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Medium-voltage transformers

Arc-reduction VFI transformer

Eaton’s Cooper Power series Arc-Reduction VFI transformer is built with the intelligence to reduce incident energy in downstream arc flash zones and mitigate the danger posed by power distribution equipment. Utilizing Eaton’s proven Vacuum Fault Interrupter (VFI) technology paired with a microprocessor-based relay system, anomalies are sensed and transmitted through the integral control package to isolate the downstream equipment in 4 cycles or less clearing time, maximizing electrical safety and system reliability.

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Comprehensive solution
4 cycles (67 ms) or less for secondary faults
Arc reduction scheme
Factory integrated, fully programmed and tested
Reduce secondary incident energy
Achieve OSHA PPE Level 3 or less

Core features

  • Primary and secondary 50/51 overcurrent protection
  • Self-powered, adjustable differential protection
  • Direct trip Integral VFI
  • Direct trip to local or remote breakers
  • Metering and monitoring capabilities
  • Eliminates human-to-energized equipment interaction
  • Faster clearing time (<67 ms)
  • Increases ease of maintenance and asset preservation and decreases annual substation downtime
  • Transformer and VFI tested per IEEE C57.12.00 standard
  • Preprogrammed relay overcurrent settings
  • Compartmental padmount or substation transformer designed per specification

Eaton’s Arc-reduction VFI transformer

Learn about Eaton’s Cooper Power series AR-VFI medium-voltage transformer and its features to minimize arc flash dangers.

Advantageous design, proven technology

Eaton’s AR-VFI transformer is based on legacy arc-reduction schemes built into one fully integrated package. Utilizing traditional sensing, computing and trip methods, the arc flash reduction system minimizes signal proximity to reduce fault clearing times to four cycles or less.
ETR-5000 differential relay

Discover the many advantages of the AR-VFI transformer

Don’t compromise safety for space

The Eaton AR-VFI transformer reduces the footprint of a comparable legacy system (MVS + Dry-type xfmr + LVA) by up to 60%, allowing a fully functioning arc flash reduction system to be installed in locations that may previously have been impossible.
AR-VFI transformer one-line diagram

IoT network compatible

Electronic intercommunication drastically increases the speed of information and subsequent power reliability. Zone-interlocking protection built into Eaton E-Series relays network the AR-VFI transformer with upstream mains, adjacent low voltage assemblies and auxiliary control systems.

True arc flash safety per IEEE 1584-2018

In comparison with traditional means of primary overcurrent protection Eaton's Arc-Reduction VFI (AR-VFI) Transformer reduces incident energy in transformer secondary compartment by a factor a seven, granting access to transformer secondaries and increasing safety and ease of maintenance for the transformer and low voltage assemblies.
Transformer incident energy graph
Specifications

Ratings

Transformer Padmount or substation
Available in kVA range 150 kVA to 12,500 kVA
Primary configuration Delta or Wye connected
Primary voltage 2400 V to 34,500 V
Secondary voltage 208Y/120 V to 14, 400 V
Basic Impulse Level (BIL) Up to 150 kV
Temperature rise 55 °C, 65 °C or 75 °C (PEAK) rise ratings available
Vacuum fault interrupter Manual or motor-operated
Vacuum fault interrupter rating 900 A cont up to 35 kV
Interrupt rating 12.5 kA at 15/25/35 kV or 16 kA at 15 kV
Additional interrupt Up to 50 kA when in series with PRCLF

Standards

ANSI/IEEE
 C57.12.00, C57.12.34 and C57.12.36
Arc flash calculation standard
 IEEE 1584-2018
CSA
 C227.4 or C88-M90
NEMA (sound level)
 NEMA TR-1
Third-party approval/recognition FM Global (Indoor & Outdoor), UL/cUL

Enclosure

Layout
 Padmount or substation
Tamper resistance
 3-point latching and padlock system terminal chambers
Enclosure rating
 IEEE C57.12.28 (or 12.29 w/stainless steel)
Material 
 Mild or stainless steel (304L)
Enclosure environment
 Indoor and outdoor
Insulating medium 
 Air terminal chambers
Control box 
 NEMA 4X UL listed

Devices

Distribution transformer
 Three-phase substation or padmount
Install location
 Indoor and outdoor
Power direction
 Step-down and step-up
Overcurrent protection
 Vacuum fault interrupter
Motor operator 
 (optional) remote reset of VFI
Microprocessor relay
 Eaton E-Series, SEL or approved differential relay
Integral UPS
 24-hr battery backup
Integral sensors
 CTs (optional: PTs, thermal, pressure, fluid, etc.)
Download Links
  • Arc-reduction VFI transformer product aid
    This brochure describes Eaton’s Cooper Power series AR-VFI transformer which was designed with fully integrated medium-voltage vacuum interrupter (VFI), differential relay protection package, system control power transformer and 24-hour battery backup system capable of logging/sending/receiving data through the duration of an outage.
    (PDF 615 KB , 21/02/2025)
  • Commercial and industrial medium-voltage electrical distribution products brochure
    This brochure outlines Eaton’s Cooper Power series broad commercial and industrial medium-voltage transformer, switchgear, fuse, sectionalizer, switch, regulator, tool, OEM equipment, cable accessory, lightning arrester, power capacitor and recloser offerings.
    (PDF 2 MB , 24/01/2023)
  • Copper vs. aluminum conductor product aid
    This brochure explains that Eaton’s Cooper Power series aluminum-wound coils use the same thermal, dielectric and mechanical performance requirements as its copper-wound coils and that in pad-mounted and substation designs, aluminum-wound transformers and copper-wound transformers serve their loads equally well.
    (PDF 83 KB , 01/11/2016)
  • Visible break technology product aid
    This brochure describes Eaton's Cooper Power series visible break accessory which offers smart solutions to verify the isolation of internal transformer circuitry.
    (PDF 359 KB , 28/04/2023)
  • I2t testing for current-limiting fuses
    This technical document describes how Eaton utilizes an I2t test in its Cooper Power series products to verify and guarantee that every current-limiting fuse produced will meet their published minimum melt I2t levels and will not operate prematurely.
    (PDF 87 KB , 30/11/2015)
  • VFI transformer vs. switchgear information
    This technical document discusses how a transformer equipped with an integral vacuum fault interrupter (VFI) can be an alternative to a non-VFI transformer in combination with stand-alone switchgear.
    (PDF 57 KB , 01/03/2015)
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