of shipment"
+```
+
+## Warranty commencement at shipment is the manufacturer's usual term, and it consumes the warranty during storage and construction; commencement at energization or substantial completion moves the coverage to the period the Owner is operating the equipment, and the manufacturer prices the added months into the lineup. {note}
+
+## The warranty coverage scope shall be as indicated in the datasheet.
+
+```datasheet
+label: Warranty Coverage Scope
+type: radio
+options:
+ - "Parts only"
+ - "Parts and labor"
+```
+
+## A fuse that operates on a fault is not a defect, and the warranty shall exclude fuse units consumed in clearing a fault and shall cover a fuse unit that operates with no fault on the circuit it protects.
+
+## A repair or replacement performed under this warranty shall itself be warranted for a full new term equal to the original period from the date the repair is completed, or for the remainder of the original period, whichever ends later.
+
+## The Contractor shall warrant the installation, including every field connection, the anchorage, the grounding, and the field-installed fuses and settings, for the project warranty period.
+
+# Spare Parts {toc}
+
+## The Contractor shall deliver to the Owner, before the lineup is accepted, spare power fuses of each rating and characteristic installed in the quantity indicated in the datasheet, and shall obtain a signed receipt for them.
+
+```datasheet
+label: Spare Power Fuses per Rating Installed
+type: range
+unit: fuses
+options:
+ min: 0
+ max: 12
+ setpoints: [0, 3, 6, 9, 12]
+constraint: min
+```
+
+## A blown fuse is otherwise an outage that lasts until a replacement is sourced, and a fuse of a different rating installed to end the outage defeats the coordination study and the current limitation the downstream equipment depends on; three fuses of each rating replace one three-phase set, and a plant whose fuses are of a long-lead type or whose feeders see faults often holds more. A lineup with no fused positions holds none, which is why the field asserts no default. {note}
+
+## The Contractor shall deliver the additional spare parts indicated in the datasheet to the Owner before the lineup is accepted, and shall obtain a signed receipt for them.
+
+```datasheet
+label: Additional Spare Parts to Be Furnished
+type: checkbox
+options:
+ - "One set of control fuses of each type and rating installed"
+ - "One set of voltage transformer primary fuses of each rating installed"
+ - "One set of indicating lamps and lenses of each type installed"
+ - "One spare motor operator of each type furnished"
+ - "One spare voltage sensing relay or transfer control module of each type in the transfer scheme"
+ - "One set of door gaskets for an outdoor lineup"
+ - "Touch-up finish in the exterior color"
+default:
+ - "One set of control fuses of each type and rating installed"
+ - "One set of voltage transformer primary fuses of each rating installed"
+ - "One set of indicating lamps and lenses of each type installed"
+constraint: all_of
+```
+
+## Spare parts shall be of the same manufacturer and rating as the installed items, shall be delivered in their original packaging, and shall be labeled with the designation of the section and position they serve.