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Oil insulated Voltage Transformers

Oil-insulated voltage transformers are used to convert high transmission line voltages (up to 550kV) 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 voltage transformation is essential.

The reliability and security of Trench oil-insulated instrument transformers is based on over 100 years of innovation with oil-insulated units operating under a wide range of environmental conditions. Oil-insulated voltage transformers also ensure suitable electrical insulation between high voltage and low voltage measuring equipment.

The oil-immersed inductive voltage 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 ensure reliable delivery and operation over the complete life time.


Up to

multiple chopped waves

are performed to prove the insulating material of Trench oil-insulated instrument transformers.

Thousands of oil-immersed voltage transformers installed and in service for more than 50 years all over the world and in all environmental conditions are the best guarantee of the quality and reliability of our products.


  • Complete portfolio available from 72 to 550 kV
  • Meet all lEC and ANSI metering and protection classes
  • Rated primary Voltage up to 550 kV
  • Rated Secondary Voltages 100 V, 100:i/3 V, 100:3 V, 110 V, 110:i/3 V, 110:3 V, …
  • Suitable also for Une Discharge use
  • Fully type tested according to international standards
  • Special tests are also available to meet specific customer requirements

Product Design

  • Oil/paper internal insulation
  • External insulation with porcelain or composite insulator
  • External part made of aluminum or stainless materials
  • Sealed & Robust Construction
  • Easy Customization to match all specific Customer requirements
  • Easy Installation without special tools required.
  • Available to withstand:
    • Effects of internal arc [according to IEC 61869 Standard]
    • Multichopped Test [according to IEC 61869 Standard]
    • Heavy seismic solicitations, according to IEC 62271, IEEE 693 and specific customers’ requests [i.e. Chile ETG A.0.20]
  • Hermetically sealed. A suitable Nitrogen cushion or lnox steel bellows allows the oil volume variation in every service conditions.

Product Process

  • Optimized design to manufacturing
  • Lean manufacturing concept applied to the whole supply chain
  • Optimized design allows the use of reduced numbers of components and quick Customization to all Customer specific requirements
  • 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

Mechanical and electrical data

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