Understanding the Types of Surge Protection Devices (SPDs) and Their Differences

In any modern electrical network, one of the biggest threats to the longevity and reliability of your lighting system is overvoltage (transient or sustained). This can occur due to lightning strikes, power grid disturbances, malfunctioning regulators, electrostatic discharge, or even electromagnetic pulses. For businesses operating in sensitive or hazardous environments, such risks can lead to costly downtime, equipment damage, and even catastrophic outcomes.

This is where Surge Protection Devices (SPDs) become crucial. These devices are designed to detect, absorb, and safely divert sudden electrical surges before they reach your sensitive lighting components, such as explosion-proof LED lights, junction boxes, and other critical systems. But not all SPDs function the same way, and understanding their differences can help you make more informed purchasing and installation decisions. Join our experts as they break down the importance of SPDs and how to select the best in the market.

Why SPD Matters in Lighting Systems

The lifespan of lighting equipment — especially those used in hazardous area lighting — is directly affected by how well it’s protected against power surges. Even small, frequent surges can degrade the internal electronics of your fixtures over time.

At Lumenex Asia, we understand the critical role SPDs play, particularly in IECEx and ATEX-compliant explosion-proof enclosures, Ex-proof lighting fixtures, and electrical circuits. That’s why we integrate robust surge protection: 10kV for our general lighting range to 20kV for our explosion-proof range, to safeguard our solutions and help clients minimise maintenance costs.

Explore our explosion-proof enclosures and junction boxes for your hazardous zone needs.

Two Main Types of SPDs: Parallel vs Series

Surge protection devices are generally categorised based on how they’re connected to the circuit. The two common types are parallel-connected SPDs and series-connected SPDs. Both have distinct features, advantages, and drawbacks, and the right choice depends on your application and system design.

1. Parallel-Connected SPDs

This is the most widely used configuration in commercial and industrial lighting systems. In a parallel setup, the SPD is connected across the line and neutral (or ground). It remains dormant during normal operation and only activates when a surge is detected.

One common concern many customers have is whether the surge might reach the power supply before the SPD activates. Fortunately, SPD circuits — especially when installed externally or built into the fixtures — offer a lower resistance path for the surge. That means they act first, absorbing the excess energy before it damages sensitive components like explosion-proof junction boxes or lighting drivers.

Another significant advantage of this system is that if the SPD fails in a parallel connection, the lighting fixture will still continue to operate, although it’s no longer protected. This feature ensures uninterrupted operation, especially in ex-proof lighting fixtures deployed in critical areas.

At Lumenex Asia, our explosion-proof LED fixtures are designed with this feature in mind. We use 20kV SPDs in hazardous environments and 10kV SPDs for standard applications, striking a balance between durability and cost-efficiency.

2. Series-Connected SPDs

Conversely, series SPDs align themselves directly with the power flow. This means any surge must pass through the SPD before it can reach your fixture. While this type offers effective protection, the trade-off is that if the SPD fails, it breaks the circuit,causing the lamp to go off.

Interestingly, some customers prefer this system due to its built-in diagnostic feature. If the light stops working, it’s a strong indicator that the SPD has absorbed a surge and needs replacing.

This can be especially useful in systems where continuous protection is non-negotiable, such as those involving hazardous area lighting or explosion-proof LED lights used in mission-critical operations.

Design Considerations for Optimal SPD Performance

Regardless of configuration, SPD performance is heavily influenced by its internal design, location, and wiring layout. Factors such as impedance control, grounding, and wire routing play key roles in how quickly and efficiently an SPD responds to a surge.

For example, choosing the right SPD circuit for your junction box layout ensures faster response and better coordination with other protective components.

If you're unsure which type of SPD best suits your hazard zone safety requirements, our team at Lumenex Asia is here to help. We'll walk you through the process, ensuring maximum protection for your general lighting or ex-proof lighting fixtures.

The Hidden Truth About SPD Lifespan

Here’s something many overlook: all SPDs degrade over time. Each overvoltage incident — even minor ones — slowly reduces the device’s protective capacity. While many SPDs include indicator lights to show if they’re functioning, these indicators don’t always reflect the true condition of the internal components.

That’s why we strongly recommend installing external SPDs in your distribution box — especially for hazardous environments or mission-critical applications. This small addition provides an extra line of defence and helps extend the lifespan of both your lighting systems and internal SPDs.

Choose the Right SPD Circuit for Your Needs with Lumenex Asia

In summary, selecting the right surge protection device (SPD) — and understanding how it works  is essential for businesses that depend on reliable lighting. Whether you choose a parallel-connected SPD for uninterrupted performance or a series-connected SPD for visible failure alerts, consistent maintenance and timely upgrades are crucial.

At Lumenex Asia, with our team of experts who have 15 years of experience in the lighting industry, all our solutions — from explosion-proof junction boxes to ex-proof lighting fixtures — are engineered with safety, longevity, and performance in mind. Our lighting systems come equipped with 10kV and 20kV SPDs, tailored to fit both general lighting and hazardous area lighting applications.

When it comes to lighting reliability, protection isn’t optional — it’s essential. Contact our experts for comprehensive explosion-proof lighting solutions today!

Key Takeaways

• Surge Protection Devices (SPDs) safeguard sensitive lighting systems, including explosion-proof LED lights and junction boxes, from voltage surges caused by lightning, grid disturbances, or electrostatic discharges.

• Two main SPD types—parallel and series—offer distinct advantages: parallel SPDs ensure uninterrupted operation of hazardous area lighting, while series SPDs provide diagnostic alerts when protection is compromised.

• Proper SPD design, installation, and maintenance are crucial for optimal performance, especially in explosion-proof junction boxes and mission-critical environments.

• LumeAsia integrates 10 kV and 20 kV SPDs into its lighting solutions to enhance durability and protection for both standard and hazardous area lighting applications.

Frequently Asked Questions (FAQs)

What is a junction box, and why is it important in lighting systems?

A junction box houses electrical connections safely, protecting wiring and components in both standard and hazardous area lighting setups.

What makes an explosion-proof junction box different?

An explosion-proof junction box is designed to contain sparks or heat from electrical faults, preventing ignition in hazardous environments.

Why do explosion-proof LED lights need surge protection?

Explosion-proof LED lights are sensitive to voltage spikes, and SPDs prevent damage that could compromise safety and operational reliability.

What types of surge protection are best for hazardous area lighting?

Both parallel and series SPDs can be used, but the choice depends on whether uninterrupted operation or diagnostic alerts are more critical for your hazardous area lighting.

How do I maintain my explosion-proof junction box and lighting system?

Regular inspection of SPDs and wiring ensures that explosion-proof junction boxes and LED fixtures remain fully protected against electrical surges.

Where can I get reliable surge-protected hazardous area lighting solutions?

We at LumeAsia provide explosion-proof LED lights and junction boxes with integrated SPDs designed for maximum safety and durability.