Surge Protective Device (SPD): Also known as a surge protector, over-voltage protector, or commonly referred to as a lightning arrester or surge arrester. It is primarily used to protect electrical devices from damage caused by lightning-induced electromagnetic pulses or operational over-voltages. It limits transient over-voltages that surge into power lines or signal transmission lines to a voltage level that the equipment or system can handle, or diverts powerful lightning currents to the g...

SPD-specific Disconnector (SSD): An external disconnector installed in series with the surge protective device (SPD) in low-voltage power systems, also known as a pre-SPD external disconnector. It is commonly referred to as the SPD-specific backup protection device. Its main functions are as follows:Protection Against Short-Circuit: When an abnormal transient over-voltage causes the SPD to conduct and leads to a short circuit, this can result in a power outage or even a severe fire hazard. Th...