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I can understand 4-20mA signal in a 2-wire loop powered transmitter (transmitter regulate the current in the loop; power supply (say 24VDC) provides the voltage to make that current possible). However, in a 4-wire transmitter, power supply (say 24VDC) is provided to 2 of transmitter terminals...

Okay. Thanks for your inputs

Per vendor, cables meet the highest standard (certified to IEEE 383 - tested and proven to environmental effects) for any non-nuclear use. Also, they are exposed to mild temperatures only. So cable failure is out of the question and hence, two single failure path is not an issue, except for...

Thanks danw2. I looked at the STA. Isn't that STA works with single sensor and provides 2 process alarm points + system fault? I'm in need of ONE black box (or multiple black boxes) that takes 2 level transmitters and provide me with ONE 4-20mA signal output.

Big picture question on instrumentaion logic. My existing setup is a single level transmitter (4-20mA) feeding circuit via a controller. To avoid a failure of the circuit, we would like to add a second level transmitter (so that one LT fails, the other will continue to work and feed the...

But the new excitation panel requires 2 separate CTs. That's why my original post. In the 2 CT configuration, where to connect the excitation panel, before the motor protection (nearest point is CT) or after the motor protection protection (just before the CT summation point)? Also, what...

Thanks for all responses. But the original question still remain. Where to connect the excitation panel, before the motor protection (nearest point is CT) or after the motor protection protection (just before the CT summation point) in the 2 CT (A and C) circuit?

Raghunath, Nothing to check. See picture below. Highlighted is the excitation panel that we would like to move before the summation point - either before the protection circuit or after the protection circuit like I explained in my OP

Sorry for the delay. I went through the drawings, there is a separate CT on A phase for 51N relay. This CT is completely different from the excitation panel CTs on A and C phase.

I forgot to add. Also, @Raghunath, can you please provide the reasoning behind why 2a or 2b?

Thanks Raghunath, steve and cranky108. 1) Yes, CTs are located in the 4kV switchgear panel. 2) Yes, excitation panel is near the motor (600 ft away from the swgr; hence 1200 ft of additional CT wiring) 3) No 3rd CT or zero sequence CT. Hope this clarifies.

We have 2 CTs (A and C phase) on the 3-ph motor circuit and the CTs are wired as follows: 1) 2 CTs feed motor protection relays followed by the summated CT (2 CT currents summed before) feeding the motor excitation panel. We are replacing the motor excitation panel that now requires 2 separate...