A surge arrestor (also called a surge protective device (SPD) or lightning surge protector) is a protective component that limits short-duration overvoltage events by diverting surge energy away from sensitive equipment to earth (ground). In EV charging infrastructure, surge arrestors protect chargers, meters, controllers, and communication electronics from voltage spikes caused by lightning, switching events, or grid disturbances.
Why Surge Arrestors Matter in EV Charging Installations
EV chargers contain power electronics, control boards, metering, and communications hardware that can be damaged by transient overvoltages. A correctly selected and installed surge arrestor helps:
– Reduce charger downtime and costly electronics replacement
– Prevent nuisance faults and unexpected resets in the field
– Improve reliability in exposed outdoor locations (car parks, kerbside, depots)
– Protect connected systems such as OCPP gateways, routers, and LTE modems
– Support long-term uptime targets for public and fleet charging
Common Causes of Surges at Charging Sites
Surge events can be triggered by:
– Lightning strikes (direct or nearby, including induced surges)
– Utility switching operations and feeder reconfiguration
– Large inductive loads switching on/off (motors, HVAC, lifts)
– Fault clearing events and network disturbances
– Long cable runs that act as surge coupling paths
Where Surge Arrestors Are Installed
Surge protection is typically layered across the site:
– At main LV panels or incoming switchboards (site-level protection)
– In sub-distribution boards (SDBs) feeding charger groups
– In local feeder pillars, street cabinets, or charger pedestals
– On communication lines where relevant (Ethernet, RS-485, external antennas)
Good placement reduces the surge energy that reaches the charger and its internal electronics.
Types and Ratings Used in Practice
Surge arrestors are selected based on the installation environment and risk level:
– Type 1 SPD (higher-energy protection, often used at building/service entrance in lightning-prone setups)
– Type 2 SPD (common distribution-board protection for switching surges)
– Type 3 SPD (point-of-use protection close to sensitive devices, where applicable)
– Key parameters include nominal voltage, maximum continuous operating voltage, discharge current rating, and protection level (Up)
Selection must match the earthing system and the site’s electrical architecture.
Design Considerations and Common Pitfalls
Surge arrestors only work well when installed correctly:
– Low-impedance earthing and short connection leads are critical for performance
– Incorrect coordination between SPDs can reduce protection effectiveness
– Missing protection on long feeder routes can leave charger clusters exposed
– Poor enclosure selection can compromise IP rating and reliability outdoors
– SPDs can degrade over time and may require inspection or replacement after major events
Benefits for Operators and Site Owners
– Lower maintenance cost and fewer electronics failures
– Improved charger uptime and customer satisfaction
– Reduced risk of cascading faults across multiple charge points
– Better resilience for sites with frequent storms or unstable networks
Related Glossary Terms
Surge Protection Device (SPD)
Lightning Protection
Earthing / Grounding
Protective Earth (PE)
Main LV Panels
Sub-distribution Boards
Power Quality
OCPP