−---
−title: Medium Voltage Switchgear
−category: Power Distribution
−toc_depth: 3
−description: >
− When to use: Metal-clad medium-voltage switchgear rated above 1 kV through 38 kV using drawout vacuum or SF6 circuit breakers, built to IEEE C37.20.2 and the ANSI/IEEE C37.04 / C37.06 / C37.09 series, for utility-customer substations, large commercial campuses, healthcare and higher-education central plants, data centers, and industrial facilities. Covers 5 kV, 15 kV, 27 kV, and 38 kV voltage classes, indoor and outdoor walk-in (protected aisle) configurations, arc-resistant ratings per IEEE C37.20.7, multifunction microprocessor protective relays, and optional IEC 61850 station bus communications.
− Not intended for: Metal-enclosed interrupter switchgear with load-interrupter switches and power fuses (see IEEE C37.20.3), pad-mounted distribution switchgear, low voltage switchgear rated 600V and below (see [[sync/low-voltage-switchgear]]), low voltage switchboards (see [[sync/low-voltage-switchboards]]), motor control centers (see [[sync/motor-control-centers]]), or unit substations as an assembly (the MV section of a unit substation cites this standard for the switchgear scope).
−---
−
−# Scope
−
−This specification covers metal-clad medium-voltage switchgear assemblies rated above 1 kV through 38 kV, constructed and tested in accordance with IEEE C37.20.2 (Metal-Clad Switchgear) and listed or labeled by a Nationally Recognized Testing Laboratory where such listing is available. Circuit breakers shall comply with ANSI/IEEE C37.04 (Rating Structure), IEEE C37.06 (Preferred Ratings), and IEEE C37.09 (Test Procedures) and shall be drawout, three-pole, single-throw devices using vacuum or SF6 interrupters.
−
−Switchgear covered by this standard is fully metal-clad: each major primary functional component (circuit breaker, main bus, instrument transformers, cable terminations) is housed in its own grounded metal compartment, and grounded metal barriers separate compartments from one another and from the bus. Compartmentalization, automatic primary-disconnect shutters that close when the breaker is withdrawn, and insulated primary bus distinguish metal-clad construction from the metal-enclosed interrupter switchgear of IEEE C37.20.3, which uses load-interrupter switches with power fuses and lacks the same level of segregation. For metal-enclosed interrupter switchgear, refer to IEEE C37.20.3; that equipment is outside the scope of this standard.
−
−This standard addresses the typical applications of medium-voltage switchgear in the United States market: 5 kV and 15 kV utility-customer service entrance equipment downstream of utility primary metering, 15 kV main and tie switchgear for large commercial and institutional campuses, 5 kV and 15 kV motor and feeder switchgear at industrial and process facilities, and 27 kV and 38 kV equipment at sites taking service at higher subtransmission voltages. Arc-resistant construction per IEEE C37.20.7 is addressed where occupant safety, equipment density, or insurer requirements warrant it.
−
−Coordination of overcurrent protection across the medium-voltage system shall follow [[sync/protective-coordination-study]]. Arc flash hazard analysis shall be performed per IEEE 1584 and [[sync/arc-flash-study]]. Grounding of the switchgear ground bus, neutral grounding equipment, and the substation ground grid (where applicable) shall be per [[sync/grounding-and-bonding]]. Medium-voltage cable terminations, raceway, and conduit entry shall comply with [[sync/conductors-and-cables]] and [[sync/raceways-and-conduit]]. Where the switchgear feeds downstream low-voltage distribution through unit substations or pad-mounted transformers, the secondary equipment shall comply with [[sync/low-voltage-switchgear]], [[sync/low-voltage-switchboards]], or [[sync/motor-control-centers]] as applicable.
−
−# Referenced Standards
−
−Equipment and installation shall comply with the latest adopted edition of the following. Where conflicts exist between referenced standards, the more stringent requirement shall govern unless otherwise directed by the Engineer of Record.
−
−| Standard | Title |
−|----------|-------|
−| IEEE C37.20.2 | Standard for Metal-Clad Switchgear |
−| IEEE C37.20.3 | Standard for Metal-Enclosed Interrupter Switchgear (reference for distinction from metal-clad) |
−| IEEE C37.20.7 | Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults |
−| ANSI/IEEE C37.04 | Standard Rating Structure for AC High-Voltage Circuit Breakers |
−| IEEE C37.06 | AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis — Preferred Ratings and Related Required Capabilities |
−| IEEE C37.09 | Standard Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
−| IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
−| IEEE C37.011 | Application Guide for Transient Recovery Voltage for AC High-Voltage Circuit Breakers |
−| IEEE C37.100.1 | Standard of Common Requirements for High-Voltage Power Switching Devices Rated Above 1000V |
−| IEEE C37.90 | Standard for Relays and Relay Systems Associated with Electric Power Apparatus |
−| IEEE C37.90.1 | Standard for Surge Withstand Capability (SWC) Tests for Relays and Relay Systems |
−| IEEE C37.90.2 | Standard for Withstand Capability of Relay Systems to Radiated Electromagnetic Interference from Transceivers |
−| IEEE C37.90.3 | Standard for Electrostatic Discharge Tests for Protective Relays |
−| IEEE C57.13 | Requirements for Instrument Transformers |
−| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
−| IEEE 81 | Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System |
−| IEC 61850 | Communication Networks and Systems for Power Utility Automation (where station bus is specified) |
−| ANSI C84.1 | Electric Power Systems and Equipment — Voltage Ratings (60 Hz) |
−| ANSI/NEMA SG 4 | Alternating-Current High-Voltage Circuit Breakers |
−| ANSI/NEMA SG 5 | Power Switchgear Assemblies |
−| NFPA 70 | National Electrical Code (Article 490 — Equipment Over 1000 Volts) |
−| NFPA 70E | Standard for Electrical Safety in the Workplace |
−| NETA ATS | Acceptance Testing Specifications for Electrical Power Equipment and Systems |
−| IBC | International Building Code |
−| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
−| ICC ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing |
−
−# Submittals
−
−## Action Submittals
−
−Contractor shall submit the following for review prior to fabrication. Procurement and fabrication shall not proceed until the corresponding submittals have been reviewed and returned.
−
−- Shop drawings showing front, side, and rear elevations with overall dimensions, weight per section, and shipping splits
−- Single line diagram indicating voltage class, BIL, continuous current rating, short-circuit interrupting and momentary ratings, breaker types, instrument transformer ratios and accuracy classes, and protective relay designations
−- Bill of materials listing all major components by type, rating, and quantity
−- Time-current coordination curves for all protective devices, plotted on a common log-log axis at the system base voltage
−- Relay setting tables for all protection functions, with reference to the coordination study
−- Control schematic and wiring diagrams for each circuit breaker, instrument transformer circuit, relay, metering device, and station battery interface
−- IEC 61850 SCL files (SSD, SCD, and IID as applicable), where station bus is specified
−- Cable termination details for primary cable, including lug type, stress relief, and ground shield bond
−- Bus bracing and short-circuit withstand calculations or reference to design-tested ratings
−- Heat loss data per section for ventilation and HVAC coordination of the electrical room
−- Arc-resistance qualification test report per IEEE C37.20.7, where arc-resistant construction is specified
−- Seismic certification documentation per ICC ES AC156 or analysis per ASCE 7, where required
−- Conduit and cable entry diagrams for top, bottom, and side entry zones
−- Recommended spare parts list
−
−```datasheet
−label: Submittal Documentation
−type: checkbox
−options:
− - "Shop drawings (front, side, rear elevations) with shipping splits"
− - "Single line diagram with full ratings"
− - "Bill of materials"
− - "Time-current coordination curves and relay setting tables"
− - "Control schematics and wiring diagrams"
− - "IEC 61850 SCL files (where station bus specified)"
− - "Cable termination details"
− - "Bus bracing and short-circuit calculations"
− - "Heat loss data per section"
− - "Arc-resistance qualification test report"
− - "Seismic certification (IBC/ASCE 7)"
− - "Conduit/cable entry diagrams"
− - "Recommended spare parts list"
−default: "Shop drawings (front, side, rear elevations) with shipping splits"
−```
−
−## Closeout Submittals
−
−Contractor shall provide at substantial completion:
−
−- Operation and maintenance manuals, bound with table of contents and indexed by section
−- As-built shop drawings, schematics, and one-line diagrams reflecting field modifications
−- Factory production test reports and design test certifications
−- Field acceptance test reports per NETA ATS
−- Arc flash incident energy analysis and installed labels
−- Protective relay setting files in the manufacturer's native format and a vendor-neutral export (e.g., CSV or COMTRADE-compatible event records)
−- Warranty documentation
−- Spare parts inventory with reorder information and storage location
−
−# Quality Assurance
−
−## Manufacturer Qualifications
−
−Switchgear shall be manufactured by a single company responsible for the assembly, primary bus, circuit breakers, primary disconnects, instrument transformers, and protective relay integration as a coordinated package. The manufacturer shall have a minimum of ten years documented experience producing metal-clad switchgear at the specified voltage class and shall maintain an ISO 9001 certified quality management system.
−
−The manufacturer shall maintain a 24/7 service organization with factory-trained field representatives available within 24 hours of notification for the duration of the warranty period.
−
−## Source Limitations
−
−All switchgear sections, primary bus, circuit breakers, instrument transformers, protective relays, and metering equipment shall be produced or furnished by the switchgear manufacturer as an integrated assembly. Field-assembled metal-clad enclosures and third-party retrofit assemblies are not acceptable. Devices and accessories shall be the manufacturer's standard catalog components for the listed assembly.
−
−## Design Tests
−
−The manufacturer shall provide certification that the switchgear design has passed all design tests required by IEEE C37.20.2 (for the assembly) and IEEE C37.09 (for the circuit breakers), including but not limited to dielectric withstand, continuous current temperature rise, short-time current, momentary withstand, mechanical operation endurance, and interrupting capability. Where arc-resistant construction is specified, the design shall have passed internal arcing fault testing per IEEE C37.20.7 at the specified short-circuit current and arc duration for the accessibility type required.
−
−## Testing Personnel Qualifications
−
−Field acceptance testing shall be performed by a firm regularly engaged in testing electrical power equipment, employing technicians certified by NETA or equivalent. Testing personnel shall have a minimum of five years documented experience testing metal-clad switchgear at the specified voltage class.
−
−# Environmental and Service Conditions
−
−Switchgear shall be suitable for continuous operation under the usual service conditions defined by IEEE C37.20.2 and IEEE C37.04. Where site conditions exceed these parameters, notify the manufacturer and apply the appropriate derating per the applicable standard.
−
−```datasheet
−label: Ambient Temperature (Maximum)
−type: select
−unit: °C
−options:
− - "40°C (standard rating)"
− - "50°C (elevated ambient)"
− - "55°C (desert/rooftop rating)"
−default: "40°C (standard rating)"
−```
−
−```datasheet
−label: Installation Altitude
−type: select
−options:
− - "Below 3,300 ft (1,000 m) - No derating"
− - "3,300 - 6,600 ft (1,000 - 2,000 m) - Derating may apply"
− - "Above 6,600 ft (2,000 m) - Derating required per IEEE C37.04"
−default: "Below 3,300 ft (1,000 m) - No derating"
−```
−
−Altitude derating for medium-voltage switchgear begins at lower elevations than for low-voltage equipment because the reduced air density at higher altitudes reduces dielectric strength and degrades convective cooling. The Engineer shall document derating calculations on the contract drawings and coordinate the corrected ratings with the system short-circuit and coordination studies.
−
−```datasheet
−label: Corrosion Severity
−type: select
−options:
− - "C2 - Low (indoor, climate-controlled)"
− - "C3 - Medium (indoor, unconditioned)"
− - "C4 - High (coastal, chemical exposure)"
− - "C5 - Very High (industrial, marine)"
−default: "C2 - Low (indoor, climate-controlled)"
−```
−
−For installations classified C4 or C5, primary bus shall be silver-plated copper at all joint contact surfaces, hardware shall be stainless steel, and the enclosure paint system shall provide enhanced corrosion protection. Outdoor walk-in (protected aisle) enclosures in C4 or C5 environments shall additionally include conditioned ventilation to maintain interior humidity below condensation thresholds.
−
−## Seismic Requirements
−
−Where required by the applicable building code, switchgear shall be seismically certified by shake-table testing per ICC ES AC156 or by analysis per ASCE 7.
−
−```datasheet
−label: Seismic Certification
−type: select
−options:
− - "Not required"
− - "IBC/ASCE 7 - Importance Factor 1.0"
− - "IBC/ASCE 7 - Importance Factor 1.5 (essential facility)"
− - "OSHPD pre-approval required (California healthcare)"
−default: "Not required"
−```
−
−Seismic certification shall be by an independent third-party testing laboratory and shall cover the complete assembly as installed, including all circuit breakers, primary bus, instrument transformers, and ancillary components in their service configuration. Certification of individual components in isolation is not acceptable. Anchorage details and base anchor force/moment values shall be coordinated with the structural engineer of record.
−
−# Electrical Requirements
−
−## System Ratings
−
−```datasheet
−label: Service Entrance Equipment
−type: radio
−options:
− - "Yes - Utility-customer service entrance"
− - "No - Downstream distribution"
−default: "No - Downstream distribution"
−```
−
−Where switchgear serves as utility-customer service entrance equipment, it shall comply with NFPA 70 Article 490 and the serving utility's interconnection requirements, including provisions for utility metering current and voltage transformers, primary disconnect, and available fault current verification. Coordinate primary metering compartment configuration, sealability, and clearances with the serving utility prior to submittal.
−
−```datasheet
−label: Nominal System Voltage Class
−type: select
−unit: kV
−options:
− - "4.16 kV (5 kV class)"
− - "12.47 kV (15 kV class)"
− - "13.2 kV (15 kV class)"
− - "13.8 kV (15 kV class)"
− - "24.94 kV (27 kV class)"
− - "34.5 kV (38 kV class)"
−default: "13.8 kV (15 kV class)"
−```
−
−Nominal system voltage shall be one of the standard values defined in ANSI C84.1. The voltage class designates the rated maximum voltage of the equipment per IEEE C37.06 (e.g., 4.76 kV equipment is referred to as 5 kV class and is suitable for 4.16 kV nominal systems). Coordinate the selected voltage class with the serving utility distribution voltage.
