ASD-412 digital motor differential protection device 3kV to 10kV high voltage motor system suitable for use with the ASD-411 motor protection and monitoring device with the completion of the the motor spacer layer secondary function. Main functions: a) the differential speed off protection function: split-phase differential quick-break protection action time is less than 25ms; b) differential protection function: sub-phase differential protection (with a ratio of braking characteristics and neutral side of the CT ratio adjustment function); c) CT disconnection detection and differential current is too large alarm functions: real-time detection of CT disconnection, locking differential protection, and when the current large mutation but differential current alarm; d) event logging, fault recorder e) communication function