Altitude Derating
The reduction in transformer capacity and insulation performance required at high altitudes where air density is lower.
Altitude derating refers to required performance reduction when installed above 1,000m, where reduced air density affects cooling and external insulation (bushings clearances).
Per IEC 60076 and IEEE C57, above 1,000m: reduced temperature rise limits (~0.4% per 100m for ONAN), increased clearances, and potentially enhanced BIL ratings.
For altitudes above 3,000m, special designs include oversized radiators, forced cooling, and modified insulation clearances. See our high altitude and temperature derating guide.
QDTB has extensive experience with high-altitude projects across Southeast Asia, South America, and Africa, with designs for altitudes up to 5,000m. Contact our engineering team for altitude-specific requirements.
Related Products
Related Terms
Temperature Rise
The temperature increase of transformer components above ambient at rated load, a key design parameter.
Cooling Class (ONAN/ONAF/ODAF)
Standardized codes describing transformer cooling methods: O=Oil, N=Natural, A=Air, F=Forced, D=Directed flow.
BIL (Basic Impulse Level)
The ability of transformer insulation to withstand high-voltage surges from lightning or switching, measured in kV peak.
More Terms Starting with “A”
Autotransformer
A transformer with a single winding acting as both primary and secondary, providing voltage conversion through electromagnetic induction and direct electrical connection.
Apparent Power (kVA)
The total power in an AC circuit combining real (active) and reactive power, measured in kilovolt-amperes (kVA).
Arc Furnace Transformer
A heavy-duty transformer designed to supply power to electric arc furnaces used in steelmaking and metal smelting.
ANSI C57
The American National Standards Institute standard series covering power transformer requirements for the North American market.
More in “Design & Engineering”
Cooling Class (ONAN/ONAF/ODAF)
Standardized codes describing transformer cooling methods: O=Oil, N=Natural, A=Air, F=Forced, D=Directed flow.
Faraday Shield
An electrostatic shield between transformer windings blocking capacitive coupling of high-frequency noise.
Leakage Reactance
Reactance from magnetic flux not linking both windings, a major component of transformer impedance.
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