I presume when you design/modify a CT circuit that you should do some check regarding CT saturation. If you have CT's A and B feeding the meter, then current in CT B contributes to voltage seen at CT A secondary. Since both CT circuits are similar I presume for simplicity you could assume that each individual CT circuit sees double the impedance of the meter and any shared wiring.
Saturation is not an issue with properly applied metering class CTs.
I believe that the spec on metering class CTs is to maintain acceptable accuracy at rated burden and 200% current.
Saturation is an issue with protection class CTs. Acceptance testing includes checking saturation voltages to verify acceptable operation at anticipated fault current levels.
Bill
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"Why not the best?"
Jimmy Carter
I think ePete is considering CT burden rather than saturation. Burden certainly does need to be considered, although most modern electronic meters have such a low burden that it is unlikely to be a problem, maybe more so with long leads and an electro-mechanical meter.
Metering class CTs are designed to saturate to protect the meter from high secondary currents in the event of a through-fault.
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If we learn from our mistakes I'm getting a great education!
Yes, accuracy is certainly the relevant issue, not "saturation". My apologies for sloppy terminology.
The more direct calc (instead of doubling impedance) would of course be:
Va = Ia * Za_unshared + (Ia + Ib) * Za_shared
Since Scotty mentioned protecting the meter, it brings to mind a question what kind of thermal limit the meter input has? (and could it be challenged?)
