That's about the only way that you can retrofit a modern relay into old switchgear that never had a B-phase CT. Not great, but it works; a resistance grounded system helps.
It's recommended by SEL for these situations. We have used this multiple times and it does work. Just make sure both the CTs have the same ratio. That has come up once on some older switchgear.
What kind of reference? I've seen it before. Assuming low ground fault currents (resistance grounded system), then Ib = -(Ia + Ic) and that's what that wiring achieves. That relay is replacing two phase relays and one ground relay. If you don't connect anything to the Ib inputs the relay will see a standing residual current.
mostly david i was looking for a industry standard configuration to defend that wiring config to go along with the pdf description of what i was planning on doing
The most common place I've seen the 2-CT wiring is in the instruction manuals of some digital 3-phase panel meters such as a Tyco Integra or Accuenergy meter.
