which CTs to use for 400 amp service via 4 wires

[mwall]

ben,

what is the best CT configuration for 400 amp service?

we are installing 4 GEMs in a small industrial application. there is 400 amp service in the form of 4 conductors from the power company (plus two more neutral). there is also a backup generator that provides 400 amp service when the utility service fails. this enters the panel as 4 separate conductors.

the intent is to monitor power from the utility and power from the generator. normally we expect one or the other. the generator is run regularly each weekend for testing, and we want to be sure that the weekly failover tests work properly.

are there split-400 CTs available that will go around a pair of 200 amp conductors? that would result in 2 split CTs for the utility service and 2 split CTs for the generator output, using two channels on a GEM.

or should we use 4 split-200 CTs for the utility service, and 4 split-200 CTs for the generator output, using 4 channels on a GEM (then add channels to get the total)?

m

[ben]

I'll have to get Paul to reply as I'm not sure.

Is this 3-phase by any chance?

[mwall]

Is this 3-phase by any chance?

it is not 3-phase. a split-200 CT just fits around a single wire. i have included a picture of the transfer panel with markup.

[ben]

Paul will have to confirm but I think the mains would be installed like this (except using Split-200s instead of 400s), ignoring the commons:

4. 120V/240V Electric Service Panel Using Two-Wire Feed for Each Line or Using Two Double Main Breakers.

Sometimes the power feed to the service panel has two conductors for each, Line1 and Line2. In this case it would require a substantially large, cumbersome and expensive CT to be able to snap around the conductor pair. The resolution in this case is to use two CTs for each line. The CT amperage in this case can be 1/2 that of the panel amperage. For example, four SPLIT-100 CTs would be used to meter a 200A panel.

[mwall]

Paul will have to confirm but I think the mains would be installed like this (except using Split-200s instead of 400s), ignoring the commons:

4. 120V/240V Electric Service Panel Using Two-Wire Feed for Each Line or Using Two Double Main Breakers.

thanks ben. good thing we did not use all 128 channels yet