Wholesale Medium Voltage RMU Factories & Company

Air-Insulated RMUs (e.g., SM6 series) utilize atmospheric air as the primary insulation medium between live phases and ground, requiring larger physical clearances, which results in wider cubicle dimensions (typically 375mm to 500mm per bay). In contrast, Gas-Insulated RMUs (e.g., RM6, SafeRing-12/24) seal the busbars, disconnector switches, and vacuum circuit breakers inside a hermetically sealed stainless steel tank filled with SF6 or eco-gas at slight positive pressure. This reduces dielectric clearance distances dramatically, compressing the cubicle width to just 320mm per module, while rendering the internal components completely impervious to external dust, humidity, salt air, and airborne pollution.

Chinese manufacturers offer fully customizable modular and compact non-extensible or extensible architectures. Common configurations include: CCF (two cable incomers with load break switches + one fuse-switch combination for transformer protection), CCC (three incoming/outgoing feeder switches for ring splitting), CCV (two cable switches + one vacuum circuit breaker for high-current or automated substation protection), and CCVV or CCCC combinations. Modular extensible designs feature external top or side plug-in solid-insulated busbar connectors, allowing EPC contractors to expand substations on-site by adding metering (M) or breaker (V) modules without discharging factory-sealed gas tanks.

Safety is built into the physical mechanical linkages governed by IEC 62271-200. The mechanism features a strict three-position mechanical interlock: (1) The load break switch can only be closed when the earthing switch is fully open; (2) The earthing switch can only be engaged when the main switch contacts are completely disengaged; (3) The cable compartment access door is mechanically locked and cannot be opened unless the earthing switch is firmly grounded. Furthermore, capacitive voltage indicators (VPIS) integrated onto bushing dividers visually illuminate to warn technicians if incoming underground cables remain energized prior to closing the earth switch.

Standard switchgear ratings are valid up to 1000 meters above sea level under IEC guidelines. At altitudes exceeding 1000m, the reduced atmospheric air density degrades the external dielectric breakdown strength across open air bushings, cable termination boots, and low-voltage secondary terminals. For installations at 2000m, 3000m, or higher (common in Andean or Central Asian mining projects), Chinese factories apply altitude correction derating factors (Ka) derived from IEC 62271-1, or upgrade external creepage clearances from 12kV-rated insulation bushings to 24kV or 36kV dimensioned components while retaining standard 12kV internal operating mechanics.

Standard configurations (e.g., 12kV 3-way or 4-way CCF/CCV units) carry lead times of 15 to 25 business days from single-line diagram (SLD) approval. Custom engineering requiring complex protection relays, smart DTUs, or special dual-power ATS panels generally ships within 30 to 40 days. For international maritime transit, units are sealed in vapor-barrier foil pouches with silica desiccant, enclosed in IP-protective vapor shrink-wrap, and bolted inside heavy-duty, fumigated IPPC-certified wooden crates engineered to endure ocean container vibration, humidity shifts, and multimodal overland trucking.