Cable Protection - Protecting Shield Wire from a Ground Fault? 1

[BINGMD]

Protection Guru,

When checking 34.5kV feeder relay ground element settings for cable protection, is it necessary to consider protecting a cable from a feeder ground fault with all the ground fault current returned via the shield wire (1/3 netural)?

Thank you,
Best Regards,
Bing

 

[dpc]

You need to be concerned about the short-time thermal rating of the shield. Even with a separate external ground wire, the shield will carry a lot of current during ground faults. It's generally not a big problem. Okonite has data on this in their cable handbook, IIRC.