"Bret Ludwig" wrote in message
oups.com
Strictly speaking that's correct, but the two hot lines
are equally distant from the ground line at all times,
except at zero crossing when they are all the same and
zero with reference to earth. When the positive one is at
positive peak the negative one is at negative peak.

Yup, which means that none of the three voltages is the same, even though
two have the same magnitude.