What is an electrical surge?
A transient overvoltage is a very short rise in voltage. It can originate from lightning activity transmitted through the supply network or from switching events within a network or installation.
Many modern homes contain sensitive electronics in boilers, appliances, alarms, smart controls, computers and entertainment equipment. A damaging surge may cause an immediate failure or contribute to premature deterioration.
What does an SPD do?
A surge protection device diverts or limits excess transient voltage. It does not replace circuit breakers, residual current protection or lightning protection, and it cannot prevent every possible equipment failure. It is one coordinated layer of protection.
Why are they now common?
BS 7671:2018+A2:2022 strengthened the approach to protection against transient overvoltages. For most new domestic installations and significant alterations, surge protection is now the normal design choice unless an appropriate documented exception applies.
An electrician must select and coordinate the SPD for the supply and installation. Plug-in extension leads are not a substitute for correctly designed protection at the installation.
Technical source: IET Wiring Matters — Amendment 2 overview.