Recently I have come across quite a few people that work with low emissivity materials like copper busbar. Generally they are under the impression that so long as they keep away exact temperature measurement then they will be ok. They just stick to looking for thermal gradients.
In fact, materials like copper busbar have such a low emissivity that it is possible that problems may exist, and simply not be visible in the infrared. If the emissivity of a material is this low, thermography may not be much help, and thermal gradients may not be noticeable. When the emissivity is very low, the reflectivity is very high, and the busbar essentially just shows reflections of the surroundings. This masks problems and may render them undetectable with a thermal imaging camera. If you do detect a problem on a bare copper busbar, remember it is very probably extremely hot, and close to failure, so standing around taking pictures might not be such a good idea.
The best solution is to change the emissivity. By this I do not mean changing the emissivity in the camera, this will not help, as changing this only changes the calculated temperature. You need to change the emissivity of the material itself, and this can be done by applying a coating to the busbar. This is best done when the busbar is powered off (if you want to become an old thermographer). There are various materials that can be used for this, the most obvious is paint. The paint that I would recommend for this is a product called “Glyptal”, this is an electrically insulating paint. It does not need to be applied to the entire busbar, just a few spots for measurement around the joints. Remember, it is really not likely to fail in the middle of the busbar itself, but the bolted joints are likely to become loose, so just some spots around these areas.

 

Leave a Reply

Your email address will not be published. Required fields are marked *