Hi, do you have any experience with the after lying cable sheath testing in case the cable is placed in a protective plastic tube/pipe? I mean the whole lenght. Nice for protection, bad for testing and for fault location. The sheath has no direct contact to the ground so you can not guarantee...
Zogzog is almost right, I would add sheath test for sure.
We are talking about completly NEW cables - Tan delta is not predicative in this case. We can expect strict cable manufacturer test in the factory, if the sheath test is ok we can expect good insulation and only mounting faults (joints...
My opinion is that 40 old years cables are quite old but not neccessary close to dead.It depends on history of each one - rate of faults, loading, overstressing... and the real condition (make the diagnostics). You did not mention type of insulation which is important for tests recommended too...
I agree with davidbeach and testbeforetouch last posts:Once the grounds are removed it has to be treated as energized as it is no longer grounded! Testing the cables you apply sometimes higher voltage then Uo.It means from the point you connect your test equipement and remove the ground you MUST...
Ben: I have studied the article. It is very interesting AND usefull again :-)
In that study, WT seems to be like a protection for ET growth.
My opinion is that most of the mentioned examples had PDIV above Uo(p.u.), that is why it took so many years till defect.
Different situation would be if...
Back to the discussion regarding HiPot and PD test. Excuse me for the simplyfied way I am trying to explain my feeling about: You can not really compare Hipot and PD tests because it is not the same method, the target and result is not the same as well. It is a mistake thinking both can find the...
BenLanz: as usually, your writting is very interesting. I have one notice - you mentioned that water trees do not damage the cable directly. Of course it is true. But I am not sure if you are right claiming that after changing the water tree to electrical tree it takes a peiod of years to the...
1. How close will the PD results from factory and those of field in harsh noisy environment match and how can they be compared with each other? To me PD testing and evaluation is still evolving and will take some time before it gets accepted. IEEE has issued some draft guides in this regard...
IEEE 400-2001 General Guide Shielded Power Cable Testing
IEEE 48-1996 Terminations No PD ? 5pC at ? 1.5Uo
IEEE 404-2000 Joints No PD ? 3pC at ? 1.5Uo
I have 3 things:
1)unfortunately these values are mostly not detectable in the field during PD...
I do not think it´s so easy to learn MV cable jointing and terminationing from the www site... According to my experience the biggest rate of cable faults (excluding the external damage) are caused because of pure workman ship.I recommend a course as well but only the long praxis experience will...
one notice: energized but not loaded cable still causes the losses, if this is important for someone,should think about...I agree the switching on the long time de-energized cable-it could be a problem. I am sure you know there are many predictive diagnostic methodes to estimate the cable...
