The IEC 60099-5 PDF is a standard published by the International Electrotechnical Commission (IEC) that outlines the requirements for surge arresters used in electrical power systems. Specifically, this part of the standard (Edition 2.0, 2018-03) focuses on surge arresters for grids with nominal voltages above 1 kV.
: Must be greater than the maximum power-frequency voltage at the installation site. Temporary Overvoltage (TOV)
(L1 to L6) for line surge arresters to better reflect specific performance levels.