−
−```datasheet
−label: System Frequency
−type: radio
−unit: Hz
−options:
− - "60 Hz"
− - "50 Hz"
−default: "60 Hz"
−```
−
−```datasheet
−label: System Grounding
−type: select
−options:
− - "Solidly grounded wye"
− - "Low-resistance grounded wye"
− - "High-resistance grounded wye"
− - "Ungrounded"
− - "Resonant grounded (Petersen coil)"
−default: "Low-resistance grounded wye"
−```
−
−System grounding selection drives ground fault sensing scheme, ground current magnitude, neutral grounding equipment design, and protective relay configuration. Low-resistance grounding (typically 200 A to 400 A let-through) is the most common configuration for utility-customer 5 kV and 15 kV distribution because it limits ground fault current to levels that minimize equipment damage while still allowing selective coordination of feeder ground fault elements. Solidly grounded systems are more common where the medium-voltage system feeds low-voltage transformers exclusively and ground fault current must be high enough to trip phase overcurrent devices. High-resistance grounding is selected where service continuity on a first ground fault is required (typically industrial process loads). Coordinate the grounding method with [[sync/grounding-and-bonding]] and any associated neutral grounding resistor or transformer.
−
−## Insulation Level (BIL)
−
−```datasheet
−label: Basic Impulse Level (BIL)
−type: select
−unit: kV
−options:
− - "60 kV BIL (5 kV class)"
− - "75 kV BIL (5 kV class, special)"
− - "95 kV BIL (15 kV class)"
− - "125 kV BIL (27 kV class)"
− - "150 kV BIL (38 kV class)"
− - "200 kV BIL (38 kV class, special)"
−default: "95 kV BIL (15 kV class)"
−```
−
−BIL shall match the rated maximum voltage of the switchgear per IEEE C37.06. Standard BIL is sufficient for most utility-fed distribution applications. Increased BIL ratings should be considered for systems exposed to lightning surge environments where surge arresters at the service may not provide sufficient margin, or where the system topology can produce transient overvoltages that exceed standard insulation coordination.
−
−## Continuous Current and Short-Circuit Ratings
−
−Main bus continuous current rating shall be [[drawing: as indicated on the one-line diagram]]. Bus shall be braced for the available short-circuit current at the point of installation as determined by a short-circuit analysis per IEEE C37.010.
−
−```datasheet
−label: Main Bus Continuous Current
−type: range
−unit: A
−drawing_ref: true
−options:
− min: 1200
− max: 4000
− setpoints: [1200, 2000, 3000, 4000]
−default: 2000
−```
−
−```datasheet
−label: Short-Circuit Interrupting Rating (symmetrical)
−type: select
−unit: kA
−options:
− - "25 kA sym"
− - "31.5 kA sym"
− - "40 kA sym"
− - "50 kA sym"
− - "63 kA sym"
−default: "40 kA sym"
−```
−
−Short-circuit interrupting rating, expressed as a symmetrical rms current value per IEEE C37.04, shall equal or exceed the available three-phase fault current at the switchgear terminals. The application short-circuit current shall be determined per IEEE C37.010, which includes evaluation of the X/R ratio of the system and the resulting asymmetry factor. Where the system X/R ratio exceeds the test X/R used to qualify the breaker, the breaker's interrupting rating shall be derated per IEEE C37.010. Verify available fault current with the utility provider and perform a short-circuit study per [[sync/short-circuit-study]] prior to equipment procurement.
−
−```datasheet
−label: Close-and-Latch Rating (asymmetrical, peak)
−type: select
−options:
− - "Matched to interrupting rating per IEEE C37.06"
− - "Increased above standard - specify per project requirements"
−default: "Matched to interrupting rating per IEEE C37.06"
−```
−
−Close-and-latch rating, also referred to as the momentary or making current rating, shall be the IEEE C37.06 preferred value associated with the selected interrupting rating. The close-and-latch rating represents the peak asymmetrical current the breaker can close into and latch without damage; it is approximately 2.6 to 2.7 times the symmetrical interrupting rating depending on the rating standard generation.
−
−```datasheet
−label: Short-Time Withstand (Momentary) Duration
−type: select
−options:
− - "2 seconds (per IEEE C37.04)"
− - "3 seconds (extended duration)"
−default: "2 seconds (per IEEE C37.04)"
−```
−
−The short-time current withstand duration governs how long the breaker and bus can carry the rated short-circuit current without operating. The standard 2-second rating is sufficient for most coordinated protection schemes. Extended 3-second ratings should be specified only where the coordination study identifies clearing times that approach 2 seconds at the main breaker.
−
−## Ground Bus
−
−```datasheet
−label: Ground Bus
−type: radio
−options:
− - "Included - Full length of assembly"
− - "Not required"
−default: "Included - Full length of assembly"
−```
−
−Ground bus shall be bare copper, minimum 1/4 in. x 2 in. cross-section, extending the full length of the switchgear assembly. Ground bus shall be accessible without removing any covers or barriers required for safe operation. The ground bus shall be bonded to the building grounding electrode system, and, where the switchgear is part of a substation, to the substation ground grid, per [[sync/grounding-and-bonding]]. Bonding between the ground bus and each removable element (circuit breaker, instrument transformer drawer, voltage transformer roll-out) shall be continuous through automatic ground contacts that engage as the element is racked toward the connected position.
−
−# Physical Construction
−
−## Metal-Clad Compartmentalization
−
−Switchgear shall be metal-clad per IEEE C37.20.2: each major primary functional component shall be enclosed in its own grounded metal compartment, and grounded metal barriers shall separate compartments from one another and from the main bus. The following compartments shall be provided as a minimum for each circuit breaker cubicle:
−
−- Circuit breaker compartment with automatic primary-disconnect shutters
−- Main bus compartment, isolated by grounded metal barriers
−- Cable termination compartment for primary cable entry
−- Instrument transformer compartment (typically combined with the cable compartment), with drawout or roll-out CTs and VTs
−- Low-voltage control compartment, with a grounded metal barrier separating control wiring from all primary components
−
−### Primary Disconnect Shutters
−
−Automatic shutters shall close over the primary stationary disconnect contacts whenever the circuit breaker is withdrawn from the connected position, isolating the primary contacts from personnel reaching into the empty breaker compartment. Shutters shall be padlockable in the closed position to allow lock-out for maintenance.
−
−### Barriers Between Sections
−
−Insulated or metal barriers shall be provided between the main bus of adjacent sections such that an arc fault in one section cannot propagate along the main bus to adjacent sections without first burning through the barrier. Inter-section bus joint covers shall be removable for re-torquing without removing the section bus barriers.
−
−## Enclosure
−
−```datasheet
−label: Enclosure Type
−type: select
−options:
− - "Indoor - NEMA 1 (standard)"
− - "Indoor - NEMA 1A (gasketed)"
− - "Outdoor - Non-walk-in (NEMA 3R aisleless)"
− - "Outdoor - Walk-in (protected aisle)"
−default: "Indoor - NEMA 1 (standard)"
−```
−
−Indoor metal-clad switchgear is the standard configuration for medium-voltage equipment located inside dedicated electrical rooms. Outdoor non-walk-in switchgear places the breaker, bus, and cable compartments inside a weatherproof outer enclosure but does not provide an interior maintenance aisle; all maintenance is performed from outside the cubicle. Outdoor walk-in (protected aisle) configurations include an integrated, weatherproof, heated and ventilated aisle along the front (and rear, where rear-accessible) of the switchgear; the protected aisle allows breaker racking and maintenance to occur in a controlled environment regardless of outdoor conditions and is the preferred outdoor configuration for installations in cold climates, in occupied facilities, or where breaker maintenance frequency is high.
−
−```datasheet
−label: Accessibility
−type: radio
−options:
− - "Front accessible only (cable entry from front lower compartment)"
− - "Front and rear accessible (rear cable and bus access)"
−default: "Front and rear accessible (rear cable and bus access)"
−```
−
−Rear access is the standard configuration for metal-clad switchgear because primary cable terminations, main bus connections, and section splices are located in rear compartments. Front-only access configurations are available from some manufacturers but typically require additional vertical depth in the breaker cubicle and limit cable termination options.
−
−```datasheet
−label: Number of Vertical Sections
−type: range
−drawing_ref: true
−options:
− min: 1
− max: 20
− step: 1
−default: 4
−```
−
−Switchgear overall dimensions, section count, and arrangement shall be [[drawing: per the equipment room layout drawings]]. Coordinate section count and overall length with shipping splits to ensure equipment can be transported to and through the installation pathway. Indoor sections typically ship in groups of two or three; outdoor walk-in assemblies ship in larger shipping splits with reassembly of the protected aisle in the field.
−
−```datasheet
−label: Primary Cable Entry
−type: select
−options:
− - "Bottom entry"
− - "Top entry"
− - "Top and bottom entry"
−default: "Bottom entry"
−```
−
−## Arc-Resistant Construction
−
−```datasheet
−label: Arc-Resistant Rating (IEEE C37.20.7)
−type: select
−options:
− - "Not required"
− - "Type 1 - Front only"
− - "Type 2 - Front, rear, and sides"
− - "Type 2B - Type 2 plus low-voltage compartment door open"
− - "Type 2C - Type 2 plus between compartments"
−default: "Not required"
−```
−
−Arc-resistant construction per IEEE C37.20.7 provides a defined level of protection against the effects of an internal arcing fault by redirecting arc gases and pressure through plenums, ducts, or pressure relief flaps to areas where personnel are not present, while reinforced enclosure construction contains the arc event. The accessibility type designates which sides of the equipment provide protection when personnel are present:
−
−- **Type 1** protects personnel only at the front of the equipment
−- **Type 2** protects personnel at the front, rear, and both sides
−- **Type 2B** additionally protects when the low-voltage compartment door is open during maintenance
−- **Type 2C** additionally protects against arc propagation between compartments within the assembly
−
−Where arc-resistant construction is specified, switchgear shall be design-tested per IEEE C37.20.7 at the rated short-circuit current and at the specified arc duration (typically 0.5 seconds; extended durations require explicit specification). Arc plenums and gas exhaust paths shall be coordinated with the electrical room layout so that arc gases vent to a location that is not occupied. The arc-resistant rating is invalidated if doors, covers, or plenums are not in their as-tested configuration during operation; this requirement applies to maintenance personnel and shall be enforced through procedural controls and labeling.
−
−Arc-resistant construction does not eliminate the need for arc flash hazard analysis per IEEE 1584. See [[sync/arc-flash-study]] for arc flash study requirements and labeling.
−
−## Primary Bus
−
−```datasheet
−label: Primary Bus Material
−type: radio
−options:
− - "Copper (tin-plated)"
− - "Copper (silver-plated)"
−default: "Copper (silver-plated)"
−```
−
−Primary bus shall be high-conductivity copper. All joint contact surfaces shall be silver-plated to maintain low contact resistance over the equipment's service life; tin-plating is acceptable in non-corrosive environments where the Owner accepts the lower service life of tin contacts. Aluminum primary bus is not acceptable for metal-clad switchgear at any voltage class covered by this standard.
−
−```datasheet
−label: Primary Bus Insulation
−type: radio
−options:
− - "Fully insulated (epoxy or flame-retardant sleeving)"
− - "Bare bus with phase-to-phase and phase-to-ground clearances"
−default: "Fully insulated (epoxy or flame-retardant sleeving)"
−```
−
−Fully insulated primary bus is the modern standard for metal-clad switchgear and shall be specified for all installations except where the Owner expressly accepts the higher risk of bus faults associated with bare bus construction. Insulation shall be continuous through compartment barriers and inter-section bus splices, with insulating boots provided at splice joints. Bus insulation shall be flame-retardant, track-resistant, and rated for the operating temperature of the bus at full continuous current.
−
−Bus joints shall be bolted with Belleville washers to maintain contact pressure under thermal cycling. Splice joints between sections shall be accessible for re-torquing during maintenance from the rear of the switchgear without disturbing primary cables.
−
−```datasheet
−label: Bus Extension Provisions
−type: radio
−options:
− - "No future extension"
− - "Provision for future extension at one end"
− - "Provision for future extension at both ends"
−default: "No future extension"
−```
−
−## Infrared Scanning Provisions
−
−Enclosure shall include removable infrared inspection windows or cover plates at each primary bus splice joint between sections, at the main breaker compartment, and at the primary cable termination compartment of each feeder. Windows shall be rated for the maximum voltage class of the switchgear and shall allow thermographic inspection of energized primary connections without removing covers or de-energizing equipment. Window glazings shall be impact-resistant and shall be replaceable from the front or accessible side.
−
−# Circuit Breakers
−
−## Breaker Type
−
−```datasheet
−label: Circuit Breaker Interrupting Medium
−type: radio
−options:
− - "Vacuum"
− - "SF6 gas"
−default: "Vacuum"
−```
−
−Vacuum circuit breakers are the dominant technology for metal-clad switchgear at 5 kV, 15 kV, and 27 kV classes in the US market. Vacuum interrupters provide long contact life (typically 10,000+ mechanical operations and 30+ rated short-circuit operations), low maintenance requirements, and excellent interrupting performance with minimal arc energy. SF6 breakers are more common at 38 kV and above and may be specified at 27 kV where the manufacturer's specific design favors SF6. SF6 equipment carries refrigerant-equivalent reporting obligations under EPA regulations and may be subject to phase-down requirements in certain jurisdictions; verify the regulatory status before specifying SF6.
−
−## Drawout Construction
−
−Circuit breakers shall be drawout, stored-energy, three-position devices with three distinct positions: connected, test, and disconnected. The mechanical position indicator shall be visible from the front of the breaker compartment with the door closed. It shall not be possible to move the breaker between positions with the cubicle door closed unless the manufacturer's standard motor-operated racking mechanism is provided and operated from a remote location outside the arc flash boundary.
