Labs · Transformers · Winding Resistance

Transformer Winding Resistance Test Report

Record, analyze, and trend DC winding-resistance measurements with phase-balance deviation, temperature correction, and NETA-style acceptance guidelines.

NETA ATS-2025 NETA MTS-2023 IEEE C57.152 Temp correction · 234.5 Cu / 225 Al 1–33 tap positions Field / Professional

For education & field documentation only · Verify against codes Documentation aid — not a compliance certification. Thresholds shown are configurable guidelines, not automatic pass/fail rulings. Record the applicable standard edition (e.g. ANSI/NETA ATS-2025 acceptance, ANSI/NETA MTS-2023 maintenance, IEEE C57.152 diagnostic guidance) and the manufacturer/project criteria. Manufacturer/project criteria govern final acceptance.

Standard / Acceptance Profile

Within-guideline limit (%)

Review/outside limit (%)

Deviation method

Display / input unit

Customer

Testing Organization

Address

City / State / ZIP

Site / Facility

Location / Area

Equipment ID

Job Number

Test Date

Ambient Temp (°F)

Humidity (%)

Test Status

Tested By (Technician)

Manufacturer

Serial Number

Specification Number

Type

Class

Phase

kVA Rating

Primary Voltage (V)

Secondary Voltage (V)

Impedance (%Z)

Total Weight (lbs)

Coolant Type

Gallons

Winding Material

Temp Rise (°C)

BIL (kV)

K-Factor

Rated Current Primary (A)

Rated Current Secondary (A)

Cooling Class

Winding Polarity

Dry Type

Fans Count

Tap Changer

Tap Voltages

Tap Setting

Winding / Oil Temp at Measurement

Temp Unit

Temperature Source

Reference Temp (°C)

Correction: Rs = Rm × ((Ts + Tk) / (Tm + Tk)), with Tk = 234.5°C (copper) or 225°C (aluminum) per IEEE C57 practice. Material is taken from the Nameplate section. Use the same reference temperature for every comparison in the record — correction is applied to prior/factory trend comparisons when both measurement temperatures are available.

Instrument Make

Instrument Model

Instrument Serial

Calibration Due Date

Test Current — Primary (A)

Test Current — Secondary (A)

Test Current — Tertiary (A)

Guidance: DC test current is generally kept above 1% of the rated winding current for a stable, low-noise reading and at or below 15% of rated so the test current itself does not heat the winding and shift the measurement (IEEE C57 practice). Allow the current to fully stabilize before recording, and demagnetize the core afterward so a subsequent excitation-current, ratio, or differential-relay energization is not affected by residual magnetism. Enter rated currents in the Nameplate section to enable validation.

Transformer isolated, de-energized, locked out/tagged out, tested dead and grounded (NFPA 70E electrically safe work condition) Kelvin (four-wire) connections used Current stabilized before recording Core saturation / stabilization observed Winding discharged through the instrument before test leads removed Demagnetization completed after test

Configuration Preset

Tap Positions (1–33)

General Comments

Deficiencies / Action Items

Exception Notes