On Saturday, 14 April 2018 21:03:15 UTC+1, Johnny B Good wrote:

An effective way to avoid saturation issues when monitoring for
excessively high voltage excursions is to wire up an identical pair with
their 240v primaries in series and their low voltage (6 or 7 vac?)
secondaries in parallel (in phase current aiding) so as to help maintain
voltage balance between the primaries. Not only will this allow for 100%
excursions beyond the nominal 240vac supply, it should also allow high
frequency transients to be registered without molestation by saturation
effects. However, unless the transformers incorporate a 'grounded' inter
winding screen, high frequency transients can couple capacitively into
the secondary circuit, effectively magnifying their prominence.

A very good approach if two identical transformers are available.

John