Siemens SIMOSEC metal-enclosed MV switchgear (to 24 kV)
Manufacturer: Siemens
Siemens SIMOSEC secondary switchgear to 24 kV, a hybrid of air-insulated busbars and SF6 switch vessels
This model is part of SecondWatt’s switchgear research catalogue. Specifications and price observations are included where supported by sources. Equipment availability and commercial terms require confirmation.
Siemens SIMOSEC dossier: hybrid metal-enclosed switchgear to 24 kV and 25 kA with SF6 switch vessels, ANSI crossover, F-gas notes, inspection points.
SIMOSEC is Siemens AG Smart Infrastructure's metal-enclosed, extendable MV switchgear for secondary distribution. It is often described as air-insulated, which is only half the construction: the busbar compartment is air-insulated while the switching devices sit in an SF6-filled vessel. Voltage classes run 7.2/12/17.5/24 kV with BIL of 60/75/95/125 kV phase-to-earth, busbars at 630 A standard (800 or 1,250 A optional), feeders to 1,250 A on breaker panels, and short-time withstand to 25 kA for up to 2 seconds, with internal arc classes IAC A FL and A FLR at up to 21 kA/1 s under IEC 62271-200. Panel widths run 375-875 mm.
Siemens actively markets SIMOSEC into the US/ANSI space through selection guides and unit-substation reference designs, an unusual IEC-to-ANSI crossover.
As with all hybrid-SF6 gear, the switch vessel brings F-gas obligations that pure-air successors avoid.
Why it matters
SIMOSEC's hybrid construction means one lineup carries two insulation regimes and two inspection paths. Its ANSI-market push also matters, because IEC secondary gear entering US campuses creates exactly the orphaned-spares situations a secondary marketplace exists to solve.
Who buys it
Utilities, campuses, and industrial secondary networks specify SIMOSEC new, with US unit-substation designs an emerging channel. Used demand would come from installed-base spares, but no open supply exists; rebuilder interest (BCS rebuilds Siemens MV gear) shows the service channel is live.
Role in the data center
Secondary medium-voltage distribution and unit-substation primaries on campus networks, sitting downstream of the intake switchgear and feeding hall-level transformers. The US reference-design push targets exactly the data center unit-substation duty, which is how an IEC-family product ends up in ANSI-market electrical rooms.
Key specifications
| Voltage classes | 7.2 / 12 / 17.5 / 24 kV |
|---|---|
| BIL (phase-earth) | 60 / 75 / 95 / 125 kV |
| Busbar current | 630 (opt. 800 / 1,250) A |
| Short-time withstand | 25 kA / up to 2 s |
| Internal arc | IAC A FL / FLR to 21 kA 1 s |
| Construction | air busbar + SF6 switch vessel |
| Panel widths | 375-875 mm |
| Business unit | Siemens AG, Smart Infrastructure (Electrification & Automation) |
| US/ANSI channel | selection guide + substation reference designs |
| BIL across isolating distance | 70-145 kV |
Technical summary
Voltage classes: 7.2 / 12 / 17.5 / 24 kV. BIL: 60 / 75 / 95 / 125 kV (phase-earth); 70-145 kV across isolating distance. Busbar: 630 A standard; 800 / 1,250 A optional. Feeders: to 800 A (ring/metering); 1,250 A (breaker panels). Short-time withstand: up to 25 kA / 1-2 s. Internal arc: IAC A FL / A FLR up to 21 kA / 1 s. Construction: air-insulated busbar + SF6 switch vessel. Panel widths: 375 / 500 / 750 / 875 mm. Standards: IEC 62271-1/-100/-102/-103/-105/-200.
Major variations
Ring-main, switch-fuse, circuit-breaker and metering panels in four widths (375, 500, 750 and 875 mm), across the 7.2, 12, 17.5 and 24 kV classes, with busbars at 630 A standard and 800 or 1,250 A optional. Siemens documents US and ANSI unit-substation configurations in separate reference guides, so the same product appears in two very different design packages. The SF6-filled switch vessel is the F-gas-relevant component on every variant; the busbar compartment is air.
