Compact Ring Main Unit

The Compact Padmounted Ring Main Unit (RMU) is a medium-voltage switchgear assembly engineered for North American secondary distribution networks up to 38 kV. Integrating load break switches and vacuum circuit breakers into a tamper-resistant, deadfront outdoor enclosure, it provides a maintenance-free switching solution for underground loop-feed distribution systems and commercial padmounted substations. 

Deadfront Construction: Fully shielded, grounded elbow connectors and internal barriers eliminate exposed live parts, ensuring operator safety during switching operations.

Tamper-Resistant Padmounted Enclosure: Heavy-gauge steel cabinet finished with an electro-deposition primer and polyester topcoat, featuring concealed hinges, multi-point penta-head padlocking, and weather-resistant structural design.

Sealed Switch Tank: Laser-welded 304 stainless steel enclosure housing the switching components, completely isolated from external environmental contaminants like humidity, dust, and wildlife.

Configurable Way Layouts: Flexible grouping of source-switching ways and transformer-protection tap ways utilizing current-limiting fuses or vacuum interrupters.

Automation Ready: Provisioned for motor actuators, fault circuit indicators (FCIs), and standard RTUs for distribution automation and smart grid deployment.

Utility Underground Distribution: Loop-feed sectionalizing switches for investor-owned utilities (IOUs) and municipal power systems.

Commercial & Industrial Parks: Padmounted transformer primary switching for office complexes, data centers, and light industrial facilities.

Renewable Energy Integration: Solar PV farm collector loops and wind energy collection systems requiring outdoor weather-resistant enclosures.

Institutional Campuses: University, hospital, and military microgrid distribution networks.

Switching Configuration: Selectable 2-way, 3-way, or 4-way loop configurations with integrated grounding switches and test points.

Bushing Interfaces: ANSI/IEEE 381 deadbreak and loadbreak apparatus bushings (200A loadbreak wells or 600A deadbreak interfaces).

Enclosure Materials: 12-gauge mild steel with marine-grade undercoating, or full 304/316 stainless steel construction for coastal and high-corrosion installations.

Engineering Data Access: Download IEEE-compliant 2D/3D CAD Drawings (DWG/REVIT) and submittal packages.

Production utilizes automated CNC laser cutting, precision brake forming, and robotic MIG/TIG welding to fabricate rugged outdoor padmounted housings and sealed tank assemblies.

Pressure & Leakage Verification: 100% helium mass spectrometry leak testing on all gas or solid-insulated primary tanks to ensure long-term dielectric integrity.

Dielectric Routine Testing: Power frequency withstand and partial discharge screening performed on every unit prior to factory release.

Mechanical Interlock Verification: Rigorous functional checks on operating handles, padlocking provisions, and mechanism trip-free characteristics.

Standards Compliance: Designed, tested, and validated in accordance with IEEE C37.20.3, IEEE C37.74, IEEE 386, and ANSI C57.12.28 (pad-mounted enclosure integrity).

Type Test Reports: Certified seismic, short-circuit, and thermal rise test reports available from independent testing facilities.

Supplied Documentation: Comprehensive submittal drawings, factory test reports (FTR), wiring diagrams, and installation/maintenance manuals.

Packaging Method: Secured to heavy-duty, forklift-compatible wooden skids with VCI (Volatile Corrosion Inhibitor) wrapping, heavy-duty edge protection, and weather-resistant shrink-wrapping.

Lifting & Handling: Equipped with lifting provisions designed for crane rigging and positioning onto concrete pads.

Lead Time: Standard loop configurations ship in 6 to 8 weeks; custom-engineered multi-way assemblies require 10 to 12 weeks.