28.3 Measurement technique for thermographic inspection
of electrical installations
28.3.1 How to correctly set the equipment
A thermal image may show high temperature variations:
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Figure 28.2 Temperature variations in a fusebox
In the images above, the fuse to the right has a maximum temperature of +61°C
(+142°F), whereas the one to the left is maximum +32°C (+90°F) and the one in the
middle somewhere in between. The three images are different inasmuch as the tem-
perature scale enhances only one fuse in each image. However, it is the same image
and all the information about all three fuses is there. It is only a matter of setting the
temperature scale values.
28.3.2 Temperature measurement
Some cameras today can automatically find the highest temperature in the image.
The image below shows how it looks to the operator.
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Figure 28.3 An infrared image of a fusebox where the maximum temperature is displayed
The maximum temperature in the area is +62.2°C (+144.0°F). The spot meter shows
the exact location of the hot spot. The image can easily be stored in the camera
memory.
The correct temperature measurement depends, however, not only on the function
of the evaluation software or the camera. It may happen that the actual fault is, for
example, a connection, which is hidden from the camera in the position it happens
Publ. No. T559597 Rev. a554 – ENGLISH (EN) – September 27, 2011 133
28 – Introduction to thermographic inspections of electrical installations
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