GM-SG non-arc-resistant, air-insulated, metal-clad switchgear

Siemens GM-SG medium-voltage metal-clad air-insulated switchgear

5-27 kV
  • Rated short-time withstand current up to 63 kA

  • Rated continuous current up to 4,000 A to 17.5 kV and 3,000 A 27 kV

  • Lightning impulse (BIL) up to 125 kV

Air-insulated, medium-voltage, non-arc-resistant switchgear

Siemens type GM-SG 5 kV, 7.2 kV, 15 kV, 17.5 kV, and 27 kV metal-clad power switchgear assemblies with horizontal drawout type GMSG vacuum circuit breakers take advantage of the latest developments in vacuum interrupter technology. Up to two circuit breakers can be stacked in a single vertical section, allowing significant space savings.


The equipment meets or exceeds the latest standards of ANSI, IEEE and NEMA.


Type GM-SG switchgear is designed for use in industrial plants, commercial buildings, electric utility systems, cogeneration installations and other electrical systems. It is commonly used for protection and switching of transformers, motors, generators, capacitors, buses, distribution feeder lines and, in general, for protection of any medium-voltage power circuit.


Siemens experience gained in over 80 years of supplying metal-clad switchgear in the U.S. has been captured in the type GM-SG design. The objective has been to incorporate features designed to provide safety, while simplifying operation, maintenance and minimizing installation cost.


The switchgear structure and the drawout vacuum circuit breaker are an integrated design, with dielectric, thermal and interruption integrity built directly into the basic design, not as an afterthought.


Siemens Integrated Electric-Racking System (SIERS) is optionally available with type GM-SG switchgear.


Watch the videos below to learn more about GM-SG switchgear, its Sm@rtGear option, and Shelter-Clad+ type enclosures.

Vacuum interrupters

Vacuum interrupters are the centerpiece of our medium-voltage products. The hermetically sealed vacuum contact gap keeps the switching characteristics of the interrupters constant throughout their entire lifecycle. Special contact materials made by Siemens ensure that our vacuum interrupters offer absolutely top performance. With valuable features that include high short-circuit switching capacity and minimum forward resistance, they ensure reliable switching even under difficult environmental conditions – like vibration and fluctuating frequencies – regardless of whether they’re installed horizontally or vertically. Our vacuum interrupters can perform up to 30,000 operating cycles when used in circuit breakers and up to three million for contactors.

Air-insulated, medium-voltage, non-arc-resistant switchgear


Features include:

  • One-high or two-high construction
  • Up to 100 full-fault interruptions
  • Universal spare circuit breaker for 50 kA and lower ratings
  • Universal spare circuit breaker for 63 kA ratings
  • Interlocks permit insertion of higher rating vacuum circuit breaker into lower rated cell but not vice versa
  • Closed door racking
  • Front accessible circuit breaker operating mechanism for ease of maintenance
  • Floor rollout circuit breaker in lower cell without a dolly
  • Visible secondary disconnect
  • Circuit breaker ships inside of cell, thus reducing installation cost and transit damage
  • Pair with Siemens protective relays to match any typical application
  • Horizontal drawout type GMSG vacuum circuit breaker with type 3AH3 operating mechanism
  • Uses the latest developments in vacuum interrupter technology
  • Highly reliable vacuum interrupters - MTTF over 50,000 years
  • Common type 3AH3 operator platform for all ratings
  • Over 120,000 type 3AH3 operators produced since 1998
  • Generator circuit breakers (to IEEE C37.013 optionally available)
  • 10,000 operations to overhaul
  • Three-cycle interrupting time (optional)
  • Siemens integrated electric-racking system (SIERS) available (option)
  • Optional Sm@rtGearTM functionality provides predictive diagnostics, continuous monitoring, and control from a remote location
  • Meets or exceeds the latest ANSI, IEEE and NEMA standards
  • UL or C-UL Listing available.

Type GM-SG switchgear available as:

  • Indoor (type GM-SG)
  • Outdoor walk-in Shelter-Clad NEMA 3R (type SGM-SG) single-aisle (factory-assembled aisle) or factory-insulated and assembled aisle (optional)
  • Outdoor walk-in Shelter-Clad+ factory-assembled switchgear and aisle on common base with power equipment center type options (type S+GM-SG).
  • Outdoor, aisleless non-walk-in (type OGM-SG).



Standard accessories include:

  • Manual racking crank

  • Spring charging crank

  • Drawout extension rails (facilitate handling of circuit breakers in upper cell)

  • Lifting sling (for circuit breakers above floor level)

  • Split plug jumper (standard unless test cabinet is furnished)

  • Contact lubricant

  • Touch-up paint.

