Earth grids and hard drawn copper Vs annealed copper 3

[don01]

Hi All
We are building a 132KV/33KV substation.
The designer has specified the conductor for the grid to be 150mm2 uninsulated multistranded HD copper.
The inevitable supply issues has drawn out the response " we have lots of annealed available lets use that"
we have not done so (we'll wait for the spec'd cable).
But it begs the question-
what feature or quality is the designer looking for in a HD conductor
corrosion? strength? surface conductivity - we don't know it could be the phase of the moon

Any ideas or reference would be really appreciated
thanks
Don

ps we have a specified pH and resistivity for the soil and fills if that's helpful

 

[desertfox]

Hi

Hard drawn copper does a much better job at resisting creep than annealed copper other than that I cannot see why you cannot use the annealed copper.
Is the grid loaded such that it might suffer creep?

 

[jghrist]

We normally use SD copper because it is easier to install. I know of no advantage to HD copper for an earth grid. There is no tension, so there is no problem with tensile strength or creep.

 

[Kiribanda]

don01,
In addition to easy working SD copper has higher conductivity than HD copper means lesser copper weight for the same fault current.

 

[don01]

Thanks desertfox, jghrist, Kiribanda
I really appreciate your responses.
It would seem we can give a little push back here and ask to use the available materials
(desertfox, these are laid very loosely in the trench and covered with conductive sand & soil mix
there should be no creep or forces at play )

again thanks very much
I look forward to some of the threads here
Don