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Apex Power DistributionApexPower.ai

Low-voltage systems

Switchboards, power switchgear and the controls between the sources

208 V through 600 V distribution engineered from the fault study up: switchboards, drawout LV power switchgear, automatic transfer switches, main-tie-main and paralleling, metering, control integration, PDC/E-house packaging and modernization of what is already installed.

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Rendering of a low-voltage power switchgear lineup with stacked drawout breaker compartments and a metering section
Illustrative rendering — not a specific Apex project.

What we engineer and integrate

Low-voltage scope

Each item below is specified against the project's fault study, coordination study and operating requirements — not as a catalog line.

  • LV Switchboards

    Service-entrance and distribution switchboards, 208 V–600 V, with group- or individually-mounted molded-case and insulated-case breakers.

    Details +
    • · Main-lug, main-breaker and service-entrance configurations with utility CT/pull sections
    • · Fixed-mount MCCB/ICCB feeders; drawout ICCB mains where maintainability justifies it
    • · Bus bracing and short-circuit ratings matched to the available fault current study
    • · Arc energy reduction for devices 1,200 A and larger (ZSI, ERMS, differential or instantaneous methods per NEC 240.87)
    • · Metering, surge protection and communications modules integrated at the factory

    Typical applications: Commercial buildings, light industrial, tenant distribution, EV charging sites, healthcare normal branch

    Switchboard vs. Switchgear: What Actually DiffersUL 891 Switchboards: Scope, Construction and ApplicationNEC Requirements for Switchgear and Switchboards

  • LV Power Switchgear

    Compartmentalized, rear-accessible switchgear with drawout low-voltage power circuit breakers for facilities that cannot afford to shut down for maintenance.

    Details +
    • · Drawout LVPCBs, 800–5,000 A frames, 100 %-rated, 30-cycle short-time withstand
    • · Individual breaker compartments with barriers; CONNECTED/TEST/DISCONNECTED positions
    • · Electronic LSIG trip units with zone-selective interlocking and maintenance mode
    • · Double-ended (main-tie-main) and multi-source arrangements with automatic transfer controllers
    • · Continuous temperature monitoring at stabs and bus joints available as a factory option

    Typical applications: Data centers, hospitals (essential systems), process plants, critical infrastructure

    UL 1558 Low-Voltage Power Circuit Breaker SwitchgearLow-Voltage Circuit Breaker Types: MCCB, ICCB, LVPCBSwitchboard vs. Switchgear: What Actually Differs

  • Automatic Transfer Switches

    Open-, closed- and delayed-transition transfer switches, bypass-isolation where maintenance without interruption is required.

    Details +
    • · 100–5,000 A, 2-, 3- and 4-pole, service-entrance rated options
    • · Closed transition (make-before-break) where the utility permits brief paralleling
    • · Delayed transition for large motor and UPS loads to avoid out-of-phase reclosing
    • · Bypass-isolation construction for maintenance without dropping the load
    • · Controller integration with generators, BMS and SCADA over Modbus TCP

    Typical applications: Emergency and legally required standby systems (NEC 700/701), optional standby (702), healthcare essential electrical systems (517)

    Automatic Transfer Switches: Types, Transitions and ApplicationMain-Tie-Main Systems: Design and Automatic Transfer Logic

  • Main-Tie-Main

    Double-ended substations with automatic transfer logic that distinguishes a lost source from a faulted bus — and only closes the tie when it should.

    Details +
    • · Two-of-three interlocking (electrical and controller logic)
    • · Undervoltage sensing (27) with ride-through timers; fault-trip discrimination blocks transfer into a fault
    • · Open-transition transfer, or closed-transition with 25 sync-check where permitted
    • · Load-shed and transformer FA-rating checks before tie close
    • · Auto / Manual / Maintenance modes with SCADA visibility of permissives and timers

    Typical applications: Data centers, hospitals, water plants, manufacturing with dual utility feeds or dual transformers

    Main-Tie-Main Systems: Design and Automatic Transfer LogicProtective Relaying Fundamentals for Switchgear

  • Paralleling Switchboards

    Generator paralleling and load management for multi-set standby and prime power plants.