Optional accessories include:

  • Circuit breaker lift device

  • Test cabinet (in place of split plug jumper)

  • Test plugs (if required by devices)

  • Electrical racking motor assembly (to enable racking while operator is at a distance from the switchgear)

  • Manual or electrical ground and test device.

Test provisions, either a split plug jumper or a test cabinet, are available for testing the circuit breaker outside its cubicle.


The split plug jumper is used to bridge the secondary disconnects with a flexible cable, so the circuit breaker may be electrically closed and tripped with the control switch on the instrument panel while the circuit breaker is outside of its compartment. The test cabinet, including a control switch, is used for closing and tripping the circuit breaker at a location remote from the switchgear.

Siemens integrated electrical-racking system (SIERS 1.0)

Features and benefits

Siemens integrated electric-racking system (SIERS) is an option that is available with Siemens type GM-SG non-arc-resistant, medium-voltage switchgear. It provides additional personnel protection against arc-flash exposure for operators by providing a means of remotely racking the type GMSG drawout circuit breaker. SIERS reduces the need for personal protective equipment (P.P.E.) per the NFPA-70E® standard.


Standard features:

  • Maintain all of the safety interlocks as required by IEEE standard C37.20.2
  • Logic control module for control and circuit protection
  • Interference detection
  • Control pendant (hand-held controller)
  • High-torque, fixed-mounted dc motor
  • Available for 125 V dc external power supply
  • Factory installed and tested as a complete racking system.

Optional features:

  • Powered from 120 V ac sources in switchgear
  • Provision for external power source
  • Integrated into the switchgear secondary control circuits or with the protection relay to provide interface with local HMI or SCADA systems
  • Field retrofit for existing Siemens type GM-SG non-arc-resistant, medium-voltage switchgear.

Optional configurations:
Type SIERS device is available in three configurations:

Press release:

Siemens integrated electrical-racking system (SIERS 2.0)

SIERS 2.0 provides increased safety, ease of use, and improved reliability options and features to enable users to remotely rack GMSG drawout circuit breakers, ground and test devices, and auxiliary trays. SIERS 2.0 also includes the feature to remotely open and close circuit breakers. To meet the particular user’s cost and application requirements, SIERS 2.0 is available in two configuration setups, 1) portable HMI with carry case, and 2) local HMI smart. SIERS 2.0 provides both an innovative and flexible approach to monitoring and controlling metal-clad switchgear while safely standing outside of the arc-flash zone in front of the equipment or in a control room, which reduces the need for personal protective equipment (PPE) per the NFPA-70E® standard.


Key features and benefits:

  • Maintain all of the safety interlocks as required by IEEE Std. C37.20.2
  • Interference detection to prevent damage to the motor
  • HMI touchscreen provides a user-friendly and visible display
  • Local override and permissive control
  • Troubleshooting and diagnostic
  • High-torque, fixed-mounted motor
  • Available in two configurations (portable HMI and local HMI smart)
  • Powered from a control power transformer located in the switchgear at 120 Vac or available 125 Vdc
  • External 120 Vac power supply with extension cord (optional)
  • Ethernet connection via standard protocols: Modbus or Profinet
  • SCADA interface optional
  • Field retrofit for existing Siemens GM-SG and GM-SG-AR switchgear.
1. Optionally available for VT and CPT auxiliary drawout trucks. Also, when required, a half-high switchgear compartment is required.
Portable HMI with carry case

• Logic controller and HMI touchsceen installed

in a portable carry case

• Fixed-mounted motor in each VCB compartment1

Local HMI smart

• CPU controller installed in LV compartment

or control cabinet

• Portable HMI touchscreen

• 30-foot cord

• Fixed-mounted smart motor in each VCB compartment1

Sm@rtgear technology option

Intelligent devices (circuit breakers, relays, meters, etc.) have existed for more than 30 years. These devices are self-monitoring, configurable, and communicating, but individually they are only islands of intelligence. Historically integrated remote monitoring, configuration, and control have only been available with the inclusion of upstream PMCS, PCS, DCS, or SCADA systems.


With the advent of Siemens Sma@rtGear technology, remote monitoring, configuration, and control are standard features that are integral to the electrical apparatus product.


Advantages at a glance:

  • Keeping business operational with maximum uptime
  • Reliable energy-efficient products and systems
  • Ease of operation and maintenance
  • Remote access for arc-flash mitigation
  • Integration with existing equipment
  • One supplier for all power distribution needs
  • Long-term partner over entire lifecycle
  • Technology leader with durable solutions
  • 24/7 hotline support.

