Fault level of cable 1

[eejacky]

Dear all,

Which part of the 132kV XLPE cable will determine the fault level of cable? In other words, when there is a short circuit, which part of the cable (i.e conductor shield, insulation, insulation shield or metallic sheath)will be the most electric stress one.
Thank you!

 

[redtrumpet]

Thermal stress rather than electrical stress is the concern under short circuit, and the insulation is usually the weakest link.

 

[peebee]

I generally agree with redtrumpet, but it seems to me if you have a semi-conducting conductor shield that would go first just because it's closer to the heat source.

So far as electrical stress goes, though, well, that's the whole point of having insulation and insulation shields, to ensure that the entire field drops across the insulation.

 

[joan271273]

Power cable literature is veru specific about two thinngs when designing and installing power cables:

a) If the cable is shielded, shield be able to handle and maintain its integrity under specified short circuit level. Cable vendors provide standard cable products, therefore you must specify your shield cross-sectional area or indicate tha the cable must comply with your kA requirements and provide data to support it.

b)Cable if braced in trays, etc must comply with certain separation requirements ( distance between supports points ) these will change with the max. possible short circuit value. European standards such as VDE have formulas for this, but also some IEEE-IAS papers have addressed the subject.