GM38 non-arc-resistant, air-insulated, metal-clad switchgear

GM38 non-arc-resistant, air-insulated, metal-clad switchgear

23-38 kV
  • Rated short-time withstand current up to 40 kA

  • Rated continuous current up to 3,000 A*

  • Lightning impulse (BIL) up to 150 kV

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

Type GM38 metal-clad air-insulated switchgear can meet almost any switchgear application from 23 kV through 38 kV.


The horizontal drawout vacuum circuit breakers occupy the lower cell with voltage transformers (VTs) or drawout fuses available in the upper cell.


The lower cell may be used for auxiliaries, such as VTs, a control power transformer (CPT) or drawout fuses.


Two types of outdoor housing are offered: non-walk-in and Shelter-Clad.


Siemens Integrated Electric-Racking System (SIERS) is optionally available with type GM38 non-arc-resistant switchgear.


Watch the videos below to learn more about GM38 switchgear, and its Sm@rtGear option.

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 construction 
  • Up to 50 full-fault interruptions 
  • Universal spare circuit breaker 
  • Closed door racking 
  • Interlocks permit insertion of higher rated vacuum circuit breaker into lower rated cell but not vice versa 
  • Front accessible circuit breaker operating mechanism for ease of maintenance • Floor rollout circuit breaker in lower cell without a dolly 
  • Visible secondary disconnect 
  • Pair with Siemens protective relays to match any typical application 
  • Horizontal drawout type 38-3AH3 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 
  • 10,000 operations to overhaul 
  • Three-cycle interrupting time (optional) 
  • SIERS integrated electrical-racking system available (optional) 
  • Optional Sm@rtGear™ functionality provides predictive diagnostics, continuous monitoring, and control from a remote location 
  • Meets or exceeds the latest ANSI, IEEE and NEMA standards 
  • UL Listing for 40 kA available.

Type GM38 switchgear available as:

  • Indoor (type GM38)
  • Outdoor, walk-in, Shelter-Clad NEMA 3R (type SGM38) single aisle or common aisle
  • Outdoor, aisleless non-walk-in (type OGM38).



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)

Features and benefits

Siemens Integrated Electric-Racking System (SIERS) is an option that is available with Siemens type GM38 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 38-3AH3 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 GM38 non-arc-resistant, medium-voltage switchgear.

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

Press release:


Type 38-3AH3 circuit breaker ratings constant kA basis - ANSI/IEEE C37.06-2009

Maximum design voltage kV
Rated interrupting rating kA
Maximum interrupting and short time kA
Voltage range factor
Continuous current1 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
1,200, 2,000, 3,000
1,200, 2,000, 3,000


1 3,000 A circuit breaker together with a modified switchgear structure incorporating fan-cooling equipment. 3,000 A is not available in outdoor equipment.


Dimensions in inches (mm) 2
Height (H)
Width (W)
Depth (D)
Drawout aisle (DA)3,4
110.0 (2,794)
48.0 (1,219)
130.0 (3,302)
96.0 (2,438) recommended
SGM38 single aisle
132.5 (3,366)
48.0 (1,219)
234.5 (5,956)
96.0 (2,438) included
SGM38 common aisle
132.5 (3,366)
48.0 (1,219)
363.8 (9,239)
96.0 (2,438) included
OGM38 non-walk-in aisleless
48.0 (1,219)
48.0 (1,219)
139.4 (3,539)
96.0 (2,438) recommended



1 Add 6“ (152 mm) to each end of lineup for aisle extension 12” (305 mm) total.


2 Add for roof and enclosure overhang:

Rear (cable side):

  • Non-walk-in: 3.9” (98 mm)
  • Shelter-Clad 3.9” (98 mm).

Front (drawout side):

  • Non-walk-in: 6.9” (175 mm)
  • Shelter-Clad 1.5” (38 mm).

3 If indoor switchgear is installed on a raised housekeeping pad, the pad must not extend further than 3“ (75 mm) from the front of the switchgear to avoid interference with the use of the portable lift truck.


4 96.0” (2,438 mm) aisle space recommended and allows room for interchange of circuit breakers. Minimum aisle space required for handling circuit breakers with lift truck is 80” (2,030 mm)

TechTopics is a series of papers that discuss issues of interest to users or specifiers of electrical equipment.

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