Electricity functions as the essential life force which sustains both our residential and commercial operations and industrial operations in our modern interconnected world. This essential power supply, however, remains at risk from imperceptible power surges, which scientists call transient overvoltages. These electrical potential spikes – sudden increases in voltage – that originate from nearby lightning strikes or heavy load changes in our facilities create destructive effects on modern electronic equipment. While the dramatic display of lightning attracts our attention, everyday power surges and transients remain a continuous threat to the electrical system. The defense against these threats needs a coordinated surge protection strategy, where the Type 2 Surge Protective Device (SPD) stands as a fundamental component. The knowledge of how these types of SPD operate and their advantages has become mandatory for ensuring electrical safety and resilience.
Electricity functions as the essential life force which sustains both our residential and commercial operations and industrial operations in our modern interconnected world. This essential power supply, however, remains at risk from imperceptible power surges, which scientists call transient overvoltages. These electrical potential spikes – sudden increases in voltage – that originate from nearby lightning strikes or heavy load changes in our facilities create destructive effects on modern electronic equipment. While the dramatic display of lightning attracts our attention, everyday power surges and transients remain a continuous threat to the electrical system. The defense against these threats needs a coordinated surge protection strategy, where the Type 2 Surge Protective Device (SPD) stands as a fundamental component in compliance with BS standards. The knowledge of how these types of SPD operate and their advantages has become mandatory for ensuring electrical safety and resilience.
What Exactly is a Type 2 Surge Protective Device (SPD)?
According to international standard IEC 61643-11 and North American standardUL 1449, the overall surge protection system defines Type 2 Surge Protective Devices (SPDs) as essential components in a layered electrical protection strategy. Type 2 SPDs are designed for installation on the load side, meaning downstream of the main service entrance overcurrent protective device, serving specific applications across a facility’s power distribution network. These devices are typically located in main distribution boards (MDBs) and sub-distribution boards (SDBs) to safeguard the building’s electrical system.
- Type 2 SPDs work in conjunction with Type 1 SPDs to protect the electrical system from external high-energy surges, such as those caused by direct lightning strikes or nearby lightning rods. While Type 1 SPDs installed at the service entrance perform initial surge suppression for the majority of external surge energy, they may not eliminate all transient overvoltages. Type 2 SPDs act as a secondary layer of protection, functioning as a vital protective device to attenuate any residual surges before they can reach and damage sensitive downstream equipment, including common household appliances.
- In addition to external threats, many damaging power surges originate within the facility itself. Operations involving large motor startups, HVAC cycling, welding equipment, or even faulty wiring can generate significant voltage spikes. Installing Type 2 SPDs at distribution panels provides effective surge suppression, helping to clamp these localized transients at their source, protecting connected circuits and equipment from internal disturbances.
A Type 2 SPD serves as a dedicated surge protection device against overvoltages characterized by an 8/20µs current waveform, which represents typical indirect lightning effects and switching surges. Most Type 2 SPDs utilize Metal Oxide Varistors (MOVs) as their core protective elements. These MOVs are carefully selected and configured to absorb and limit transient overvoltages, enhancing the safety and resilience of the building wiring systems and connected equipment.
How Does Type 2 SPD Work to Protect Against Surges?
The operation of Type 2 Surge Protective Devices (SPD) is simple and relies mostly on the non-linear characteristics of Metal Oxide Varistors (MOV). An MOV is a semiconductor, which switches a circuit on or off depending on voltage levels.
| Step | Description |
| 1. Standard Operation | As long as the system is operating at standard level voltages, the resistance of the MOV is extremely high. During these periods, the protective device operates as a non-entity, allowing standard AC power signals to reach the connected loads without interruption and consuming very little power while allowing the system to continue functioning. |
| 2. Surge Event Trigger | A surge event occurs when an overwhelming transient overvoltage – a sudden voltage spike – exceeds the device’s clamping voltage. The MOV effectively causes its impedance to drop dramatically during this time, resulting in a very low value. |
| 3. Surge Suppression Response | In response to a surge event, the device’s low impedance creates the lowest resistance path possible, connecting from the surge location on the conductors to the ground system or neutral point. In this state, the Type 2 SPD acts like a fast-acting pressure relief valve, providing effective surge suppression by creating a low impedance path to divert dangerous surge currents to the grounding system where they are harmlessly dissipated. |
| 4. Return to Normal Operation | Once the transient voltage returns to the normal operational level (below the MOV’s threshold), the MOV instantly reverts to its high-impedance state, effectively ceasing the diversion and allowing the system to operate normally. |
Hardware like microprocessors, control systems, and other sensitive electronics connected to the panel are protected from power surges by this protective mechanism. An entire surge protection sequence is completed within billionths of a second, so harmful transients do not reach critical distances. A swift response time and the ability to absorb huge surge currents during short time periods help maintain a secure voltage level, also referred to as the Voltage Protection Level (Up).
