Since there's no solution provided for Earth leakage protection for NW40-63, can I use extenal CTs, connect their secondary to the primary of the torroid and then to the vigirex? See attached.
The idea is OK , it would work because you can consider the CTs secondary currents are representative of the primary currents in value and phase.
Each CTs have a current ratio (the primary current to secondary current ratio) and introduces a phase shift . As all the 4 CTs aren't identical, their curent ratio and phase shift won't be identical, so the CTs introduce errors in the measurement chain.
The Vigirex setting calibration doesn't take in consideration these additional errors, so we aren't able to promote this solution because we've never tested our Vigirex in such a connection. In other words, today we aren't able to say to clients that we have the same accuracy using a rectangular sensor than using the secondary CT schema you mention.
We've never tested such a configuration to know which accuracy we'd have and then adapt the Vigirex setting calibration to that condition.