Thermography in UPS Maintenance - Jason Marriott Managing Director, Power Protect Pty Ltd

Thermography in UPS Maintenance

 Not so long ago the practice of thermography was limited to scientific applications primarily due to the cost and difficulty in setting up and using the equipment. These days the cost of thermal cameras has come down sufficiently for them to be a standard part of the service technician's toolkit. Power Protect purchased our first thermal camera in 2012 and the benefits to our service team were instantly obvious. Shortly after we made the thermal camera a standard item supplied to each and every one of our service techs. While having a thermal camera is a good first step, it is just as important to have the training in how to collect and interpret the thermal images that we use for the basis of our service recommendations. This has led us to a combination of in-house training, accredited training through the University of Melbourne, and certification with the Australian Institute of Non-Destructive Testing (AINDT) Armed with the right tools and training for the job, we've found many issues that could have gone unnoticed if not for our use of the thermal camera on each and every UPS maintenance visit. Here we have a collection of some of the images that have been captured.

As part of a commissioning on a new 80kVA UPS, the system was subjected to a discharge test to confirm the batteries were performing in line with the manufacturers specifications. While the batteries performed as required a scan of the batteries during the discharge test identified that the positive post on this block had a higher temperature than others in the string. The battery itself did not show any signs of an issue with the float and discharge block voltage consistent with those around it, however the post temperature clearly indicates that the internal post connection is a higher resistance than it should be while under load. After being presented with this image the manufacturer immediately authorised a warranty replacement, and just like preventative maintenance should the problem was fixed before it became a problem.

This output filter capacitor is from a smaller UPS and features 'spade' style crimped connections. These are notorious for spreading apart leaving a poor connection. While not warm enough to leave a visible mark on the crimp's insulation, the elevated temperature would at best shorten the service life of the capacitor and at worst fail completely potentially damaging the UPS or customers equipment.

Here is another spade terminal, however on a battery this time. UPS batteries systems are made up of a string of batteries in series. The inherent weakness is that an open circuit failure at any point along the string will render the entire string out of service. Being able to see the poor connection on this battery link allowed us to replace it straight away as part of the preventative maintenance.

Finally, this image shows a loose termination on an external maintenance bypass switch. The bypass switch in this image is for the 'A' UPS on a 2N (or A/B redundant) system. This means that a failure of the 'B' system would result in a doubling of the load on the A UPS and its bypass switch. With the temperature rise shown for 50% of the site load it is unlikely this would have survived long if required to support 100% of the load. LINK ORIGINAL
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