Voltage, Maximum Continuous Operating (MCOV) : The maximum designated rms value of the power frequency voltage that can be continuously applied to the mode of protection of a surge protective device (SPD)
NFPA 780 Standard for the Installation of Lightning Protection Systems, 2008 ed. http://www.uscg.mil/Petaluma/TPF/ET_SMS/Manuals/NF PA_780.pdf, (Std: Instll of Lightning Prot Sys - Amer) {347 NFC}