Substation VFI Transformer


The VFI transformer combines a conventional Cooper Power Systems distribution transformer with the proven Kyle Vacuum Fault Interrupter (VFI). This combination provides both voltage transformation and transformer over current protection in one space saving and money saving package. The substation VFI transformer with transformer protection protects the transformer and provides proper coordination with upstream protective devices. When a transformer fault or overload condition occurs, the VFI breaker trips and isolates the transformer.

The three-phase VFI breaker has independent single-phase initiation, but is three-phase mechanically gang-tripped. A trip signal on any phase will open all three phases. This feature eliminates single-phasing of three phase loads. It also enables the VFI breaker to be used as a three-phase load break switch.

Due to the resettable characteristics of the VFI breaker, restoring three-phase service is faster and easier.

kVA 500-10,000
Primary Voltage Delta or Wye Connected 2400-34,500 V
Secondary Voltage 208Y/120 V to 14,400 V


Standard Features

  • Overcurrent protection using Cooper Power Systems proven Vacuum Fault Interrupter (VFI) technology
  • Envirotemp™ FR3™ fluid or electrical grade mineral insulating oil (upon special request)
  • De-energized tap changer, externally operable
  • Sidewall-mounted high-voltage porcelain bushings
  • Sidewall-mounted low-voltage molded epoxy bushings with NEMA spades
  • Tank bases designed for skidding or rolling in any direction
  • Extra-heavy, welded-in-place lifting lugs and jack pads (4)
  • Stainless steel grounding pads (4)
  • Cooling radiators are welded directly to the tank
  • Dial-type thermometer
  • Dial-type liquid level gauge
  • Pressure vacuum gauge
  • Cover mounted automatic pressure relief device
  • Pressure test connection
  • 1” upper fill plug with filter press connection
  • 1” drain valve with sampler combination (2500 kVA and below)
  • 2” drain valve with sampler (over 2500 kVA)
  • 1” upper filter valve (over 2500 kVA)
  • Painted using ANSI #61 Light Gray; ANSI #70 Sky Gray; or Special paint available per request
  • Laser-scribed anodized aluminum nameplate

Envirotemp™ and FR3™ are licensed trademarks of Cargill, Incorporated.