Comprehensive Guide to Types of Surge Protection Devices : Type 1, 2, 3 and 4 SPDs

Surge Protection Devices (SPDs) are essential components in electrical systems, safeguarding equipment from damaging voltage surges. These surges, often caused by lightning, power grid switching, or other electrical disturbances, result in sudden and excessive voltage spikes. Without proper surge protection, these spikes can severely damage sensitive electronics, appliances, and electrical systems. SPDs offer a critical defense by diverting excess voltage away from protected devices, ensuring their safety and extending their lifespan.

This article will explore the different types of surge protection devices (SPDs), including Type 1, Type 2, Type 3, and Type 4 surge protectors, each designed for specific protective roles. We’ll also delve into the functions of various SPD technologies, such as GDT (Gas Discharge Tube), TSPD (Thyristor Surge Protection Devices), TVS (Transient Voltage Suppressor), MOV (Metal Oxide Varistor), and PESD (Polymer device), and examine their differences.

What are Surge Protective Devices (SPD)?

Introduction:

• Surge protectors, also known as surge suppressors, are devices designed to prevent damage to electronic or electrical equipment from voltage spikes or transients.
• They are inserted in AC utility lines and/or telephone lines.
• They are also referred to as transient suppressors.
• Surge protectors offer protection by dissipating any excess power, preventing it from reaching connected equipment/devices.

Electronic devices like desktops, laptops, and hard drives are engineered to operate within specific power ranges. If excessive voltage is supplied, they can suffer permanent damage.

• SPDs help protect equipment from transients originating from lightning and other switching sources.

Figure 1: Surge Protection Device

As shown in Figure 1, the SPD is connected in parallel on the power supply circuit of the loads that need protection. It diverts current waves to the earth, thus limiting the amplitude of overvoltage to a level that is not hazardous for electrical installations.

Type 1 SPD

• This SPD device is mounted on the line side of the main service entrance.
• Type 1 SPDs are characterized by a 10/350 µs current wave and are used for outdoor applications.
• They protect against external power surges caused by lightning or utility capacitor bank switching. Type 1 SPDs are considered the first line of defense for your home or office.
• Built-in alarm systems indicate when the device needs to be replaced based on its lifecycle.
• They are also known as secondary surge arresters.

Type 2 SPD

• This SPD device is mounted on the load side of the main service entrance.
• Type 2 SPDs are characterized by an 8/20 µs current wave.
• They are used to protect branch circuits or service entrances against residual lightning energy, surges from motors, and other surges.
• Their primary function is to limit transient voltage, protecting sensitive electronics and microprocessor-based boards.
• They are used in commercial and industrial applications.

Type 3 SPD

• Type 3 SPDs are characterized by a combination of voltage waves (1.2/50 µs) and current waves (8/20 µs).
• Their main function is to limit low-level surges that can damage sensitive electronic circuits in TVs, PCs, and electric appliances.
• They are considered the last line of defense in a surge protective network.
• They are commonly known as power strips.

Type 4 SPD

• Type 4 SPDs are also known as surge protection modules.
• They provide protection for servo motors, PLCs, and other devices used in industrial applications.
• These surge protectors provide wired-in surge protection.

Other SPD Types: GDT, TSPD, TVS, MOV, PESD

The following are overvoltage protection devices. Let’s understand the construction and functions of these surge protective device types:

Thyristors: These are crowbar devices used as surge protective devices. They are based on a pair of intertwined bipolar transistors created by a four-layer stack of n and p doped silicon regions.

Transient Voltage Suppressors (TVS): These are based on avalanche diodes and zener diodes. Diodes are made of semiconductors, usually silicon, at a junction between n and p doped regions. TVS devices provide protection through a combination of forward bias and reverse bias breakdown conduction.

MOV (Metal Oxide Varistor): Varistors are typically made of ceramic of zinc oxide grains in a matrix of other oxides. The grains form diodes with the surrounding matrix, creating a complex array of parallel and anti-parallel diodes. At higher voltages, the individual diodes begin to conduct, and the resistance of the varistor drops dramatically.

Polymer ESD Devices: Polymer devices are bidirectional crowbar devices. They have very high turn-on voltages, often over 200 Volts, but they turn on quickly, limiting exposure to high voltage. Polymer ESD devices consist of a polymer embedded with conducting particles.

Gas Discharge Tubes (GDT): These are usually formed with a ceramic body filled with a gas mixture containing neon and argon and two or more electrodes. When the voltage across the electrodes exceeds a specified value, an arc occurs within the tube, providing a low current path.

Fuses: Fuses are used as overcurrent protection devices.

The following table outlines the differences between SPD types regarding high-power surge events (8x20µs, 10x1000µs):

The following table outlines the differences between SPD types regarding Very Fast Surge Events - ESD (IEC61000-4-2):

Conclusion

In summary, understanding the distinct functions and applications of the various types of surge protection devices (SPDs), such as Type 1, Type 2, Type 3, and Type 4 surge protectors, is essential for comprehensive surge protection across different electrical systems. Each SPD type is designed for a specific role, from defending against direct lightning strikes to shielding sensitive electronics from transient voltage spikes.

Additionally, the range of surge protection devices—including GDTs (Gas Discharge Tubes), TSPDs (Thyristor Surge Protection Devices), TVS (Transient Voltage Suppressors), MOVs (Metal Oxide Varistors), and PESDs (Polymer devices) - together form a robust defense against voltage transients. Each device type provides unique characteristics tailored to meet diverse protection needs.