When lightning strikes, the consequences can be catastrophic, especially for sensitive electronic systems and industrial equipment. Surge protectors are often marketed as a first line of defence against transient overvoltages. But can surge protectors really handle lightning strikes? Let’s dive into how surge protectors are tested, what their true capabilities are, and where their limitations lie.
Understanding Lightning-Induced Surges
Lightning doesn’t need to strike your building directly to cause damage. A strike even a kilometre away can induce powerful electromagnetic fields, leading to voltage spikes on power lines, communication cables, and data networks. These spikes, known as transient overvoltages, can exceed several thousand volts in microseconds.
Common consequences include:
- Damage to computers, PLCs, and industrial sensors
- Insulation failure in wiring
- Fire hazards in extreme cases
This is where Surge Protection Devices (SPDs) step in, but the level of protection they offer depends on several factors.
How Surge Protectors Work
Surge protectors are designed to divert excess voltage away from sensitive circuits, typically to earth ground. They usually rely on components like:
- Metal Oxide Varistors (MOVs): Change resistance rapidly under high voltage
- Gas Discharge Tubes (GDTs): Break down under extreme voltage and divert the surge
- Transient Voltage Suppression (TVS) Diodes: Clamp the voltage within safe limits
The key metric here is the clamping voltage, the voltage level at which the SPD begins to divert the surge.
SPD Types by Application:
|
Type |
Purpose |
Lightning Capability |
|
Type 1 SPD |
Installed at main panel; handles direct lightning currents |
Yes – tested with 10/350µs waveforms |
|
Type 2 SPD |
Installed at sub-panels; handles indirect surges |
Limited |
|
Type 3 SPD |
Point-of-use (e.g., power boards) |
No – only for small transients |
Can They Withstand Direct Lightning Strikes?
Short answer: Only high-capacity, Type 1 SPDs offer any meaningful protection against direct lightning strikes, and even then, only as part of a properly grounded and layered protection system.
Even then, they are not designed to absorb the full energy of a direct strike, which can exceed 200,000 amps. Instead, they act to divert the current safely to ground, provided that:
- The grounding system is properly designed and maintained
- The surge protector is correctly sized and installed
- There’s coordination between SPDs across the facility
Consumer-grade surge protectors or power strips are not built to withstand this. These are only suitable for low-energy surges like those caused by switching operations or nearby equipment.
Testing Surge Protectors Against Lightning – Surge Protector Ratings and Standards
Surge protectors are tested and rated according to standards such as:
- IEC 61643-11: Standard for low-voltage SPDs
- AS/NZS 1768:2021: Australian standard for lightning protection
These standards specify test waveforms, 8/20 µs for typical surge conditions and 10/350 µs for simulating direct lightning currents, to evaluate SPD performance.
- 8/20µs waveform: Represents surges caused by switching or indirect lightning, used for testing Type 2 SPDs
- 10/350µs waveform: Mimics the energy of a direct lightning strike and is used for testing Type 1 SPDs
Type 1 SPDs are tested with 10/350µs impulses at test currents ranging from 25kA to 100kA, depending on the application. These tests determine:
- Let-through voltage (residual voltage)
- Response time
- Thermal protection performance
It’s important to note that real lightning events are more complex than standard waveforms can simulate, involving multiple pulses, long durations, and side flashes. Therefore, while testing provides a benchmark, they do not replicate the full force of a direct lightning strike and real-world performance can vary.
Limitations of Surge Protectors
Surge protectors are essential, but they are not invincible. Some limitations include:
1. Limited Energy Capacity
Each SPD has a maximum surge current it can safely divert, often between 500 to 3000 joules. Once exceeded, it can fail catastrophically. A lightning strike can exceed 1 billion joules, far beyond what any consumer-grade SPD can handle.
2. Degradation Over Time
MOV-based surge protectors degrade with every surge. After repeated events, their protection level decreases, sometimes without visual indication.
3. Dependence on Earthing System
Even a high-quality SPD cannot perform if the earthing impedance is too high. Poor grounding leads to dangerous rise in potential and possible equipment failure.
4. No Protection Against Direct Hits to Equipment
If lightning strikes a building or equipment directly, the surge path bypasses the SPD entirely. That’s why additional lightning protection (e.g., lightning rods, shielding) is required for critical infrastructure.
Best Practices for Lightning Protection
To effectively protect against lightning-induced surges:
- Use a multi-stage surge protection system:
– Type 1 at main panel
– Type 2 at distribution boards
– Type 3 at sensitive equipment - Inspect and maintain grounding regularly
- Install lightning arrestors where needed — these are different from surge protectors and designed to intercept direct strikes
- Isolate vulnerable lines (e.g., using fibre optics instead of copper where possible)
- Replace surge protectors periodically or after known surge events
Surge protectors play a critical role in shielding electrical systems from transient overvoltages, but their ability to handle lightning strikes depends entirely on type, quality, installation, and grounding. They are a crucial line of defence against voltage spikes, including those caused by indirect lightning strikes. However, they are not designed to withstand direct lightning hit. Understanding the limitations of surge protectors and implementing a multi-layered protection strategy is key to safeguarding your equipment and infrastructure.
- Type 1 SPDs offer limited protection against lightning currents, but only when properly integrated into a comprehensive system
- Consumer-grade power boards provide no real lightning protection
- Lightning protection systems and surge protectors must work together
If your facility is in a lightning-prone area, consult with an electrical protection specialist to design a robust surge and lightning protection plan.
At Transtech, we specialize in surge protection devices, offering solutions such as RJ45 surge protectors, RS485 surge protectors, RS485 lightning protection, lightning and surge protectors, and electrical surge protector devices. Our products ensure uninterrupted system operation and long-term reliability, even in harsh environments.
Need help selecting the right surge protection for industrial or high-risk applications?
Contact Transtech to speak with our team to ensure your systems are ready for anything nature throws at them.