DOWEI

Altitude Corrections per IEEE 

MV Air-insulated Equipment De-rating for High Altitude

As stated by ANSI C37.20.2-1986, clause 8.1.3, for unusual conditions such as altitude, it recommends the use of correction factors for the voltage and current, given in the following table:

*From standard ANSI C37.20-1999.

Medium voltage transformer De-rating for High Altitude

The guidelines are based on IEEE C57.12.01 which covers low and medium voltage transformers. IEEE C57.12.01 is referenced in NEMA ST20:2014 section 5.3.2. An altitude of 1000 meters or less is considered a standard altitude.

For operation at higher altitudes, a deration factor is applied for the kVA rating and dielectric strength.

-Dielectric strength is a measure of the voltage a transformer can withstand

-kVA is the measure of power a transformer can supply

*Derating at 30°C average ambient air temperature

DOWEI transformers are designed to meet all nameplate values at the nameplate’s specified altitude. The nameplate will list an altitude and the values for the kVA and BIL are the derated values, unless specifically stated otherwise. DOWEI has experience in designing units to meet the full nameplate ratings for installations above 1000 meters upon request.