Transformer Oil Sampling and DGA Submittal Inspection

Inspection template for verifying transformer insulating oil sampling, chain-of-custody, laboratory submittal, and dissolved gas analysis documentation in accordance with IEEE C57.104 and Duval triangle interpretation practices.

Inspection Identification and Sample Context

• Transformer identification recorded
  Verify transformer asset ID, location, voltage class, and unit designation are documented on the inspection record.
• Sampling date and time recorded
  Record the exact date and time the oil sample was collected.
• Sampling purpose documented
  Identify whether the sample was routine trending, post-event, alarm follow-up, acceptance testing, or corrective maintenance.
• Sampling personnel are trained and authorized
  Confirm the person collecting the sample is trained on transformer oil sampling procedures and authorized by the site program.

Sampling Safety and Field Conditions

• Work area made safe before sampling
  Verify applicable electrical safety controls were in place, including required PPE, approach boundaries, and any lockout-tagout or energized work controls as applicable.
• Sampling port and surrounding area clean and accessible
  Inspect that the sampling valve, fittings, and surrounding surfaces are clean, dry, and unobstructed before collection.
• Sample container is clean, sealed, and appropriate for DGA
  Confirm the container is suitable for dissolved gas analysis, intact, and free of visible contamination or damage.
• Ambient conditions noted if relevant
  Document weather, temperature, or site conditions that could affect sampling quality or handling.

Sampling Method and Sample Integrity

• Sampling line flushed before final sample collection
  Verify the sampling line or valve was flushed per site procedure to remove stagnant oil before the final sample was taken.
• Air excluded from sample during collection
  Confirm the sample was collected in a manner that minimizes air ingress and bubble formation.
• Sample volume adequate for laboratory DGA
  Record the collected sample volume and verify it meets the laboratory's minimum requirement for gas chromatography analysis.
• Sample identification label complete
  Confirm the sample label includes asset ID, sample date/time, sampler name or ID, and unique sample number.

Chain of Custody and Laboratory Submittal

• Chain-of-custody form completed
  Verify the chain-of-custody form is complete, legible, and matches the sample label and asset identification.
• Sample custody transfer documented
  Record each handoff from collector to courier to laboratory, including date/time and responsible party.
• Shipping method protects sample integrity
  Confirm the sample was packaged and shipped to prevent leakage, breakage, heat exposure, and contamination.
• Laboratory receiving confirmation obtained
  Document laboratory receipt date/time and confirmation that the sample was accepted for DGA testing.

DGA Results and Interpretation

• Required dissolved gas results reported
  Verify the report includes the key gases needed for transformer condition assessment, including hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide as applicable.
• IEEE C57.104 interpretation included
  Confirm the report or review notes include interpretation consistent with IEEE C57.104 guidance and any applicable trending comparison.
• Duval triangle assessment documented
  Record whether the Duval triangle result indicates thermal fault, partial discharge, arcing, or no clear fault signature.
• Recommended follow-up action documented
  Document the next action, such as resample, trend monitoring, maintenance review, or urgent engineering evaluation.