Surge Protective Device for EV Charging Stations
Electric vehicles (EVs) are revolutionizing the way we move, offering a clear path toward a more sustainable future. Yet, as adoption scales and charging infrastructure expands to meet demand, a significant technical challenge emerges: protecting these high-tech hubs from the elements. Specifically, EV charging stations are highly vulnerable to lightning strikes, making robust surge protection a critical necessity for the reliability of the grid.
Lightning surge, switching overvoltage, and grid instability can destroy:
Power modules
DC output stages
Communication boards
Control circuits
Insulation systems
For EV charger manufactures and project integrators, incorporating compliant SPD designs is essential for ensuring long-term equipment reliability.
1. What Is Transient Overvoltage in EV Charging Systems?
Overvoltage refers to abnormal voltage increases that threaten insulation and electronic components.
According to IEC 62305, lightning-induced surges can be categorized as:
Direct lightning strike (10/350μs waveform)
Induced lightning (8/20μs waveform)
Switching surge
Ground potential rise
Typical surge current values per conductor:
| Scenario | Waveform | Expected Surge |
|---|---|---|
| Direct lightning | 10/350μs | up to 25 kA |
| Induced lightning | 8/20μs | 5–10 kA |
For high-power DC chargers, surge levels can be even higher depending on installation environment.
2. DC Charger Requirements – IEC 61851-23:2023
The latest IEC 61851-23 defines surge protection requirements for DC chargers.
Key requirements:
SPD required between ± and PE
Switching-type SPD recommended
USDC ≥ 1200V
Voltage protection level Up ≤ 2500V
Proper installation at AC input and DC output side
This is especially critical for:
120kW–480kW fast chargers
800V architecture
Transformer-direct supply systems
3. New Global DC SPD Standard – IEC 61643-41:2025
The newest standard for low-voltage DC SPD is IEC 61643-41. It applies to DC systems up to 1500V and introduces three major safety tests:
1) Short-Circuit Current Test
Ensures SPD will not:
Catch fire
Carbonize
Explode
Open enclosure
Even under declared short-circuit current.
2) DC Overload Test
Test verifies SPD behavior under sustained overcurrent conditions and evaluates failure mode safety.
3) DC TOV (Temporary Overvoltage) Test
SPD must survive temporary overvoltage conditions without causing fire risk.
This is especially important in:
Ungrounded DC systems
Floating DC networks
High-voltage battery systems
4. Surge Protection Selection Guide for EV Chargers
The following surge protection selection guide is developed based on the requirements of IEC 61851, IEC 61851-23, IEC 61643-11 and IEC 61643-41, combined with typical EV charger engineering practices. Actual SPD configuration shall be determined according to system voltage, grounding method, installation environment and project-specific requirements.
1) AC Charging Stations (7–22 kW)
Applicable standards:
- IEC 61851
- UL 2594
- UL 2231
Typical surge protection configuration:
- MOV (Metal Oxide Varistor)
- GDT (Gas Discharge Tube)
- Thermal fuse or current fuse
- Class II SPD (Type 2)
Typical applications:
- Residential wall-mounted chargers
- Commercial AC charging stations
- On-board chargers (OBC)
2) DC Fast Charging Stations (30–480 kW)
Applicable standards:
- IEC 61851-23
- IEC 61643-11
- IEC 61643-41
Typical surge protection configuration:
AC input side:
- Type 2 SPD
- Nominal discharge current In ≥ 20 kA
DC output side:
- DC SPD compliant with IEC 61643-41
- Coordinated low-voltage fuse
Typical applications:
- Public DC fast chargers
- Commercial fleet charging
- 800 V DC charging platforms
3) Ultra-Fast Charging Systems (>600 kW)
Applicable standards:
- IEC 62305
- IEC 61851-23
- IEC 61643-11 / IEC 61643-41
Typical surge protection configuration:
- Type 1 or Type 1+2 SPD
- Nominal discharge current In ≥ 20 kA
- Lightning impulse current Iimp ≥ 5 kA
Typical applications:
- Transformer-direct supply systems
- Highway ultra-fast charging hubs
- Megawatt-level DC charging infrastructure
Engineering Note
Surge protection devices must be coordinated with upstream protection, grounding system design and insulation coordination. The final SPD selection shall always be verified through system-level risk assessment and applicable conformity evaluation.
5. Conclusion
As EV charging power levels continue to rise, surge protection must evolve accordingly.
Compliance with:
IEC 61851-23
IEC 61643-41:2025
IEC 62305
is no longer optional for serious EV charger manufacturers.
Designing surge protection correctly means:
Safer products
Faster certification
Lower failure rate
Stronger global competitiveness
Need Technical Support?
BESSUN’s engineering team can support customized surge protection(Surge Protective Device) integration.
Feel free to reach out to us at info@bes-sun.com to discuss your project.