Temporary overvoltage (TOV) is the term used to describe temporary surges that can
arise as a result of faults within the medium- and low-voltage networks. To TN systems
as well as the L–N path in TT systems and for a measuring time of 5 s, the following
applies: UTOV ¼ 1.45 U0, where U0 represents the nominal a.c. voltage of the line
to earth.