CT IN SECONDARY

SHHHHHHHHHHHHHHH! <Burp>

First, it seems you are describing a three phase power feed of some kind. Each phase can provide a different amount of power so using a single CT for metering would assume an equal amount of power consumption on the other two. That would be a bad assumption.

For the same reasons, picking an arbitrary phase for protection dosen't make since. Perhaps you have not examined the connections closely enough. All three CT's would or could be used for either purpose mentioned. Unbalanced consumption of power is quite common even though attempts are made to avoid it. But when it comes to metering, you can be sure that every KWH is captured using all three CT's.

Lastly, lower your voice (tone) by turning off the CAPs LOCK button

Generally, in the protection of the power line, there will be 3 CT install in each phase. These CT are for as follows:

a) 1 CT for Metering

b) 1 CT for Protection such as over Current

c) 1 CT for Differential Relay and Restricted Earth Faults.

Some may use the 3^rd CT for Quality Power Analyzer

Thanks ,Simon Wan............