Infrared Inspection Helps Avoid Catastrophe
On
a routine quarterly infrared inspection of plant electrical
power distribution equipment, a high-voltage switch
for a transformer was found arcing to the insulation
board.
A quick and effective response to the dangerous condition
avoided a catastrophe at the plant.
The environment at
the plant is very humid and the physical assets are 30
years old. The quarterly infrared inspections of electrical
distribution equipment routinely reveal significant
problems
that were not present in the previous inspection.
During one such infrared
inspection during the summer, a 12,500-volt disconnect
switch for a transformer on the plant roof was found
arcing
from the switch to an insulation board. Even with
a low temperature difference between the fault and the
reference
temperature, 7 degrees Fahrenheit in this case, this
condition had the potential to start a fire in the transformer
and
cause an explosion if the arcing burned through the
insulation board and arced to ground.
The thermographer
understood
the seriousness of the fault and immediately reported
the condition to the maintenance manager. After
consultation with high voltage experts, a controlled
shut-down
was planned to repair the arcing condition and minimize
process losses.
The repair was completed
within 48 hours
of detection
without incident and the plant was brought back
on line with only about six hours at reduced rate.
Figure
1 shows
digital and thermographic images of the back
of the
switch before repair. Figure
2 is the digital image
of the insulation
board where the arc was occurring.
This is a great example
of a serious fault with a small temperature difference
across components. It also shows the importance
of the thermographer understanding the system being inspected
and potential consequences of failure. In this
case,
the
effective infrared inspection program certainly
avoided a catastrophe.
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