Sm@rtGear features, benefits and details for medium-voltage air-insulated switchgear:

  • Types: GMSG vacuum circuit breakers
  • Maintenance mode: yes
  • Metering: Q200, Q100, P855
  • Protective relays: Yes, standard Siemens SIPROTEC
  • Remote racking: Yes, optional integrated accessory
  • Remote open/close: Yes
  • HMI size: 22"
  • Auto-throwover: Yes
  • Temperature sensing: Yes, optional
  • Optional accessories: High-resistance grounding, partial-discharge monitoring.

For more information about the entire Sm@rtGear portfolio for low- and medium-voltage power distribution equipment, please go to Sm@rtGear™ power distribution solution.




Maximum design voltage kV
Rated interrupting rating kA
Maximum interrupting and short time1, 2 kA
Voltage range factor
Continuous current3 A rms
Withstand voltage levels - power frequency kV rms
Withstand voltage levels - lightning impulse (BIL) kV peak
Closing and latching (momentary) -asymmetrical (1.55 x I) kA rms
Closing and latching (momentary) -peak (2.6 x I) kA peak
40, 50, 63
40, 50, 63
1,200, 2,000, 3,000, 4,000FC
62, 78, 98
104, 130, 164
1,200, 2,000, 3,000, 4,000FC
25, 40, 50, 63
25, 40, 50, 63
1,200, 2,000, 3,000, 4,000FC
39, 62, 78, 98
65, 104, 130, 164
50, 63
50, 63
1,200, 2,000, 3,000, 4,000FC
78, 98
130, 164
25, 40
25, 40
1,200, 2,000, 2,500, 3,000FC
39, 62
65, 104


  1. All values apply to polyphase and line-to-line faults.
  2. Standard duty cycle is O - 0.3 s - CO - 3 min. - CO.
  3. Fan-cooled rating available using a circuit breaker together with a modified switchegar structure incorporating fan-cooling equipment. Consult factory for rating in Shelter-Clad and Shelter-Clad+ outdoor switchgear. FC rating is not available in OGM-SG non-walk-in. When FC circuit breakers are furnished, main bus is self-cooled.


Height (H)
Width (W)
Depth (D)
Drawout aisle (DA)
Weight lbs (kg)
GM-SG up to 17.5 kV
95.3 (2,419)
36.0 (914)
98.7 (2,507)
72 (1,829) recommended
3,300 (1,497)
SGM-SG up to 17.5 kV
114.8 (2,915)
36.0 (914)
173.4 (4,404)
72.0 (1,829) included
5,000 (2,268)
OGM-SG up to 17.5 kV
113.6 (2,886)
36.0 (914)
101.9 (2,588)
72 (1,829) recommended
3,950 (1,792)
GM-SG 27 kV
103.0 (2,616)
36.0 (914)
120.0 (3,048)
72.0 (1,829) recommended
3,800 (1,723)



  1. Dimensions are approximate.
  2. Add 6“ (152 mm) to each end of lineup for aisle extension 12“ (304 mm) total.
  3. 72” (1,829 mm) aisle space recommended allows room for interchange of circuit breakers. Minimum aisle space required for handling circuit breaker with lift truck is 65” (1,651 mm). Minimum aisle space required if all circuit breakers are at floor level is 55” (1,397 mm).
  4. If indoor switchgear is installed on a raised housekeeping pad, the pad must not extend farther than 3” (75 mm) from the front of the switchgear to avoid interference with the use of the portable lift truck. Add for roof & enclosure overhang: Rear: Non-walk-in: 3.6” (92 mm),  Shelter-Clad: 3.6” (92 mm). Front (drawout aisle): Non-walk-in: 3.7” (94 mm), Shelter-Clad: 1.7” (43 mm).
  5. The switchgear must have at least 6” (152 mm) horizontal clearance. 
  6. Add 4.5” (114 mm) to depth for front and rear doors. 
  7. Add weight of circuit breakers. 
  8. Maximum shipping group five sections. 
  9. Shelter-Clad+ switchgear assemblies (types S+GM-SG) are built in partnership with Siemens-qualified vendors, who provide detailed drawings of each custom assembly, which include dimensions and weights. Please be sure to carefully review and follow all instructions provided in the order-specific Shelter-Clad+ drawing package. 

10. For transfer bus arrangements, add 15" (381 mm) to the depth.


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