A harmonic network model needs transformer data beyond rated kVA and fundamental-frequency percent impedance. Depending on study frequency, leakage reactance scaling, winding resistance, connection, grounding, zero-sequence path and stray capacitance may matter. The required detail should match the frequency range and study purpose; a fundamental short-circuit model should not be silently reused for high-frequency resonance.
A fundamental-frequency equivalent has a limited scope
Scaling leakage reactance approximately with harmonic order can be a useful low-order approximation because XL = 2πfL for a constant inductance. It does not imply that winding resistance remains constant or that the model is valid into the switching-frequency range. Skin effect, proximity effect and capacitance become increasingly relevant as frequency rises. State the study band and the model assumptions before requesting data, so the supplier can distinguish ordinary harmonic load flow from a wide-band transient model.
Retain the paths that depend on harmonic sequence
Winding connection and grounding determine whether a component transfers between windings, circulates internally or returns through a neutral path. A balanced characteristic triplen component does not see the same network as a positive-sequence fundamental. Include neutral impedances and any delta winding explicitly. Where unbalance is material, use a phase-domain or otherwise suitable model rather than assigning every harmonic to a sequence category without checking the actual source relationships.
Deliver parameter provenance with the model
Identify which frequency-dependent parameters come from measurements, design calculations or generic assumptions. Preserve the referred winding, bases, terminal conditions and fitting range. If a resonance prediction depends strongly on an assumed capacitance or damping value, report sensitivity to that uncertainty. A detailed-looking model is not automatically more accurate than a simpler one; its usefulness depends on verified parameters and a frequency range that matches the question being asked.
Technical reference framework
[1] IEEE C57.110-2018 — Transformer capability with nonsinusoidal load currents.
[2] IEC 60076-1:2011 — Power transformers, General.
[3] IEC 60076-8:1997 — Application guide.