External Earth Fault Loop Impedance (Ze) Flashcards
1
Q
Where is it measured and why?
A
Measured at the supply as this is where the impedance will be lowest
2
Q
What can it be used for?
A
Gives the Ze value which can be used to calculate the Zs of all circuits (Zs=Ze+r1-r2), this allows all earth loop impedance values can be calculated dead. Meaning only one live test has to be carried out
3
Q
Why are Zs values required
A
Required to ensure all protective devices can operate within their required time constraints of 0.4s for 32A or less or sockets up to 63A and everything else is allowed 5s
4
Q
What can this be used to calculate?
A
Earth loop impedance can be used to calculate the prospective fault current
