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SF6 Insulated Current Transformers

SF6 insulated current transformer are used to convert high transmission line currents (up to 6000 A) to standardized low and easily measurable values, which will be used for metering, protection and control of the high voltage system. As such, the need for accurate and reliable current transformation is essential.

The reliability and security of Trench gas-insulated instrument transformers is based on over 50 years of innovation with gas-insulated units operating under a wide range of environmental conditions. Current transformers also ensure suitable electrical insulation between high voltage and low voltage measuring equipment.

Our gas-insulated current transformers are compliant to the latest international safety standard requirements in terms of explosion-proof, insulating material multiple chopped ageing, seismic qualification and extreme temperature conditions.

Modern production and testing facilities guarentee not only short delivery times but also a reliable operation for many years.


Up to kV

operation voltage

Trench SF6 CTs have proven their reliability for the highest requirements for decades.

Thousands of gas-insulated current transformers installed and in service for more than 50 years all over the world and in all environmental conditions are the best proof of the quality and reliability of our products.


  • Complete portfolio available from 72 to 800 kV
  • 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 tinme 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

  • SF6 is the main insulation medium
  • Explosion-proof design
  • External insulation with composite insulator; porcelain insulator available on request
  • External parts made of aluminum or stainless materials
  • 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 – protection stage 1)
    • Heavy seismic solicitations, according to IEC 62271,IEEE 693 and specific customers’ requests

Product Process

  • Optimized 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

Mechanical and electrical data

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