Introduction

In today's technology-dependent world, electronic devices and electrical systems have become more sophisticated, yet increasingly sensitive to electrical disturbances. This reality raises an essential question: Is a surge protection device (SPD) truly necessary?

Many homeowners and facility managers underestimate the frequency and impact of voltage surges, assuming their equipment is safe behind standard circuit breakers or even lightning rods. Unfortunately, transient voltage spikes—triggered by lightning strikes, utility switching, or everyday events such as motors cycling—can silently degrade or catastrophically damage sensitive electronics.

A surge protective device, also known as a surge arrester or surge suppressor, plays a critical role in safeguarding electrical and electronic equipment by limiting excessive voltage and redirecting harmful energy safely to ground. While some people consider SPDs optional, the hidden consequences of unprotected surges can include significant downtime, data loss, and costly equipment replacements.

Whether you're protecting sophisticated industrial control systems, data centers with critical Ethernet connections, residential smart appliances, or coaxial and signal line communications infrastructure, surge protection is not merely beneficial—it’s necessary.

In this article, we'll thoroughly examine the necessity of SPDs and help you understand why surge protection is a critical investment for modern electrical systems.

What if i already have a lightning rod?

Lightning rods provide essential structural protection by safely directing lightning strikes to the ground, preventing catastrophic building damage or fire. However, having a lightning rod alone doesn't completely safeguard your electrical systems from voltage surges. When lightning strikes nearby—even without directly hitting your building—significant transient voltages can travel through power lines, communication cables, and other conductive pathways, entering your premises and damaging sensitive electronics and systems.

A lightning rod's primary role is structural: it doesn't address indirect surges that propagate through wiring and connected devices.

Figure 1 - Lightning rods aren't enough for comprehensive electrical protection

Even overvoltages as low as a few hundred volts—let alone multikilovolt lightning - induced spikes—can exceed the insulation ratings of today’s microelectronics. Modern standards such as NEC 2020 Article 242 and IEC 62305-4 stress a coordinated SPD approach: a robust Type 1 surge arrester at the service entrance, followed by cascaded Type 2 or Type 3 surge suppressors positioned closer to sensitive loads. Proper earthing, bonding, and periodic SPD maintenance are also necessary to keep protection levels within specification throughout the product’s lifespan. 

For comprehensive protection, you need surge protection devices strategically installed at key points within your electrical infrastructure. These SPDs intercept and divert the dangerous voltage spikes away from sensitive electronics such as industrial controllers, Ethernet equipment, coaxial cable-connected devices, and signal line communications.

Figure 2 - Lightning rod and cascaded SPDs protecting a building: lightning current path illustration

Installing SPDs alongside lightning rods is a necessary practice recommended by electrical safety standards and industry guidelines to ensure comprehensive protection against both direct lightning strikes and indirect voltage surges.

Do surge protection devices really work?

When properly selected, installed, and maintained, surge protection devices (SPDs) are highly effective at mitigating voltage transients. These devices function by detecting abnormal overvoltage events and safely diverting excess energy to ground before it reaches sensitive equipment. Whether you're dealing with surges from lightning-induced electromagnetic pulses, utility grid switching, or internal load fluctuations, a well-designed SPD system provides an essential layer of defense.

Most SPDs use metal oxide varistors (MOVs) as their core suppression element, which respond rapidly—often in nanoseconds—to clamp voltage levels and prevent damaging overvoltages. Advanced designs may also incorporate gas discharge tubes (GDTs) or spark gaps to handle higher surge currents or reduce follow-on energy.

Figure 3 - MOV based SPD schematic showing surge diversion to ground

Real-world tests and lab-certified standards (such as IEC 61643 and UL 1449) confirm that SPDs significantly reduce surge energy reaching downstream devices. Type 1 SPDs are designed to handle direct lightning currents at the service entrance. Type 2 surge protectors, installed at distribution panels, shield branch circuits and connected equipment. Type 3 SPDs are placed near individual devices like Ethernet switches, coaxial equipment, and industrial control panels to catch any residual surges.

Figure 4 - Cascaded surge protection device strategy concept illustration

While no SPD offers infinite protection, properly coordinated devices across all levels of your system can reduce surge impact by over 90%. In facilities where uptime, data integrity, or equipment longevity are critical, surge protection devices do more than “work”—they’re absolutely necessary.

Is investing in surge protection worth it?

Investing in a surge protection device (SPD) is not only worth it, but often essential to avoid catastrophic or cumulative losses. Many surges don’t come from dramatic lightning strikes but from routine utility switching, capacitor bank operations, elevator motors, or even HVAC systems cycling on and off. These small but frequent voltage spikes can gradually wear down insulation and sensitive components, reducing equipment lifespan without immediate visible failure.

Figure 5 - Electrical failure caused by transient overvoltages

When these events go unchecked, the costs add up. Replacing damaged industrial automation systems, coaxial surveillance DVRs, or Ethernet-connected servers can cost thousands—often far exceeding the one-time investment in properly rated Type 1, Type 2, or Type 3 surge protective devices. Surge suppressors with MOV or hybrid GDT technology act as silent guardians, protecting critical loads every day.

