Neutral Current Transformer Polarity

Seems to me that you have a lot of CT's to coop with. You have a nice drawing but I cannot read the info that comes with the CT's. Neither we get a diagram of the build of the CT's. Most important is that all the CT's in the separate phases are in the right direction. The neutral CT will deal with the vector currents differences.

I think it is early and not possible with the info you give us to determine how the current flow in the neutral will be, behave, change once you power up the set.

Perhaps your client knows more already? When the CT has symmetric tabs, you can still play with it, just beware the connector rank.

Some more info would be very welcome.

Like DVMSC, I do not see enough to be sure with what we are dealing.

At first glance, it looks like a star-delta transfo, the box to the right of the red ringed CT, being its top-plate with terminals. H0, H1, H2, H3 and Y1, Y2, Y3. The solid black bars are windings, drawn out at the bottom (and top? not visible) to fit a two dimension drawing.

If that is so, then H0 is just a terminal, the CT above it (T14?) is inside the transfo bushing for the star point. But if that is true, then T14? polarity is consistent with the "Outdoor Ring Type" red-ringed - traveling through both, via H0 the two polarities are consistent e.g. P1 - T15 - P2 - H0 - P1 - T14 - P2?

So if you change the "outdoor" CT polarity, T14 will be "wrong".

Maybe the box to right of T15, is some kind of apparatus - something inside it is connected to H0 and draws current - else the current through T14 is the same as through T15 and their primary polarities are consistent "as drawn". By Consistent, I mean that if you pass a current through T15 and T14, with P1 voltage positive, then their secondary terminals 1 will be positive to secondary terminals 2.

On the other hand, If you have a star transfo winding at the top, and pass a single phase current P1 - T15 - H0 - T1 -H1, then T1 and T15 (red-ringed) will give opposite secondary polarities (but so will T14 versus T1). That can only be compensated on the secondary side, to a relay for example. Is it possible the "red-ring" inconsistency is with another CT, maybe on busbar or switchgear - which is not on this drawing.

If, say, the transfo maker assigns P1 to external end of any bushing CT and switchgear maker assigns P1 to external end of his CTs, then if you interconnect switchgear to transfo, the secondary polarities will be opposite. But drawings have to show what you actually have embossed on the equipment terminals, not "double-label" equipment spreading confusion. One documentation rule (that can be frustrating) is that a piece of information should be given only once - if it is in two places then maybe only one gets modified.

The real "maddening" error would be to not mark the P1 and P2 ends of each CT physically on the CT and on the drawing consistent with physical connection!

I hope this helps, when one can see only part of the drawing [and only part of the system] , speculation can just confuse.

67model

"One of the customers" - - but who drew the drawing ? The EE that drew it should know your answer. If the customer who is questioning the drawing is the one who is paying the fees, and disagrees with the engineering drawing, and the drawing is "correct " then you as a contractor should let the Customer and the EE draftsman sort it out - then you do the work as specified.

Someone approved that drawing ! Take the question to them. If its your own design and drawing, then you ought to be able to argue your own case. If it's a simple issue of a mistake in drawing, there should be a basic layout from which that drawing was made - do they agree ? Go back to the source and compare notes; but it's really a difference of opinion between a "customer" who comissioned the work and the EE who laid out the design. Unless you are one of them, then it's not your issue to resolve, IMHO.

By the way, interesting background on the photo, curious to know how that was done lol.

While it is a direct and practical communication channel you expose, it may not be allowed fit in the hierarchic line and policies of the company. When the O.P. doesn't solve the issue, his position as middle man or contractor might be questioned?

Yeah, I hate company politics that get in the way of solving problems. I see the OP will not reveal any further info so our questions are left to speculation and our best efforts go unrewarded.