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VFI substation transformers

Eaton’s Cooper Power series VFI substation transformer combines a conventional distribution transformer with a vacuum fault interrupter (VFI) — delivering both voltage transformation and transformer overcurrent protection in a single space- and money- saving package. Transformers intended for indoor use are filled with safe, efficient Envirotemp FR3 dielectric fluid, offering enhanced fire protection and longer lifespan. 

VFI substation transformer
Primary voltage
Delta or Wye connected 2400-34,500 V
45-12,000 kVA
Interrupt rating
12.5 kA at 25/35 kV, up to 16 kA at 15 kV (up to 65 kA w/PRCL fusing)

Core features

  • Resettable characteristics of VFI breaker make restoring three-phase service faster and easier
  • Three-phase VFI breaker has independent single-phase initiation, but is three-phase mechanically gang-tripped — a trip signal on any phase opens all three phases, eliminating single-phasing of three-phase loads
  • VFI breaker can be used as a three-phase load break switch
  • Biodegradable and sustainable Envirotemp FR3 dielectric fluid provides fire safety benefits with a projected lifespan well beyond that of a traditional mineral-oil transformer
  • Sealed visible disconnect window allows operators to verify contact position
  • Can be paired with a motor operator for remote resetting of VFI
  • Available up to 35 kV and 900 A

Double the performance

Combining a conventional distribution transformer with a VFI breaker in a single package enhances reliability and protection. Restore three-phase service faster and easier, while eliminating single-phasing of three-phase loads.

A wider range of protection

Eaton's Cooper Power series VFI substation transformer offers a larger scope of protection than conventional transformer fusing. Up to 35 kV and 900 Amps continuous the VFI transformer provides resettable protection that increases asset uptime and system safety.

The safer, greener choice

Filled with Envirotemp FR3 fluid, VFI transformers offer enhanced fire safety and longer lifespan. They are also friendlier to the environment with a carbon-neutral footprint that is biodegradable, non-toxic and non-hazardous.

Save space and reduce equipment coordination

Close-couple medium-voltage liquid-filled transformers with low and medium-voltage assemblies in a streamlined unit substation design.