Created by: Glen Zhu | Updated Date: Jul 05, 2023
Direct lightning stroke
Indirect lightning stroke
Indirect lightning stroke
Class I test
Class II test
Class III test
Type 1; T1
Type 2; T2
Type 3; T3
EN 61643-11:2012 + A11:2018
Type 1; T1
Type 2; T2
Type 3; T3
Type of test wave
Type 1 Surge Protective Device are intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures, and are intended to be installed without an external overcurrent protective device.
Type 1 devices are dual-rated for Type 2 applications as well, providing the highest ratings available for installation at the service entrance.
Type 1 SPD can discharge lightning current with waveform 10/350 μs. It will be installed in the primary distribution board at the origin of the electrical installation.
A Type 1 SPD does not in itself offer the required protection level and must be used in conjunction with coordinated type 2 devices. An installation with a lightning protection system will require a Type 1 SPD.
Type 1 surge protection device is developed as the best solution available to protect service entrance at an industrial site, especially those with existing lightning protection systems or meshed cage applications.
Type 1 surge protection device is particularly useful in a high lightning density area where the risk of heavy surge current or even direct strike is high (eg: buildings equipped with lightning rods).
Type 1 SPD is characterized by a 10/350 µs lightning current waveform and installed at the load center’s main circuit breaker, e.g. main distribution board.
Type 1+2 surge protection device installed at the origin of the AC installation equipped with LPS.
Type 1+2 surge protection devices use Metal Oxide Varistor (MOV) and/or Gas Discharge Tube (GDT) circuits to protect electrical devices from spikes in alternating current power.
Type 1+2 SPD is designed to be connected in multi-pole configuration to protect single-phase, 3-phase and 3-phase+Neutral AC networks, and for TN-C, TN-S, TN-C-S TT, and IT power supply systems.
Type 2 Surge Protective Devices are intended for installation on the load side of the service equipment overcurrent device, including SPDs located at the branch panel.
Type 2 SPD can discharge 8/20 μs current wave, they can prevent the damage of transient overvoltage in the electrical installations and protects equipment connected to it.
It usually employs metal oxide varistor (MOV) technology. The device would normally be installed in sub-distribution boards and in the primary distribution board if there was no requirement for a type 1 device.
Type 2 surge protection device is characterized by an 8/20 µs lightning current waveform.
Type 2 SPD is designed to be installed at the service entrance of low voltage systems or close to sensitive equipment to protect against transient overvoltages.
Type 2 surge protection device is for nominal working voltage (50/60Hz) Un = 120V 230V 400V ac applications and for maximum continuous operating voltage (50/60Hz) Uc = 150V 275V 320V 385V 440V ac applications.
Type 2 SPD is generally installed in sub-distribution or machine control cabinets, for indoor use or fixed into a waterproof box for outdoor use.
Type 2+3 surge protection devices are normally installed right before the protected equipment.
Type 2+3 SPD is characterized by current waves (8/20 μs) and a combination of voltage waves (1.2/50 μs).
These SPDs have a low discharge capacity. They must therefore only be installed as a supplement to Type 2 SPD and in the vicinity of sensitive loads.
Type 3 SPD is characterized by a combination of voltage waves (1.2/50 μs) and current waves (8/20 μs) and load current IL.
Type 3 surge protection devices are normally installed right before the protected equipment.
Type 3 SPD is generally installed near the protected load, to protect sensitive equipment for 24V 48V 60V 120V 230V, in coordination with Type 2 surge arrester installation head.
Arresters tested and found AC Type 3 surge protection devices are intended to be installed near sensitive equipment, in coordination with Type 2 surge arrester installation head.
The table below provides a more thorough comparison of the characteristics of SPD types 1, type 2, and type 3:
Surge Protection Device Types
Maximum Discharge Current (Imax)
Voltage Protection Level (Up) Rating
Location of Installation
Application & Coverage
≤ 2.5 kV
Main service entrance or source of power supply
For large facilities and high-threat locations
≤ 1.5 kV
Sub-distribution panel or electrical panel
For facilities of medium size
Combination of voltage waves (1.2/50 μs) & current waves (8/20 μs)
≤ 1.0 kV
Outlets or near the specific terminal equipment.
For certain devices and circuits
SPD Type 1 provides primary protection against high-level surges caused by direct lightning strikes. It is often put on the main distribution board to safeguard a building’s whole electrical system.
SPD Type 2 provides secondary-level protection, the majority of common surges generated by electrical switching or nearby lightning strikes could be effectively protected, which are installed at the sub-distribution panel or electrical panel.
SPD Type 3 is designed specifically aimed at protecting specific terminal equipment, they should be installed close to sensitive loads as a supplement to Type 2 SPDs.
Overall, the selection of the appropriate SPD type will depend on several factors including the location of installation, maximum discharge current, voltage protection level, and application.
It’s important to note that the actual applications of each type can change based on the particular requirements of a given facility or piece of equipment that has to be protected.
Iimp – Impulse current of Type 1 SPDs with 10/350 μs waveform.
In – Norminal discharge current of Type 2 SPDs with 8/20 μs waveform.
Imax – Maximum discharge current of Type 2 SPDs with 8/20 μs waveform.
Uoc – Open-circuit voltage of Type 3 SPDs with a combination of voltage waves (1.2/50 μs).
Up – The residual voltage that is measured across the terminal of the SPD when In is applied.
Uc – The maximum voltage which may be continuously applied to the SPD without damage the SPD.
LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!