−
−Self-aligning primary disconnects shall engage automatically when the breaker is racked from the test position to the connected position. Secondary disconnects for control wiring shall remain engaged in both the test and connected positions, allowing electrical operation of the breaker for trip testing while in the test position without energizing the primary circuit. Automatic shutters in the cubicle (described above) shall close over the stationary primary contacts whenever the breaker is moved to the disconnected position or withdrawn from the cubicle.
−
−```datasheet
−label: Racking Mechanism
−type: select
−options:
− - "Manual racking handle"
− - "Motor-operated racking (local pushbutton)"
− - "Motor-operated racking (remote operation from outside arc flash boundary)"
−default: "Manual racking handle"
−```
−
−Motor-operated racking with remote operation is the preferred method where the available incident energy at the breaker exceeds Category 2 levels or where the Owner's electrical safety program requires racking to be performed from outside the arc flash boundary. Remote racking is increasingly specified for new construction at any incident energy level as a best-practice safety measure.
−
−## Operating Mechanism
−
−```datasheet
−label: Operating Mechanism Type
−type: radio
−options:
− - "Stored-energy spring (motor-charged, manually chargeable)"
− - "Magnetic actuator"
−default: "Stored-energy spring (motor-charged, manually chargeable)"
−```
−
−Stored-energy spring mechanisms are the established standard for metal-clad switchgear breakers and are available from all major manufacturers across all voltage classes. Magnetic actuator mechanisms are available from select manufacturers at 5 kV and 15 kV classes and offer reduced mechanical part count and longer maintenance intervals, but the technology is not yet universal and shall not be specified where multi-source procurement is required.
−
−## Control Voltage
−
−```datasheet
−label: Breaker Control Voltage (DC)
−type: select
−unit: VDC
−options:
− - "48 VDC"
− - "125 VDC"
− - "250 VDC"
−default: "125 VDC"
−```
−
−DC control voltage is supplied from the station battery system and operates the trip coil, close coil, and spring charging motor. 125 VDC is the dominant control voltage for industrial and utility-customer installations in the US market. 48 VDC is used in some telecommunications and data center environments where a 48 VDC plant already exists. 250 VDC is reserved for larger utility-style substations.
−
−Where the switchgear is supplied with a station battery, the battery and charger shall comply with [[sync/dc-battery-systems]]. Where DC control power is sourced from a remote battery system, coordinate the available battery voltage at the switchgear terminals (including voltage drop on the DC distribution feeders) with the breaker manufacturer's minimum operating voltage requirements.
−
−```datasheet
−label: Breaker Control Voltage (AC, for spring charging where DC is not available)
−type: select
−options:
− - "Not required - DC control"
− - "120 VAC (single-phase, from local control transformer)"
−default: "Not required - DC control"
−```
−
−## Main Circuit Breaker
−
−```datasheet
−label: Main Breaker Configuration
−type: select
−options:
− - "Main circuit breaker (drawout)"
− - "Main disconnect switch (utility-furnished primary disconnect)"
− - "Main lugs only (no main device)"
−default: "Main circuit breaker (drawout)"
−```
−
−Main breaker frame size and continuous current rating shall be [[drawing: as indicated on the one-line diagram]].
−
−Main lugs only configurations are limited applications where the upstream device provides main protection for the switchgear bus, typically at utility-customer secondary unit substations where the medium-voltage section is a tap from a larger distribution system. Main disconnect switch configurations are utility-furnished primary disconnects at the service entrance, ahead of the customer's main breaker.
−
−## Tie Circuit Breaker
−
−```datasheet
−label: Main-Tie-Main Configuration
−type: radio
−options:
− - "Single-ended (no tie breaker)"
− - "Double-ended with normally-open tie breaker (manual transfer)"
− - "Double-ended with automatic transfer (closed-transition or open-transition)"
−default: "Single-ended (no tie breaker)"
−```
−
−Double-ended switchgear with a tie breaker between two main breakers provides redundancy for critical loads served from two independent primary sources. Manual transfer schemes require an operator to close the tie breaker after opening the failed main; automatic transfer schemes accomplish the same function via control logic and may use open-transition (momentary loss of power) or closed-transition (no loss of power, with brief paralleling of sources) sequences. Closed-transition transfer requires utility coordination because it briefly parallels two utility sources and may have synchronizing, fault current, and protection implications.
−
−## Feeder Circuit Breakers
−
−Feeder breaker sizes, quantities, and continuous current ratings are [[drawing: as indicated on the one-line diagram and breaker schedules]].
−
−```datasheet
−label: Feeder Breaker Accessories
−type: checkbox
−options:
− - "Auxiliary contacts (minimum 2a + 2b)"
− - "Shunt trip"
− - "Undervoltage release"
− - "Trip-free mechanical interlock (paired breakers)"
− - "Kirk key interlock"
− - "Motor operator for remote close/trip"
− - "Breaker position indication (drawout connected/test/disconnected)"
−default: "Auxiliary contacts (minimum 2a + 2b)"
−```
−
−Auxiliary contacts shall be provided on every breaker for control, indication, and interlock purposes regardless of other accessory selections. Contacts shall indicate breaker open/close status and shall be wired to terminal blocks accessible without removing the breaker from its compartment.
−
−# Protective Relaying
−
−## Relay Platform
−
−Protective relays shall be multifunction microprocessor-based devices complying with IEEE C37.90, IEEE C37.90.1 (surge withstand), IEEE C37.90.2 (radiated EMI), and IEEE C37.90.3 (electrostatic discharge). Relays shall provide a local human-machine interface (display and pushbuttons), event recording with time stamps from a station time source, oscillographic fault recording (COMTRADE-compatible), self-diagnostics with alarm output, and a communications interface for remote settings, retrieval, and monitoring.
−
−```datasheet
−label: Protective Relay Platform
−type: radio
−options:
− - "Single multifunction relay per breaker"
− - "Centralized relay with breaker-mounted interface units"
−default: "Single multifunction relay per breaker"
−```
−
−A single multifunction relay per breaker is the dominant architecture in the US market and provides clear physical and logical separation between protection zones. Centralized relay architectures with breaker-mounted interface units are used at large substations and where IEC 61850 process bus integration is specified.
−
−## Protection Functions
−
−```datasheet
−label: Main Breaker Protection Functions
−type: checkbox
−options:
− - "Phase overcurrent (50/51)"
− - "Ground overcurrent (50G/51G or 50N/51N)"
− - "Differential (87) - main breaker or bus differential"
− - "Under/overvoltage (27/59)"
− - "Under/overfrequency (81U/81O)"
− - "Reverse power (32)"
− - "Negative sequence overcurrent (46) - unbalance protection"
− - "Breaker failure (50BF)"
− - "Synchronism check (25)"
−default: "Phase overcurrent (50/51)"
−```
−
−```datasheet
−label: Feeder Breaker Protection Functions
−type: checkbox
−options:
− - "Phase overcurrent (50/51)"
− - "Ground overcurrent (50G/51G or 50N/51N)"
− - "Negative sequence overcurrent (46)"
− - "Recloser logic (79) - overhead feeders"
− - "Breaker failure (50BF)"
−default: "Phase overcurrent (50/51)"
−```
−
−```datasheet
−label: Motor Feeder Protection Functions (where motor loads are served)
−type: checkbox
−options:
− - "Not applicable - no motor feeders"
− - "Thermal model (49)"
− - "Locked rotor / acceleration time (48/51LR)"
− - "Phase unbalance / negative sequence (46)"
− - "Loss of load (37)"
− - "Differential (87M)"
− - "Stator ground fault (50G)"
− - "Restart inhibit / starts-per-hour (66)"
−default: "Not applicable - no motor feeders"
−```
−
−Protection function selection shall be coordinated with the protection coordination study per [[sync/protective-coordination-study]] and shall result in selective tripping for all faults within the protected zone while allowing downstream devices to clear faults within their respective zones. Relay settings are [[drawing: as indicated on the relay setting schedule]].
−
−## Ground Fault Sensing
−
−```datasheet
−label: Ground Fault Sensing Method
−type: select
−options:
− - "Residually connected from phase CTs (3I0)"
− - "Zero-sequence (window/donut) CT on each feeder"
− - "Neutral CT on grounding resistor/transformer"
−default: "Zero-sequence (window/donut) CT on each feeder"
−```
−
−Zero-sequence CTs (also called window CTs or donut CTs) installed around the three-phase conductors of each feeder provide the most sensitive ground fault detection by directly measuring 3I0, with sensitivity typically one or two orders of magnitude better than residual sensing from phase CTs. Zero-sequence CTs are required for sensitive ground fault detection on resistance-grounded systems where the let-through current is intentionally limited.
−
−## Bus Differential Protection
−
−```datasheet
−label: Bus Differential Protection (87B)
−type: select
−options:
− - "Not required"
− - "High-impedance differential"
− - "Low-impedance differential (numerical)"
−default: "Not required"
−```
−
−Bus differential protection (ANSI 87B) provides fast (typically less than one cycle) clearing of faults on the main bus. It is recommended for switchgear where the main breaker upstream clearing time is too long to limit damage from a main bus fault, for installations with high available fault current, and for arc-resistant switchgear where reducing arc duration significantly reduces incident energy. Low-impedance numerical bus differential is the modern standard and tolerates CT saturation more gracefully than high-impedance designs.
−
−## Communications
−
−```datasheet
−label: Relay Communications Protocol
−type: select
−options:
− - "DNP3 (serial or TCP/IP)"
− - "Modbus RTU (RS-485)"
− - "Modbus TCP/IP (Ethernet)"
− - "IEC 61850 MMS (station bus only)"
− - "IEC 61850 MMS + GOOSE (station bus with peer-to-peer)"
−default: "DNP3 (serial or TCP/IP)"
−```
−
−IEC 61850 GOOSE messaging enables fast peer-to-peer signaling between relays for functions such as breaker failure tripping, bus differential blocking, and arc flash mitigation interlocking, with delivery times typically below 4 milliseconds. Where GOOSE is specified, the Ethernet station bus shall be a managed, redundant network (HSR, PRP, or RSTP rings as appropriate) and time synchronization shall be provided per IEEE 1588 PTPv2. IEC 61850 SCL files shall be delivered as part of the action submittals and updated at closeout.
−
−# Metering and Instrumentation
−
−## Instrument Transformers
−
−Current transformers and voltage transformers shall comply with IEEE C57.13. CTs shall be window type (toroidal) for zero-sequence applications and bushing or wound type for phase metering and relaying. VTs shall be drawout or roll-out with current-limiting primary fuses.
−
−Accuracy class shall be appropriate for the connected function:
−
−- Revenue metering: 0.3 accuracy class (B0.1 through B0.9 burden as required)
−- Protective relaying: C200 or higher (per IEEE C57.13 standard burden designations)
−- General monitoring and indication: 0.6 or 1.2 accuracy class
−
−Current transformers for metering and relaying shall be provided on separate cores. CTs shall not be shared between metering and protection functions. Where the switchgear includes utility metering, the utility CT and VT compartments shall be sized, located, and sealable per the serving utility's standards.
−
−```datasheet
−label: Voltage Transformer Configuration
−type: select
−options:
− - "Not required (no VTs)"
− - "Open delta (2 VTs) - line-to-line metering"
− - "Wye-wye (3 VTs) - line-to-neutral and line-to-line metering"
− - "Wye-wye with broken delta tertiary (3 VTs + tertiary) - ground fault detection"
−default: "Wye-wye (3 VTs) - line-to-neutral and line-to-line metering"
−```
−
−Wye-wye VTs with broken delta tertiary windings are required for ground fault detection by zero-sequence voltage (59N) on ungrounded and resonant-grounded systems. For solidly grounded and low-resistance grounded systems, current-based ground fault sensing is the primary scheme and broken delta tertiary VTs are typically not required.
−
−## Power Monitoring
−
−```datasheet
−label: Metering Type
−type: select
−options:
− - "No metering"
− - "Multifunction relay metering only (no dedicated meters)"
− - "Digital multifunction meter (main only)"
− - "Digital multifunction meter (main and each feeder)"
− - "Revenue-grade metering per utility requirements"
−default: "Digital multifunction meter (main only)"
−```
−
−```datasheet
−label: Meter Functions
−type: checkbox
−options:
− - "Voltage (L-L and L-N all phases)"
− - "Current (per phase and neutral/ground)"
− - "Power factor (per phase and total)"
− - "kW / kVA / kVAR (demand and instantaneous)"
− - "kWh / kVARh energy accumulation"
− - "Harmonics (THD per phase, individual to 31st)"
− - "Min/max recording with time stamp"
− - "Waveform capture"
− - "Sequence-of-events recording"
−default: "Voltage (L-L and L-N all phases)"
−```
−
−Where the relay platform provides metering with sufficient accuracy for the intended use, dedicated meters may be omitted. Modern multifunction relays provide 0.2% accuracy on voltage and current and meet most utility metering accuracy requirements; consult the utility provider before omitting a dedicated revenue meter.
−
−# Finish and Identification
−
−Enclosure shall receive a minimum two-coat paint system: corrosion-resistant primer and manufacturer's standard polyester powder coat finish. Minimum total dry film thickness shall be 3 mils (75 microns). For outdoor installations or environments classified C3 or higher, an enhanced paint system with a minimum of 5 mils dry film thickness shall be applied. All internal structural members shall receive the same corrosion treatment as exterior surfaces.
