Electrical thermography as evidence, not a colourful gallery

Infrared on electrical gear is useful when it is treated as a measurement with conditions: load as a fraction of rating, ambient, wind on outdoor gear, emissivity of the surface, focus, and whether you are looking at a conductor, a lug, or a reflection of a light. A rainbow JPEG without those notes is marketing. The studio uses thermography as engineering evidence in a written file: comparison, mechanism, and a recommended action that a competent electrician can execute.

How the investigation is actually run

Schedule the survey for a load that represents the complaint, not for an empty Sunday. If the process cannot run, say in the first paragraph that the images are a baseline, not a clearance. Open gear only under the electrical safety plan the site already uses; the camera does not create a right to ignore covers. Record load, ambient, and whether the surface is painted, oxidized, or bare metal. If you must compare a shiny lug to a painted bus, say that the emissivity is the weak point of the file.

Build the report as paired images: the suspect and the adjacent phase or the adjacent similar device, same range, same moment. A single framed hot spot without a sibling is a poster. Recommend an action that a licensed electrician can perform: retorque to a named value if the manufacturer gives one, replace a lug, investigate unbalance with a meter, clear a blocked grille. Do not invent a remaining-life percentage. If the heat is uniform along a conductor, write harmonic or overload as the working hypothesis and send the reader to a current-logger, not to a torque gun.

Re-image after the mechanical work if the site will allow it. The second visit is the evidence that the first finding was causal. Without it, you have a temperature, not a closed file.

Symptoms that bring a camera

Smell of heat, discoloration, breakers that feel hot by hand, unexplained trips, or a maintenance program that wants a baseline. The camera does not replace torque, and torque does not replace a load that actually stresses the joint. A lightly loaded feeder can hide a bad lug until the process peaks.

Causes

High-resistance connections: under-torque, creep, dissimilar metals, corrosion, broken strands. Unbalanced load that is real (process) versus a high-impedance phase. Harmonic heating that is distributed along a conductor rather than a single lug — the image looks “warm all the way,” which is a different conclusion. Internal breaker or fuse degradation. Ventilation blocked on an enclosure, which is environmental, not a connection defect.

Investigation

Record load on each phase at the moment of the image. Compare phases on the same bus under the same load; a 3 K difference at 40 percent load is not the same finding as 3 K at 90 percent. Use a known-emissivity patch or a contact check when the surface is shiny. Repeat after a controlled load change if the first pass was empty. Pair with electrical diagnostics when the heat is intermittent. Do not publish severity scores that imply a false precision.

The written outcome names the component, the delta, the load, and the next physical action (retorque, replace lug, investigate unbalance, clear ventilation). Related trips: nuisance tripping. Related power electronics: UPS under real load.