ABB, OVR Surge Suppressor Unit 275 V ac Maximum Voltage Rating 15kA Maximum Surge Current 3 Phase

Single-pole Modules for IT and TN-C wiring networks
Multi-pole Modules for TT and TN-S wiring networks
Mechanical status indicator
Optional safety reserve indication

IP55 enclosed units with clear lids include the following surge arresters & suppressors

Voltage surges, often referred to as spikes or transients are typically caused by switching of fluorescent lights, fuses blowing or nearby lightning activity. The worst voltage spikes are usually caused by lightning strikes and can reach up to 6000V, with current surges of over 3000A. The maximum size of the let-through voltage and current inrush depends on the location within the building's wiring system. BS7671: 2011 Amendment 1 Sections 443 and 534 cover risk assessment and provides guidance on protection of electronic equipment for installation engineers to follow. The fullest information on lightning and surge protection comes from the BSEN 62305 series of standards.