Transformer Testing Reference

Test methods

Test methods applied to electrical power equipment at acceptance and in maintenance, each with its purpose, principle and the standards that govern it.

Test methods per groupInsulation: 11; Ratio: 4; Resistance: 4; Control: 1; Inspection: 1; Liquid: 1; Protection: 1Insulation11Ratio4Resistance4Control1Inspection1Liquid1Protection1
Test methods per group. Entries in this family grouped by the equipment or system they apply to. Each bar links to its group below.
Test methods per group: entries per row.
CategoryCount
Insulation11
Ratio4
Resistance4
Control1
Inspection1
Liquid1
Protection1

Control

  1. Control and functional verification

    Control and Functional Verification is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.11 of ANSI/NETA ATS-2025. Value: step voltage regulators.

Inspection

  1. Visual and mechanical inspection

    Visual and Mechanical Inspection is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.A of ANSI/NETA ATS-2025. Value: step voltage regulators.

Insulation

  1. Bushing power factor and capacitance

    Bushing Power Factor and Capacitance is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.4 of ANSI/NETA ATS-2025. Value: step voltage regulators.

  2. Dielectric frequency response

    Dielectric Frequency Response is specified for liquid-filled transformers in acceptance testing at clause 7.2.2.B.13 of ANSI/NETA ATS-2025. Value: liquid-filled transformers.

  3. Dielectric withstand

    Dielectric Withstand is specified for large air-cooled dry-type transformers in acceptance testing at clause 7.2.1.2.B.9 of ANSI/NETA ATS-2025. Value: large air-cooled dry-type transformers.

  4. Insulation power factor dissipation factor

    Insulation Power Factor Dissipation Factor is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.3 of ANSI/NETA ATS-2025. Value: step voltage regulators.

  5. Insulation resistance

    Insulation Resistance is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.2 of ANSI/NETA ATS-2025. Value: step voltage regulators.

  6. Partial discharge online

    Partial Discharge Online is specified for large air-cooled dry-type transformers in acceptance testing at clause 7.2.1.2.B.12 of ANSI/NETA ATS-2025. Value: large air-cooled dry-type transformers.

  7. Polarization index and dielectric absorption

    Polarization Index and Dielectric Absorption is specified for induction voltage regulators in maintenance testing at clause 7.12.1.2.B.2 of ANSI/NETA MTS-2023. Value: induction voltage regulators.

  8. Power factor tip up

    Power Factor Tip Up is specified for large air-cooled dry-type transformers in acceptance testing at clause 7.2.1.2.B.4 of ANSI/NETA ATS-2025. Value: large air-cooled dry-type transformers.

  9. Transformer Core Insulation Resistance

    Transformer Core Insulation Resistance is addressed in ANSI/NETA ATS-2025.

  10. Vacuum interrupter integrity

    Vacuum Interrupter Integrity is specified for load tap changers in acceptance testing at clause 7.12.3.B.11 of ANSI/NETA ATS-2025. Value: load tap changers.

  11. Vacuum interrupter mac test

    Vacuum Interrupter MAC Test is specified for load tap changers in acceptance testing at clause 7.12.3.B.10 of ANSI/NETA ATS-2025. Value: load tap changers.

Liquid

  1. Gas Blanket Oxygen Content

    Gas Blanket Oxygen Content is addressed in ANSI/NETA ATS-2025.

Protection

  1. Surge arrester and spd tests

    Surge Arrester and SPD Tests is specified for liquid-filled transformers in acceptance testing at clause 7.2.2.B.17 of ANSI/NETA ATS-2025. Value: liquid-filled transformers.

Ratio

  1. Leakage Reactance

    IEEE C57.12.90-2021 defines impedance voltage as the voltage required to circulate rated current through one winding while the other winding is short-circuited, with the windings connected for rated voltage; it is stated relative to the energized winding's rated voltage and resolves into an in-phase resistance drop and a quadrature reactance drop that combine as a phasor sum.

  2. Sweep Frequency Response Analysis

    Sweep Frequency Response Analysis is addressed in ANSI/NETA ATS-2025.

  3. Transformer Excitation Current

    Transformer Excitation Current is addressed in ANSI/NETA ATS-2025.

  4. Transformer Turns Ratio

    IEEE C57.12.90-2021 defines turns ratio as the turns of the high-voltage winding divided by the turns of the low-voltage winding, with a tapped winding taken at the turns for its normal rated voltage, and clause 7.1.1 has the ratio determined for every tap and for the full winding.

Resistance

  1. Bolted connection resistance

    Bolted Connection Resistance is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.1 of ANSI/NETA ATS-2025. Value: step voltage regulators.

  2. Dynamic Winding Resistance

    Dynamic Winding Resistance is addressed in ANSI/NETA ATS-2025.

  3. Resistor and coil resistance

    Resistor and Coil Resistance is specified for liquid-filled transformers in acceptance testing at clause 7.2.2.B.18 of ANSI/NETA ATS-2025. Value: liquid-filled transformers.

  4. Winding resistance

    Winding Resistance is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.5 of ANSI/NETA ATS-2025. Value: step voltage regulators.