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Conducting Inspection of Utility Substations

As we approach the summer “peak” of electrical usage in North America and other parts of world, many of us realize how vulnerable the grid has become. Much of it is old, poorly maintained, and loaded beyond design. While I hope we won’t see a huge cascading blackout, we can expect to see outages this summer—many of which could be avoided if the thermography was being well used to identify problems before they fail.

On August 14, 2003 45 million people in North America were affected by a heat-related failure of the power grid that left the lights out for a night or two.

Heat is the enemy of all electrical systems. Rarely does an entire component, whether a transformer, a switch or a line, heat up, but the points of contact and connections do—often to the point where the metal melts and fails. Properly used, we can identify these “hot spots” and manage them to prevent the outage.

There are several key issues that must be addressed if the inspections of electrical line and substation equipment are to be successful. Failure to follow these simple guidelines may result in dangerously misleading results!

  • Load: the system should be loaded to 40% or more of peak, the higher the better. If you find a hot spot and loads are likely to increase during peak, pay attention to how much more heating will occur.
  • Wind: if winds at the component are in excess of 10mph (16k/h), and especially if they are likely to diminish at some point during the summer, great care should be taken to note any and all abnormal heating.
  • Compare phases: unless there is a load imbalance among the three phases, all will typically function at similar temperatures. If a component on one phase is warmer than on another, make a note and determine why.
  • Don’t base decisions on temperature alone: if you find a hotspot, don’t ignore it, even if it is small and not very hot! When you do measure temperatures, work well within the measurement resolution of the imager and compensate accurately for both emissivity and background.
  • Note any abnormal temperature rise: even small rises can indicate serious problems depending on conditions and the equipment. Ultimately, let the consequences of failure help drive the response rather than some predetermined temperature-based prioritization.

You won’t be able to fix every problem you find, but you can prioritize them, fixing those that are critical and managing the rest until repairs can be made. Next week we’ll talk about what you might find and show you some more thermal images.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

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