maybe it has to do with dummy loads?
This seems to be addressing the actual loading of a transformer prior to it being overloaded."3.2.8.3 Overloads. Transformers have certain overload capabilities, varying with ambienttemperature, pre-loading, and overload duration. These capabilities are defined in ANSI Std.C57.92, Guide for Loading Mineral-Oil-Immersed Distribution and Power Transformers, andANSI Std. C57.96, Guide for Loading Dry-Type Distribution and Power Transformers"
but this concept is cited on naval electrical guide when talking of overload conditions of powertransformers, I see no relationship
"3.2.8.3 Overloads. Transformers have certain overload capabilities, varying with ambienttemperature, pre-loading, and overload duration. These capabilities are defined in ANSI Std.C57.92, Guide for Loading Mineral-Oil-Immersed Distribution and Power Transformers, andANSI Std. C57.96, Guide for Loading Dry-Type Distribution and Power Transformers"