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HV/MV Equipment
Gas-Insulated Substations up to 420 kV

Home > HV/MV Equipment > Gas-Insulated Substations > GIS

T155 Dual Gas
SF6 and g3 Gas-Insulated Substations up to 420 kV

GE's T155 Dual Gas GIS meets the challenges of networks up to 420 kV for power generation, transmission, and heavy industry applications.

Ready for future SF6 gas regulations

Anticipating future SF6 regulations, this Dual-Gas equipment is available with either g³ or SF6 gas as an insulating and switching medium. Based on having the same foundational design, Transmission System Operators (TSOs) can buy the SF6 version today and easily switch to GE’s g³ solution at a later time.

The T155 Dual Gas GIS is very compact and accessible, with a bay footprint equivalent to the previous SF6 T155 model. Complete bays are fully assembled in the factory (wired, tested, packaged, and shipped), enabling shorter site works.

In addition, the T155 Dual-Gas GIS features an advanced SF6 sealing system with a sealing length divided by two compared to the previous version, improving tightness.

Full digital monitoring control and protection capabilities enable the T155 Dual Gas to be readily integrated into the smart grid.


GE Advantage

Transition from SF6 to g³ technology today to reach your carbon neutrality targets faster. Compare the carbon footprint of your substation using g³ products in place of SF6.

g3 Insulating & Switch Gas Interactive App

Customer Benefits

Customer Benefits



  • 100% SF6-free version available with T155 Dual Gas GIS (with g³ gas)
  • The gas contribution to global warming is reduced by 99% using GE’s g³ gas instead of SF6
  • First-in-class gas sealing system
  • Improved tightness due to sealing length divided by two, compared to the previous version

High availability

  • Current transformers located outside SF6/g3 gas compartment
  • Pure-spring circuit breaker drives
  • State-of-the-art maintenance isolating device: major repair and HV tests with no more than one bay down
  • Outstanding accessibility to drives and accessories


Low costs of land and civil works

  • Very compact GIS: bay footprint remains the same as latest SF6 GIS

Short site works

  • Complete bays are fully assembled in the factory (wired, tested, packaged, and shipped)

Smart grid features

  • Full-digital monitoring, control and protection


g3 Combined g3 bay-SF6 CB SF6
GIS Type T155g 420 kV T155 420 kV T155 420 kV
Reference electrotechnical standards IEC IEC/IEEE IEC/IEEE
Rated voltage 362-420 kV 362-420 kV 362-420 kV
Withstand voltages
 Short-duration power-frequency, phase-to-earth/across open switching device 650/815 kV 650/815 kV 650/815 kV
Switching impulse, phase-to-earth / across isolating distance 1050/900(+345) kVp 1050/900(+345) kVp 1050/900(+345) kVp
Lightning impulse, phase-to-earth / across open switching device 1425/1425(+240) kVp 1425/1425(+240) kVp 1425/1425(+240) kVp
Frequency 50 Hz 50/60 Hz 50/60 Hz
Continuous current up to 5000 A up to 5000 A up to 5000 A
Short-time withstand current 63 kA 63 kA 63 kA
Peak withstand current 170 kAp 170 kAp 170 kAp
Duration of short-circuit 3s 3s 3s
Installation indoor/outdoor indoor/outdoor indoor/outdoor
Circuit Breaker Ratings
Short-circuit breaking current 63 kA 63 kA 63 kA
Short-circuit making current 170 kAp 170 kAp 170 kAp
Operating sequence O-0.3s-CO-3 min-CO/CO-15s-CO O-0.3s-CO-3 min-CO/CO-15s-CO O-0.3s-CO-3 min-CO/CO-15s-CO
Drive type Pure-spring Pure-spring Pure-spring
Mechanical endurance M2 class M2 class M2 class
Capacitive switching C2 class C2 class C2 class
Disconnector and Low-speed Earthing Switch Ratings
Capacitive current switching 0.5 A 0.5 A 0.5 A
Bus-transfer current switching capability 3000 A / 20 V 3000 A / 20 V 3000 A / 20 V
Mechanical endurance M2 class M2 class M2 class
Make-proof Earthing Switch Ratings
Making current capability 170 kAp 170 kAp 170 kAp
Switching capability-electromagnetic coupling 160 A / 10 kV
Switching capability-electrostatic coupling 18 A / 20 kV 18 A / 20 kV 18 A / 20 kV
Mechanical endurance M1 class M1 class M1 class