Surge Arrestor Rating

[power2020]

Dear Folks,
Pl. clarify the different ratings of surge arrestor given in brackets (for 13800V system) as per IEEE C62.22-1997, table No.7 attached herewith.
Advanced thanks...

 

[Marmite]

The figure in brackets is the minimum MCOV required for the maximum L-G rms system voltage. The figure outside the brackets is the commonly used MCOV.
Regards
Marmite

 

[jghrist]

The figure inside the bracket is the duty cycle rating. From the RUS Rural Substation Guide:

Voltage Rating–Duty Cycle (kV rms): The designated maximum permissible operating voltage between its terminals at which an arrester is designed to perform its duty cycle. It is the voltage rating specified on the nameplate. This rating is applicable specifically to the silicon-carbide valve arrester and is also typically listed with the MCOV rating for the metal oxide arrester.