Type 2 SPD vs. Type 1 and Type 3: Knowing the Differences
Understanding the distinct roles and types of SPD – specifically Type 1, Type 2, and Type 3SPDs – is crucial for implementing a comprehensive and effective surge protection strategy. They are not interchangeable; rather, they work together in a coordinated electrical system.
| Feature | Type 1 SPD | Type 2 SPD | Type 3 SPD |
| Location | Service entrance (before main breaker, line side); may be integrated in switchgear | After main breaker (load side); typically at main/sub-distribution panels | Point of use; close to sensitive equipment (e.g., power strips, appliances) |
| Primary Function | Protects against high-energy external surges (e.g., lightning strikes) | Protects against residual and internal surges (e.g., machinery, switching events) | Final protection for sensitive devices; filters noise and clamps small surges |
| Test Waveform | 10/350µs impulse current (Iimp) | 8/20µs nominal discharge current (In) | Combination waveform: 1.2/50µs voltage & 8/20µs current |
| Key Feature | High robustness and surge current capability | Central protection for multiple circuits; critical for internal transient management | Lowest clamping voltage (Up); individual device protection |
| Voltage Protection Level (Up) | Higher (due to high-energy focus) | Medium | Lowest |
| Installation Note | Must handle large surge energy | Must be coordinated with Type 1 and Type 3 for layered protection | Must be within 10 meters (30 ft) of upstream Type 2 SPD for effectiveness |
Following the comparison, it is evident that everySPD classification has a very specific and irreplaceable responsibility in a multi layer protective framework. Type 1 deals with very high external surges, Type 2 provides subsystem protection for internal and external events, and Type 3 protects the most sensitive endpoints. This hierarchical arrangement points out that one protective device cannot achieve total defense by itself. Proper surge defense necessitates cooperation. In this case, the location of the device correlates to the strength of each SPD Type. It is not only absorbing the surge, but creating a robust structure that foresees multiple threats to an electrical network.
Where and How Should a Type 2 SPD Be Installed?
Proper installation is paramount to the effectiveness of a Type 2 SPD. Incorrect installation can severely compromise its protective capabilities, rendering even the best protective device ineffective.
Location:
- Primary Location: The main distribution panel (MDP) or main distribution board (MDB) that receives power directly after the main service entrance disconnect. This protects all sub-circuits fed from this panel.
- Secondary Locations: Sub-distribution panels (SDPs) or sub-distribution boards (SDBs) that feed critical loads or areas with equipment known to generate power surges (e.g., panels supplying large motors, industrial machinery, or variable frequency drives).
- Proximity: The SPD should be located as close as possible to the panel bus bars or circuit breakers it is protecting to minimize conductor length in the wiring.
Installation Procedure (Must be performed by a qualified electrician):
*Example：Single-phase Type 2 AC Surge Protection Device SPD Installation and Wiring Diagram
- Safety First: De-energize the panel completely according to standard lockout/tagout procedures before beginning any work.
- Mounting: Mount the SPD enclosure securely adjacent to or within the distribution panel, adhering to manufacturer instructions and local electrical codes. Ensure environmental ratings (NEMA/IP) match the installation location.
- Connection: Type 2 SPDs are typically connected in parallel with the circuits they protect. This involves connecting the SPD‘s line terminals to the corresponding phase conductors (L1, L2, L3) via an appropriate overcurrent protection device (OCPD – usually a circuit breaker or fuses, as specified by the SPD manufacturer), its neutral terminal (if applicable) to the neutral bus, and its ground terminal to the panel’s ground bus. The integrity of this wiring is crucial.
- Conductor Length: This is CRITICAL. The connecting wiring (leads) between the panel bus/breakers and the SPD terminals must be kept as short and straight as possible. Every inch of wire adds inductance, which increases the voltage let-through during a fast-rising surge event. Long, looping wires can render the SPD ineffective. Short, direct pathways are like express lanes for diverting unwanted energy, minimizing impedance.
- Wire Gauge: Use the appropriate wire gauge for the connecting wiring as specified by the SPD manufacturer and electrical codes, ensuring it can handle both normal operation and potential surge currents.
- Grounding: Ensure the panel has a robust, low-impedance connection to the building’s electrical system grounding electrode system. The SPD relies entirely on this path to safely divert surge energy. A poor ground connection negates SPD’s function.
