AI-generated illustration for this transformer turns-ratio report guide; not an actual HEAKOR factory, test report, connection drawing or test result.
A transformer turns-ratio report should identify the expected ratio, the reported ratio basis, and the winding, phase and tap condition for every required result. A “pass” label without that context is not a complete purchasing record. Before ordering a three-phase liquid-immersed substation transformer, agree the coverage and acceptance reference with the supplier and the responsible engineer. Keep missing evidence separate from a confirmed technical deviation.
This guide is for EPC procurement teams and owners’ engineers on IEC-based industrial projects. It addresses report requirements, not instrument connections, tap-changing procedures, fault diagnosis or permission to energize equipment.
First establish what the ratio column means
Nameplate voltage ratio and a test instrument’s reported ratio are not automatically the same quantity. Instrument-maker guidance distinguishes nameplate ratio, measured voltage ratio and winding turns ratio, and explains that the winding connection can require a conversion between reporting bases. Ask which basis the report uses before comparing its numbers with the approved nameplate. Technical background on ratio terminology.
For procurement, the useful deliverable is an explicit explanation—not an undocumented calculation in the buyer’s spreadsheet. Request:
- The approved nameplate and connection-drawing references used to establish the expected values.
- The winding pair and terminal or phase designations represented by each result.
- Whether the reported ratio is an instrument-measured quantity or a value converted to another basis.
- The expected value on that same basis and the source of any conversion.
Do not apply a familiar connection factor just because two documents use different column headings. Have the responsible technical parties reconcile the reporting convention and retain their explanation with the accepted report.
Agree the coverage before the test package is priced
A result at one tap does not document another tap. Prepare a coverage table for the proposed configuration and ask the supplier to identify the records it will deliver. The table below is an original purchasing aid, not a claim that IEC mandates this particular form.
| Coverage item | Entry to agree | Decision enabled |
|---|---|---|
| Winding relationship | Named winding pair and approved connection reference | Which voltage relationship is being assessed? |
| Tap condition | Position identifiers matching the accepted tap schedule | Which required positions have report rows? |
| Other relevant changer positions | Recorded positions or agreed configuration reference | Can the tested state be reconstructed? |
| Phase coverage | Identifiable phase results and any required connection or phase-displacement evidence | Is the reported scope complete for the agreed plan? |
| Expected result | Ratio basis and expected value for each applicable row | Is each comparison against the correct reference? |
| Acceptance reference | Governing document, edition and authorized interpretation | Who decides whether the results meet the order? |
Where the project specifies more than two windings, have the engineer identify the required winding-pair coverage. Do not assume that a satisfactory HV–LV result settles a separate tertiary-winding requirement. Where a row is omitted, state whether it is not required, not performed, or awaiting clarification. An empty cell is not a passed test.
Preserve the method context without prescribing a method
The report needs enough method information for an engineer to interpret an unexpected result. A 2019 instrument-maker paper discusses the influence of test voltage, excitation arrangement, winding configuration and single-phase versus three-phase measurement. Its examples are technical context, not acceptance limits for a new HEAKOR order. Original technical paper.
Ask the performing organization to identify the instrument, relevant settings and test-method reference in the agreed documentation package. Retain any method deviation that affects interpretation. If two reports disagree, request a technical assessment of whether they describe corresponding conditions before treating the difference as a transformer defect.
Procurement should not instruct technicians to change excitation voltage, reverse test connections or operate a tap changer to obtain a preferred result. Those decisions belong to qualified personnel working under the applicable equipment instructions, approved method and site safety arrangements.
Separate the acceptance rule from the software result
A software pass/fail indication is meaningful only against an identified acceptance basis. Record the requirement used, the configured limit where applicable, and the authorized disposition of exceptions. Do not copy a percentage from an old technical article and present it as a universal limit for every winding or tap arrangement.
For IEC-based purchases, IEC 60076-1:2011 provides general requirements within its stated power-transformer scope. The publicly accessible catalogue establishes that scope and edition; it does not replace the full standard or the purchaser’s requirements. Ask the engineer to establish the applicable clauses and resolve any additional project requirements.
A supplier statement such as “ratio test passed” should therefore lead to a short clarification: Which expected values, covered positions and governing acceptance criteria support that conclusion? Keep the response with the purchase record rather than substituting a sales assurance for the results.
Close the report review, not just the document request
Use three dispositions: accepted for the agreed scope, clarification required, or technical deviation requiring decision. Identify the affected row, responsible party and closure evidence. A corrected reference value may resolve a reporting error; it must not silently erase the original record or an unresolved physical discrepancy.
Identity remains a separate check. The test-report traceability guide explains how to link a report to the supplied unit and drawing revision. Correct identity cannot compensate for missing ratio coverage, and complete ratio coverage does not establish the transformer’s entire acceptance status.
Frequently asked questions
Does a satisfactory ratio report prove the rated kVA is available on every tap?
No. Ratio evidence and the tap-position capacity commitment address different purchasing questions. Retain the approved rating schedule and its conditions separately; do not infer thermal or load capability from the ratio table.
Can a ratio result replace the specified connection or phase-displacement evidence?
Do not assume so. Identify exactly what the agreed test plan requires and what the delivered report demonstrates. A ratio magnitude without the required connection information leaves that part of the review open.
Should procurement reject a unit whenever the ratio display differs from the nameplate calculation?
Not automatically. First have the engineer confirm the reporting basis, configuration, expected values and test context. Preserve any unresolved discrepancy for an authorized technical decision rather than granting an automatic pass or rejection.
Does a factory ratio report include site testing after delivery?
Only if that work is included in the accepted scope. State separately who performs any required site work, who reviews it, and which records will be delivered. A factory document request does not establish a site-service commitment.
Include the ratio-report scope in your HEAKOR enquiry
Start with the substation transformer enquiry page. Include the required rating, winding voltages, phase/frequency, connection arrangement, tap schedule and destination, or attach the specification containing those details. Use the technical document centre to organize the requested report package.
Request a Quotation that addresses the equipment and ratio-report requirements, with inclusions and exceptions identified. Proposed configuration, test arrangements, reporting scope and document availability require written project-specific confirmation; this guide does not promise a particular HEAKOR test capability or approval.