    Details +
    • · Generator breakers with 25 sync-check, 32 reverse power, 40 loss of field, 81 frequency protection
    • · First-up/priority-start, load add/shed sequences, soft loading and unloading
    • · Utility paralleling and export control where the utility interconnection agreement allows
    • · PLC-based or dedicated paralleling controllers with redundant control power
    • · Test modes (with and without load) and event recording for compliance testing

    Typical applications: Data centers, hospitals, campuses, remote industrial sites, microgrids

    Main-Tie-Main Systems: Design and Automatic Transfer LogicSCADA for Power Distribution Systems

  • Distribution

    Downstream distribution sections, panelboard feeds, busway and MCC interfaces designed for selective coordination where the code or the owner requires it.

    Details +
    • · Feeder schedules built from load studies, not nameplates alone
    • · Selective coordination across MCCB/ICCB/LVPCB families
    • · Spare and space provisions sized for realistic load growth

    Low-Voltage Circuit Breaker Types: MCCB, ICCB, LVPCBNEC Requirements for Switchgear and Switchboards

  • Metering

    Revenue, submetering and Class A power-quality metering integrated into the lineup and the data layer.

    Details +
    • · Utility metering provisions per the serving utility
    • · Tenant and departmental submetering with Modbus TCP or BACnet/IP gateways
    • · Power-quality meters with waveform capture and sequence-of-events at mains and critical feeders

    Power Quality Fundamentals for Distribution SystemsSCADA for Power Distribution Systems

  • Control Integration

    Transfer controllers, PLC/RTU logic, HMIs and SCADA connections engineered with the switchgear, not bolted on afterward.

    Details +
    • · Control narratives and I/O lists reviewed with the owner before build
    • · Factory acceptance testing of logic with simulated inputs
    • · Site acceptance testing with the generators, UPS and utility present

    SCADA for Power Distribution SystemsCybersecurity for Digital Switchgear and Power SCADA

  • PDC / E-House

    Power distribution centers and electrical houses: switchgear, MCCs, transformers and controls delivered in a pre-wired, tested enclosure.

    Details +
    • · Electrical design, equipment integration and testing of the electrical scope
    • · Coordination with the building/packaging supplier on HVAC, fire detection and cable entry
    • · Hazardous-area siting considerations (purged/pressurized where required)

    Typical applications: Oil and gas, utilities, mining, BESS and renewable sites, industrial expansions

    Metal-Clad vs. Metal-Enclosed MV SwitchgearArc-Resistant Switchgear: Types, Testing and Limits

  • Retrofit & Modernization

    Extend the life of installed switchboards and switchgear: new trip units, breaker retrofill, relay upgrades, monitoring and controls — often without replacing the structure.

    Details +
    • · Condition assessment and modernization roadmap
    • · Trip-unit and relay replacement; breaker retrofill or replacement
    • · Add continuous monitoring, remote operation and SCADA to legacy lineups
    • · Phased cutovers planned around the facility's outage windows

    What Is Digital Switchgear?Switchgear Condition Monitoring: What to Measure and WhyNFPA 70E, Maintenance and Switchgear Design Choices

Interactive LV equipment

Switchboard vs. low-voltage power switchgear

Toggle between a UL 891 switchboard and UL 1558 drawout switchgear. Open doors, look at the bus, find the trip units and see where sensors sit.

Demonstration model — simulated states

Construction class described by UL 1558 / IEEE C37.20.1; breakers per UL 1066 / IEEE C37.13

Doors closed — as an operator sees it.

Loading 3D switchgear model…

Inspector

Select a compartment on the 3D model or a device on the one-line. The model, the one-line and the data panel stay in sync: physical equipment ↔ digital twin ↔ data.

  • · Click MV Main 52-M1 on the one-line to highlight its breaker compartment.
  • · Click the bus to cut the enclosure away to the main bus compartment.
  • · Choose the Sensors mode to see where each sensor physically sits.

Brand-neutral demonstration architecture. Compartment arrangement, ratings and sensor placements are representative of common ANSI practice, not a specific manufacturer's design or a specific Apex project. Values are simulated.

Comparison of switchboards and low-voltage power switchgear
SwitchboardLV power switchgear
Listing / standardUL 891UL 1558 · IEEE C37.20.1
BreakersMolded-case and insulated-case (UL 489), mostly fixedDrawout low-voltage power circuit breakers (UL 1066 / IEEE C37.13)
RatingsDevices often 80 %-rated unless specified 100 %100 %-rated; 30-cycle short-time withstand
ConstructionGroup-mounted on a common panel; front or front/rear accessIndividual compartments with barriers; rear cable access
MaintenanceDe-energize section to replace a deviceRack out one breaker while the bus stays energized
Footprint & costSmaller, lowerLarger, higher
Where it fitsCommercial, light industrial, tenant distributionCritical facilities, high available fault current, long service life
Applicable listings, standards and design requirements depend on equipment type, configuration, project specifications and jurisdiction. See the standards register for current editions.