- Torque: Tighten all connections to the manufacturer’s specified torque values to ensure solid electrical contact and prevent overheating.
- Verification: After installation and re-energizing the panel, check the SPD‘s status indicators (if equipped) to confirm it is operational.
Adherence to manufacturer instructions and relevant electrical codes is non-negotiable for a safe and effective installation of this protective device.
The Crucial Benefits of Implementing Type 2 Surge Protection Device
Incorporating a Type 2 surge protector is not a simple purchase – it is an investment towards business continuity, equipment lifespan, and safety within the electrical system. The benefits go beyond just immediate savings:
| Benefit | Description |
| Protection of Sensitive Electronics | Devices such as computers, servers, PLCs, communication systems, smart appliances, and LED lights rely on microprocessors that are highly vulnerable to voltage transients. |
| Prevention of Downtime | Type 2 SPDs help mitigate data loss, service interruptions, equipment failures, and manufacturing pauses caused by power surges, reducing the costs of downtime. |
| Reduced Maintenance & Replacement Costs | Surge-damaged devices can be costly to repair or replace. Investing in Type 2 SPDs is more economical than replacing equipment due to uncontrolled surge damage. |
| Enhanced Safety | By safely redirecting the energy of a surge, Type 2 SPDs enhance safety by preventing damage or hazards to critical control equipment. |
| Counteracting Internal Surges | Type 2 SPDs protect against internal power surges from equipment cycling, which are highly damaging and not covered by Type 1 devices at the service entrance. |
| Compliance and Best Practice | With the rise in the use of Type 2 SPDs in industrial and commercial applications, surge protection may soon be mandatory or recommended by standards, codes, and insurers. |
| Peace of Mind | Implementing surge protection improves peace of mind for business owners, facility managers, and homeowners, as it protects against costly surge damage. |
Finally, Type 2 surge protection devices are highly beneficial for sensitive electronics, minimal downtime, maintenance cost, and safety. Protection from both internal and external surges guarantee business continuity, safeguard critical infrastructure, and provide peace of mind which improves safety for all. Protection from surges is becoming more common due to industry standards and best practices, Type 2 SPDs are a good investment for both cost and protection of your electrical systems for the long term.
Choosing the Right Type 2 SPD: Key Factors to Consider
To select the right Type 2 SPD, specific characteristics of the electrical system and the expected power surge threats need to be analyzed. This isn’t a straightforward task. The first thing to focus on is Nominal System Voltage and Configuration. The SPD has to support the system voltage, whether it’s a 120/240V split-phase or 277/480V Wye, and its Maximum Continuous Operating Voltage (MCOV) has to be higher than the nominal voltage, usually by 15-25%, in order to avoid undue wear and tear or nuisance tripping. Following that, you will want to look at the Nominal Discharge Current (In), which speaks to how much surge current the SPD is capable of enduring for a prolonged period without succumbing to damage. Generally, the higher the In rating, 10kA to 40kA, for instance, the more durable the equipment for usage in surge-prone environments.
Voltage Protection Rating (VPR) or Rating of Voltage Protection Level (Up) is one more important characteristic, as it defines the maximum voltage which the SPD will let to protective circuits during impulse on electric equipment. To minimize insulation damage, it’s better if these values are lower. Equally critical is Short-Circuit Current Rating (SCCR); the SPD should be able to survive the available fault current at the point of installation. Insufficient SCCR can create extremely dangerous situations, which requires disabling coordination with upstream OCPD, such as breakers or fuses.
Other important details are in the consideration of Modes of Protection L-N, L-G, and N-G in Delta systems referred to as L-L where protection normally is “All Modes.” Another point of view is the Status Indication; LEDs, alarms, or remote contacts that notify the maintenance people when the maintenance is due to be performed. Last, but not least, make sure that the SPD is marked to the appropriate standards like safety for UL 1449 and IEC 61643-11 and that it is in the proper protective type enclosure, that is, NEMA 1 for inside and NEMA 4X for outside. Due to these details, consulting with an expert for industrial or commercial installations is recommended.
LSP: Your Expert in High-Quality Type 2 Surge Protection Devices
At LSP, we know how important it is to protect your electrical systems from the erosive effects of power surges. With years of experience offering the best surge protection solutions, we pride ourselves in providing modern Type 2 Surge Protection Devices (SPDs) of unparalleled dependability and high quality. Our SPDs are specifically built to shield your equipment from unanticipated surges, thus preserving the effectiveness and prolonging the life of your system.
