Substation And Earthing

[epsngr]

Hi All,

 

I have an issue that has kept me busy for sometime. i will appreciate so advise/help here.

 

I am having a substation installed in a site xformer = 11Kv/400v, 500KVA, 400v. The supply authority requires me to terminate my main cable in an LV panel which is part of the transformer and has confirmed that the supply is PME. I am expected to use a 4 x 1c 240mm cables. My main concern is how to determine a suitable earth bond.

 

Normally by BS7671, we use the size of the suppliers cable but in this instance there is no secondary cable since the LV panel is part of the xformer substation arrangement.

 

Has anyone worked on such a system before and what did base your earth calculation on?

 

Response will be really appreciated.