It is an external neutral current transformer (ENCT) for ComPact NSX100-250 with Micrologic 5/6 trip unit. In 3-pole devices, the distributed neutral of the installation can be protected by installing this external sensor. The sensor's nominal current is between 25 A and 100 A. The ENCT must be connected to the Micrologic trip unit using a shielded twisted pair cable. The maximum cable length is 10 m and the cross-section must be between 0.4 mm² and 1.5 mm².