Schneider SM6-36 Air Insulated Medium Voltage Switchgear

SM6-36 is a metal-enclosed, air insulated medium voltage switchgear range engineered for distribution networks up to 36 kV, combining SF6 or vacuum interrupting technology inside sealed-for-life switching poles with a modular cubicle architecture that allows incoming, outgoing, circuit-breaker, ring main unit, and metering functions to be assembled into a single harmonized line-up. This article covers the SM6-36 functional unit types, its key technical ratings, internal arc classification, selection criteria for utility and industrial substations, applicable IEC standards, and answers to the most common buyer questions. Power Solutions Hub supplies and supports SM6-36 switchgear across export markets including the Middle East and Gulf incl. Egypt and Saudi Arabia, North Africa, CIS, and Sub-Saharan Africa, where compact, low-maintenance MV switchgear is a standard requirement for grid and industrial substations.

What Is SM6-36 Air Insulated Medium Voltage Switchgear?

SM6 is a modular medium voltage cubicle range built on more than forty years of Schneider Electric experience in protection, monitoring, and control solutions for MV networks, with the switching poles based on more than thirty years of SF6 interruption technology. The SM6-36 variant extends the harmonized SM6 platform up to 36 kV, allowing operators to combine multiple functional cubicles — incoming/outgoing feeders, circuit-breaker units, ring main units, and metering panels — to build a complete distribution substation. Globally, more than 1,700,000 SM6 cubicles have been installed worldwide , following an earlier milestone of over 1,500,000 units by 2015 , reflecting broad reference deployment across utility, industrial, and infrastructure projects.

Each SM6-36 cubicle is designed with switching and earthing parts housed inside a sealed-for-life SF6-filled unit for the operational life of the equipment , and the overall product range is rated for a 30-year service life . All cubicles are 100% factory tested and do not require on-site testing before commissioning , which shortens installation time for export projects where local test facilities may be limited.

Functional Units and Variants Available in SM6-36

The SM6 platform is built around a common set of functional cubicle types, which can be combined to match the single-line diagram of the substation:

• Ring main unit (RMU) cubicles — load-break switch disconnector functions for ring or radial distribution feeders.
• Circuit-breaker cubicles — withdrawable or fixed circuit-breaker units for protected incoming/outgoing feeders and transformer protection.
• Metering cubicles — voltage/current transformer compartments for revenue or protection metering.
• Bus coupler and bus riser cubicles — for busbar sectionalizing and extension between switchboard sections.
• Fuse-combination cubicles — combined switch-fuse protection for transformer feeders where fuse-based protection is preferred over a circuit breaker.

At 36 kV, switching devices are based on the SF1 circuit-breaker range; the Evolis vacuum circuit breaker is not available at 36 kV and is used only on lower-voltage SM6 cubicles . Rated current for the switching devices is available at 630 A and 1250 A, with associated rated short-circuit breaking currents of 16 kA and 25 kA , giving buyers a choice of breaker duty depending on the transformer or feeder load to be protected.

Technical Specifications and IAC Comparison Table

The table below summarizes the key numeric ratings for SM6-36, alongside the SM6-24 variant from the same harmonized platform, to help specifiers compare internal arc classification (IAC) and voltage class options when selecting the correct cubicle family.

Note that internal arc gas evacuation options differ between the two voltage classes: SM6-24 offers both downward and upward gas evacuation, while SM6-36 uses downward gas evacuation as the standard arrangement .

Internal Arc Protection and Operator Safety

Internal arc withstand is a decisive selection criterion for utilities and industrial plants where operator safety and continuity of service are critical. SM6-36 offers 3-sided internal arc protection classified IAC: A-FL at 16 kA for 1 second , meaning the enclosure is validated to contain and vent arc fault energy away from the front, sides, and rear-adjacent accessible zones, protecting personnel standing in front of the switchgear during an internal fault event. Beyond the enclosure rating, SM6 cubicles incorporate a three-position switch structure to prevent incorrect switching sequences, a fully closed earthing switch, positive-indication position indicators, internal arc withstand in cable and connection compartments, clear mimic diagrams, an anti-reflex operating lever, and physically segregated compartments — all standard mechanical and procedural safeguards built into the SM6 design philosophy.

Selection Criteria for SM6-36 Switchgear

When specifying SM6-36 for a project, buyers and consulting engineers should evaluate:

• Rated voltage and insulation level — confirm the network’s nominal voltage falls within the SM6-36 envelope (up to 36 kV) rather than requiring the lower SM6-24 platform.
• Rated current and short-circuit duty — match the 630 A/1250 A current rating and 16 kA/25 kA short-circuit breaking current to the transformer and feeder fault-level study for the substation.
• Internal arc classification — verify whether 3-sided (A-FL) protection is sufficient, or whether the layout requires additional rear-side (A-FLR) considerations, and confirm the gas evacuation routing (downward) fits the substation civil design.
• Functional unit mix — determine which combination of ring main unit, circuit-breaker, metering, and bus coupler cubicles matches the required single-line diagram.
• Monitoring and connectivity needs — SM6 cubicles are compatible with PowerMeter metering units, Easergy P3 and Easergy Sepam multifunction protection relays, and self-powered VIP protection relays, plus connectable sensors (SC110, CL110, TH110) for continuous asset condition monitoring; the Easergy TH110 conductor temperature sensor is fitted as standard on cable terminations of relevant cubicles .
• Maintenance regime — factor in the reduced maintenance burden from sealed-for-life SF6 switching and earthing parts, versus operating mechanisms designed for lower maintenance frequency under normal service conditions.
• End-of-life SF6 handling — plan for certified SF6 recovery and disposal procedures in line with local environmental regulation before decommissioning.

Applications

SM6-36 switchgear is applied in primary and secondary MV distribution substations, industrial plant intake switchrooms, transformer feeder protection, ring main distribution networks, and utility distribution feeders where a 36 kV insulation class is required. Reference installations spanning airports, universities, hospitals, cement plants, data centers, and government facilities across multiple regions demonstrate the platform’s applicability to both utility-grade and industrial-grade MV distribution projects, including installations referenced in Egypt and Saudi Arabia among other Middle East and Gulf, North Africa, CIS, and Sub-Saharan Africa markets.

Standards and Compliance

SM6 switchgear is designed in accordance with the IEC standard framework applicable to metal-enclosed medium voltage switchgear . End-of-life SF6 gas recovery is compliant with IEC 62271-4:2013 , and disposal must follow local environmental regulation, including Regulation (EU) No 517/2014 for European countries, given SF6’s classification as a powerful greenhouse gas requiring certified recovery rather than atmospheric release .