A mineral-oil substation transformer DGA baseline should be agreed before order by defining the required sample stages, methods, report content and review responsibility. Identify which accepted record will become the reference for later comparisons, and retain the context behind it. A quotation saying “DGA included” leaves these decisions open. Dissolved gas analysis, or DGA, needs a defined place in the purchase and handover documents.
This guide is for owners, EPC teams and procurement engineers buying mineral-oil-filled substation transformers for IEC-based industrial projects. It addresses the agreement and records, rather than sampling procedures, fault diagnosis or permission to energize equipment.
AI-generated illustration of a transformer document-review setting; not an actual HEAKOR unit, laboratory, test report or project.
Separate liquid sampling, gas analysis and interpretation
Specify these three activities separately because their standards address different scopes.
- Liquid sampling: IEC 60475:2022, edition 3, covers insulating-liquid sampling from containers and electrical equipment, within its stated liquid and viscosity scope.
- Gas sampling and analysis: IEC 60567:2023, edition 5, addresses free-gas sampling from gas-collecting relays and the analysis of free and dissolved gases. Its public description directs oil-sampling techniques to IEC 60475:2022. Listing IEC 60567 alone as the oil-sampling procedure misses that distinction.
- In-service interpretation: IEC 60599:2022, edition 4, concerns equipment in service with mineral oil and cellulosic insulation. Its guidance requires engineering judgment. It should not be presented as an automatic new-transformer acceptance rule.
These scope summaries use IEC’s public catalogue descriptions, not the paid standards’ full text. The responsible engineer must establish the applicable editions, detailed requirements and project acceptance basis from the complete governing documents.
Choose sample stages for the actual purchase
Agree stages around the project’s evidence needs and milestones, rather than importing another project’s timetable. The purchaser, transformer supplier and responsible technical reviewer should decide what each requested record must establish.
Potential stages to discuss include a specified factory condition, a defined point after site preparation, and an initial operating reference if the project requires one. These are planning categories, not a mandatory sequence or directions for when to collect samples. For each selected stage, record the relevant test, treatment or handling context and the party responsible for arranging the work.
A published autotransformer procurement specification, for example, expressly includes site DGA and commissioning records. That demonstrates why the purchase scope matters. Its timing and technical requirements belong to that particular contract and should not be transferred into an unrelated industrial order.
Use a DGA baseline agreement matrix
Complete one working matrix before accepting the quotation. Use the fields below to document the project agreement; they are not a mandatory IEC template or a substitute for the standards’ full requirements.
| Decision to agree | Entry to put in the purchase file | Question the entry closes |
|---|---|---|
| Evidence purpose and stage | Required stage, associated project milestone and intended use of the result. | Is this factory evidence, a site-stage record or a reference for later comparison? |
| Sampling and analysis scope | Separate method references and editions, agreed analytical/reporting scope, laboratory and any purchaser-required qualifications. | Who will produce the evidence, and on what agreed basis? |
| Sample and unit context | Transformer identifier, sampled compartment, mineral-oil designation, sample identifier and relevant treatment or handling record references. | What equipment and condition does the result describe? |
| Baseline designation | Person authorized to designate the baseline, required review milestone and record-reference field to complete at handover. | Which accepted result will be used as the reference, and why? |
| Acceptance and exceptions | Governing acceptance document, reviewer, unresolved-result route and applicable release conditions. | Who decides whether the evidence satisfies this purchase? |
| Delivery and ownership | Included work, separately arranged work, report format, submission dates and final record custodian. | Will the owner receive the agreed evidence when it is needed? |
Keep requirements separate from commitments. A requested laboratory, test stage or report is not included merely because it appears in the RFQ. The supplier’s offer should identify included scope, exclusions and matters awaiting agreement.
Make the baseline a traceable reference
Designate the baseline by an accepted report and sample reference, with its stage and limitations attached. Avoid leaving “baseline” as an unexplained label on whichever report arrives last.
Ask the report package to preserve:
- The transformer and compartment identity, fluid designation and sample reference.
- Sample date, analysis date, issuing laboratory, methods and editions.
- Reported gas results with units, the laboratory’s reporting conventions and any stated limitations or deviations.
- Relevant factory-test, oil-treatment, filling, transport or site-work records, as applicable to that sample’s history.
- The reviewer’s conclusion, baseline designation and reference to any unresolved question.
This is a proposed record set for agreement. It does not claim that every item is mandatory on every laboratory report. Supporting details may sit in a controlled companion record if the links are clear.
Retain earlier stage records alongside the selected reference. If treatment, a method change or another intervening event raises a comparability question, ask the reviewer how the records should be used together. Do not silently replace the earlier baseline or select the lowest result as the preferred reference.
Agree what happens when a result needs review
Define the decision route before results arrive. An unexplained difference, incomplete context or departure from the agreed criterion should enter the project’s technical review process, with an owner and a documented disposition.
Record the affected sample and report, the question raised, the requested clarification, the responsible reviewer and the milestone awaiting that decision. If further analysis or another sample is requested, agree responsibility, cost and the required evidence through the authorized project process.
Keep laboratory reporting, technical acceptance, shipment release and energization authorization distinct. Agreeing a reference record does not supply a universal gas-concentration limit or close the rest of the transformer acceptance package.
Frequently asked questions
Can a factory DGA report replace a required site report?
Only if the project’s authorized reviewer accepts that change to the evidence scope. Preserve the factory record’s actual stage and context; do not relabel it as a site result. Record any accepted substitution in the purchase or handover documents.
Must the same laboratory analyze every sample?
Establish any laboratory-continuity requirement in the project specification. If a different laboratory is proposed, request the methods, reporting basis and relevant limitations for review before treating its results as directly comparable. A shared standard number alone does not resolve every comparison question.
What if the site contractor has not been appointed when we order?
Name the purchaser’s interim owner for the site-stage scope and keep the unassigned work visible. Agree when the final responsibility, required records and review arrangements must be confirmed. Do not let an unallocated task become an assumed supplier commitment.
Can this guide be applied directly to a natural-ester transformer?
No. The interpretation scope discussed here is mineral oil with cellulosic insulation. A different insulating-liquid system needs its own assessment of applicable methods, interpretation guidance and acceptance criteria.
Include the baseline agreement in your HEAKOR enquiry
Use HEAKOR’s substation transformer category and technical document centre to organize the proposed equipment and document scope. DGA work, laboratory arrangements and report availability require explicit confirmation for the offer.
Request a Quotation. Include destination, quantity, phase/frequency, kVA or MVA, winding voltages, mineral-oil designation, governing specification, requested DGA stages and methods, document requirements, reviewer and target schedule. Ask the quotation to identify the proposed baseline agreement, included responsibilities and open conditions.