Main-tie-main demonstration

Nine states of a double-ended substation

Step through normal operation, source loss, closed transition, generator pickup, high load, a thermal alarm, a fault trip and maintenance mode. Watch which breakers move — and, more importantly, which ones the controller refuses to move.

Demonstration — not a live switchgear control interface

Main-tie-main one-line — Normal Utility

LV Bus 1 — 480Y/277 V, 4000 ALV BUS 1 · 480Y/277 V · 4000 ALV Bus 2 — 480Y/277 V, 4000 ALV BUS 2 · 480Y/277 V · 4000 A52-F1 MV Feeder 1 → T1 — Feeds transformer T1. Relay settings coordinate with the transformer damage curve and the LV main.52-F1■ CLOSED60 A52-F2 MV Feeder 2 → T2 — Feeds transformer T2 (second source of the double-ended LV switchgear).52-F2■ CLOSED53 AT1 Transformer T1 — Unit-substation transformer feeding LV Bus 1 through the 52-LM1 main.T1 · 2000 kVA13.8 kV Δ – 480Y/277 V · Z 5.75 %T2 Transformer T2 — Unit-substation transformer feeding LV Bus 2 through the 52-LM2 main.T2 · 2000 kVA13.8 kV Δ – 480Y/277 V · Z 5.75 %52-LM1 LV Main 1 — Main breaker for LV Bus 1. Participates in the main-tie-main automatic transfer scheme.52-LM1■ CLOSED1,732 A52-T Tie — Tie breaker between LV Bus 1 and LV Bus 2. Closed automatically by the MTM controller after a main opens on loss of source (open transition).52-T□ OPEN0 A52-LM2 LV Main 2 — Main breaker for LV Bus 2.52-LM2■ CLOSED1,510 A52-G Generator Breaker — Connects the standby generator to LV Bus 2 after both utility sources are lost and the mains are open (open transition).52-G□ OPEN0 AG1 Standby Generator G1 — Standby generator (system demo). Emergency system classification and transfer times depend on the facility's code requirements.GG1 · 1500 kW52-C1 UPS A Input — Feeds the UPS A input (critical load path).52-C1■ CLOSED640 A52-C2 Mechanical A — Feeds the mechanical MCC A (chillers, pumps, fans).52-C2■ CLOSED830 A52-C3 Process & Lighting A — Feeds process and lighting distribution panels.52-C3■ CLOSED262 A52-C4 UPS B Input — Feeds the UPS B input.52-C4■ CLOSED600 A52-C5 Mechanical B — Feeds the mechanical MCC B. Communication loss on this trip unit is one demo scenario.52-C5■ CLOSED690 A UPS A → Critical Load — Critical IT / process load via UPS A.UPS A → Critical Load Mechanical MCC A — Mechanical loads.Mechanical MCC A Process / Lighting — Distribution panels.Process / Lighting UPS B → Critical Load — Critical load via UPS B.UPS B → Critical Load Mechanical MCC B — Mechanical loads.Mechanical MCC BDemonstration — simulated values, not a live control interface
Bus 1 load (of 3200 A main)54 %
Bus 2 load (of 3200 A main)47 %
  • CLOSED
  • OPEN
  • TRIPPED
  • MAINTENANCE
  • COMMUNICATION LOST
  • Energized
  • De-energized

Normal Utility

Both mains closed, tie open. Each transformer carries its own bus; the system is two independent radial feeds with a manual/automatic tie available.

Controller sequence

  1. Monitors 27 undervoltage on both buses via bus VTs
  2. Timers (62) armed; AUTO mode selected
  3. Publishes positions, permissives and timers to SCADA

Interlocks & permissives

Only two of 52-LM1, 52-T and 52-LM2 may be closed (electrical interlock plus controller logic).

Simulated states for explanation only. Actual transfer logic, timers, interlocks and generator sequences are engineered per project, verified in factory and site acceptance testing, and documented in the approved control narrative.

Apex Power Distribution · ApexPower.ai

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