ASB-4101 digital plant transformer protection and monitoring devices applicable to auxiliary transformer protection, complete protection, monitoring and control functions. Main functions: a) three-stage complex voltage startup overcurrent protection; b) zero-sequence voltage latch the high-pressure side of the zero-sequence two-stage over-current and high-voltage side of the zero-sequence current lockout zero sequence overvoltage protection; c) low-voltage side of the zero-sequence segment overcurrent protection; d) The overload protection function; e) low-voltage protection function; f) body protection function: the heavy gas action, over-temperature trip, light gas alarms and over-temperature alarm; g) of the PT disconnection and insulation monitor function ; h) event logging, fault recording.