Current Transformer & Energy Meter Connections For a Changeover System

It does not matter (from a current measurement perspective) whether the CTs are on the line side (upstream) or load side (downstream) of the main breakers. When a breaker is open, no current will flow through it or the stub of busbar connecting it to the main bus.

The current will flow through the closed breaker(s) to the loads. Current needs a circuit to flow, so it won't "run upstream" and bump up against the open breaker to be measured in your CTs. Draw a 3-phase diagram of your system and add arrows for the currents that will flow when one main breaker is open, and you will see.

But the voltage will exist . Kindly Refer the schematic which i uploaded and let me know.

The previous comments are correct; the location of metering CT's in relation to the breaker doesn't matter (if they were for protection it would be a different matter).

There are two main reasons for the vendor to design this way. First, there's usually more room for CT and PT connections on the bus side of the breaker, when compared to the cable side. Second, the energy meter is most often a digital device which requires external power, usually obtained from the sensing PTs. As you indicated, there will always be voltage present, so the meters will have power for the display, datalogging and any electronic communications.

The CT/Fuse connections are okay as wired (downstream of each breaker).

If the connections are installed UPSTREAM OF EACH BREAKER, even if the current is ZERO (because circuit breaker is opened), the ENERGY METER will still read something (because it will still read VOLTAGE). Thus the ENERGY METER reading will NOT BE ACCURATE.

Hence the connection downstream of each breaker is CORRECT.