Transformer temperature-rise criteria (IEC 60076-7) — quick reference
Enter the transformer nameplate loss data and the loading; the engine returns the top-oil, average-winding and hot-spot temperature rise and the hot-spot temperature, judged against the rated rises (top-oil 55 K, hot-spot 80 K) and the 140 °C hot-spot limit. Quantities the engine does not output are shown as not available - never as zero.
Reference case: 1000 kVA, uk 6 %, P0 1700 W, Pk 14500 W, 40 °C ambient, 800 kW load.
RequiredRecommendedLeft bar: blue = required, gold = recommended. Optional and advanced fields are collapsed by default.
Not calculated yet - fill in the input data and press the button.
Model: Δθ_oil = 55 × ((1 + R·K²)/(1 + R))^0.8 and Δθ_hs = Δθ_oil + 25 × K^1.6 (R = Pk/P0, K = load rate), the engine exponential ONAN model in IEC 60076-7; hot-spot temperature = ambient + Δθ_hs.
Criteria constants: rated top-oil rise 55 K, rated hot-spot rise 80 K (average winding 65 K), hot-spot limit 140 °C - read from the engine, not entered here.
Scope: criteria and limits quick reference only. No transient thermal model, no cooler-stage switching and no long-term ageing loop; the complete limit table by cooling class is not held in the engine, so it is not shown.
Values are the engine output for the entered data; the rated rises and the 140 °C limit are the engine criteria constants (engines/params.js tempRiseAt, engines/trafo-ageing.js). Units K (kelvin, temperature rise) and °C (temperature) are explicit.
This page only looks up the criteria and limits; it is not a transient thermal model. The rises follow the engine exponential model in IEC 60076-7 (single source); values are read from the engine, not recomputed here.