K-Factor Transformer Assessment
Assessment of whether transformers are adequately rated for the non-sinusoidal load they actually carry. Harmonic currents produce eddy-current losses that rise with the square of frequency, so a transformer fully loaded on distorted current runs far hotter than its nameplate suggests.
What this study establishes.
K-factor calculation from measured load spectra at each transformer.
Harmonic loss factor and derating determined per IEEE C57.110 for existing units.
Permissible loading statement for each transformer under its measured harmonic duty.
Comparison against nameplate K-rating where the unit is K-rated.
Thermal correlation with infrared survey and any winding temperature indication.
Replacement or derating recommendation, or mitigation upstream to reduce distortion.
What the work covers.
Assessment of whether transformers are adequately rated for the non-sinusoidal load they actually carry. Harmonic currents produce eddy-current losses that rise with the square of frequency, so a transformer fully loaded on distorted current runs far hotter than its nameplate suggests.
K-rating and derating are two routes to the same outcome. A K-rated unit is built to absorb the extra eddy losses; a standard unit must be derated instead. Substituting a standard transformer for a K-rated one on a like-for-like kVA basis removes that margin silently.
What lands in your inbox.
K-factor calculation from measured load spectra at
K-factor calculation from measured load spectra at each transformer.
Harmonic loss factor and derating determined per
Harmonic loss factor and derating determined per IEEE C57.110 for existing units.
Permissible loading statement for each transformer under
Permissible loading statement for each transformer under its measured harmonic duty.
Comparison against nameplate K-rating where the unit
Comparison against nameplate K-rating where the unit is K-rated.
Thermal correlation
Thermal correlation with infrared survey and any winding temperature indication.
Replacement or derating recommendation, or mitigation upstream
Replacement or derating recommendation, or mitigation upstream to reduce distortion.
How we run it.
Scope & data capture
We confirm the question the study must answer, agree the measurement or modelling points, and collect what the work depends on: measured harmonic current spectrum at each transformer's secondary; transformer nameplate data including any k-rating and the cooling class; loading history, ideally with winding or top-oil.
Measurement & modelling
Engineers carry out the measurement and modelling on site and in software, under operating conditions representative of the problem rather than a single convenient snapshot.
Analysis against standard
Results are assessed against IEEE C57.110, IEC 61378-1, IEC 60076-7, with the assessment basis and any measurement uncertainty stated rather than implied.
Report & recommendations
You receive a signed engineering report with findings ranked by consequence, the reasoning behind each conclusion, and mitigation options costed so they can be acted on or deferred deliberately.
Assessed against the published limits.
Common questions.
Typically in one of these situations: transformers running hot at loads well below nameplate rating; high vfd, ups or led lighting content downstream of a standard transformer; specifying a replacement transformer for a distorted load. If none of these apply, the study is unlikely to be the right next step and we will say so.
To scope and run the work we need measured harmonic current spectrum at each transformer's secondary; transformer nameplate data including any k-rating and the cooling class; loading history, ideally with winding or top-oil temperature records. Where any of it is missing we can establish it on site, which changes the scope rather than blocking the work.
Primarily IEEE C57.110, IEC 61378-1, IEC 60076-7, IEC 60076-11. The applicable framework depends on your connection agreement and jurisdiction, so we confirm which applies before measurement rather than after.
Ready to start the engagement?
Tell us about your site and the problem you are seeing. We come back with a fixed scope, a fixed fee, and a named lead engineer.