[Optional Product] Can a step-up transformer be used as a substitute for the isolation transformer used in lightning surge testers?

[Optional Product] Can a step-up transformer be used as a substitute for the isolation transformer used in lightning surge testers?

There is no problem as long as it is an isolation transformer.
However, general step-up transformers and variable autotransformers (slidacs) have PE connected between the primary and secondary sides,
and are not completely isolated, so they cannot be used as substitutes.