Nominal voltage to earth explanation please

[dave30]

hello and thanks for all your help as always

page 181 osg

says fault current can be measured buy I = Uo / Zs

know what Zs

it says that Uo is nominal voltage to earth

is this 230 volts on a domestic system single phaze .........

or not please explaine

 

[keniff]

Yes I=v/r

 

[Adam]

Yes, in a typical low voltage installation it is 230 volts. It applies to single and three phase supplies.