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Hot spot investigations
On underground power cable circuits
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Do you want to improve the current rating of cable circuits without jeopardizing their reliability? Then you should know where the critical thermal points and the hot spots are located. How do you find them? What do you do to get rid of them? How do you use the results?
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Selection of circuits
Your asset management program can provide clues for the selection of circuits to investigate hot spots, e.g. circuits with increasing load, or circuits operating near the known design limits, or having a history of failures.
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Cable route check for critical points
Studying the
cable route can identify potential hot spots. Typical areas of
concern include road crossings, canal/river crossings, a change in
soil characteristics, other infrastructure networks such as heat
pipes, sewers, electric power cables, changes of the situation
after the initial installation and so on.
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Local or distributed temperature measurement, if necessary
After the
potential hot spot locations have been identified, it may be
necessary to measure the outer sheath temperature locally and then
use a computer model to calculate the maximum local conductor
temperature. Using this approach, the location of the hot spots can
be pinpointed.
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Local soil/ambient investigation
After the hot spots have been located, you can investigate
options for reducing the temperatures. Investigation of the local
conditions will provide clues. For instance, in the case of buried
cables the thermal soil properties should be determined. Actions
can then be identified that should reduce the temperatures at the
hot spots.
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Results
The hot spot
locations will be identified and an action plan developed to reduce
the hot spot temperatures. After implementing the improvements, the
current loading can be re-calculated for the static or cyclic
loading condition or for the dynamic situation. The asset manager
now has an improved cable circuit available with increased loading
capacity.
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