Additionally, hidden costs—such as production downtime, data corruption, warranty voidance, or even fire hazards—must be considered. In healthcare, telecom, and industrial facilities where reliability is non-negotiable, surge protection is a foundational part of the electrical safety design.

Table 1 - Surge Protection vs. Potential Losses

Even in residential settings, protecting solar inverters, smart TVs, routers, and home automation systems with affordable SPDs adds long-term value. SPDs installed at key entry points and along signal lines (e.g., Ethernet, coaxial, RS485) ensure multi-layered, effective surge suppression.

Whether you’re managing a data center, factory floor, or household with growing smart infrastructure, SPDs don’t just protect—they pay for themselves. Compared to the high cost of damage and operational disruption, surge protection is one of the smartest and most necessary investments you can make.

Is surge protection mandatory?

Surge protection devices (SPDs) are becoming increasingly mandatory across numerous electrical codes and regulatory standards worldwide. Regulatory authorities recognize surge protection as an essential measure to maintain electrical safety, equipment reliability, and operational continuity, particularly as reliance on sensitive electronics grows.

Figure 6 - Global SPD mandatory map

In the United States, the National Electrical Code (NEC 2020, Article 242) explicitly mandates SPDs at service entrances for specific facility types, including commercial, industrial, and certain residential applications. Facilities containing critical systems—such as hospitals, data centers, airports, and telecommunications infrastructure—are especially targeted, due to the high stakes associated with equipment damage or downtime.

International standards reinforce the same perspective. IEC standards like IEC 60364 and IEC 62305-4 outline detailed requirements for surge protection. These standards emphasize a coordinated, cascaded approach—installing Type 1 SPDs at the service entrance, Type 2 SPDs at sub-distribution panels, and Type 3 SPDs near sensitive end devices—to ensure comprehensive surge suppression. Many jurisdictions globally incorporate IEC guidelines into local building regulations, effectively mandating surge protection device installation.

Table 2 - Global SPD compliance overview by country and standard

Specific industries also impose strict SPD requirements. Telecom regulations typically mandate robust surge protection to preserve network stability and maintain emergency communications. Similarly, healthcare facilities, financial institutions, and critical manufacturing plants must comply with rigorous surge protection guidelines, often stipulated explicitly by insurers or safety auditors.

Even where regulations don't strictly mandate SPD installation, not implementing surge protection devices can carry significant financial risk. Insurance claims related to surge damage may be denied if facilities fail to follow recognized best practices or standards, making SPD compliance practically mandatory from a risk management standpoint.

Overall, the trend toward mandatory surge protection compliance is clear. Investing proactively in appropriate SPD solutions is now considered a necessary measure—not merely an option—to maintain safety, comply with regulations, and protect infrastructure investments.

Are SPDs the only method for surge protection?

Surge protection devices (SPDs) are essential but not the sole method available for mitigating transient voltage surges. While SPDs form the backbone of any robust surge protection strategy—effectively diverting damaging currents safely to ground—other complementary practices and techniques enhance overall system protection.

A lightning protection system before the implementation of equipotentail bonding, as illustrated in figure 7, provides a defined path for lightning current to safely discharge into the ground, thereby protecting the structure from physical damage. In this setup, the air terminal intercepts the lightning strike and channels the high-energy current toward the ground via a network of down conductors. The current is then directed through multiple grounding electrodes—marked as A, B, and C—which dissipate the energy into the surrounding earth. 

Figure 7 - lightning protection system without equipotential bonding

In addition to SPDs and lighning protection systems, equipotential bonding plays a crucial role in mitigating lightning-related surges. Without it, even a well-designed external lightning protection system can become a source of internal overvoltages.

When lightning current is injected at the air terminal and flows down the grounding conductors, potential differences can develop between separate grounded parts of the system. If not equalized through bonding, they may cause high voltages to appear across internal wiring, especially between protective earth and the electrical circuit neutral. As a result, current may arc through insulation or damage connected equipment, even if SPDs are present.

Figure 8 - Equipotential bonding implementation diagram

A typical pre-bonding scenario shows lightning current traveling to ground via multiple paths, but without a low-impedance bond at key junctions, hazardous voltage gradients can form. This underlines why equipotential bonding, along with proper grounding and SPD deployment, forms an inseparable part of comprehensive surge protection. SPDs alone are not enough—they must be coordinated with bonding and grounding to maintain the same reference potential and safely dissipate surge energy without causing dangerous internal voltage stress.

An effective way to achieve this coordination is illustrated clearly through the integration of an SPD with an equipotential earth bar. As shown in figure 9, the SPD directly connects to the incoming power supply, safely diverting surge currents into the grounding network.

The earth bar acts as a central bonding node, linking all critical conductive components such as lightning protection systems, metallic pipework, cable screens, and electronic equipment to a common ground reference.

Figure 9 - Integrated surge protection and equipotential bonding layout

Shielding methods also play a critical supporting role, particularly in telecommunications, data centers, and critical infrastructures. Shielded cables—such as shielded Ethernet or coaxial cables—can minimize induced surges and electromagnetic interference (EMI), enhancing the overall effectiveness of surge protection devices installed along those lines.

