surge/overvoltage

Very little, they are both forms of overvoltage, however, a surge usually means a quick or temporary event, while an overvoltage can mean a permanently high voltage, due to a transformer tap being incorrectly set etc...

Also, a surge can mean a current increase as well as a voltage change...

John.

Surge results from sustained Overvoltage in an electric conductor.

This overoltage could come from either electric fault or lightning strike

Cheers

ethobil