SPD Classification: Standards and Test Types

Surge Protection Devices (SPD) are classified and tested based on parameters provided by the manufacturer. According to HD 60364-5-534 and EN 62305 standards, there are three test classes corresponding to three types of SPDs, designed for specific electrical protection applications.

SPD Test Classes

Class I SPD

Tested with an impulse current Iimp (10/350 μs) and nominal discharge current In (8/20 μs), these SPDs protect against direct lightning currents and are ideal for heavy-duty industrial and commercial installations.

Class II SPD

Tested with nominal discharge current In (8/20 μs) and, optionally, with maximum discharge current Imax (8/20 μs). These SPDs are commonly used in residential and light commercial applications. In some cases, they are also tested with voltage impulses (1.2/50 μs) when they contain triggering components.

Class III SPD

Tested with a combined generator providing an open-circuit voltage Uoc (1.2/50 μs) and a presumed short-circuit current Icw (8/20 μs) with a nominal output impedance of 2 Ω. Used for the final protection of sensitive electronic devices.

Preferred Maximum Discharge Current Values for Type 1, 2, and 3 SPDs

According to the EN 61643-11 standard, maximum discharge current values are set to ensure maximum protection for electrical systems.

For more information on selecting the right SPDs for your needs, contact us or explore our product range.