Steel cable trench lids used for cable shielding? 1

[BLadewig]

It's that time again... Round N^1983248 of Eng vs Maint. In this corner we have 'steel cable trench lids for shielding control cable' and in the other we have 'concrete lids to reduce decapitations.'

I'm curious just generally if any of the eng-tips members hvae experience with choosing lids specifically for shielding. This would be in a 500kV yard.

Thanks in advance for any replies.

 

[dpc]

Shielding from what? I suppose there could be some shielding effect, but I sure wouldn't be depending on it for anything important. The steel covers won't be electrically continuous, especially for any high frequency or RF noise. The variable resistance contacts between cover sections or between the covers and the trench can create their own RF noise if given half a chance due to rectification.

Also seems to defeat the purpose of the crushed rock that likely covers the rest of the substation??

I've only seen concrete trench sections and covers used in HV substations.

 

[BLadewig]

Thanks for the comments, dpc, they gave me some food for thought and further research. It turns out that the group wanting the steel for shielding was basing this on some tests they did a few decades ago. Once things slow down a bit they're going to get out in this station, bring a scope, and see how 20 years of better grounding and (presumably) better cable shielding might have changed the conclusions they had previously reached.

 

[dpc]

I'd be interested in what you find out. Again, the answer may depend on the frequency ranges that you are concerned about.