What is a Surge Protection Device (SPD)?
Definition
A surge protection device (SPD) is an electrical safety component that protects equipment from sudden voltage surges or spikes. In EV charging, SPDs prevent damage to chargers, vehicles, and connected systems caused by lightning strikes, switching operations, or grid disturbances.
Why SPDs Matter
EV chargers are sensitive electronic systems that can be damaged by even short-lived voltage surges. Without SPDs, operators risk equipment failure, downtime, and costly repairs. For residential installations, SPDs ensure compliance with safety standards and give users confidence in charger reliability.
How it Works
An SPD is installed in parallel with the circuit, diverting excess voltage away from equipment and safely discharging it to earth. When normal voltage resumes, the SPD resets to standby. Different SPD types (Type 1, 2, or 3) are used depending on installation size and risk level.
Key Technologies / Features
SPDs use components such as varistors or spark gaps to absorb transient energy. Modern devices include thermal disconnects, monitoring indicators, and integration with earthing and bonding systems. Standards require SPDs in all new electrical circuits where EVSE is installed.
Applications
- Residential EVSE installations for household safety.
- Public charging stations exposed to lightning and grid surges.
- Commercial fleet depots with large-scale EV infrastructure.
- Solar-powered EVSE systems with additional surge risk.
Benefits
SPDs prevent costly equipment damage, ensure continuous operation, and protect users from electrical hazards. They also ensure compliance with modern electrical regulations, avoiding legal or insurance issues.
Use Cases
A public charging hub may install multiple SPDs to protect both AC input and DC output lines. Residential wallboxes now typically include SPD integration as standard. Solar carports use SPDs to mitigate risk from lightning-induced surges.