Choose your region and language



EconiQ retrofill for gas-insulated lines ELK-3, 420 kV

Replacing SF₆ in installed high-voltage gas-insulated lines (GIL) with an eco-efficient gas mixture to improve the environmental and lifecycle performance of the equipment

The innovative EconiQ retrofill solution uses eco-efficient fluoronitrile based gas mixture to replace SF6 in installed gas-insulated lines. This can be done with minimum changes to existing equipment while ensuring performance of the equipment and significantly lowering environmental impact.

In this process, SF6 from the installed gas-insulated lines is evacuated and filled into gas bottles for recycling or disposal and the GIL is then flushed to remove any humidity. The new eco-efficient gas mixture is then filled into the GIL and the switchgear is re-energized to connect back to the grid. The process is relatively quick and enables the reuse of passive gas components designed for SF6 to be converted into non-SF6 equipment, thereby improving their environmental and lifecycle performance.

EconiQ is Hitachi Energy's eco-efficient portfolio for sustainability where products, services and solutions are proven to deliver exceptional environmental performance.


  • Installed ELK-3, 420 kV gas-insulated lines

Why Hitachi Energy?

  • Our solution is developed specifically to reduce the quantity of SF6 in installed high-voltage equipment without doing any major changes or upgrades on the existing equipment. All work can be performed without opening and dismantling the installed GIL. There is no need to change installed sealings, only gas is replaced.
  • Our eco-efficient gas mixture significantly reduces the CO2 equivalent emissions as compared to SF6  while providing the identical ratings, same reliability and life cycle performance.
  • Extensive GIS know-how and service support for smooth process in planning and execution at site.

Benefits of EconiQ retrofill solution:

  • Convert an existing GIL designed for SF6 to eco-friendly GIL without any dismantling and opening of gas compartment and with minimum outage.
  • Eliminate approximately 50% SF6 from the typical substation and thus reduces the carbon footprint and any financial and environmental implications thereof.
  • Reduce SF6 inventory from the network.
  • Future-proof solution to comply with environmental regulation changes.
EconiQ™ retrofill for gas-insulated lines

Brief performance data

EconiQ retrofill for gas-insulated lines ELK-3, 420 kV

CO2 equivalent relative reduction to SF6



Rated nominal voltage Um

420 kV (440 kV 60min)

Power frequency withstand voltage

650 kV (r.m.s. value)

Rated switching / lightning impulse withstand voltage

1,050 kV / 1,425 kV (peak value)

Rated current at 40 °C (50 Hz, 60 Hz)

4,000 A

5,000 A

Rated short time withstand current/duration

63 kA / 3 s

Rated peak-withstand current (peak value)

171 kA

Temperature range



-25° / +40 °C (+55 °C @ 4,000 A)

Get to know more

Hitachi Energy partners with National Grid on world’s first replacement of SF₆ in existing high-voltage equipment

Press release

EconiQ retrofill for gas-insulated lines ELK-3, 420 kV

Product leaflet

Achieving the world’s first SF6 replacement with National Grid

Success case

Implementation of a pioneering eco-efficient solution, EconiQ retrofill


Something caught your eye?

Our sales team will get in touch with you