−
−```datasheet
−label: Finish Color
−type: text
−default: "ANSI 61 gray"
−```
−
−## Labeling
−
−Manufacturer shall provide engraved phenolic nameplates for the switchgear assembly and each individual device. Nameplates shall identify:
−
−- Switchgear designation and one-line reference
−- Bus ratings (voltage class, BIL, continuous current, short-circuit interrupting and momentary)
−- Individual breaker designation, continuous current rating, and interrupting rating
−- Current transformer ratios and accuracy class
−- Voltage transformer ratios and accuracy class
−- Arc-resistant rating (Type and arc duration) where applicable
−- Arc flash warning labels per NFPA 70E and IEEE 1584
−
−```datasheet
−label: Nameplate Material
−type: radio
−options:
− - "Laminated phenolic (indoor)"
− - "Stainless steel (outdoor or corrosive)"
− - "Aluminum (anodized)"
−default: "Laminated phenolic (indoor)"
−```
−
−Mimic bus diagram shall be provided on the front of each main and tie breaker section showing the bus configuration, breaker position, and source identification. Equipment labeling shall follow [[sync/equipment-labeling]] conventions.
−
−# Testing
−
−## Factory Production Tests
−
−The manufacturer shall perform the following production tests on the completed switchgear assembly per IEEE C37.20.2 and IEEE C37.09:
−
−- Power-frequency dielectric withstand test on primary bus and primary disconnects
−- Insulation resistance measurement on each phase bus
−- Mechanical operation of each circuit breaker (minimum 5 open/close cycles, with the breaker in the connected, test, and disconnected positions as applicable)
−- Electrical operation of each circuit breaker (trip and close via control circuits)
−- Control wiring continuity verification against the approved schematics
−- Current transformer ratio, polarity, and saturation curve test
−- Voltage transformer ratio and polarity test
−- Protective relay functional test, including pickup at set values and time delays
−- Trip and close circuit functional test
−- Verification of arc-resistant exhaust path integrity, where applicable
−- Visual and dimensional inspection against approved shop drawings
−
−```datasheet
−label: Factory Acceptance Test
−type: radio
−options:
− - "Witnessed by Owner's representative"
− - "Unwitnessed with certified test report"
− - "Not required beyond standard production tests"
−default: "Witnessed by Owner's representative"
−```
−
−Where witnessed factory testing is specified, the manufacturer shall provide a minimum of two weeks advance notice of test readiness. Test procedures shall be submitted for review prior to testing, and the witnessed test shall include a representative sample of the production tests above plus a partial-discharge test on the primary bus.
−
−# Field Quality Control
−
−## Field Acceptance Tests
−
−Contractor shall engage a qualified independent testing firm to perform acceptance testing per NETA ATS Section 7.2 (medium-voltage switchgear) and Section 7.6 (medium-voltage circuit breakers). Testing shall occur after installation is complete and before the equipment is energized.
−
−```datasheet
−label: Field Testing Requirements
−type: radio
−options:
− - "NETA acceptance testing and manufacturer startup"
− - "NETA acceptance testing only"
− - "Manufacturer startup only"
−default: "NETA acceptance testing and manufacturer startup"
−```
−
−Field acceptance tests shall include as a minimum:
−
−- Visual and mechanical inspection of all sections, bus joints, primary cable terminations, and devices
−- Bolted connection torque verification using a calibrated torque wrench, on a sampled basis per NETA ATS
−- Insulation resistance testing of primary bus (phase-to-phase and phase-to-ground), minimum one minute, recorded at 30 seconds and 60 seconds
−- Power-frequency overpotential (AC hi-pot) or very-low-frequency (VLF) withstand test on primary bus and primary cable terminations, at the field test voltage specified by IEEE C37.20.2 and the applicable cable standard
−- Partial-discharge measurement on the primary bus (where specified)
−- Contact resistance measurement on all bolted bus connections and primary disconnect contacts (micro-ohmmeter, minimum 100 ADC injection)
−- Vacuum integrity test on each vacuum interrupter (vacuum bottle hi-pot)
−- Circuit breaker operational testing in connected, test, and disconnected positions (mechanical and electrical)
−- Breaker close and open times, and contact bounce, measured by a circuit breaker analyzer
−- Primary current injection testing of all main and feeder protection functions, including pickup, time-delay, and instantaneous functions
−- Secondary injection testing of all relay protection functions not covered by primary injection
−- Current transformer ratio, polarity, and saturation verification
−- Voltage transformer ratio and polarity verification
−- Metering accuracy verification against a calibrated reference
−- Ground impedance measurement of the switchgear ground bus and substation ground grid per IEEE 81
−- Functional testing of all control circuits, interlocks, alarms, and breaker failure schemes
−- Verification of IEC 61850 GOOSE messages and trip times, where applicable
−
−## Infrared Thermographic Inspection
−
−```datasheet
−label: Infrared Thermographic Inspection
−type: radio
−options:
− - "Initial scan within 90 days of energization, follow-up at 11 months"
− - "Initial scan within 90 days of energization only"
− - "Not required"
−default: "Initial scan within 90 days of energization, follow-up at 11 months"
−```
−
−Infrared scanning shall be performed under normal operating load conditions (minimum 40% of rated load where practical) through the infrared inspection windows specified above. All connections exceeding 10°C rise above ambient shall be reported and corrected. The 11-month follow-up scan captures connections that may loosen during the initial thermal cycling period and falls within the standard one-year warranty window.
−
−# Installation
−
−## Concrete Housekeeping Pad
−
−Switchgear shall be mounted on a reinforced concrete housekeeping pad extending a minimum of 4 in. beyond the base of the equipment on all sides. Pad shall be a minimum of 4 in. above finished floor for indoor installations and 6 in. above finished grade for outdoor installations. Anchor bolt size and pattern shall match the manufacturer's shop drawings and shall develop the seismic anchorage force/moment values certified per the seismic basis.
−
−Coordinate pad dimensions, conduit penetrations, primary and control cable entry locations, and anchor bolt locations with equipment shop drawings prior to concrete placement. See [[sync/concrete-pads]] for construction requirements.
−
−## Equipment Setting
−
−Contractor shall comply with the manufacturer's installation instructions and applicable rigging requirements. Sections shall be lifted only by the manufacturer's designated lifting points and shall not be lifted by bus, doors, or device handles. Remove all temporary shipping braces, blocking, and desiccants prior to final assembly.
−
−After assembly, verify the following before energizing:
−
−- All shipping restraints and temporary grounds removed
−- Bus splice joints torqued per the manufacturer's specifications using a calibrated torque wrench, with witness marks applied
−- Primary cable terminations completed per the cable manufacturer's instructions, including stress relief, ground shield bonding, and torqued lug connections
−- Primary cable terminations sealed against moisture intrusion at the cable entry point
−- All circuit breakers rack and operate freely in all three positions
−- Automatic primary disconnect shutters operate freely and close completely when the breaker is withdrawn
−- Space heaters energized for outdoor or unconditioned installations
−- DC control power present and within the manufacturer's specified range at the switchgear terminals
−- Working clearances per NFPA 70 Article 110.34 maintained
−- Switchgear ground bus bonded to the building grounding electrode system and substation ground grid per [[sync/grounding-and-bonding]]
−
−## Working Clearance
−
−Minimum working space shall be maintained per NFPA 70 Article 110.34 for equipment over 1000 volts. Working space dimensions depend on the nominal voltage and the accessibility configuration (exposed live parts on one side, both sides, or both sides with the operator between):
−
−| Nominal voltage to ground | Condition 1 | Condition 2 | Condition 3 |
−|---------------------------|-------------|-------------|-------------|
−| 601 V – 2500 V | 3 ft | 4 ft | 5 ft |
−| 2501 V – 9000 V | 4 ft | 5 ft | 6 ft |
−| 9001 V – 25,000 V | 5 ft | 6 ft | 9 ft |
−| 25,001 V – 75 kV | 6 ft | 8 ft | 10 ft |
−
−Working space shall not be used for storage. Dedicated electrical space above and below the equipment shall be maintained per NFPA 70 Article 110.34(F). At least two entrances of sufficient area shall be provided to give access to the working space about electrical equipment per NFPA 70 Article 110.33; one entrance shall be permitted where the working space layout meets the exceptions of that section. Coordinate room layout with [[sync/electrical-rooms]].
−
−## Cable Terminations
−
−Primary cable termination shall be performed by personnel certified by the cable termination kit manufacturer or holding equivalent third-party qualifications. Shielded medium-voltage cables shall be terminated with stress-relief terminations rated for the cable insulation class and for the application (indoor, outdoor, or wet location). Cable shields shall be bonded to the switchgear ground bus through a dedicated ground shield connection at each termination per [[sync/grounding-and-bonding]] and the cable manufacturer's instructions.
−
−Medium-voltage cable selection, routing, supports, raceway sizing, and bend radius shall comply with [[sync/conductors-and-cables]] and [[sync/raceways-and-conduit]].
−
−## Identification of Source
−
−Where the switchgear is fed from a remote source or from two or more sources, permanent labels per NFPA 70 Article 490 shall identify each source location and circuit designation at the switchgear and at each remote source. Where the switchgear supplies emergency, legally required standby, or critical operations loads downstream through low-voltage transformers, source identification shall be coordinated with [[sync/low-voltage-switchgear]] and the downstream distribution equipment labeling.
−
−# Delivery, Storage, and Handling
−
−Switchgear shall be shipped in the largest factory-assembled sections that can be transported to and within the installation site. Verify all pathway dimensions (doors, hallways, elevator shafts, turning radii, structural floor loading) between the delivery point and the final installation location prior to ordering. Coordinate shipping splits with the manufacturer on the approved shop drawings.
−
−Outdoor walk-in switchgear shall ship with the protected aisle disassembled for transport. Aisle reassembly, seal verification, and pressure relief flap inspection shall be performed at the site by the manufacturer's authorized field service representative.
−
−Equipment shall be stored indoors in a clean, dry location. Where indoor storage is not available, the manufacturer shall provide weatherproof packaging and desiccants. Condensation heaters shall be connected and energized during storage if the equipment will be stored for more than 30 days or if the storage environment is not climate-controlled. Vacuum interrupters and SF6 breakers shall be stored within the temperature range specified by the manufacturer; SF6 gas pressure shall be verified before energization and topped off if necessary.
−
−# Warranty
−
−```datasheet
−label: Warranty Period
−type: select
−options:
− - "1 year from substantial completion"
− - "2 years from substantial completion"
− - "3 years from substantial completion"
− - "5 years from substantial completion"
−default: "2 years from substantial completion"
−```
−
−Warranty shall cover defects in materials and workmanship under normal use and service conditions. The manufacturer shall maintain a service organization capable of providing emergency replacement parts and field service within 24 hours during the warranty period.
−
−```datasheet
−label: Extended Warranty Coverage
−type: checkbox
−options:
− - "Parts only"
− - "Parts and labor"
− - "Emergency response (24/7 with 4-hour commitment)"
− - "Scheduled preventive maintenance (annual)"
− - "Protective relay setting management and version control"
−default: "Parts only"
−```
−
−# Spare Parts
−
−```datasheet
−label: Spare Circuit Breakers
−type: radio
−options:
− - "None"
− - "One spare breaker of each frame size installed"
− - "10% of each frame size (minimum one)"
−default: "One spare breaker of each frame size installed"
−```
−
−Spare circuit breakers shall be of the same type, rating, and configuration as the installed breakers and shall be fully interchangeable in any cubicle of the same frame size. Spare breakers shall be stored on a breaker handling/lift truck supplied by the manufacturer, located in the electrical room or substation control building.
−
−Manufacturer shall provide the following additional spare parts at substantial completion:
−
−- One spare set of primary disconnect contact fingers for each breaker frame size
−- One spare set of control fuses, indicating lights, and auxiliary switches for each type installed
−- One set of vacuum bottle replacements for the smallest breaker frame (where the manufacturer supports field replacement of vacuum interrupters)
−- One spare set of voltage transformer primary fuses for each VT rating installed
−- One spare protective relay of each model installed (or documented availability from manufacturer stock with 48-hour delivery commitment)
−- One breaker handling/lift truck appropriate for the heaviest breaker installed
−- One set of breaker test plugs and secondary injection couplers
−- One complete set of keys for all door locks and Kirk key interlocks
−- Touch-up paint matching the finish color (minimum one quart)
+---
+title: Medium Voltage Switchgear
+category: Power Distribution
+toc_depth: 3
+description: >
+ When to use: Metal-clad medium-voltage switchgear rated above 1 kV through 38 kV using drawout vacuum or SF6 circuit breakers, built to IEEE C37.20.2 and the ANSI/IEEE C37.04 / C37.06 / C37.09 series, for utility-customer substations, large commercial campuses, healthcare and higher-education central plants, data centers, and industrial facilities. Covers 5 kV, 15 kV, 27 kV, and 38 kV voltage classes, indoor and outdoor walk-in (protected aisle) configurations, arc-resistant ratings per IEEE C37.20.7, multifunction microprocessor protective relays, and optional IEC 61850 station bus communications.
+ Not intended for: Metal-enclosed interrupter switchgear with load-interrupter switches and power fuses (see IEEE C37.20.3), pad-mounted distribution switchgear, low voltage switchgear rated 600V and below (see [[sync/low-voltage-switchgear]]), low voltage switchboards (see [[sync/low-voltage-switchboards]]), motor control centers (see [[sync/motor-control-centers]]), or unit substations as an assembly (the MV section of a unit substation cites this standard for the switchgear scope).
+---
+
+# Scope {toc}
+
+## This specification covers metal-clad medium-voltage switchgear assemblies rated above 1 kV through 38 kV. {note}
+
+## Switchgear shall be constructed and tested in accordance with IEEE C37.20.2 (Metal-Clad Switchgear) and listed or labeled by a Nationally Recognized Testing Laboratory where such listing is available.
+
+## Circuit breakers shall comply with ANSI/IEEE C37.04 (Rating Structure), IEEE C37.06 (Preferred Ratings), and IEEE C37.09 (Test Procedures).
+
+## Circuit breakers shall be drawout, three-pole, single-throw devices using vacuum or SF6 interrupters.
+
+## Switchgear shall be fully metal-clad: each major primary functional component (circuit breaker, main bus, instrument transformers, cable terminations) shall be housed in its own grounded metal compartment, and grounded metal barriers shall separate compartments from one another and from the bus.
