short circuit capacity

[144x]

please somebody tell me how can I know that a specified maximum current capacity that runs through the metallic shield of a power cable is enough.
I mean when for example the conductor short circuit capacity of a cable is 25 KA then what should be the limit
for the shield.assume that the cable is single core and
it may be directly burried in the ground or may be laid
on trays.I have specified the 25KA and one manufacturer
has specified about 700 A for the shield .another one has specified 2.3KA and so on. the cable is going to be solid
bonded at both ends.

another problem is that in measurement centers sometimes
we use output contacts to send pulses to a remote center.
some manufacturers use 2 output contacts and some offer
4 output contacts to send information about both imported
and exported energy and in both active and reactive states.
I want to know if we use 2 output pulses what would be
lost? what is the disadvantage?is it too critical to have
the second type?lets assume that we can measure all for states in the first type of device.
thanks

 

[gordonl]

The short circuit rating of cable shield is generalyy given in Amps for a given number of seconds. So you need to look at the amount of ground fault current available on your system, and how fast a ground fault will be cleared and specify that the cable manufacturers meet this requirement.

Okonite had a good description of this on their site:

http://www.okonite.com/engineering/shielding-currents.html

Gord

 

[144x]

Thank you gordonl ,that was very helpful.
can you help me on second question too?