SF6 Replacement

The Energy Innovation Centre (EIC) works in partnership with the UK electricity and gas distribution network operators to identify and support businesses in developing and commercialising products for the energy sector.

The Call for Innovation process, managed by the EIC, offers innovators the opportunity to register
interest in, and offer potential solutions to, targeted energy distribution sector problems. The problem
areas are identified by the distribution network operators (DNOs). They are seeking new and innovative products or services that will benefit the industry and the customers they support.

The latest in a series of Calls for Innovation seeks potential solutions to a problem area identified by
the distribution network operators (DNOs) with a focus on looking at SF6 alternatives.

For many years the power networks have been using Sulfur Hexafluoride (SF6) gas as a dielectric and insulating material in their transmission and distribution equipment.

SF6 with a dielectric strength of approximately three times that of air at atmospheric pressure lends itself well to being used as an insulator within substations (Gas Insulated Substations – GIS). Using SF6to insulate high voltage components from earthed metal closures has enabled such assemblies to be more compact and allowed substation footprints to be reduced.

It is recognised that SF6 is an extremely effective insulator and interrupting medium. However, SF6 is also an extremely potent greenhouse gas. As responsible businesses the power networks have investigated and developed new ways to manage and reduce the impact of their network, business activities and operations on the environment and this includes their use of SF6.

The ultimate objective of this call is to identify whether there are any known SF6 replacements that are currently available that could be used in existing or new equipment or whether there are potential new systems or materials that could be developed to replace the reliance of SF6 as an insulating and interrupting medium within power networks equipment in the future.

This call can be considered to have two areas of interest. Firstly replacing SF6 for its insulating properties and then for its interruption properties.
SF6 insulating properties allows Gas Insulated Substations (GIS) substations to have more compact
designs which has importance for network operators where space premiums exist on urban sites. Any
replacement material or system would have to exert the following properties:

• Still permit smaller substation foot print compared to, for example traditional air insulated
  substations
• If a new material, it would have to be non-toxic, have good thermal conductivity and be able to
  maintain its physical properties at high voltages
• Could be used in new equipment and/or utilised in existing equipment
• Low maintenance requirements
• Reliable
• Cost competitive

SF6 interrupting properties allow load and fault interrupting switches to be compact, reliable and low
maintenance. These types of switches can perform various duties like interrupting fault current,
opening unloaded transmission lines, capacitor bank switching, transformer reactor switching etc. without any discernable degradation of the circuit breaker contacts or insulation systems. Any
replacement material or system would have to be comparable and exert the following properties:

• High dielectric strength
• Good arc extinguishing properties
• Non-inflammable and chemically stable
• Decomposition products non-explosive and non-toxic
• Could be used in new equipment and/or utilized in existing equipment
• No over voltage problems
• Noiseless operation
• Minimum maintenance
• Could be retrofittable
• Cost competitive