Testing

[lamb.a]

When using a meter to carry out earth loop impedance measurement on final circuits by disconnecting the earth conductor. Is it neccessary to check the line to neutral impedance, this should be carried out with all earths connected.

 

[Tiger]

you should take both measurements and record the highest of the two

 

[Guest123]

Hey.

Dont quite understand your post.

You only disconnect the main earth to carry out the Ze measurement at supply tails with main switch open and all circuits de-energised.

The measurement on final circuits that you describe is Zs and this is done with all earths connected and circuits energised

Please clarify??

Cheers

 

[Tiger]

are you talking about a pfc measurment

didn't read the final circuit bit, beer goggles

 

[ian.settle1]

When using a meter to carry out earth loop impedance measurement on final circuits by disconnecting the earth conductor. Is it neccessary to check the line to neutral impedance, this should be carried out with all earths connected.

If you disconnect the earth conductor you would not have a path to obtain the Zs of the circuit.

Why would you want to do a line/neutral impedence test on a final circuit?

This is only done at the point of supply to find to find which of the fault currents is the higher.

 

[lamb.a]

Hey.

Dont quite understand your post.

You only disconnect the main earth to carry out the Ze measurement at supply tails with main switch open and all circuits de-energised.

The measurement on final circuits that you describe is Zs and this is done with all earths connected and circuits energised

Please clarify??

Cheers

When you have a steel wired armour cable with a seperate earthing conductor the armouring provides a parallel path so how would you know if the earth conductor was properly connected - by disconnecting the earth conductor at the farthest point and with earth still connected at distribution unit using an impedance meter with test lead connected to this earth conductor confirms good earth path (circuit is live) reconnect check impedance of the earthing conducting the steel wired armour gland. Use the lowest voltage if three phase and devide by 1.732 and divide the highest impedance to check prospective earth fault current. These swa cables feed dedicated equipment just wanted to confirm if line neutral tests required. Thanks