Earth Fault Loop Impedance Calculation

[PRincez]

I have 16A RCBO supplying a socket 170m away from source via 3c x 16mm cable - the armouring will be used for earthing and no CPC will be run with the supply cable.

The supply voltage is 110V (CTE); can someone show me formula to calculate if the 16A RCBO will trip within allowable disconnecting time of 4s or 5s. I've been looking at the regs but the values there don't make sense to me just a fixed figure with no reference to lengths or anything. This is actually doing my swede in.

Any help please! i'd appreciate formulars or equations. Thanks

 

[dpc]

If I understand correctly, you are relying on the armor as the return path? If so, then the impedance value used for the armor and the assumed inductance will be the critical factor in the calculation. I'd expect a low value of ground fault current in a 110 V circuit 170 meters long.

 

[ScottyUK]

You're running a 3c/16mm² cable for a CTE supply and not using one of the cores for an earth connection? What are you doing with the third core?