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Gas-Insulated Substations

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



SF6-free g3-Gas-Insulated Substations up to 145 kV

GE's F35g is a g3-gas-insulated substation up to 145 kV, up to 3,150 A and 40 kA using GE’s revolutionary g3 gas mixture as an insulating and switching alternative to SF6.

The F35g g3-GIS is designed to deliver the same performances and reliability features as today’s existing SF6 switchgear, without SF6's environmental impacts. Compared to SF6 switchgear, they feature:

  • Same dimensions and footprint, no drastic addition of raw material such as aluminum compared with other SF6 alternatives
  • Same technical performance
  • Same safety level
  • Same reliability feature

Key Characteristics

  • A drastically reduced impact of gas releases to atmosphere (99% vs. SF6)
  • The lowest environmental impact during the whole life cycle:
    • Impact on climate change: 72% reduction,
    • Best-in-class Life Cycle Assessment (LCA) considering all environmental aspects from manufacturing to end-of-life

The F35 is a compact and accessible GIS solution, with a bay footprint below the market average. Up to 2 bays are assembled together, wired, tested and shipped enabling shorter site works.

GE’s F35g is the first SF6-free g3-gas-insulated substation up to 145 kV to complete ENA assessment in the UK.


Main Characteristics

Environment friendliness

  • SF6-free using GE’s g3 gas mixture instead of SF6
  • No pollution transfer in form of raw material increase
  • GWP of the gas mass reduced by 99%
  • Advanced sealing system

High availability

  • Same principles, interfaces, operating mechanisms for both product in g3 and SF6
  • Easy access to drives and accessories
  • Pure-spring circuit breaker drives

Low costs of land and civil works

  • One of the most compact GIS with bay footprint up to 45% below market average depending on kV rating allows to have low civil work and compact switchgear buildings
  • Up to 2 bays 145 kV assembled, wired, tested and shipped
  • Isolating device for voltage transformer and surge arrester

Smart Grid ready

  • Smart grid features including full-digital monitoring, control and protection
  • One of the best experiences and high data reliability
  • Digital substation ready with LPITs (Low Power Instrument Transformers)


General ratings
Reference electrotechnical standards IEC
Voltages Up to 145 kV
Insulating and switching medium g3 gas mixture
Withstand voltages
Short-duration power-frequency, phase-to-earth / across isolating distance 275/315 kV
Lightning impulse, phase-to-earth / across isolating distance 650/750 kVp
Frequency 50 Hz
Continuous current up to 3150 A
Short-time withstand current 40 kA
Peak withstand current 108 kAp
Duration of short-circuit 3s
Circuit-breaker ratings
First-pole-to-clear factor 1.5
Short-circuit breaking current 40 kA
Short-circuit making current 108 kAp
Operating sequence O-0.3s-CO-3 min-CO
Drive type (three-phase or single-phase) Pure-spring
Breaking time 50ms
Closing time 95ms
Mechanical endurance M2 class
Capacitive switching C2 class
Disconnector and low-speed earthing switch ratings
Capacitive current switching 0.1 A
Bus-transfer current switching capability 2520/20 A / V
Mechanical endurance M2 class
Make-proof earthing switch ratings
Making current capability 108 kAp
Switching capability - electromagnetic coupling 80/2 A / kV
Switching capability - electrostatic coupling 2/6 A / kV
Mechanical endurance M1 class