The ABB 1SDA058218R1 is an external neutral current transformer sensor accessory designed for use with ABB SACE Emax low-voltage air circuit breakers. It is specifically configured for E3 and E6 frame breakers with a primary current rating up to 3200 A. This neutral sensor measures the current in the neutral conductor and provides accurate neutral current feedback for breaker protection, monitoring, and control systems. It is used where enhanced neutral current detection is required by protection relays or trip units.