Surge protection devices (commonly SPDs) are protective components installed in electrical and communication circuits to limit transient overvoltages (surges) and divert surge energy safely to earth (ground). In EV charging infrastructure, SPDs protect chargers, meters, controllers, and networking equipment from voltage spikes caused by lightning-induced events, grid switching, and fault disturbances.
SPDs are used as part of a coordinated protection strategy across main LV panels, sub-distribution boards (SDBs), feeder pillars, street cabinets, and sometimes within charger enclosures.
Why Surge Protection Devices Matter in EV Charging
EV chargers contain sensitive power electronics and communication hardware. Without adequate surge protection, sites can experience:
– Charger outages after storms or network switching
– Damaged PCBs, meters, or communication modules
– Intermittent faults and nuisance resets that are hard to diagnose
– Higher OPEX from repeat call-outs and component replacement
– Reduced customer satisfaction and lower public network reliability
For exposed outdoor installations (kerbside, depots, open car parks), SPDs are often essential for long-term uptime.
What Surges SPDs Are Designed to Handle
SPDs are intended to protect against short-duration transient events such as:
– Lightning-induced surges (nearby strikes, induced voltages)
– Utility switching surges and feeder reconfiguration
– Fault clearing transients on nearby circuits
– Switching of inductive loads (motors, HVAC, lifts, compressors)
SPDs do not solve sustained overvoltage/undervoltage issues or poor power quality by themselves.
How Surge Protection Devices Work
During normal operation, an SPD remains inactive. When a surge occurs:
– It rapidly switches to a low-impedance state
– It clamps the voltage to a safer level (limits overvoltage)
– It diverts surge current to the earthing system
– It returns to a high-impedance state after the transient
Common technologies include MOVs (metal-oxide varistors), gas discharge tubes (GDTs), and TVS devices, often combined depending on the SPD type and rating.
Common SPD Types and Where They Are Used
SPDs are typically selected by installation location and expected surge energy:
– Type 1 SPDs: higher-energy protection, often installed at service entrances where lightning currents can enter
– Type 2 SPDs: commonly installed in distribution boards feeding charger groups and building loads
– Type 3 SPDs: point-of-use protection close to sensitive devices where needed
Many charging sites use layered protection (for example, Type 1 at the main intake and Type 2 at local SDBs), depending on lightning exposure and feeder layout.
Where SPDs Are Installed in EV Charging Sites
Typical SPD locations include:
– Main LV panels (incoming protection for the site)
– Sub-distribution boards (SDBs) serving charger clusters
– Street cabinets or feeder pillars supplying on-street chargers
– Outdoor charger islands with long feeder runs
– Communication entry points where relevant (Ethernet, antennas, RS-485) to protect network devices and LTE modems
Key Selection and Design Considerations
Important factors when specifying SPDs include:
– System voltage and earthing arrangement (TN, TT, IT)
– Maximum continuous operating voltage (Uc)
– Discharge current ratings and impulse capability
– Voltage protection level (Up) and coordination with downstream equipment
– Protection modes required (L–N, L–PE, N–PE)
– Short lead lengths and strong protective earth (PE) bonding for real performance
– Environmental and enclosure requirements (IP rating, temperature, mounting)
Common Pitfalls
– Installing SPDs with long connection leads, increasing voltage let-through
– Missing local SPDs near charger clusters on long cable runs
– Poor earthing or bonding that prevents effective surge diversion
– Ignoring surge risk on communication lines and external antennas
– Not replacing SPDs after end-of-life indication or major surge events
Benefits for Operators and Site Owners
– Higher charger uptime and fewer storm-related failures
– Reduced component replacement costs and fewer service visits
– Better reliability for metering, payment, and backend connectivity
– Improved customer experience and network reputation
Related Glossary Terms
Surge Protection Device (SPD)
Surge Protection
Surge Arrestor
Surge Immunity Test
Earthing / Grounding
Protective Earth (PE)
Equipotential Bonding
Main LV Panels
Sub-distribution Boards
Power Quality