Figure 10 - Electromagnetic interference issue

However, shielding alone is insufficient for comprehensive protection, as it primarily reduces electromagnetic interference rather than fully addressing direct line surges or conducted transients.

Additionally, careful cable routing, separation of power and signal cables, and proper electrical panel layout can significantly reduce vulnerability to surges. Still, these measures complement rather than replace the essential protective function provided by SPDs.

In practice, comprehensive surge protection demands a layered approach combining SPD installations, grounding, bonding, shielding, and proper electrical design practices. Nonetheless, surge protection devices remain the most critical and necessary element of the system, effectively limiting surges to safe levels and protecting equipment against catastrophic damage.

Figure 11 - Complete lightning and surge protection system layout with air terminals, SPDs, proper grounding and equipotential bonding

Who needs surge protection and what type should you use?

Surge protection is increasingly necessary across residential, commercial, industrial, and critical infrastructure sectors, driven by growing dependence on sensitive electronics and interconnected systems.

Residential: Homes today contain valuable, surge-sensitive electronics—from smart appliances and LED lighting to home automation systems, computers, and televisions. For comprehensive residential protection, a Type 1 or Type 2 SPD at the service entrance panel is crucial, complemented by Type 3 SPDs at individual sensitive devices or outlets to ensure total protection.

Commercial Buildings: Offices, retail stores, and other commercial premises rely heavily on electronic equipment, such as computer servers, Ethernet network hardware, security systems, and HVAC controllers. A multi-layered protection strategy is essential here—starting with robust Type 1 or Type 2 SPDs at electrical entry points, and additional Type 3 protection near critical electronics or communication lines (Ethernet, coaxial cables).

Industrial Facilities: Industrial environments, including factories, plants, and warehouses, have equipment particularly vulnerable to surges, such as PLCs, motors, drives, and automated production systems. A coordinated protection approach using Type 1 SPDs at main distribution panels and Type 2 or Type 3 surge arresters directly installed near sensitive industrial equipment and control panels ensures maximum protection.

Critical Infrastructure: Hospitals, airports, data centers, telecom networks, and utilities cannot afford downtime or equipment damage. These facilities mandate the strictest surge protection, typically a multi-stage, cascaded SPD arrangement: Type 1 SPDs for incoming high-energy surges, Type 2 SPDs at key sub-distribution panels, and Type 3 SPDs protecting individual sensitive devices and data transmission lines (signal, Ethernet, coaxial).

In short, nearly every sector benefits from surge protection, but the type and arrangement of SPDs depend heavily on application specifics, equipment sensitivity, and risk exposure. Careful planning, including a coordinated approach with grounding and bonding systems, ensures that every installation receives exactly the protection required.

Example Application: Surge Protection in a Data Center

In a typical data center operating on a TN-S earthing system with a 400/230 V, 50 Hz three-phase power supply, surge protection must be multi-layered, coordinated, and compliant with IEC 61643 standards.

At the main power distribution board, where high-energy surges from lightning or utility switching may enter the facility, a Type 1＋2 SPD is required. For TN-S systems, the ideal configuration is a 3+1 SPD—three MOV paths from each phase (L1, L2, L3) to PE and one spark gap or GDT from N to PE. Thor’s TRS5-B+C is well-suited for this role, capable of safely discharging large surge currents while minimizing follow current risk between N and PE.

Further downstream, each sub-distribution panel should be fitted with a Type 2 SPD to suppress residual overvoltages. A 4-pole MOV-based SPD is appropriate here (L1, L2, L3, N), such as Thor’s TRS4-C40-4P, offering fast response and effective energy clamping for branch circuits.

TRS5-B+C 275v surge protective device	AC Type 2 TRS4-C40 surge suppressor

Close to sensitive end equipment like servers, switches, and UPS units, Type 3 SPDs provide localized protection. Devices such as Thor’s TRS3-2PTRSS series are installed in socket boxes or PDUs, offering low let-through voltage and high-speed response to protect delicate electronics.

Type 3 AC surge protection device TRSS series	TRSS-RJ45-8 Aluminum signal surge protector

In addition to power line protection, signal and data interfaces must also be protected. Use Thor’s TRSS-RJ45-5KA for RJ45 Ethernet lines, TRSS-485 surge arresters for signal controllers, and TNC type coaxial surge protective device for communication equipments.

TRSS-485 18mm Din Rail Signal Control Surge Protector	TNC type coaxial surge protective device

Final thoughts

In today’s surge-prone, electronics-driven world, relying on luck or basic circuit protection is no longer sufficient. Whether you're safeguarding a home, business, or critical infrastructure, a surge protection device is not a luxury—it’s a necessary component of electrical reliability. SPDs, when properly selected, installed, and coordinated with grounding, bonding, and shielding, offer a proven defense against costly damage and operational disruption.

While lightning rods protect structures, only SPDs protect what's inside—your systems, your data, and your uptime. With the increasing sensitivity and value of modern electronics, investing in a complete surge protection strategy is both practical and essential.

If you're unsure what type of SPD fits your application, consult a qualified professional—or reach out to our team for expert guidance backed by nearly two decades of SPD innovation.