Type 2 DC PV Solar Surge Protective Device SLP-PV1200-S
Main Features:
- DIN rail installation
- For 1200V DC / PV / Solar power system
- High discharge capacity due to zinc oxide varistor
Applications:
- Location of Use: String box, Inverter
- Mode of Protection: (DC+) – PE, (DC-) – PE, (DC+) – (DC-)
- Housing: Pluggable Design
- Compliance: IEC/EN 61643-41
Specification
| Max. continuous operating voltage Uc | 1200V |
|---|---|
| Type | Type 2 / Class II / Class C |
| Nominal discharge current (8/20 μs) In | 20kA @ Type 2 |
| Total discharge current (8/20 μs) Itotal | 40KA |
| Maximum Discharge Current (8/20 μs) Imax | 40kA @ Type 2 |
| Protective elements | Metal Oxide Varistor (MOV) |
Type 2 AC Surge Protective Device SLP40-275/1S
Main Features:
- TUV, CB, and CE certifications
- Single Phase
- High discharge capacity due to heavy-duty zinc oxide varistor
Applications:
- Location of Use: Sub-Distribution Boards
- Network Systems: TN-S, TN-C, TT (only L-N)
- Mode of Protection: L-PE, N-PE (only TN-S), L-PEN, L-N
- Housing: Pluggable Design
- Compliance: IEC 61643-11:2011, EN 61643-11:2012
Specification
| Nominal voltage Un | 230V |
|---|---|
| Max. continuous operating voltage Uc | 275V |
| Type | Type 2 / Class II / Class C |
| Nominal discharge current (8/20 μs) In | 20kA @ Type 2 |
| Maximum discharge current (8/20 μs) Imax | 50kA @ Type 2 |
| Voltage protection level (L-N) / (N-PE) Up | 1.5KV / 1.5KV |
| Protective elements | Metal Oxide Varistor (MOV) and Gas Discharge Tube (GDT) |
Type 2 AC Surge Protective Device SLP40-275/3S
Main Features:
- TUV, CB, and CE certifications
- Three Phase
- High discharge capacity due to heavy-duty zinc oxide varistor
Applications:
- Location of Use: Sub-Distribution Boards
- Network Systems: TN-C
- Mode of Protection: L-PE, N-PE
- Housing: Pluggable Design
- Compliance: IEC 61643-11:2011, EN 61643-11:2012
Specification
| Nominal voltage Un | 230V |
|---|---|
| Max. continuous operating voltage Uc | 275V |
| Type | Type 2 / Class II / Class C |
| Nominal discharge current (8/20 μs) In | 20kA @ Type 2 |
| Maximum discharge current (8/20 μs) Imax | 50kA @ Type 2 |
| Voltage protection level (L-N) / (N-PE) Up | 1.5KV / 1.5KV |
| Protective elements | Metal Oxide Varistor (MOV) |
Surge protection is incredibly important, which is why LSP prioritizes your needs with our state-of-the-art technology, unparalleled performance, and optimum safety features. Our Type 2 SPDs guarantee protection for residential, commercial, and even industrial electrical systems, ensuring that these systems avoid failing or suffering costly downtimes. With LSP, you can relax effortlessly while knowing that your surge protection needs are fully taken care of.
Conclusion: Why Type 2 SPD is an Essential Part of Your Protection Strategy
In an era defined by electronic sophistication and dependency, the threat posed by power surges—both dramatic external events and common internal fluctuations (transients) within the electrical system—cannot be ignored. While Type 1 SPD offers frontline defense at the service entrance, it’s Type 2 SPD installed at distribution points that provides indispensable surge protection for the internal electrical ecosystem. It guards against residual incoming surges and, crucially, tackles the damage caused by internally generated transients.
Implementing Type 2surge protection is a fundamental step towards ensuring equipment longevity, maintaining operational continuity, enhancing electrical safety, and achieving comprehensive power quality. It bridges the gap between coarse service entrance protection and fine point-of-use protection, forming the backbone of a well-designed, coordinated surge protection strategy. In the modern electrical landscape, Type 2 SPDs are not a luxury; they are an essential component of resilient and reliable power infrastructure.
Here at LSP, we understand modern electrical systems continue to evolve with time therefore we strive to deliver Type 2 Surge Protection Devices of the highest quality. With our top of the line components LKD MOVs, Vactech GDTs, and reinforced plastic materials, our devices guarantee performance and reliability. Furthermore, our advanced features such as the internal disconnection device moisture and surge resistant construction enables protection from external surges as well as internal transients. We offer a variety of customization options and back our products with a 5-year warranty, showcasing our confidence in their reliability. count on LSP for dependable, premium quality surge protection devices that ensure safety, security or your electrical infrastructure.
