A (SPD) is designed to protect electrical systems and equipment from surge events by limiting transient voltages and diverting surge currents.
Surges can originate externally, most intensely by lightning, or internally by the switching of electrical loads. The sources of these internal surges, which , can include loads turning on and off, relays and/or breakers operating, heating systems, and office equipment.
Without the appropriate SPD, transient events can harm electronic equipment and cause costly downtime.
In the most basic sense, when a transient voltage occurs on the protected circuit, an SPD limits the transient voltage and diverts the current back to its source or ground.
To work, there must be at least one non-linear component of the SPD, which under different conditions transitions between a high and low impedance state.