Discuss Underground Cable Joints - Location? in the Electrical Forum area at ElectriciansForums.net

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mjmarkey1967

Morning gents (and ladies)

I have a job the now at a hydro power station where the client is experiencing a loss in production and believes this is due to moisture ingress into underound electrical joints along the 3km route of the 10core 5 pair BS5308 Type 2 Part 2 hill instrumentation cable. These are supposed to be epoxy scotch cast joints according to the as-builts, which have northing and eastings also kindly provided, however the client doesn't want to entertain verifying the accuracy of the drawings by inputting the co-ordinates into a suitable GPS device and digging trial holes which I have previously suggested.

The electrical contractor has since went bust, and we have learned the complete route wasn't reticulated in ducting, obviously a £ saving measure on the contractors part.

I have tried the use of the Bicotest T625 time domain reflectometer on site to identify any changes of impedance at these joint locations but also had no joy. Loop continuity and megger testing was also carried out between cores and individual cores to earth and although IR ohmic values has degraded over time, all seems that it should still function as intended as a signal path.

Does any body else have any similar experiences to trying to locate such buried items or ideas how I can keep a long running client happy?

Many thanks in advance.
 
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sparky-s-w

sound like a nightmare, and can't realy advise since accessing the cable joints would be the best bet.
However if the test's are all clear, the issue might not be with the cable/joints.
does your client only have a problem after a good rain soaking?
 
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Engineer54

All i can say is that it serves the client right!! On a project such as this, ALL cable joints should be accurately shown as to there location, on an overall site layout services drawing, and be also be marked on the ground with a propriety made for purpose concrete/stone marker. This should also be the case for underground cable routes, where ground markers will indicate routes, depths, number of cables and changes of direction etc,etc...

And now you know WHY this is normally a standard requirement on such high profile projects....
 
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