Surge Protection Devices

Surge Protective Devices (SPDs) safeguard electrical systems from voltage spikes (transients) caused by lightning, utility switching, or large equipment.
They work by diverting excess energy to the ground, clamping the voltage to a safe level for connected equipment.
PDs are classified by where they are installed and the level of surge they are designed to handle.

Type 1 (Class I) SPDs
Purpose: Protect against very high-energy, external surges like direct lightning strikes.
Location: Installed at the service entrance, on the utility side of the main breaker.
Key Feature: Tested with the severe 10/350µs lightning current waveform.

Type 2 (Class II) SPDs
Purpose: Protect against internally generated surges and residual lightning currents that enter the building.
Location: Installed at sub-panels and distribution boards (after the main breaker).
Key Feature: The most common type; tested with the standard 8/20µs current waveform.

Type 3 (Class III) SPDs
Purpose: Provide point-of-use, fine protection for sensitive electronic devices.
Location: Installed very close to the equipment, like in plug strips or as plug-in units.
Key Feature: Offers a final level of defence with a low let-through voltage.

Type 1+2 (Combination Class) SPDs
Purpose: A versatile hybrid that provides both Type 1 and Type 2 protection in a single device.
Location: Can be installed at the service entrance, simplifying design.
Key Feature: Tested to both Type 1 and Type 2 standards, offering robust, all-in-one primary protection.