+
+## Compartmentalization, automatic primary-disconnect shutters that close when the breaker is withdrawn, and insulated primary bus distinguish metal-clad construction from the metal-enclosed interrupter switchgear of IEEE C37.20.3, which uses load-interrupter switches with power fuses and lacks the same level of segregation. {note}
+
+## For metal-enclosed interrupter switchgear, refer to IEEE C37.20.3; that equipment is outside the scope of this standard. {note}
+
+## This standard addresses the typical applications of medium-voltage switchgear in the United States market: 5 kV and 15 kV utility-customer service entrance equipment downstream of utility primary metering, 15 kV main and tie switchgear for large commercial and institutional campuses, 5 kV and 15 kV motor and feeder switchgear at industrial and process facilities, and 27 kV and 38 kV equipment at sites taking service at higher subtransmission voltages. {note}
+
+## Arc-resistant construction per IEEE C37.20.7 is addressed where occupant safety, equipment density, or insurer requirements warrant it. {note}
+
+## Coordination of overcurrent protection across the medium-voltage system shall follow [[sync/protective-coordination-study]].
+
+## Arc flash hazard analysis shall be performed per IEEE 1584 and [[sync/arc-flash-study]].
+
+## Grounding of the switchgear ground bus, neutral grounding equipment, and the substation ground grid (where applicable) shall be per [[sync/grounding-and-bonding]].
+
+## Medium-voltage cable terminations, raceway, and conduit entry shall comply with [[sync/conductors-and-cables]] and [[sync/raceways-and-conduit]].
+
+## Where the switchgear feeds downstream low-voltage distribution through unit substations or pad-mounted transformers, the secondary equipment shall comply with [[sync/low-voltage-switchgear]], [[sync/low-voltage-switchboards]], or [[sync/motor-control-centers]] as applicable.
+
+# Referenced Standards {toc}
+
+## Equipment and installation shall comply with the latest adopted edition of the standards listed below.
+
+## Where conflicts exist between referenced standards, the more stringent requirement shall govern unless otherwise directed by the Engineer of Record.
+
+## Reference Table {toc}
+
+| Standard | Title |
+|----------|-------|
+| IEEE C37.20.2 | Standard for Metal-Clad Switchgear |
+| IEEE C37.20.3 | Standard for Metal-Enclosed Interrupter Switchgear (reference for distinction from metal-clad) |
+| IEEE C37.20.7 | Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults |
+| ANSI/IEEE C37.04 | Standard Rating Structure for AC High-Voltage Circuit Breakers |
+| IEEE C37.06 | AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis — Preferred Ratings and Related Required Capabilities |
+| IEEE C37.09 | Standard Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
+| IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
+| IEEE C37.011 | Application Guide for Transient Recovery Voltage for AC High-Voltage Circuit Breakers |
+| IEEE C37.100.1 | Standard of Common Requirements for High-Voltage Power Switching Devices Rated Above 1000V |
+| IEEE C37.90 | Standard for Relays and Relay Systems Associated with Electric Power Apparatus |
+| IEEE C37.90.1 | Standard for Surge Withstand Capability (SWC) Tests for Relays and Relay Systems |
+| IEEE C37.90.2 | Standard for Withstand Capability of Relay Systems to Radiated Electromagnetic Interference from Transceivers |
+| IEEE C37.90.3 | Standard for Electrostatic Discharge Tests for Protective Relays |
+| IEEE C57.13 | Requirements for Instrument Transformers |
+| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
+| IEEE 81 | Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System |
+| IEC 61850 | Communication Networks and Systems for Power Utility Automation (where station bus is specified) |
+| ANSI C84.1 | Electric Power Systems and Equipment — Voltage Ratings (60 Hz) |
+| ANSI/NEMA SG 4 | Alternating-Current High-Voltage Circuit Breakers |
+| ANSI/NEMA SG 5 | Power Switchgear Assemblies |
+| NFPA 70 | National Electrical Code (Article 490 — Equipment Over 1000 Volts) |
+| NFPA 70E | Standard for Electrical Safety in the Workplace |
+| NETA ATS | Acceptance Testing Specifications for Electrical Power Equipment and Systems |
+| IBC | International Building Code |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
+| ICC ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### Contractor shall submit the following for review prior to fabrication.
+### Action submittals shall include the deliverables listed below.
+
+- Shop drawings showing front, side, and rear elevations with overall dimensions, weight per section, and shipping splits
+- Single line diagram indicating voltage class, BIL, continuous current rating, short-circuit interrupting and momentary ratings, breaker types, instrument transformer ratios and accuracy classes, and protective relay designations
+- Bill of materials listing all major components by type, rating, and quantity
+- Time-current coordination curves for all protective devices, plotted on a common log-log axis at the system base voltage
+- Relay setting tables for all protection functions, with reference to the coordination study
+- Control schematic and wiring diagrams for each circuit breaker, instrument transformer circuit, relay, metering device, and station battery interface
+- IEC 61850 SCL files (SSD, SCD, and IID as applicable), where station bus is specified
+- Cable termination details for primary cable, including lug type, stress relief, and ground shield bond
+- Bus bracing and short-circuit withstand calculations or reference to design-tested ratings
+- Heat loss data per section for ventilation and HVAC coordination of the electrical room
+- Arc-resistance qualification test report per IEEE C37.20.7, where arc-resistant construction is specified
+- Seismic certification documentation per ICC ES AC156 or analysis per ASCE 7, where required
+- Conduit and cable entry diagrams for top, bottom, and side entry zones
+- Recommended spare parts list
+
+```datasheet
+label: Submittal Documentation
+type: checkbox
+options:
+ - "Shop drawings (front, side, rear elevations) with shipping splits"
+ - "Single line diagram with full ratings"
+ - "Bill of materials"
+ - "Time-current coordination curves and relay setting tables"
+ - "Control schematics and wiring diagrams"
+ - "IEC 61850 SCL files (where station bus specified)"
+ - "Cable termination details"
+ - "Bus bracing and short-circuit calculations"
+ - "Heat loss data per section"
+ - "Arc-resistance qualification test report"
+ - "Seismic certification (IBC/ASCE 7)"
+ - "Conduit/cable entry diagrams"
+ - "Recommended spare parts list"
+default: "Shop drawings (front, side, rear elevations) with shipping splits"
+```
+
+### Procurement and fabrication shall not proceed until the corresponding submittals have been reviewed and returned.
+
+## Closeout Submittals {toc}
+
+### Contractor shall provide the following at substantial completion.
+
+- Operation and maintenance manuals, bound with table of contents and indexed by section
+- As-built shop drawings, schematics, and one-line diagrams reflecting field modifications
+- Factory production test reports and design test certifications
+- Field acceptance test reports per NETA ATS
+- Arc flash incident energy analysis and installed labels
+- Protective relay setting files in the manufacturer's native format and a vendor-neutral export (e.g., CSV or COMTRADE-compatible event records)
+- Warranty documentation
+- Spare parts inventory with reorder information and storage location
+
+```datasheet
+label: Closeout Submittals
+type: checkbox
+options:
+ - "Operation and maintenance manuals"
+ - "As-built shop drawings, schematics, and one-line diagrams"
+ - "Factory production test reports and design test certifications"
+ - "Field acceptance test reports per NETA ATS"
+ - "Arc flash incident energy analysis and installed labels"
+ - "Protective relay setting files (native and vendor-neutral export)"
+ - "Warranty documentation"
+ - "Spare parts inventory with reorder information and storage location"
+default: [Operation and maintenance manuals, As-built shop drawings, schematics, and one-line diagrams, Factory production test reports and design test certifications, Field acceptance test reports per NETA ATS, Arc flash incident energy analysis and installed labels, Protective relay setting files (native and vendor-neutral export), Warranty documentation, Spare parts inventory with reorder information and storage location]
+```
+
+# Quality Assurance {toc}
+
+## Manufacturer Qualifications {toc}
+
+### Switchgear shall be manufactured by a single company responsible for the assembly, primary bus, circuit breakers, primary disconnects, instrument transformers, and protective relay integration as a coordinated package.
+
+### The manufacturer shall have a minimum of ten years documented experience producing metal-clad switchgear at the specified voltage class.
+
+### The manufacturer shall maintain an ISO 9001 certified quality management system.
+
+### The manufacturer shall maintain a 24/7 service organization with factory-trained field representatives available within 24 hours of notification for the duration of the warranty period.
+
+## Source Limitations {toc}
+
+### All switchgear sections, primary bus, circuit breakers, instrument transformers, protective relays, and metering equipment shall be produced or furnished by the switchgear manufacturer as an integrated assembly.
+
+### Field-assembled metal-clad enclosures and third-party retrofit assemblies are not acceptable.
+
+### Devices and accessories shall be the manufacturer's standard catalog components for the listed assembly.
+
+## Design Tests {toc}
+
+### The manufacturer shall provide certification that the switchgear design has passed all design tests required by IEEE C37.20.2 (for the assembly) and IEEE C37.09 (for the circuit breakers), including but not limited to dielectric withstand, continuous current temperature rise, short-time current, momentary withstand, mechanical operation endurance, and interrupting capability.
+
+### Where arc-resistant construction is specified, the design shall have passed internal arcing fault testing per IEEE C37.20.7 at the specified short-circuit current and arc duration for the accessibility type required.
+
+## Testing Personnel Qualifications {toc}
+
+### Field acceptance testing shall be performed by a firm regularly engaged in testing electrical power equipment, employing technicians certified by NETA or equivalent.
+
+### Testing personnel shall have a minimum of five years documented experience testing metal-clad switchgear at the specified voltage class.
+
+# Environmental and Service Conditions {toc}
+
+## Switchgear shall be suitable for continuous operation under the usual service conditions defined by IEEE C37.20.2 and IEEE C37.04.
+
+## Where site conditions exceed these parameters, notify the manufacturer and apply the appropriate derating per the applicable standard.
+
+## Ambient and Altitude {toc}
+
+```datasheet
+label: Ambient Temperature (Maximum)
+type: select
+unit: °C
+options:
+ - "40°C (standard rating)"
+ - "50°C (elevated ambient)"
+ - "55°C (desert/rooftop rating)"
+default: "40°C (standard rating)"
+```
+
+```datasheet
+label: Installation Altitude
+type: select
+options:
+ - "Below 3,300 ft (1,000 m) - No derating"
+ - "3,300 - 6,600 ft (1,000 - 2,000 m) - Derating may apply"
+ - "Above 6,600 ft (2,000 m) - Derating required per IEEE C37.04"
+default: "Below 3,300 ft (1,000 m) - No derating"
+```
+
+### Altitude derating for medium-voltage switchgear begins at lower elevations than for low-voltage equipment because the reduced air density at higher altitudes reduces dielectric strength and degrades convective cooling. {note}
+
+### The Engineer shall document derating calculations on the contract drawings and coordinate the corrected ratings with the system short-circuit and coordination studies.
+
+## Corrosion Severity {toc}
+
+```datasheet
+label: Corrosion Severity
+type: select
+options:
+ - "C2 - Low (indoor, climate-controlled)"
+ - "C3 - Medium (indoor, unconditioned)"
+ - "C4 - High (coastal, chemical exposure)"
+ - "C5 - Very High (industrial, marine)"
+default: "C2 - Low (indoor, climate-controlled)"
+```
+
+### For installations classified C4 or C5, primary bus shall be silver-plated copper at all joint contact surfaces, hardware shall be stainless steel, and the enclosure paint system shall provide enhanced corrosion protection.
+
+### Outdoor walk-in (protected aisle) enclosures in C4 or C5 environments shall additionally include conditioned ventilation to maintain interior humidity below condensation thresholds.
+
+## Seismic Requirements {toc}
+
+```datasheet
+label: Seismic Certification
+type: select
+options:
+ - "Not required"
+ - "IBC/ASCE 7 - Importance Factor 1.0"
+ - "IBC/ASCE 7 - Importance Factor 1.5 (essential facility)"
+ - "OSHPD pre-approval required (California healthcare)"
+default: "Not required"
+```
+
+### Where required by the applicable building code, switchgear shall be seismically certified by shake-table testing per ICC ES AC156 or by analysis per ASCE 7.
+
+### Seismic certification shall be by an independent third-party testing laboratory and shall cover the complete assembly as installed, including all circuit breakers, primary bus, instrument transformers, and ancillary components in their service configuration.
+
+### Certification of individual components in isolation is not acceptable.
+
+### Anchorage details and base anchor force/moment values shall be coordinated with the structural engineer of record.
+
+# Electrical Requirements {toc}
+
+## System Ratings {toc}
+
+```datasheet
+label: Service Entrance Equipment
+type: radio
+options:
+ - "Yes - Utility-customer service entrance"
+ - "No - Downstream distribution"
+default: "No - Downstream distribution"
+```
+
+```datasheet
+label: Nominal System Voltage Class
+type: select
+unit: kV
+options:
+ - "4.16 kV (5 kV class)"
+ - "12.47 kV (15 kV class)"
+ - "13.2 kV (15 kV class)"
+ - "13.8 kV (15 kV class)"
+ - "24.94 kV (27 kV class)"
+ - "34.5 kV (38 kV class)"
+default: "13.8 kV (15 kV class)"
+```
+
+```datasheet
+label: System Frequency
+type: radio
+unit: Hz
+options:
+ - "60 Hz"
+ - "50 Hz"
+default: "60 Hz"
+```
+
+```datasheet
+label: System Grounding
+type: select
+options:
+ - "Solidly grounded wye"
+ - "Low-resistance grounded wye"
+ - "High-resistance grounded wye"
+ - "Ungrounded"
+ - "Resonant grounded (Petersen coil)"
+default: "Low-resistance grounded wye"
+```
+
+### Where switchgear serves as utility-customer service entrance equipment, it shall comply with NFPA 70 Article 490 and the serving utility's interconnection requirements, including provisions for utility metering current and voltage transformers, primary disconnect, and available fault current verification.
+
+### Coordinate primary metering compartment configuration, sealability, and clearances with the serving utility prior to submittal.
+
+### Nominal system voltage shall be one of the standard values defined in ANSI C84.1.
