Voltage Rating of a Lightning Arrester?

to protect equip attached

http://www.polyphaser.com/default.aspx

It depends on the surge arrester design (gapped silicon carbide; gapless metal-oxide). The rated voltage is actually higher than the maximum line to ground operating voltage and that relationship is determined by system grounding (effectively grounded, impedance-grounded or ungrounded). The maximum 60 Hz line to ground operating voltage of a gapped type arrester is dictated by its 60 Hz sparkover and duty cycle rating (that is, the voltage at which the arrester can discharge a surge current to ground and reseal against system voltage). Gapless surge arresters are defined by their MCOV (maximum continuous rms line to ground operating voltage) and TOV (temporary 60 Hz overvoltage capability).

Surge arresters are voltage sensitive devices that are designed to protect insulation from impulse overvoltages; not 60 Hz. Gapless metal-oxide arresters will rapidly fail if subjected to 60 Hz overvoltages and times that exceed their TOV rating. A similar situation occurs with gapped surge arresters when sustained 60 Hz overvoltages exceed their interrupting capability.

Refer to IEEE Std C62 (IEEE Standard for Metal-Oxide Surge Arrester for Alternating Current Power Circuits) for additional information as well as manufacturers' catalogs such as Ohio Brass (www.hubbellpowersystems.com).

Should your system be connected to a low resistance ground for detection and trip, You should have a fully rated line to line voltage surge arrester. Only if your system is solidly grounded should you consider a Line to Neutral voltage rated arrester.