The #1 US-owned power transformer manufacturer in North America Core type transformers up to 500 MVA, 525kV Shortest lead time in the industry Shell type power transformers up to 1400MVA 500kV The most reliable transformers made right here in the USA


Our transformers are tested to assure they are well designed, well manufactured and in accordance with: IEEE/ANSI, CEI/IEC, CAN/CSA and Customer Specifications

Large Power Testing Capability Features:

  • Test area able to accommodate extra large power transformers & autotransformers
  • Maximum Rating:  900 MVA 3Ø  and  300 MVA 1Ø
  • HV Maximum Voltage:  765 kV
  • Maximum BIL: 2050 kV
  • Maximum Applied Potential: 500 kV 5A
  • In House oil testing: DGA, Moisture, PF, DBDV, IT, Acid.

Factory Acceptance Tests

Routine Tests:

  • Preliminary
  • Losses
  • Dielectrics
  • Control wiring and CT’s
  • Operation of devices

Design / other Tests:

  • Temperature Rise
  • Audible Sound Level
  • Single Phase Excitation

Special Tests:

  • Sweep Frequency Response
  • Overload Test
  • Overvoltage Test
  • Leakage Reactance
  • 1/3 Octave Band

Insulating Oil Analysis:

  • Moisture content
  • Neutralization Number
  • Interfacial Tension
  • Color
  • Power Factor
  • Dielectric Breakdown
  • Dissolved gases in oil

Test  Categories:

  • Preliminary Tests
  • Insulation Resistance of Windings
  • Magnetic Circuit
  • Insulation Power Factor and Capacitance on
  • Windings
  • Bushings
  • Voltage-Turns Ratio
  • Winding DC Resistance


  • No Load Loss
  • Excitation Current
  • Load Loss
  • Impedance Voltage
  • Zero Sequence Impedance


  • Lightning Impulse
  • Switching Impulse
  • Applied Voltage
  • Induced Voltage with Partial Discharge measurement


IEEE C.57 12 00, IEEE C.57 12 90

IEC 60076-01, IEC 60076-02,  IEC 60076-03, IEC 60076-10


Routine tests as per IEEE C57.12.90-2015 performed on All Transformers

  1. Transformation Ratio or Voltage Ratio.
  2. Verification of the vector group by turn ratio meter
  3. Winding resistances up to 50A
  4. Insulation Resistance up to 10kV Meggar
  5. Insulation Resistance to Ground for Core. (up to 10kV DC)
  6. Capacitance and Tan delta as per Doble method up to 10kV AC Voltage.
  7. Lightning Impulse Withstand Test up to 550kV
  8. Applied voltage tests up to 300kV
  9. Short-circuit Impedance and Short-circuit losses
  10. No Load Loss and No Load Current
  11. Induced Voltage withstand tests
  12. Partial discharge at 1.58x of Rated for 1 hour with Corona detection (Class II Transformer).
  13. Control Function & wiring
  14. Dissolved Gas Analysis

Special/Type/Optional Tests may be performed when requested as per IEEE C57.12.90-2015

  1. Temperature Rise test.
  2. Overload Temperature Rise test.
  3. Infra-Red Thermal Image
  4. Zero-Sequence Impedance on Three-Phase Transformers
  5. Switching Surge Impulse Test up to 550kV class
  6. Acoustic noise level
  7. Harmonics of the No-Load Current
  8. Sweep Frequency Response Analysis (SFRA)Doble5400
  9. Oil Breakdown Voltage
  10. PPM (Water Content in the oil)
  11. Dew Point (only “routine” for transformers shipped without oil)

We maintain records of all tests results and certified test reports which are provided to the customer.


We welcome hundreds of customers/consultants to our plants every year who personally witness the testing of their units. Customer rooms with high speed internet connections are available in the plants. Experienced test engineers and application engineers are always available to plant tour with customers if desired, explaining our processes and manufacturing equipment.

Going away party for Sarah McDonald, Ph.D..  McDonald was a early primary investigator at VTCRI.  (David Hungate/ VTCRI)
Going away party for Sarah McDonald, Ph.D..  McDonald was a early primary investigator at VTCRI.  (David Hungate/ VTCRI)

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