used mainly for primary protection of single and 4- phase networks at the main electrical panel. They provide common-mode or common and differential mode. This SPD is based on high energy varistor equipped with thermal disconnector and failure indicator, to comply with standards. The DS40 surge protectors are designed to be used in a multipolar configuration to protect single-phase, 3-phase or 3-phase+Neutral AC networks.They are sometimes associated with dedicated N/PE surge protector based on gas tube technology.