How Existing Switchgear Temperature Monitoring Solutions Fall Short

Why are traditional monitoring solutions insufficient?

There are a few temperature monitoring solutions currently being used in switchgear—but they all have their drawbacks. One problem is the lack of any means of monitoring switchgear on a continuous basis. In addition, some of these methods expose maintenance teams to significant risk.

*Infrared Inspection

Visual inspection is necessary to assess conditions like the buildup of particulates, dust, and debris, but is not effective at detecting loosening bolts caused by thermal cycling or other age-related deterioration effects. Visual inspection can be effectively performed on de-energized equipment, which is a relatively safer process, but this is not sufficient by itself. Plus, since inspections occur only periodically, problems can easily build up in the interval between inspections without your knowledge.

Infrared imaging can be used to visually locate thermal ‘hot-spots’ in the switchgear equipment. Unfortunately, infrared imagers require line-of-sight between the image and the component being monitored and faults are most easily spotted when equipment is energized and live. This requires that protective panels be removed and access doors opened while the switchgear is energized—a highly dangerous proposition for the inspector.

Infrared imager and port for monitoring switchgear hot spots

To minimize the risk, some switchgear cabinets incorporate infrared imaging ports which allow inspectors to use the infrared imagers without opening access panels. While is this much safer, these ports provide limited visibility inside the enclosure. It becomes easy to miss something hidden behind other equipment. In addition, infrared windows are not typically blast-proof, making them a liability in the event of a catastrophic failure. Infrared imaging equipment can only be used during periodic inspections. It does not provide continuous monitoring—meaning that again, there’s no way to know what’s going on in the intervals between inspections.

Equipment torque checks look for loose connections caused by thermal cycling and age-related stress, which increase the risk of arcing and other faults. Torqueing mechanical bolts that connect bus bars, etc., can extend the equipment’s operational life. However, finding all appropriate connections can be highly difficult and expose inspectors to risky conditions.

SAW devices (surface acoustic wave devices) are made of interdigitated fingers of metal on a ceramic substrate. When the ceramic gets hotter or colder, it stretches or contracts, which changes the wavelength of the energy that it radiates back to the reader.

SAW system for measuring and reporting temperature

The issue is that these devices are easily affected by interference and prone to false positives. They’re especially unreliable in an environment like a switchgear cabinet, where arcing events confuse the readings.

Run-to-failure is the default approach to maintenance—doing nothing and simply letting switchgear operate until a fault occurs. With such high voltages running through switchgear, letting switchgear fail is exceedingly dangerous to adjacent equipment and to anyone working on inspections or maintenance.

Ultimately, with traditional methods there is a trade-off between safety and reliability. To get better data, maintenance teams may feel pressured to cut corners or take risks with their safety. With RFMicron, however, there’s a better way. We can help you can get more reliable readings while keeping your people safe during routine inspections.

Switchgear explosion**

 

*Image sourced from: http://www.instrumentation.co.za/48889n on Aug 28, 2017.

**Image sourced from: https://www.impomag.com/article/2011/04/infrared-window-solution-arc-flashes on Aug 28, 2017.


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