+
+### The voltage class designates the rated maximum voltage of the equipment per IEEE C37.06 (e.g., 4.76 kV equipment is referred to as 5 kV class and is suitable for 4.16 kV nominal systems). {note}
+
+### Coordinate the selected voltage class with the serving utility distribution voltage.
+
+### System grounding selection drives ground fault sensing scheme, ground current magnitude, neutral grounding equipment design, and protective relay configuration. {note}
+
+### Low-resistance grounding (typically 200 A to 400 A let-through) is the most common configuration for utility-customer 5 kV and 15 kV distribution because it limits ground fault current to levels that minimize equipment damage while still allowing selective coordination of feeder ground fault elements. {note}
+
+### Solidly grounded systems are more common where the medium-voltage system feeds low-voltage transformers exclusively and ground fault current must be high enough to trip phase overcurrent devices. {note}
+
+### High-resistance grounding is selected where service continuity on a first ground fault is required (typically industrial process loads). {note}
+
+### Coordinate the grounding method with [[sync/grounding-and-bonding]] and any associated neutral grounding resistor or transformer.
+
+## Insulation Level (BIL) {toc}
+
+```datasheet
+label: Basic Impulse Level (BIL)
+type: select
+unit: kV
+options:
+ - "60 kV BIL (5 kV class)"
+ - "75 kV BIL (5 kV class, special)"
+ - "95 kV BIL (15 kV class)"
+ - "125 kV BIL (27 kV class)"
+ - "150 kV BIL (38 kV class)"
+ - "200 kV BIL (38 kV class, special)"
+default: "95 kV BIL (15 kV class)"
+```
+
+### BIL shall match the rated maximum voltage of the switchgear per IEEE C37.06.
+
+### Standard BIL is sufficient for most utility-fed distribution applications. {note}
+
+### Increased BIL ratings should be considered for systems exposed to lightning surge environments where surge arresters at the service may not provide sufficient margin, or where the system topology can produce transient overvoltages that exceed standard insulation coordination.
+
+## Continuous Current and Short-Circuit Ratings {toc}
+
+```datasheet
+label: Main Bus Continuous Current
+type: range
+unit: A
+drawing_ref: true
+options:
+ min: 1200
+ max: 4000
+ setpoints: [1200, 2000, 3000, 4000]
+default: 2000
+```
+
+```datasheet
+label: Short-Circuit Interrupting Rating (symmetrical)
+type: select
+unit: kA
+options:
+ - "25 kA sym"
+ - "31.5 kA sym"
+ - "40 kA sym"
+ - "50 kA sym"
+ - "63 kA sym"
+default: "40 kA sym"
+```
+
+```datasheet
+label: Close-and-Latch Rating (asymmetrical, peak)
+type: select
+options:
+ - "Matched to interrupting rating per IEEE C37.06"
+ - "Increased above standard - specify per project requirements"
+default: "Matched to interrupting rating per IEEE C37.06"
+```
+
+```datasheet
+label: Short-Time Withstand (Momentary) Duration
+type: select
+options:
+ - "2 seconds (per IEEE C37.04)"
+ - "3 seconds (extended duration)"
+default: "2 seconds (per IEEE C37.04)"
+```
+
+### Main bus continuous current rating shall be [[drawing: as indicated on the one-line diagram]].
+
+### Bus shall be braced for the available short-circuit current at the point of installation as determined by a short-circuit analysis per IEEE C37.010.
+
+### Short-circuit interrupting rating, expressed as a symmetrical rms current value per IEEE C37.04, shall equal or exceed the available three-phase fault current at the switchgear terminals.
+
+### The application short-circuit current shall be determined per IEEE C37.010, which includes evaluation of the X/R ratio of the system and the resulting asymmetry factor.
+
+### Where the system X/R ratio exceeds the test X/R used to qualify the breaker, the breaker's interrupting rating shall be derated per IEEE C37.010.
+
+### Verify available fault current with the utility provider and perform a short-circuit study per [[sync/short-circuit-study]] prior to equipment procurement.
+
+### Close-and-latch rating, also referred to as the momentary or making current rating, shall be the IEEE C37.06 preferred value associated with the selected interrupting rating.
+
+### The close-and-latch rating represents the peak asymmetrical current the breaker can close into and latch without damage; it is approximately 2.6 to 2.7 times the symmetrical interrupting rating depending on the rating standard generation. {note}
+
+### The short-time current withstand duration governs how long the breaker and bus can carry the rated short-circuit current without operating. {note}
+
+### The standard 2-second rating is sufficient for most coordinated protection schemes. {note}
+
+### Extended 3-second ratings should be specified only where the coordination study identifies clearing times that approach 2 seconds at the main breaker.
+
+## Ground Bus {toc}
+
+```datasheet
+label: Ground Bus
+type: radio
+options:
+ - "Included - Full length of assembly"
+ - "Not required"
+default: "Included - Full length of assembly"
+```
+
+### Ground bus shall be bare copper, minimum 1/4 in. x 2 in. cross-section, extending the full length of the switchgear assembly.
+
+### Ground bus shall be accessible without removing any covers or barriers required for safe operation.
+
+### The ground bus shall be bonded to the building grounding electrode system, and, where the switchgear is part of a substation, to the substation ground grid, per [[sync/grounding-and-bonding]].
+
+### Bonding between the ground bus and each removable element (circuit breaker, instrument transformer drawer, voltage transformer roll-out) shall be continuous through automatic ground contacts that engage as the element is racked toward the connected position.
+
+# Physical Construction {toc}
+
+## Metal-Clad Compartmentalization {toc}
+
+### The following compartments shall be provided as a minimum for each circuit breaker cubicle:
+
+- Circuit breaker compartment with automatic primary-disconnect shutters
+- Main bus compartment, isolated by grounded metal barriers
+- Cable termination compartment for primary cable entry
+- Instrument transformer compartment (typically combined with the cable compartment), with drawout or roll-out CTs and VTs
+- Low-voltage control compartment, with a grounded metal barrier separating control wiring from all primary components
+
+### Switchgear shall be metal-clad per IEEE C37.20.2: each major primary functional component shall be enclosed in its own grounded metal compartment, and grounded metal barriers shall separate compartments from one another and from the main bus.
+
+### The compartments listed above shall be provided as a minimum for each circuit breaker cubicle.
+
+### Primary Disconnect Shutters {toc}
+
+#### Automatic shutters shall close over the primary stationary disconnect contacts whenever the circuit breaker is withdrawn from the connected position, isolating the primary contacts from personnel reaching into the empty breaker compartment.
+
+#### Shutters shall be padlockable in the closed position to allow lock-out for maintenance.
+
+### Barriers Between Sections {toc}
+
+#### Insulated or metal barriers shall be provided between the main bus of adjacent sections such that an arc fault in one section cannot propagate along the main bus to adjacent sections without first burning through the barrier.
+
+#### Inter-section bus joint covers shall be removable for re-torquing without removing the section bus barriers.
+
+## Enclosure {toc}
+
+```datasheet
+label: Enclosure Type
+type: select
+options:
+ - "Indoor - NEMA 1 (standard)"
+ - "Indoor - NEMA 1A (gasketed)"
+ - "Outdoor - Non-walk-in (NEMA 3R aisleless)"
+ - "Outdoor - Walk-in (protected aisle)"
+default: "Indoor - NEMA 1 (standard)"
+```
+
+```datasheet
+label: Accessibility
+type: radio
+options:
+ - "Front accessible only (cable entry from front lower compartment)"
+ - "Front and rear accessible (rear cable and bus access)"
+default: "Front and rear accessible (rear cable and bus access)"
+```
+
+```datasheet
+label: Number of Vertical Sections
+type: range
+drawing_ref: true
+options:
+ min: 1
+ max: 20
+ step: 1
+default: 4
+```
+
+```datasheet
+label: Primary Cable Entry
+type: select
+options:
+ - "Bottom entry"
+ - "Top entry"
+ - "Top and bottom entry"
+default: "Bottom entry"
+```
+
+### Indoor metal-clad switchgear is the standard configuration for medium-voltage equipment located inside dedicated electrical rooms. Outdoor non-walk-in switchgear places the breaker, bus, and cable compartments inside a weatherproof outer enclosure but does not provide an interior maintenance aisle; all maintenance is performed from outside the cubicle. {note}
+
+### Outdoor walk-in (protected aisle) configurations include an integrated, weatherproof, heated and ventilated aisle along the front (and rear, where rear-accessible) of the switchgear; the protected aisle allows breaker racking and maintenance to occur in a controlled environment regardless of outdoor conditions and is the preferred outdoor configuration for installations in cold climates, in occupied facilities, or where breaker maintenance frequency is high. {note}
+
+### Rear access is the standard configuration for metal-clad switchgear because primary cable terminations, main bus connections, and section splices are located in rear compartments. Front-only access configurations are available from some manufacturers but typically require additional vertical depth in the breaker cubicle and limit cable termination options. {note}
+
+### Switchgear overall dimensions, section count, and arrangement shall be [[drawing: per the equipment room layout drawings]].
+
+### Coordinate section count and overall length with shipping splits to ensure equipment can be transported to and through the installation pathway.
+
+### Indoor sections typically ship in groups of two or three; outdoor walk-in assemblies ship in larger shipping splits with reassembly of the protected aisle in the field. {note}
+
+## Arc-Resistant Construction {toc}
+
+```datasheet
+label: Arc-Resistant Rating (IEEE C37.20.7)
+type: select
+options:
+ - "Not required"
+ - "Type 1 - Front only"
+ - "Type 2 - Front, rear, and sides"
+ - "Type 2B - Type 2 plus low-voltage compartment door open"
+ - "Type 2C - Type 2 plus between compartments"
+default: "Not required"
+```
+
+### Arc-resistant construction per IEEE C37.20.7 provides a defined level of protection against the effects of an internal arcing fault by redirecting arc gases and pressure through plenums, ducts, or pressure relief flaps to areas where personnel are not present, while reinforced enclosure construction contains the arc event. {note}
+### The accessibility type designates which sides of the equipment provide protection when personnel are present: {note}
+
+- **Type 1** protects personnel only at the front of the equipment
+- **Type 2** protects personnel at the front, rear, and both sides
+- **Type 2B** additionally protects when the low-voltage compartment door is open during maintenance
+- **Type 2C** additionally protects against arc propagation between compartments within the assembly
+
+### Where arc-resistant construction is specified, switchgear shall be design-tested per IEEE C37.20.7 at the rated short-circuit current and at the specified arc duration (typically 0.5 seconds; extended durations require explicit specification).
+
+### Arc plenums and gas exhaust paths shall be coordinated with the electrical room layout so that arc gases vent to a location that is not occupied.
+
+### The arc-resistant rating is invalidated if doors, covers, or plenums are not in their as-tested configuration during operation; this requirement applies to maintenance personnel and shall be enforced through procedural controls and labeling.
+
+### Arc-resistant construction does not eliminate the need for arc flash hazard analysis per IEEE 1584; see [[sync/arc-flash-study]] for arc flash study requirements and labeling.
+
+## Primary Bus {toc}
+
+```datasheet
+label: Primary Bus Material
+type: radio
+options:
+ - "Copper (tin-plated)"
+ - "Copper (silver-plated)"
+default: "Copper (silver-plated)"
+```
+
+```datasheet
+label: Primary Bus Insulation
+type: radio
+options:
+ - "Fully insulated (epoxy or flame-retardant sleeving)"
+ - "Bare bus with phase-to-phase and phase-to-ground clearances"
+default: "Fully insulated (epoxy or flame-retardant sleeving)"
+```
+
+```datasheet
+label: Bus Extension Provisions
+type: radio
+options:
+ - "No future extension"
+ - "Provision for future extension at one end"
+ - "Provision for future extension at both ends"
+default: "No future extension"
+```
+
+### Primary bus shall be high-conductivity copper.
+
+### All joint contact surfaces shall be silver-plated to maintain low contact resistance over the equipment's service life; tin-plating is acceptable in non-corrosive environments where the Owner accepts the lower service life of tin contacts.
+
+### Aluminum primary bus is not acceptable for metal-clad switchgear at any voltage class covered by this standard.
+
+### Fully insulated primary bus is the modern standard for metal-clad switchgear and shall be specified for all installations except where the Owner expressly accepts the higher risk of bus faults associated with bare bus construction.
+
+### Insulation shall be continuous through compartment barriers and inter-section bus splices, with insulating boots provided at splice joints.
+
+### Bus insulation shall be flame-retardant, track-resistant, and rated for the operating temperature of the bus at full continuous current.
+
+### Bus joints shall be bolted with Belleville washers to maintain contact pressure under thermal cycling.
+
+### Splice joints between sections shall be accessible for re-torquing during maintenance from the rear of the switchgear without disturbing primary cables.
+
+## Infrared Scanning Provisions {toc}
+
+### Enclosure shall include removable infrared inspection windows or cover plates at each primary bus splice joint between sections, at the main breaker compartment, and at the primary cable termination compartment of each feeder.
+
+### Windows shall be rated for the maximum voltage class of the switchgear and shall allow thermographic inspection of energized primary connections without removing covers or de-energizing equipment.
+
+### Window glazings shall be impact-resistant and shall be replaceable from the front or accessible side.
+
+# Circuit Breakers {toc}
+
+## Breaker Type {toc}
+
+```datasheet
+label: Circuit Breaker Interrupting Medium
+type: radio
+options:
+ - "Vacuum"
+ - "SF6 gas"
+default: "Vacuum"
+```
+
+### Vacuum circuit breakers are the dominant technology for metal-clad switchgear at 5 kV, 15 kV, and 27 kV classes in the US market. Vacuum interrupters provide long contact life (typically 10,000+ mechanical operations and 30+ rated short-circuit operations), low maintenance requirements, and excellent interrupting performance with minimal arc energy. {note}
+
+### SF6 breakers are more common at 38 kV and above and may be specified at 27 kV where the manufacturer's specific design favors SF6. {note}
+
+### SF6 equipment carries refrigerant-equivalent reporting obligations under EPA regulations and may be subject to phase-down requirements in certain jurisdictions; verify the regulatory status before specifying SF6.
