Description
Surge Protection Devices or SPDs are an important part of any building’s Internal Lightning Protection
System (LPS). SPDs are designed to protect sensitive electronic & electrical equipment by limiting
transient overvoltage and diverting surge currents. SPDs are the most efficient and commonly used
type of overvoltage protection for any structure.
Lightning Protection Zones
The placement of SPDs within an electrical system is determined using the Lightning Protection Zones
determined for the structure as defined in IEC 62305 Part 4. The external zones (LPZ 0A and LPZ 0B) can
only house surge-resistant equipment while the internal zones (LPZ 1, LPZ2….) can house sensitive
equipment such as medical equipment.
Surge Protection Devices (SPD) are used in areas where a transition takes place between two different
LPZ’s. For example, a Type 1 or Type 2 SPD would be used at the main power distribution switchboard
where the electrical system enters the structure. The table above briefly describes the various LPZ
transitions that occur in most structures and how one can choose the SPD Type based on these transitions.
