Infra-red (IR) cameras are based on digital camera technology and therefore require a direct-line-of-site to record an accurate image. The area to be measured must be under normal operating conditions to detect a hot spot which means that it must be live and have been so for 20 minutes prior to inspection.
The use of IR windows is becoming more common place, in fact, some electrical panel manufacturers are now pre-fitting their panels with windows to make them more IR friendly. IR thermography is the fastest growing predictive maintenance technology in the world today. The number of IR equipment manufacturers has increased significantly over the last five years.
In the US, regulation NFPA 70E determines the “Flash Protection Boundary” of electrical panels. The flash protection boundaries define the safe working distances in which any tradesman can operate from an energised component. Thermographers must be fully conversant with these regulations, especially if they intend to remove covers to allow access for a live inspection to be completed. Also, the NFPA 70E regulations stipulate that unless the thermographer is a certified electrician and fully conversant and qualified on the equipment that he is inspecting they will need to be accompanied, thus increasing the manpower requirement for the inspection.
An arc flash does not happen without a trigger, it nearly always begins due to a “change of state” that causes even a momentary connection between phases. Most of the time these arc flash incidents are caused by intervention/someone contacting components, etc. Spontaneous arc flashed very rarely occur.
Although not common in South Africa, some organisations prohibit live inspection of energized higher voltage equipment. IR windows are the alternative to doing nothing. It removes the risks and downtime associated with live inspections. Their use in a thermographic inspection program removes almost all the triggers of arc flash incidents whilst improving electrical safety by allowing safe, regular Infra Red inspections of energized and loaded electrical switchgear.
An IR window sounds more complicated than it really is, and although there are several types of window available on the market today, there is nothing stopping the thermographer from designing a window for use in any particular inspection that they may wish to complete. An IR viewing window is basically an optic material that allows IR energy to pass through. The ideal IR window is one that would allow all the IR radiation to pass through it with zero losses, unfortunately with the materials available presently we cannot achieve the perfect transmission rate of 100%, but we do get very close.
Contact R&C Instrumentation, Tel 071 471-2056, email@example.com