Our partner Trench is one step ahead to reduce the presence of SF6 in instrument transformers by introducing a completely SF6 free solution up to 420 kV. Long term sustainability and no environmental compromise are now available with this innovative clean air insulated portfolio.

The unique portfolio of Clean Air instrument transformers is tested and available for worldwide applications.

Clean Air instrument transformer are installed and in service with outstanding results, proving this innovative and eco-friendly product is highly reliable for the use in AIS and GIS switchgear applications.

The Clean Air portfolio is fully compliant and tested to international standards. It provides the same electrical and insulation features as traditional insulation technologies while at the same time giving all the benefits of a SF6 free solution.


Clean Air is the only eco-friendly and innovative alternative to SF6 insulations with a GWP of ZERO.


Complete portfolio available up to 245 kV (current and combined transformers), 420 kV (inductive voltage transformers)
Meet all lEC and ANSI metering and protection classes, including special core classes TPS, TPX, TPY and TPZ ones.

CT ratings:
- Rated primary current up to 6000A
- Rated secondary current of 1A. 2A or 5A
- Rated short time thermal current up to 80 Ka
- Rated dynamic current up to 200 kAp

Primary and/or secondary reconnection available

Fully type tested according to international standards

Special tests are also available to meet specific customer requirements.

Product Design

Complete portfolio available from 72 to 245 kV: current transformers, voltage transformers and combined current-voltage transformers

No environmental compromises and never subjected to gas taxation.

Internal insulation is made by clean air, thus:

F-gas free insulation with lowest requirements on training, transport, installation, operation, reporting and recycling

C-gas free with no risk of C-decomposition
No gas recycling required

Clean air is the main insulation medium

Explosion-proof design

External insulation with composite insulator; porcelain insulator available on request

Bar-type primary conductor allows higher short circuit current and avoids large voltage drop across the primary winding

Available to withstand:

Internal arc effects [according to IEC 61869 – 1]

Heavy seismic solicitations, according to IEC 62271, IEEE 693 and specific customers’ requests

Product Process

Optimised design to manufacturing
Lean manufacturing concept applied to the whole supply chain
Modular design allows the use of reduced numbers of components
Partial discharge free design and process Maintenance free during a lang lifetime of more than 30 years
Trench Management System has been certified to ISO 9001, ISO 14001 and OHSAS 18001 standards
Testing laboratory accredited according DIN EN ISO/IEC 17025

Customer Benefits

Environmental Benefits
- No Global Warming Potential:GWP = 0
- No Ozone Depletion Potential:ODP = 0

Technical Benefits
- Based an the proven SF6 instrument transformer designs
- Suitable for low temperature applications at -50°C and below
- Maintenance free during a lang lifetime of more than 30 years
- No reporting or emission costs during operation and recycling:
- No SF6- or F-gas tax or future risk
- No C02 emission compensation or future risk
- No F-gas documentation or reporting costs
- No risk of F-gas gas recycling costs

If you have any questions, please reach out to us today on +44(0)1355236057 or on our e-mail sales@itl-uk.com