Thermal Imaging of transformers and electrical cabinets is used to locate hot-spots.
These hot-spots arise from loose connections, current overload, sparks or arcs created by high voltage.
Ideally the thermal images are taken while the system is under full load, with high ambient temperature. This thermal stress helps manifest the faults.
In oil transformers, this test, together with Dissolve Gas Analysis (DGA) oil test helps isolate the source of the problem.
Thermal image of an electric cabinet