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Medium-voltage transformers

Smart VFI transformer

Eaton’s Cooper Power series three-phase smart transformers transform more than just voltage, they are changing the face of asset control and management. Utilizing microprocessor-based control schemes the smart vacuum fault interrupter (VFI) transformer offers extensive monitoring options, transformer and loop sectionalizing, fault event recording, zone interlocking, directional protection, data exporting and more. Paired with the integral VFI or upstream breaker/recloser the smart transformer significantly reduces impact on the transformer and adjacent equipment.

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Smart VFI transformer product aid Fundamentals of medium-voltage transformers
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Wider scope of protection
Primary feeds up to 900 A cont. at 35 kV
Relay flexibility
Eaton E-series or equivalant
Stay connected
Serial, Ethernet or fiber communications standard

Core features

  • Compartmental padmount or substation transformer designed per specification
  • Integral [under-oil] Vacuum Fault Interrupter (VFI)
  • Microprocessor-based feeder relay control system
  • Logic-based ANSI devices programmable within integral relay control
  • Enhanced control with remote trip functionality
  • Extensive monitoring options for transformer and line management
  • Power Xpert compatible when used with the Eaton E-Series relay
  • Reduces installation, operation and maintenance costs when compared to a transformer plus separate switchgear
  • Automation and inter-transformer control and protection schemes available
  • Remote asset control and management over Modbus TCP
  • Relay transformer monitoring

Asset management and protection in one complete package

Combined with a transformer with the full functionality of the VFI in one cabinet, the vacuum fault interrupter (VFI) with factory installed and tested relay control package provides primary protection and digital communication in one complete package. This package eliminates the need for medium-voltage switches or other monitoring devices thereby simplifying the installation and reducing installed footprint.

The future of control

The S-VFI transformer enhances the proven VFI transformer by utilizing a microprocessor-based relay control scheme. Digital control allows the user to monitor transformer VFI status, gauge alarms and power quality and flow thereby drastically increasing the speed of information and subsequent equipment reliability and economic effectiveness.

Forward thinking features for the smart grid of tomorrow

The Smart VFI transformer is a standardized package offering engineered for ultimate flexibility with no additional lead-time as compared to standard Eaton transformers. Transformer diagnostics are available via serial, ethernet or fiber communications. Preprogrammed protection settings and modular design with flexible relay selection, including a variety of integral ANSI logic devices within the microprocessor relay. The entire assembly is factory tested and functionally verified prior to shipment.
Specifications

Ratings

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 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 coordinated with ELSP current limiting fuses

Standards

ANSI/IEEE
 C57.12.00, C57.12.34 and C57.12.36
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
Tank and cabinet material 
 Mild or stainless steel (304L)
Enclosure environment
 Indoor and outdoor
Control relay control box 
 NEMA 4X UL listed

Devices

Power direction
 Step-down and step-up (when specified)
Overcurrent protection
 Vacuum fault interrupter
Motor operator 
 Remote reset of VFI (optional)
Microprocessor relay
 Eaton E-Series, SEL or specified
Integral UPS
 24-hr battery backup
Integral sensors
 CTs (optional: PTs, thermal, pressure, fluid, etc.)
Relay communication available As specified - Modbus, DNP3, IEC 61850, RJ-45, RS-485, other
Download Links
  • 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)
  • Smart VFI transformer product aid
    This brochure describes Eaton’s Cooper Power series S-VFI transformer which pairs proven VFI technology with the superior control and monitoring capability of modern microprocessor-based relays for increased reliability and system longevity.
    (PDF 443 KB , 19/02/2025)
  • 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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