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Altitude Corrector per IEEE

These 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 HPS 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. HPS has experience in designing units to meet the full nameplate ratings for installations above 1000 meters upon request.

 Altitude Correction Factors
 Altitude Dielectric Strength
Correction
 kVA Derating
Factor*
 3300 1000 1 1
4000 1200 0.98 0.994
5000 1500 0.95 0.985
6000 1800 0.92 0.976
7000 2100 0.89 0.967
8000 2400 0.86 0.958
9000 2700 0.83 0.949
10000 3000 0.80 0.940
12000 3600 0.75 0.922
14000 4200 0.70 0.904
15000 4500 0.67 0.895
 *Derating at 30oC average ambient air temperature
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