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IEC 60076-7:2018 is applicable to mineral-oil-immersed transformers. It describes the effect of operation under various ambient temperatures and load conditions on transformer life. This document provides guidance for the specification and loading of power transformers from the point of view of operating temperatures and thermal ageing. It provides recommendations for loading above the nameplate rating and guidance for the planner to choose appropriate rated quantities and loading conditions for new installations. This edition includes the following significant technical changes with respect to the previous edition:
a) title has been updated from "oil-immersed power transformers" to "mineral-oil-immersed transformers";
b) insulation life is updated by considering latest research findings;
c) temperature limits have been reviewed and maximum core temperature is recommended;
d) number of fibre optic sensors is recommended for temperature rise test;
e) Q, S and H factors are considered;
f) thermal models are revised and rewritten in generally applicable mathematical form;
g) geomagnetic induced currents are briefly discussed and corresponding temperature limits are suggested;
h) extensive literature review has been performed and a number of references added to bibliography.