What Is a Surge Arrester? Types and Selection Guide
A surge arrester protects the installation by diverting lightning and switching overvoltages in the low voltage network to ground; a guide to types and selection.
What is a surge arrester and where is it used
A surge arrester (parafudr) is a protective device that protects the installation and connected equipment by diverting transient overvoltages caused by lightning and switching in the low voltage network to ground; its English name is surge protective device (SPD), or simply "SPD".
Surge arresters are generally used in the main distribution panel, in sub-panels and at the supply of sensitive equipment. In solar energy (photovoltaic) systems there are separate "solar surge arrester" products for the DC side. This category includes low voltage surge arresters divided by number of poles and mains system, replaceable cartridges and protectors for data lines. You can also reach the category from the general Switching and Protection Products section.
Types of surge arresters
| SPD Type | Test Waveform | Installation Location | Protection Purpose and Catalog Link |
|---|---|---|---|
| Type 1 (Class B) | 10/350 µs (Iimp) | Main service entrance (buildings with lightning rod or overhead line) | Discharges direct lightning stroke current · Low Voltage Surge Arresters |
| Type 2 (Class C) | 8/20 µs (In / Imax) | Sub-distribution boards and main boards without external LPS | Limits switching surges and induced overvoltages · Low Voltage Surge Arresters |
| Type 1+2 (Combined B+C) | 10/350 µs + 8/20 µs | Main distribution panel | Combines lightning current and surge protection in one unit · Low Voltage Surge Arresters |
The "Product Main Type" values in the product list divide surge arresters by class:
- T1 and T1-T2: Type 1 devices designed against lightning current and combined devices that join Type 1 and Type 2. They are designed for the incoming panel in places where the risk of lightning strike is high, especially in buildings with an external lightning protection system, and Type 2 protection must be present downstream.
- T2: Type 2 devices for distribution panels downstream of the incoming panel or for inputs with low lightning exposure.
- T2-T3: Products that combine Type 2 and Type 3 characteristics.
- OVR PV T1-T2: ABB's solar surge arrester series for photovoltaic systems.
- Data SPD: Devices that protect data and communication lines instead of the power line.
Some models have a replaceable cartridge design; in the list you will also see separate products called "Surge Arrester Cartridge". Verify from the manufacturer data which housing a cartridge is compatible with.
What to look at when choosing a surge arrester
- Type (class): Type 1 devices are rated by Iimp with a 10/350 µs waveform, and Type 2 devices by In and Imax with an 8/20 µs waveform. Because the waveforms are different, compare kA values only within the same type.
- Mains system and number of poles: Choose a model suitable for the system, such as TT, TN-S or TN-C, and for the configuration, such as 1P, 1P+N, 3P, 3P+N. In Siemens product names this information is stated explicitly as "for TT and TN-S systems" or "for TN-C systems".
- Uc (continuous operating voltage): The highest RMS voltage that can be applied continuously to the terminals of the device; it is chosen according to the mains system (TN-S, TN-C, TT, IT) and the rated voltage.
- Up (voltage protection level): The highest residual voltage between the device terminals while the rated current In is applied. The Up value must be compatible with, that is, lower than, the impulse withstand voltage of the equipment to be protected.
- Backup protection: The manufacturer gives the highest permitted overcurrent protection value upstream of the surge arrester in its technical documentation; take the value from the catalog. For the fuse side, you can also look at the fuse holders category.
- Remote signaling: The models described as "with changeover contact" in the Siemens list include an auxiliary contact; such contacts are used for remote status monitoring. Verify the contact function from the product data.
- Size and mounting: For the products in the list, the width, height and depth values are on the product card; plan the layout inside the panel according to these dimensions.
Selection and wiring details must be determined according to the project and the manufacturer data.
Difference between a surge arrester and a residual current relay
The two address different risks. A surge arrester limits short-duration overvoltage surges. Residual current relays, on the other hand, detect current leaking to ground and open the circuit. One does not replace the other; they can be used together in a panel.
Brands in this category
- ABB: OVR series Type 1, Type 2 and solar surge arresters, as well as models with OVR codes.
- Schneider Electric: Easy9 and IPF series surge arresters and C2 cartridges.
- Siemens: 5SD7 series, 2- and 3-pole surge arresters for TT, TN-S and TN-C systems.
Order notes
Products are sold by the piece. Some are listed as "lead-time" items; for these products, the delivery time is confirmed at the time of ordering. You can reach the right model directly by searching with the stock code or the manufacturer code (for example 5SD7442-1, A9L15597).
Frequently asked questions
What does a surge arrester do and why is it needed?
A surge arrester limits sudden voltage rises caused by lightning or mains switching and diverts the current to ground. This is intended to prevent connected equipment from being damaged by surges that exceed its withstand voltage. Which type and value is needed depends on the exposure of the installation and is determined according to project data.
What is the difference between Type 1, Type 2 and Type 3 surge arresters?
Type 1 is tested with a 10/350 µs waveform and is used in incoming panels where the risk of lightning strike is high. Type 2 is tested with an 8/20 µs waveform and is used in distribution panels. Type 3 is tested with a combined 1.2/50 µs - 8/20 µs wave; it is used downstream of Type 2, close to sensitive equipment.
What do the Uc and Up values mean when choosing a surge arrester?
Uc is the highest RMS voltage that can be applied continuously to the terminals of the surge arrester, and it is chosen according to the mains system and the rated voltage. Up is the highest residual voltage remaining between the terminals while the rated current In is applied. The Up value must be lower than the impulse withstand voltage of the equipment to be protected.
Is a fuse needed upstream of a surge arrester?
The surge arrester and its connecting cables, like other electrical equipment, must be protected against overcurrent. The manufacturer gives the highest permitted overcurrent protection value in its technical documentation. If the fuse on the line side is larger than this value, a separate backup fuse is planned. Take the value from the surge arrester's manufacturer data.
When is a surge arrester cartridge replaced?
In surge arresters with replaceable cartridges, the cartridge is replaced when it has lost its protection capacity. Many manufacturers offer a visual and remote end-of-life indicator. Cartridges are generally coded; verify the suitable cartridge code from the manufacturer data of the housing, and have the replacement carried out according to the project and the manufacturer's instructions.