The maximum continuous operating voltage (Uc, MCOV) and rated voltage (Ur), are two significant characteristic points that define the performance of a surge arrester during steady-state operation.
MCOV is the maximum power-frequency voltage, under which the surge arrester can operate. As recommended by IEC 60099-5, the MCOV of a surge arrester should be at least 5% higher than the highest continuous voltage of the power system.
The rated voltage specifies the temporary overvoltage handling capability of a surge arrester for a period of 10 to 100 seconds. The figure below depicts the typical IEEE surge arrester TOV withstand capability:
Typical TOV Curves for IEEE Arresters
Rated voltage is generally 1.25 of MCOV. The table below shows the typical surge arrester rated voltage under different system voltages and applications [4][5].
Typical Rated Voltages Ur for Highest System Voltage
For more information, see the Knowledge Base Article.