+
+## Drawout Construction {toc}
+
+```datasheet
+label: Racking Mechanism
+type: select
+options:
+ - "Manual racking handle"
+ - "Motor-operated racking (local pushbutton)"
+ - "Motor-operated racking (remote operation from outside arc flash boundary)"
+default: "Manual racking handle"
+```
+
+### Circuit breakers shall be drawout, stored-energy, three-position devices with three distinct positions: connected, test, and disconnected.
+
+### The mechanical position indicator shall be visible from the front of the breaker compartment with the door closed.
+
+### It shall not be possible to move the breaker between positions with the cubicle door closed unless the manufacturer's standard motor-operated racking mechanism is provided and operated from a remote location outside the arc flash boundary.
+
+### Self-aligning primary disconnects shall engage automatically when the breaker is racked from the test position to the connected position.
+
+### Secondary disconnects for control wiring shall remain engaged in both the test and connected positions, allowing electrical operation of the breaker for trip testing while in the test position without energizing the primary circuit.
+
+### Automatic shutters in the cubicle shall close over the stationary primary contacts whenever the breaker is moved to the disconnected position or withdrawn from the cubicle.
+
+### Motor-operated racking with remote operation is the preferred method where the available incident energy at the breaker exceeds Category 2 levels or where the Owner's electrical safety program requires racking to be performed from outside the arc flash boundary. {note}
+
+### Remote racking is increasingly specified for new construction at any incident energy level as a best-practice safety measure. {note}
+
+## Operating Mechanism {toc}
+
+```datasheet
+label: Operating Mechanism Type
+type: radio
+options:
+ - "Stored-energy spring (motor-charged, manually chargeable)"
+ - "Magnetic actuator"
+default: "Stored-energy spring (motor-charged, manually chargeable)"
+```
+
+### Stored-energy spring mechanisms are the established standard for metal-clad switchgear breakers and are available from all major manufacturers across all voltage classes. {note}
+
+### Magnetic actuator mechanisms are available from select manufacturers at 5 kV and 15 kV classes and offer reduced mechanical part count and longer maintenance intervals, but the technology is not yet universal and shall not be specified where multi-source procurement is required.
+
+## Control Voltage {toc}
+
+```datasheet
+label: Breaker Control Voltage (DC)
+type: select
+unit: VDC
+options:
+ - "48 VDC"
+ - "125 VDC"
+ - "250 VDC"
+default: "125 VDC"
+```
+
+```datasheet
+label: Breaker Control Voltage (AC, for spring charging where DC is not available)
+type: select
+options:
+ - "Not required - DC control"
+ - "120 VAC (single-phase, from local control transformer)"
+default: "Not required - DC control"
+```
+
+### DC control voltage is supplied from the station battery system and operates the trip coil, close coil, and spring charging motor. 125 VDC is the dominant control voltage for industrial and utility-customer installations in the US market. 48 VDC is used in some telecommunications and data center environments where a 48 VDC plant already exists. 250 VDC is reserved for larger utility-style substations. {note}
+
+### Where the switchgear is supplied with a station battery, the battery and charger shall comply with [[sync/dc-battery-systems]].
+
+### Where DC control power is sourced from a remote battery system, coordinate the available battery voltage at the switchgear terminals (including voltage drop on the DC distribution feeders) with the breaker manufacturer's minimum operating voltage requirements.
+
+## Main Circuit Breaker {toc}
+
+```datasheet
+label: Main Breaker Configuration
+type: select
+options:
+ - "Main circuit breaker (drawout)"
+ - "Main disconnect switch (utility-furnished primary disconnect)"
+ - "Main lugs only (no main device)"
+default: "Main circuit breaker (drawout)"
+```
+
+### Main breaker frame size and continuous current rating shall be [[drawing: as indicated on the one-line diagram]].
+
+### Main lugs only configurations are limited applications where the upstream device provides main protection for the switchgear bus, typically at utility-customer secondary unit substations where the medium-voltage section is a tap from a larger distribution system. {note}
+
+### Main disconnect switch configurations are utility-furnished primary disconnects at the service entrance, ahead of the customer's main breaker. {note}
+
+## Tie Circuit Breaker {toc}
+
+```datasheet
+label: Main-Tie-Main Configuration
+type: radio
+options:
+ - "Single-ended (no tie breaker)"
+ - "Double-ended with normally-open tie breaker (manual transfer)"
+ - "Double-ended with automatic transfer (closed-transition or open-transition)"
+default: "Single-ended (no tie breaker)"
+```
+
+### Double-ended switchgear with a tie breaker between two main breakers provides redundancy for critical loads served from two independent primary sources. Manual transfer schemes require an operator to close the tie breaker after opening the failed main; automatic transfer schemes accomplish the same function via control logic and may use open-transition (momentary loss of power) or closed-transition (no loss of power, with brief paralleling of sources) sequences. {note}
+
+### Closed-transition transfer requires utility coordination because it briefly parallels two utility sources and may have synchronizing, fault current, and protection implications.
+
+## Feeder Circuit Breakers {toc}
+
+```datasheet
+label: Feeder Breaker Accessories
+type: checkbox
+options:
+ - "Auxiliary contacts (minimum 2a + 2b)"
+ - "Shunt trip"
+ - "Undervoltage release"
+ - "Trip-free mechanical interlock (paired breakers)"
+ - "Kirk key interlock"
+ - "Motor operator for remote close/trip"
+ - "Breaker position indication (drawout connected/test/disconnected)"
+default: "Auxiliary contacts (minimum 2a + 2b)"
+```
+
+### Feeder breaker sizes, quantities, and continuous current ratings are [[drawing: as indicated on the one-line diagram and breaker schedules]].
+
+### Auxiliary contacts shall be provided on every breaker for control, indication, and interlock purposes regardless of other accessory selections.
+
+### Contacts shall indicate breaker open/close status and shall be wired to terminal blocks accessible without removing the breaker from its compartment.
+
+# Protective Relaying {toc}
+
+## Relay Platform {toc}
+
+```datasheet
+label: Protective Relay Platform
+type: radio
+options:
+ - "Single multifunction relay per breaker"
+ - "Centralized relay with breaker-mounted interface units"
+default: "Single multifunction relay per breaker"
+```
+
+### Protective relays shall be multifunction microprocessor-based devices complying with IEEE C37.90, IEEE C37.90.1 (surge withstand), IEEE C37.90.2 (radiated EMI), and IEEE C37.90.3 (electrostatic discharge).
+
+### Relays shall provide a local human-machine interface (display and pushbuttons), event recording with time stamps from a station time source, oscillographic fault recording (COMTRADE-compatible), self-diagnostics with alarm output, and a communications interface for remote settings, retrieval, and monitoring.
+
+### A single multifunction relay per breaker is the dominant architecture in the US market and provides clear physical and logical separation between protection zones. Centralized relay architectures with breaker-mounted interface units are used at large substations and where IEC 61850 process bus integration is specified. {note}
+
+## Protection Functions {toc}
+
+```datasheet
+label: Main Breaker Protection Functions
+type: checkbox
+options:
+ - "Phase overcurrent (50/51)"
+ - "Ground overcurrent (50G/51G or 50N/51N)"
+ - "Differential (87) - main breaker or bus differential"
+ - "Under/overvoltage (27/59)"
+ - "Under/overfrequency (81U/81O)"
+ - "Reverse power (32)"
+ - "Negative sequence overcurrent (46) - unbalance protection"
+ - "Breaker failure (50BF)"
+ - "Synchronism check (25)"
+default: "Phase overcurrent (50/51)"
+```
+
+```datasheet
+label: Feeder Breaker Protection Functions
+type: checkbox
+options:
+ - "Phase overcurrent (50/51)"
+ - "Ground overcurrent (50G/51G or 50N/51N)"
+ - "Negative sequence overcurrent (46)"
+ - "Recloser logic (79) - overhead feeders"
+ - "Breaker failure (50BF)"
+default: "Phase overcurrent (50/51)"
+```
+
+```datasheet
+label: Motor Feeder Protection Functions (where motor loads are served)
+type: checkbox
+options:
+ - "Not applicable - no motor feeders"
+ - "Thermal model (49)"
+ - "Locked rotor / acceleration time (48/51LR)"
+ - "Phase unbalance / negative sequence (46)"
+ - "Loss of load (37)"
+ - "Differential (87M)"
+ - "Stator ground fault (50G)"
+ - "Restart inhibit / starts-per-hour (66)"
+default: "Not applicable - no motor feeders"
+```
+
+### Protection function selection shall be coordinated with the protection coordination study per [[sync/protective-coordination-study]] and shall result in selective tripping for all faults within the protected zone while allowing downstream devices to clear faults within their respective zones.
+
+### Relay settings are [[drawing: as indicated on the relay setting schedule]].
+
+## Ground Fault Sensing {toc}
+
+```datasheet
+label: Ground Fault Sensing Method
+type: select
+options:
+ - "Residually connected from phase CTs (3I0)"
+ - "Zero-sequence (window/donut) CT on each feeder"
+ - "Neutral CT on grounding resistor/transformer"
+default: "Zero-sequence (window/donut) CT on each feeder"
+```
+
+### Zero-sequence CTs (also called window CTs or donut CTs) installed around the three-phase conductors of each feeder provide the most sensitive ground fault detection by directly measuring 3I0, with sensitivity typically one or two orders of magnitude better than residual sensing from phase CTs. {note}
+
+### Zero-sequence CTs are required for sensitive ground fault detection on resistance-grounded systems where the let-through current is intentionally limited.
+
+## Bus Differential Protection {toc}
+
+```datasheet
+label: Bus Differential Protection (87B)
+type: select
+options:
+ - "Not required"
+ - "High-impedance differential"
+ - "Low-impedance differential (numerical)"
+default: "Not required"
+```
+
+### Bus differential protection (ANSI 87B) provides fast (typically less than one cycle) clearing of faults on the main bus. It is recommended for switchgear where the main breaker upstream clearing time is too long to limit damage from a main bus fault, for installations with high available fault current, and for arc-resistant switchgear where reducing arc duration significantly reduces incident energy. {note}
+
+### Low-impedance numerical bus differential is the modern standard and tolerates CT saturation more gracefully than high-impedance designs. {note}
+
+## Communications {toc}
+
+```datasheet
+label: Relay Communications Protocol
+type: select
+options:
+ - "DNP3 (serial or TCP/IP)"
+ - "Modbus RTU (RS-485)"
+ - "Modbus TCP/IP (Ethernet)"
+ - "IEC 61850 MMS (station bus only)"
+ - "IEC 61850 MMS + GOOSE (station bus with peer-to-peer)"
+default: "DNP3 (serial or TCP/IP)"
+```
+
+### IEC 61850 GOOSE messaging enables fast peer-to-peer signaling between relays for functions such as breaker failure tripping, bus differential blocking, and arc flash mitigation interlocking, with delivery times typically below 4 milliseconds. {note}
+
+### Where GOOSE is specified, the Ethernet station bus shall be a managed, redundant network (HSR, PRP, or RSTP rings as appropriate) and time synchronization shall be provided per IEEE 1588 PTPv2.
+
+### IEC 61850 SCL files shall be delivered as part of the action submittals and updated at closeout.
+
+# Metering and Instrumentation {toc}
+
+## Instrument Transformers {toc}
+
+```datasheet
+label: Voltage Transformer Configuration
+type: select
+options:
+ - "Not required (no VTs)"
+ - "Open delta (2 VTs) - line-to-line metering"
+ - "Wye-wye (3 VTs) - line-to-neutral and line-to-line metering"
+ - "Wye-wye with broken delta tertiary (3 VTs + tertiary) - ground fault detection"
+default: "Wye-wye (3 VTs) - line-to-neutral and line-to-line metering"
+```
+
+### Accuracy class shall be appropriate for the connected function:
+
+- Revenue metering: 0.3 accuracy class (B0.1 through B0.9 burden as required)
+- Protective relaying: C200 or higher (per IEEE C57.13 standard burden designations)
+- General monitoring and indication: 0.6 or 1.2 accuracy class
+
+### Current transformers and voltage transformers shall comply with IEEE C57.13.
+
+### CTs shall be window type (toroidal) for zero-sequence applications and bushing or wound type for phase metering and relaying.
+
+### VTs shall be drawout or roll-out with current-limiting primary fuses.
+
+### Accuracy class shall be appropriate for the connected function as listed above.
+
+### Current transformers for metering and relaying shall be provided on separate cores.
+
+### CTs shall not be shared between metering and protection functions.
+
+### Where the switchgear includes utility metering, the utility CT and VT compartments shall be sized, located, and sealable per the serving utility's standards.
+
+### Wye-wye VTs with broken delta tertiary windings are required for ground fault detection by zero-sequence voltage (59N) on ungrounded and resonant-grounded systems.
+
+### For solidly grounded and low-resistance grounded systems, current-based ground fault sensing is the primary scheme and broken delta tertiary VTs are typically not required. {note}
+
+## Power Monitoring {toc}
+
+```datasheet
+label: Metering Type
+type: select
+options:
+ - "No metering"
+ - "Multifunction relay metering only (no dedicated meters)"
+ - "Digital multifunction meter (main only)"
+ - "Digital multifunction meter (main and each feeder)"
+ - "Revenue-grade metering per utility requirements"
+default: "Digital multifunction meter (main only)"
+```
+
+```datasheet
+label: Meter Functions
+type: checkbox
+options:
+ - "Voltage (L-L and L-N all phases)"
+ - "Current (per phase and neutral/ground)"
+ - "Power factor (per phase and total)"
+ - "kW / kVA / kVAR (demand and instantaneous)"
+ - "kWh / kVARh energy accumulation"
+ - "Harmonics (THD per phase, individual to 31st)"
+ - "Min/max recording with time stamp"
+ - "Waveform capture"
+ - "Sequence-of-events recording"
+default: "Voltage (L-L and L-N all phases)"
+```
+
+### Where the relay platform provides metering with sufficient accuracy for the intended use, dedicated meters may be omitted.