Configurations and options
Panels are ordered by duty, ring-main, switch-fuse, circuit-breaker or metering, in four widths, 375, 500, 750 and 875 mm, which is what sets lineup length. Ratings to confirm are the voltage class among 7.2, 12, 17.5 and 24 kV with BIL of 60, 75, 95 or 125 kV phase-to-earth, the busbar at 630 A standard or 800 and 1,250 A optional, feeders to 800 A on ring and metering panels and 1,250 A on breaker panels, short-time withstand to 25 kA for up to 2 seconds, and internal arc class IAC A FL or A FLR up to 21 kA for 1 second. Siemens publishes separate US and ANSI unit-substation configurations, so the same product appears in two very different design packages.
Compatibility and dependencies
Construction is hybrid rather than air-insulated: the busbar compartment is air while the switching devices sit in an SF6-filled vessel, so the vessel carries F-gas obligations a fully air-insulated lineup would not, and it is sealed rather than field-serviceable. The panel is extendable, which is its distinguishing feature against fixed ring main units, and extension needs matching Siemens panels. Bus rating and the 25 kA withstand have to be matched to the upstream transformer, noting the withstand duration is stated at up to 2 seconds. Internal arc classification of up to 21 kA for 1 second is lower than the short-time withstand and is the number that governs room design and personnel access.
Pricing and availability
Trend: rising Lead time, new: 52-72 weeks (MV secondary class). Lead time, used or refurbished: No open used channel. Warranty, used: 1-year typical from reconditioning dealers.
Lifecycle and maintenance
Gas-insulated switchgear targets 35-40 year service from sealed-for-life compartments with minimal maintenance: density monitoring, PD surveys, and mechanism service. Sealed tanks cannot be repaired in the field, so gas loss or internal fault usually ends the asset. EU F-gas and CARB rules add end-of-life SF6 recovery and reporting obligations that must be priced into any SF6 unit, while SF6-free designs (clean air, dry air, C4-FN mixtures) remove that liability entirely.
Thermal and emissions profile
The regulatory story is the insulation gas: SF6 carries a global warming potential of 24,300 and an atmospheric lifetime near 3,200 years. EU Regulation 2024/573 bars placing new SF6 switchgear at or below 24 kV on the EU market from 2026-01-01, extends to 52-145 kV classes from 2028, above 24 to 52 kV from 2030, and above 145 kV from 2032. California's CARB rule phases out acquisition of new SF6 gas-insulated equipment from 2025 on a staged schedule. Legacy SF6 gear remains legal to operate but faces stranded-asset discounts and end-of-life gas recovery obligations.
Common failure points
- Gas leakage — Density alarms and lockout; insulation margin lost as pressure falls
- Partial discharge in compartments — PD at spacers, particles, or terminations progressing to internal fault
- Operating mechanism — Spring and motor failures on switch and breaker drives
- Cable terminations — Tracking in cable boxes and poorly seated plug-in connectors
- Density monitor drift — False alarms or missed low-gas conditions from drifted gauges
- End-of-life gas liability — SF6 recovery and reporting costs land on the owner at decommissioning
Inspection checklist
Gas density: verify density monitors against nameplate fill (150 kPa class systems); alarm thresholds intact. Leak rate: review gas top-up logs; leakage above 0.5% per year fails modern acceptance. Gas quality: test SF6 moisture and decomposition before transfer; SO2 presence flags internal arcing. F-gas compliance: verify EU 2024/573 and CARB status; new SF6 MV gear is barred from the EU market from 2026. Partial discharge: UHF or acoustic survey per IEC 60270 practice; PD is the dominant latent defect. Vacuum interrupters: hipot test breaking units; interruption is vacuum even in gas-insulated designs. Mechanism: exercise and verify spring charge; check counters against 10,000-operation class ratings. Terminations: inspect cable boxes for tracking; verify stress cones and plug-in connectors seated.
Procurement channels
Siemens channels supply new panels. Surplus Record's Siemens switchgear category is the channel to watch for used panels; BCS Switchgear demonstrates that a live rebuild channel for Siemens MV gear exists.
Regional notes
An IEC 62271-series product that Siemens also markets into the United States, publishing an ANSI selection and application guide and unit-substation reference designs, which is an unusual crossover for an IEC secondary-distribution family. The design package rather than the product decides which rules a given lineup was built to, and that should be established before a used panel is quoted. The SF6 switch vessel brings F-gas obligations under EU Regulation 2024/573 and California's SF6 phase-out from 2025 that pure-air successors avoid. The owner is Siemens AG, Smart Infrastructure.