ASD-412 digital motor differential protection device is adapted to 3kV to 10kV high voltage motor and ASD-411 motor protection and monitoring device with the completion of the secondary function of the motor spacer layer. Main functions: a) differential quick-break protection function: split-phase differential protection, the operating time is not greater than 25ms; b) differential protection function: split-phase differential protection (with a ratio of braking characteristics and neutral side CT ratio adjustment function); c) CT disconnection detection and differential current is too large alarm function: real-time detection of CT disconnection, lockable differential protection, and d) the event, but the differential current when the current mutation when alarms; records, fault recorder e) communication functions