Surge protection devices (SPDs) protect electrical installations and connected equipment (including EV chargers) from transient overvoltages caused by lightning and switching events. The Type 1 / Type 2 / Type 3 classification describes the SPD’s intended installation point and the surge current waveform it is designed to handle.
In EV charging infrastructure, correct SPD selection and coordination helps protect sensitive electronics, reduces unexpected downtime, and improves long-term reliability in outdoor and public environments.
Why SPD Types Matter in EV Charging
EV chargers contain power electronics and communication modules that can be damaged by surges even when they are brief and rare. Correct SPD type selection helps:
– Reduce failures from lightning-induced surges and switching transients
– Improve charger uptime and reduce service callouts
– Protect backend connectivity modules (Ethernet/LTE), metering, and control boards
– Support compliance expectations for electrical safety and resilience
– Reduce “mystery faults” after storms or grid disturbances
Type 1 SPD
A Type 1 SPD is designed for high-energy surges associated with direct lightning currents or lightning current entering the building via overhead lines or a lightning protection system (LPS). It is typically installed at the origin of the installation (main incoming supply / main distribution board).
– Primary role is to handle very high surge energy
– Commonly used where there is external lightning protection or higher lightning exposure
– Usually installed upstream, before or at the main LV distribution point
– Often coordinated with Type 2 devices downstream for better equipment-level protection
Type 2 SPD
A Type 2 SPD is the most common SPD type for general distribution. It is designed for surges from indirect lightning and switching events and is typically installed in distribution boards feeding loads such as EV chargers (main LV panels or sub-distribution boards (SDBs)).
– Primary role is to protect the electrical installation and connected equipment from induced/switching surges
– Commonly used for car parks, depots, workplaces, and commercial sites with EV chargers
– Often installed at distribution boards supplying multiple chargers
– Usually the “baseline” SPD requirement in many EV charging deployments
Type 3 SPD
A Type 3 SPD is installed close to sensitive equipment and is designed for lower-energy surges after upstream protection has already reduced surge levels. Type 3 devices are typically placed at the point of use, for example in a local outlet, cabinet, or directly near sensitive electronics.
– Primary role is “fine protection” for sensitive devices
– Common in control panels, communication equipment, and sensitive subcircuits
– Used to protect electronics after Type 1/Type 2 devices clamp the larger surges
– Should not be used as the only SPD in a building exposed to significant surge risk
How the SPD Types Work Together
In many sites, SPDs are applied in a coordinated “cascade”:
– Type 1 at the main incoming supply (where lightning current risk is credible)
– Type 2 in distribution boards feeding charger groups
– Type 3 near sensitive electronics or critical devices where extra protection is needed
Coordination reduces stress on downstream devices and improves overall protection effectiveness.
Key Selection Factors for EV Charging Installations
When specifying Type 1/2/3 SPDs for EV charging, designers typically consider:
– Site exposure and lightning risk (rural/isolated sites, overhead lines, tall structures)
– Presence of a lightning protection system (LPS)
– Earthing arrangement (TN / TT / IT earthing systems) and bonding quality
– Short-circuit withstand and protective coordination with upstream breakers/fuses
– Required protection level (Up) to match equipment insulation and sensitivity
– Surge current ratings (for example lightning impulse capability for Type 1, high discharge capability for Type 2)
– Cable lengths and routing between boards and chargers (long runs increase surge vulnerability)
– Protection for data/communications lines (Ethernet/RS485/LTE antennas often need separate surge protection)
Common Pitfalls
– Installing only Type 3 protection and assuming it protects against major surges
– Incorrect coordination between SPD and upstream protection (nuisance tripping or failure to disconnect safely)
– Poor earthing/bonding, which reduces SPD effectiveness and can increase touch voltage risks
– Leaving communications and control lines unprotected while protecting only the power feed
– Placing SPDs too far from the protected equipment without considering cable-induced overvoltage
Best Practices
– Use a layered approach: Type 1 (if required) + Type 2 as baseline + Type 3 for sensitive equipment where justified
– Install Type 2 SPDs in charger feeder boards/SDBs to protect groups of chargers
– Ensure correct earthing, bonding, and low-impedance connections for SPD performance
– Include surge protection for communication lines where long runs or exposed routing exists
– Validate protection coordination (breaker/fuse selection, short-circuit rating) and document it for commissioning
– Monitor for SPD end-of-life indicators and include replacement in maintenance plans
Related Glossary Terms
Surge Protection
Surge Protection Device (SPD)
Surge Arrestor
Surge Immunity Test
Lightning Protection
Power Quality
TN / TT / IT Earthing Systems
Touch Voltage
Sub-distribution Board (SDB)
Charger Uptime