How to Choose AC or DC Surge Protection Devices?

Modern electrical and electronic systems increasingly rely on surge protection devices (SPDs) to safeguard against damaging voltage transients. Whether you’re managing a complex AC power distribution network or a DC photovoltaic (PV) installation, understanding how to choose and apply the right SPD is essential to maintain system reliability, extend equipment life, and minimize costly downtime.

What is The Key Difference between AC and DC Surge Protective Devices？

When comparing AC SPDs and DC SPDs, the first distinction lies in the nature of the current they protect. AC SPDs are crafted for alternating-current environments where the voltage swings positive and negative 50 or 60 times per second; these devices employ bidirectional metal-oxide varistors (MOVs) or gas discharge tubes (GDTs) to clamp both halves of the waveform. In contrast, DC Surge Protection Devices must endure a constant, unidirectional voltage, demanding MOVs rated for higher continuous DC voltages—often up to 1500 V DC in large solar arrays or battery energy storage systems. This difference in waveform behavior also impacts impedance: AC networks include frequency-dependent inductance and capacitance, while DC circuits are largely resistive. Without natural zero-crossing points to help extinguish arcs, DC SPDs incorporate advanced thermal disconnectors and upgraded arc-interruption mechanisms to safely clear high discharge currents. As a result of these unique requirements—continuous voltage handling, robust arc suppression, and higher MOV ratings—DC SPDs tend to carry a premium over their AC counterparts.

Types of Surge Protection Devices by Application

Hybrid Type 1+2 SPDs combine high-energy and overvoltage protection in a single, space-saving module, ideal for large rooftop or utility-scale solar farms. BESS SPDs, rated up to 1500 V DC, defend containerized battery systems and UPS installations, while telecom DC SPDs secure 85 V or 300 V busbars in base stations.

How to Choose the Right Surge Protection Devices？

Selecting the proper SPD begins with identifying your power system type—AC or DC—and its grounding configuration (TN, TT, or IT). For AC networks, ensure your SPD’s Uc (maximum continuous operating voltage) matches the grid voltage (typically 120–480 V AC) so it clamps surges without nuisance trips. In DC systems—from 600 V to 1500 V DC—your SPD’s Uc must sit just above the operating voltage to react swiftly to transients. Next, choose your SPD class: Type 1 for service-entrance lightning protection, Type 2 for distribution board defense, and Type 3 for point-of-use equipment. For solar PV arrays, combine Type 1+2 and Type 2 SPDs to cover both direct lightning and switching surges. Finally, assess the required surge capacity (In, Imax, Iimp) and form factor—DIN-rail modules for panels or plug-in cartridges for easy maintenance, while verifying environmental ratings (IP20, –40 °C to +80 °C, humidity resistance).

Surge Protection Devices: Applications and Benefits

From the home to the factory floor, SPDs play a critical role in power Surge Protection Devices. In residential settings, layered SPDs protect everything from HVAC units and smart appliances to rooftop solar inverters. Commercial and industrial facilities use SPDs to secure building management systems, lighting controls, machinery, and EV charging stations. In the renewable energy sector, PV SPDs prevent costly inverter and module failures, while BESS SPDs ensure uninterrupted backup power by safeguarding battery inverters and UPS systems. Across all applications, proper SPD selection reduces equipment failures, slashes maintenance costs, and maximizes uptime—delivering a strong return on investment and peace of mind.

FAQ

Q: Can I use an AC surge protector in a DC system?
No. AC SPDs depend on waveform zero-crossings for arc suppression and are optimized for bidirectional voltage. DC Surge Protection Devices are specifically designed for constant, unidirectional voltage and incorporate unique clamping and disconnection features.

Q: How many SPDs do I need per distribution board?
A typical setup uses one Type 1 SPD at the service entrance and one Type 2 SPD in each downstream subpanel. For critical or high-risk systems, add Type 3 SPDs at sensitive equipment points.

Q: What surge protection strategy is best for solar PV?
Implement Type 1+2 hybrid SPDs at combiner boxes, Type 2 SPDs at inverter DC inputs, and Type 3 SPDs for monitoring and control electronics to achieve full-spectrum PV surge defense.

Conclusion

Whether you’re managing a complex industrial power distribution network or deploying a large-scale solar farm, selecting the right surge protection device (SPD) is critical to safeguarding your investment and ensuring continuous operation. By understanding the key differences between AC SPDs and DC SPDs, matching voltage ratings, and choosing the appropriate SPD type (Type 1, Type 2, or Type 3), you can build a layered defense strategy that addresses everything from direct lightning strikes to residual switching transients. With the proper SPD in place—be it a DIN-rail PV SPD in your combiner box, a Type 1+2 hybrid SPD at the service entrance, or point-of-use protection for sensitive electronics—you’ll minimize downtime, reduce equipment failures, and extend the lifespan of your electrical and renewable energy assets.
Contact our technical team to specify the ideal SPD for your AC or DC application, or browse our full catalog of certified surge protection solutions.

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