Anybody used to installing CT's commercially.

[Mike2007]

It depends, those clip on CT coils look like you wouldn't need to power down, just as long as the output of the CT isn't open circuited.
If you need to disconnect to thread a doughnut one on then you'd have to power down as there really isn't any other option.

+

Spark123. Look at the diagram on my second post, #5.
This meter and most I have been studying have L1, L2, L3, N off the bus bar, into the meter. although Disinfo said the ones he uses go to the primary winding on the CT.
Don't quite get the theory here. The current drops down as it travels across the CT windings and goes to the meter after being reduced to 5va or so. How does this measure the flux or current running through the cable?

 

[RF Lighting]

Rob, a quick one, would that CT cabinet happen to be in one of the premises of my employer?

Possibly

 

[Spark123]

The mains cable is basically the primary, this passes through the centre of the CT.
The CT coil is the secondary of the transformer.
When current passes through the primary a magnetic flux will be occur around the cable, the more current the stronger the flux.
This flux will cut the windings of the secondary causing voltage to be induced into it. As this is in effect short circuit (owing to the closed loop I mentioned before) the voltage will be at almost zero volts and the current in the secondary circuit at a maximum for the given flux.
The CT manufacturer has to do is work out the amount of turnings to give a certain amount of secondary current for a given primary range i.e. you may want a secondary of 0-5A with a primary of 0-500A.

 

[Steve]

Rob, a quick one, would that CT cabinet happen to be in one of the premises of my employer?

Possibly

Bloody knew it!!!! The blue shovel gave it away