1981IEEE Std C57.91-1981 Guide for loading mineral-oil-immersed overhead and pad-mounted distribution transformers rated 500 kVA and less with 65 C or 55 C average winding rise
1979IEEE C57.91-1979 GUIDE FOR LOADING MINERAL-OIL-IMMERSED OVERHEAD AND PAD-MOUNTED DISTRIBUTION TRANSFORMERS RATED 500 KVA AND LESS WITH 65 DEGREES C OR 55 DEGREES C AVERAGE WINDING RISE (R 1991)