Transformer Turns Ratio (TTR) Test Inspection

Inspection template for recording transformer turns ratio measurements on all tap positions and comparing them to the design ratio within tolerance to confirm winding and tap changer integrity before energizing.

Test Setup and Equipment Identification

• Transformer identification matches work order and nameplate
  Verify transformer serial number, asset ID, voltage class, and phase designation against the work order and nameplate.
• Test instrument calibrated and suitable for TTR measurement
  Confirm the TTR test set is within calibration and appropriate for the transformer voltage class and winding configuration.
• Transformer isolated and de-energized under lockout-tagout
  Confirm the transformer is de-energized, grounded as required, and controlled under lockout-tagout before testing.
• Ambient conditions and test notes recorded
  Record ambient temperature, humidity if required by procedure, and any conditions that could affect test interpretation.
• Applicable test procedure or SOP referenced
  Enter the procedure, standard work instruction, or commissioning checklist used for this inspection.

Design Ratio and Tap Configuration

• Design turns ratio documented for each winding pair
  Record the expected design ratio for each applicable winding pair before testing.
• Tap changer type and range confirmed
  Identify whether the transformer uses de-energized tap changing or on-load tap changing and record the available tap range.
• All tap positions identified for test sequence
  Confirm the full tap sequence to be tested, including neutral and all raise/lower positions as applicable.
• Expected tolerance for turns ratio deviation recorded
  Enter the allowable deviation from design ratio per manufacturer specification or site acceptance criteria.

Turns Ratio Measurements by Tap Position

• Measured turns ratio at neutral tap
  Record the measured ratio at the neutral tap and compare it to the design ratio.
• Measured turns ratio at each raise tap
  Record the measured ratio for each raise tap position tested and note any deviation from the design ratio.
• Measured turns ratio at each lower tap
  Record the measured ratio for each lower tap position tested and note any deviation from the design ratio.
• Percent deviation calculated for all tested taps
  Document the percent deviation between measured and design ratio for each tap position.
• All measured values within allowable tolerance
  Confirm that every tested tap position is within the specified tolerance band.

Winding and Tap Changer Integrity

• No indication of open winding, shorted turns, or incorrect polarity
  Assess test results for signs of winding defects, incorrect connections, or polarity issues.
• Tap changer operation consistent across all positions
  Verify the tap changer moved and indexed correctly through the full range without binding, misalignment, or abnormal behavior.
• Abnormal noise, overheating, or mechanical damage observed
  Record any abnormal condition observed during setup, tap changes, or measurement.
• Deficiencies or non-conformances documented
  List any deficiencies, non-conformances, or follow-up actions required before energization.

Results, Corrective Action, and Sign-off

• Inspection result
  Select the overall outcome of the TTR inspection.
• Corrective action and retest plan
  Describe any corrective action, retest requirement, or escalation to engineering or the AHJ if applicable.
• Inspector signature
  Inspector sign-off confirming the recorded measurements and findings are accurate.