Siemens to provide UK’s first SF6 free 145kV vacuum circuit breakers in Scotland: 21-3

16 May 2019

Siemens to provide UK’s first SF6 free 145kV vacuum circuit breakers in Scotland

Siemens Gas and Power will provide the UK’s first ‘clean air’ insulated high voltage switchgear to Wood T&D, as the lead contractor for the upgrade of Dunbeath substation on the north coast of Scotland.

Siemens will deliver two live tank 145kV vacuum circuit breakers from its Blue product range that require no sulphur hexafluoride (SF6) and use only ‘clean air’ for insulation. A vacuum interrupter unit handles the switching and arc-extinguishing functions with the clean air providing insulation to the current carrying conductors inside the housing.  

It is the first time that clean air has been used instead of SF6 to insulate 145kV circuit breakers in the UK. It uses a gas mix similar to the air we breathe, made up of nitrogen (80%) and oxygen (20%), as a carbon free alternative to SF6 which has traditionally been the method of insulation in high voltage switchgear since the 1960s.


The chemical properties of SF6 gas make it ideal for electrical insulation and arc quenching in high-voltage switchgear. However, it has a high global warming potential and contributes to the greenhouse effect if released to the atmosphere. Strict regulations are in place to manage SF6 (F-gas) and there is pressure on the switchgear supply industry to provide SF6 gas alternatives to reduce the impact of any gas emissions caused by failures or handling. A conventional SF6 circuit breaker uses around 9kg of SF6, which is the equivalent of 210t of CO2, whereas the new Siemens 145kV vacuum circuit breaker has a 0t equivalent of CO2, which delivers the least possible environmental impact both in use and even if damaged.

The ‘clean air’ technology requires no special precautions to be taken during operation and recycling and offers top technical performance, maximum safety, and reliability. There is also no longer any need to report the quantities of fluorine gas used. In addition, hermetically sealed vacuum interrupters are reliable and maintenance free thanks to its “sealed for life” technology.

Mark Simblett, Head of Transmission Products, Siemens Energy Management, said: “Siemens has developed this technology to meet climate neutrality requirements by combining vacuum interruption systems for switching and for arc extinguishing with "clean air" as the high-voltage insulating medium. It represents an important step towards the company goal of developing completely environmentally friendly technologies. We’re delighted to provide this important technology for the first time in the UK.”

John Fairbairn, Senior Project Manager, Wood, said:  “Wood is delighted to be part of the introduction to the UK of this new switchgear technology which will be compliant, functional with a minimum impact on the environment”.

The replacement circuit breakers will be delivered in July and installed by Wood T&D as the lead contractor for the refurbishment of Dunbeath substation.


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Sara Crane

PR Consultant

Siemens plc

+44 (0)7921 847640

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