Without any field concentrate equipment， a novel current transducer based only on solid-state magnetic sensor array has been explored recently in the field of power system high current measurement. Aiming at reconstructing the transient current faster without sacrificing the measurement accuracy， an advanced measurement model in time domain， based on the trans-impedance at 50 Hz is proposed. In this model， the dynamic behavior of the magnetic field in the measurement range is investigated. The optimal region for locating the sensors in a three-phase rectangular bus-bar testing system is calculated， where the measurement model complies with the measurement specification. Theoretical error analysis is carried out with the help of numerical and experimental results and the final results validate the effectiveness of the theory proposed.