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The Problem with Glass and Plastic

Glass viewing windows and plastic safety barriers are common features found on medium and high voltage electrical enclosures and devices. Although glass and many plastics are transparent in the visible spectrum, they are opaque in the infrared spectrum.

Because infrared equipment cannot accurately see through glass or plastics, infrared inspections must be conducted with these materials out of the line of sight of the infrared test equipment. When plastic barriers are present, try the following:

• Shift your viewing angle to try to see around or behind the barrier
• Have the qualified assistant temporarily remove the barrier observing proper safety precautions
• If barrier is short and the subject device is connected to insulated conductors, image conductors and report any inexplicable temperature rise.

When safety glass view ports are encountered in switchgear enclosures, it will be necessary to have the qualified assistant open/remove the subject panels. If this cannot be done due to safety interlocks, other types of electrical testing should be performed during regularly-scheduled PM shutdowns. As always, any obstructed equipment or equipment not inspected should be noted as such in the final written report.

Infrared inspection of electrical equipment is one of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. This same subject is also the focus of our 16 hour application course, Infrared Inspection of Electrical Systems. For more information or to register for a course, call us at 609-239-4788 or visit us online at infraspection.com.