+
+### Modern multifunction relays provide 0.2% accuracy on voltage and current and meet most utility metering accuracy requirements; consult the utility provider before omitting a dedicated revenue meter.
+
+# Finish and Identification {toc}
+
+```datasheet
+label: Finish Color
+type: text
+default: "ANSI 61 gray"
+```
+
+## Enclosure shall receive a minimum two-coat paint system: corrosion-resistant primer and manufacturer's standard polyester powder coat finish.
+
+## Minimum total dry film thickness shall be 3 mils (75 microns).
+
+## For outdoor installations or environments classified C3 or higher, an enhanced paint system with a minimum of 5 mils dry film thickness shall be applied.
+
+## All internal structural members shall receive the same corrosion treatment as exterior surfaces.
+
+## Labeling {toc}
+
+### Nameplates shall identify:
+
+- Switchgear designation and one-line reference
+- Bus ratings (voltage class, BIL, continuous current, short-circuit interrupting and momentary)
+- Individual breaker designation, continuous current rating, and interrupting rating
+- Current transformer ratios and accuracy class
+- Voltage transformer ratios and accuracy class
+- Arc-resistant rating (Type and arc duration) where applicable
+- Arc flash warning labels per NFPA 70E and IEEE 1584
+
+```datasheet
+label: Nameplate Material
+type: radio
+options:
+ - "Laminated phenolic (indoor)"
+ - "Stainless steel (outdoor or corrosive)"
+ - "Aluminum (anodized)"
+default: "Laminated phenolic (indoor)"
+```
+
+### Manufacturer shall provide engraved phenolic nameplates for the switchgear assembly and each individual device.
+
+### Nameplates shall identify the switchgear designation, bus and device ratings, instrument transformer ratios and accuracy classes, arc-resistant rating where applicable, and arc flash warning information as listed above.
+
+### Mimic bus diagram shall be provided on the front of each main and tie breaker section showing the bus configuration, breaker position, and source identification.
+
+### Equipment labeling shall follow [[sync/equipment-labeling]] conventions.
+
+# Testing {toc}
+
+## Factory Production Tests {toc}
+
+### The manufacturer shall perform the following production tests on the completed switchgear assembly per IEEE C37.20.2 and IEEE C37.09:
+
+- Power-frequency dielectric withstand test on primary bus and primary disconnects
+- Insulation resistance measurement on each phase bus
+- Mechanical operation of each circuit breaker (minimum 5 open/close cycles, with the breaker in the connected, test, and disconnected positions as applicable)
+- Electrical operation of each circuit breaker (trip and close via control circuits)
+- Control wiring continuity verification against the approved schematics
+- Current transformer ratio, polarity, and saturation curve test
+- Voltage transformer ratio and polarity test
+- Protective relay functional test, including pickup at set values and time delays
+- Trip and close circuit functional test
+- Verification of arc-resistant exhaust path integrity, where applicable
+- Visual and dimensional inspection against approved shop drawings
+
+```datasheet
+label: Factory Acceptance Test
+type: radio
+options:
+ - "Witnessed by Owner's representative"
+ - "Unwitnessed with certified test report"
+ - "Not required beyond standard production tests"
+default: "Witnessed by Owner's representative"
+```
+
+### The manufacturer shall perform the production tests listed above on the completed switchgear assembly per IEEE C37.20.2 and IEEE C37.09.
+
+### Where witnessed factory testing is specified, the manufacturer shall provide a minimum of two weeks advance notice of test readiness.
+
+### Test procedures shall be submitted for review prior to testing, and the witnessed test shall include a representative sample of the production tests above plus a partial-discharge test on the primary bus.
+
+# Field Quality Control {toc}
+
+## Field Acceptance Tests {toc}
+
+### Field acceptance tests shall include the following as a minimum:
+
+- Visual and mechanical inspection of all sections, bus joints, primary cable terminations, and devices
+- Bolted connection torque verification using a calibrated torque wrench, on a sampled basis per NETA ATS
+- Insulation resistance testing of primary bus (phase-to-phase and phase-to-ground), minimum one minute, recorded at 30 seconds and 60 seconds
+- Power-frequency overpotential (AC hi-pot) or very-low-frequency (VLF) withstand test on primary bus and primary cable terminations, at the field test voltage specified by IEEE C37.20.2 and the applicable cable standard
+- Partial-discharge measurement on the primary bus (where specified)
+- Contact resistance measurement on all bolted bus connections and primary disconnect contacts (micro-ohmmeter, minimum 100 ADC injection)
+- Vacuum integrity test on each vacuum interrupter (vacuum bottle hi-pot)
+- Circuit breaker operational testing in connected, test, and disconnected positions (mechanical and electrical)
+- Breaker close and open times, and contact bounce, measured by a circuit breaker analyzer
+- Primary current injection testing of all main and feeder protection functions, including pickup, time-delay, and instantaneous functions
+- Secondary injection testing of all relay protection functions not covered by primary injection
+- Current transformer ratio, polarity, and saturation verification
+- Voltage transformer ratio and polarity verification
+- Metering accuracy verification against a calibrated reference
+- Ground impedance measurement of the switchgear ground bus and substation ground grid per IEEE 81
+- Functional testing of all control circuits, interlocks, alarms, and breaker failure schemes
+- Verification of IEC 61850 GOOSE messages and trip times, where applicable
+
+```datasheet
+label: Field Testing Requirements
+type: radio
+options:
+ - "NETA acceptance testing and manufacturer startup"
+ - "NETA acceptance testing only"
+ - "Manufacturer startup only"
+default: "NETA acceptance testing and manufacturer startup"
+```
+
+### Contractor shall engage a qualified independent testing firm to perform acceptance testing per NETA ATS Section 7.2 (medium-voltage switchgear) and Section 7.6 (medium-voltage circuit breakers).
+
+### Testing shall occur after installation is complete and before the equipment is energized.
+
+### Field acceptance tests shall include the items listed above as a minimum.
+
+## Infrared Thermographic Inspection {toc}
+
+```datasheet
+label: Infrared Thermographic Inspection
+type: radio
+options:
+ - "Initial scan within 90 days of energization, follow-up at 11 months"
+ - "Initial scan within 90 days of energization only"
+ - "Not required"
+default: "Initial scan within 90 days of energization, follow-up at 11 months"
+```
+
+### Infrared scanning shall be performed under normal operating load conditions (minimum 40% of rated load where practical) through the infrared inspection windows specified above.
+
+### All connections exceeding 10°C rise above ambient shall be reported and corrected.
+
+### The 11-month follow-up scan captures connections that may loosen during the initial thermal cycling period and falls within the standard one-year warranty window. {note}
+
+# Installation {toc}
+
+## Concrete Housekeeping Pad {toc}
+
+### Switchgear shall be mounted on a reinforced concrete housekeeping pad extending a minimum of 4 in. beyond the base of the equipment on all sides.
+
+### Pad shall be a minimum of 4 in. above finished floor for indoor installations and 6 in. above finished grade for outdoor installations.
+
+### Anchor bolt size and pattern shall match the manufacturer's shop drawings and shall develop the seismic anchorage force/moment values certified per the seismic basis.
+
+### Coordinate pad dimensions, conduit penetrations, primary and control cable entry locations, and anchor bolt locations with equipment shop drawings prior to concrete placement; see [[sync/concrete-pads]] for construction requirements.
+
+## Equipment Setting {toc}
+
+### After assembly, the following shall be verified before energizing:
+
+- All shipping restraints and temporary grounds removed
+- Bus splice joints torqued per the manufacturer's specifications using a calibrated torque wrench, with witness marks applied
+- Primary cable terminations completed per the cable manufacturer's instructions, including stress relief, ground shield bonding, and torqued lug connections
+- Primary cable terminations sealed against moisture intrusion at the cable entry point
+- All circuit breakers rack and operate freely in all three positions
+- Automatic primary disconnect shutters operate freely and close completely when the breaker is withdrawn
+- Space heaters energized for outdoor or unconditioned installations
+- DC control power present and within the manufacturer's specified range at the switchgear terminals
+- Working clearances per NFPA 70 Article 110.34 maintained
+- Switchgear ground bus bonded to the building grounding electrode system and substation ground grid per [[sync/grounding-and-bonding]]
+
+### Contractor shall comply with the manufacturer's installation instructions and applicable rigging requirements.
+
+### Sections shall be lifted only by the manufacturer's designated lifting points and shall not be lifted by bus, doors, or device handles.
+
+### Remove all temporary shipping braces, blocking, and desiccants prior to final assembly.
+
+### After assembly, the items listed above shall be verified before energizing.
+
+## Working Clearance {toc}
+
+### Working space dimensions depend on the nominal voltage and the accessibility configuration (exposed live parts on one side, both sides, or both sides with the operator between): {note}
+
+| Nominal voltage to ground | Condition 1 | Condition 2 | Condition 3 |
+|---------------------------|-------------|-------------|-------------|
+| 601 V – 2500 V | 3 ft | 4 ft | 5 ft |
+| 2501 V – 9000 V | 4 ft | 5 ft | 6 ft |
+| 9001 V – 25,000 V | 5 ft | 6 ft | 9 ft |
+| 25,001 V – 75 kV | 6 ft | 8 ft | 10 ft |
+
+### Minimum working space shall be maintained per NFPA 70 Article 110.34 for equipment over 1000 volts.
+
+### Working space shall not be used for storage.
+
+### Dedicated electrical space above and below the equipment shall be maintained per NFPA 70 Article 110.34(F).
+
+### At least two entrances of sufficient area shall be provided to give access to the working space about electrical equipment per NFPA 70 Article 110.33; one entrance shall be permitted where the working space layout meets the exceptions of that section.
+
+### Coordinate room layout with [[sync/electrical-rooms]].
+
+## Cable Terminations {toc}
+
+### Primary cable termination shall be performed by personnel certified by the cable termination kit manufacturer or holding equivalent third-party qualifications.
+
+### Shielded medium-voltage cables shall be terminated with stress-relief terminations rated for the cable insulation class and for the application (indoor, outdoor, or wet location).
+
+### Cable shields shall be bonded to the switchgear ground bus through a dedicated ground shield connection at each termination per [[sync/grounding-and-bonding]] and the cable manufacturer's instructions.
+
+### Medium-voltage cable selection, routing, supports, raceway sizing, and bend radius shall comply with [[sync/conductors-and-cables]] and [[sync/raceways-and-conduit]].
+
+## Identification of Source {toc}
+
+### Where the switchgear is fed from a remote source or from two or more sources, permanent labels per NFPA 70 Article 490 shall identify each source location and circuit designation at the switchgear and at each remote source.
+
+### Where the switchgear supplies emergency, legally required standby, or critical operations loads downstream through low-voltage transformers, source identification shall be coordinated with [[sync/low-voltage-switchgear]] and the downstream distribution equipment labeling.
+
+# Delivery, Storage, and Handling {toc}
+
+## Switchgear shall be shipped in the largest factory-assembled sections that can be transported to and within the installation site.
+
+## Verify all pathway dimensions (doors, hallways, elevator shafts, turning radii, structural floor loading) between the delivery point and the final installation location prior to ordering.
+
+## Coordinate shipping splits with the manufacturer on the approved shop drawings.
+
+## Outdoor walk-in switchgear shall ship with the protected aisle disassembled for transport.
+
+## Aisle reassembly, seal verification, and pressure relief flap inspection shall be performed at the site by the manufacturer's authorized field service representative.
+
+## Equipment shall be stored indoors in a clean, dry location.
+
+## Where indoor storage is not available, the manufacturer shall provide weatherproof packaging and desiccants.
+
+## Condensation heaters shall be connected and energized during storage if the equipment will be stored for more than 30 days or if the storage environment is not climate-controlled.
+
+## Vacuum interrupters and SF6 breakers shall be stored within the temperature range specified by the manufacturer; SF6 gas pressure shall be verified before energization and topped off if necessary.
+
+# Warranty {toc}
+
+```datasheet
+label: Warranty Period
+type: select
+options:
+ - "1 year from substantial completion"
+ - "2 years from substantial completion"
+ - "3 years from substantial completion"
+ - "5 years from substantial completion"
+default: "2 years from substantial completion"
+```
+
+```datasheet
+label: Extended Warranty Coverage
+type: checkbox
+options:
+ - "Parts only"
+ - "Parts and labor"
+ - "Emergency response (24/7 with 4-hour commitment)"
+ - "Scheduled preventive maintenance (annual)"
+ - "Protective relay setting management and version control"
+default: "Parts only"
+```
+
+## Warranty shall cover defects in materials and workmanship under normal use and service conditions.
+
+## The manufacturer shall maintain a service organization capable of providing emergency replacement parts and field service within 24 hours during the warranty period.
+
+# Spare Parts {toc}
+
+```datasheet
+label: Spare Circuit Breakers
+type: radio
+options:
+ - "None"
+ - "One spare breaker of each frame size installed"
+ - "10% of each frame size (minimum one)"
+default: "One spare breaker of each frame size installed"
+```
+
+## Manufacturer shall provide the following additional spare parts at substantial completion:
+
+- One spare set of primary disconnect contact fingers for each breaker frame size
+- One spare set of control fuses, indicating lights, and auxiliary switches for each type installed
+- One set of vacuum bottle replacements for the smallest breaker frame (where the manufacturer supports field replacement of vacuum interrupters)
+- One spare set of voltage transformer primary fuses for each VT rating installed
+- One spare protective relay of each model installed (or documented availability from manufacturer stock with 48-hour delivery commitment)
+- One breaker handling/lift truck appropriate for the heaviest breaker installed
+- One set of breaker test plugs and secondary injection couplers
+- One complete set of keys for all door locks and Kirk key interlocks
+- Touch-up paint matching the finish color (minimum one quart)
+
+## Spare circuit breakers shall be of the same type, rating, and configuration as the installed breakers and shall be fully interchangeable in any cubicle of the same frame size.
+
+## Spare breakers shall be stored on a breaker handling/lift truck supplied by the manufacturer, located in the electrical room or substation control building.