Is it much mor awkward working on 3 phase

[sparkticus]

OK, how about L1-L2=0, L2-L3=0, L1-N, L2-N, L3-N all =0, L1-E, L2-E, L3-E all =0, N-E=0

Would you grab hold of L1 and L3 ?

Would not an open Neutral and open L2 on a star secondary
offer those readings with PD across L1 - L3?

 

[Paul_C]

Would not an open Neutral and open L2 on a star secondary
offer those readings with PD across L1 - L3?

It would depend upon exactly where the neutral was open.

A break somewhere on the distributed neutral but which left the star point of the transformer still earthed would give 240V readings L1-E and L3-E (and, of course, there would be 415V L1-L3).

An open which left the transformer star-point disconnected from everything else (except its own three windings) could, theoretically, give those readings, since the three phase lines would then not be referenced to earth in any way. In practice the voltage measured phase-to-earth would depend upon capacitive coupling effects and the impedance of the test meter.