Excess temperatures measured directly on the faulty part are usually divided into
three categories relating to 100% of the maximum load.
The start of the overheat condi-
tion. This must be carefully
monitored.
< 5°C (9°F)I
Developed overheating. It must
be repaired as soon as possible
(but think about the load situa-
tion before a decision is made).
5–30°C (9–54°F)II
Acute overheating. Must be re-
paired immediately (but think
about the load situation before
a decision is made).
>30°C (54°F)III
Publ. No. T559382 Rev. a358 – ENGLISH (EN) – June 23, 2009 105
17 – Introduction to thermographic inspections of electrical installations