Transient Overvoltage Protection
Clause 443.4 refers to the protection of electrical installations against transient overvoltage, in part due to the increasing prevalence of lightning strikes but also relating to switching loads causing transients on a network. Where overvoltage could cause serious injury or loss of human life, disruption to commercial and industrial activity or interruption of public services, the regulations now stipulate that surge protection must be provided. Outside of these consequences, a risk assessment must be carried out to determine whether overvoltage protection is required. If deemed necessary, a surge protection device (SPD) must be installed within a suitable enclosure, designed to immediately drive any overvoltage to earth. Consumer units with pre-populated SPDs are available for new or replacement installations, whilst enclosure only units are ideal for retrofit.