Aiming at problems in traditional large-current measurement such as large size

narrow measurement range

and low digitization degree

a new measurement method based on tunnel magnetic resistance（ TMR）magnetic sensor array for large-current measurement is put forward. Current measurement mathematical model is deduced from the TMR effect and measurement principle

as well as the input-output character of magnetic sensor.Meanwhile

magnetic sensor topological structure is constructed

thus accurate measurements can be reached even in three-phase interfering magnetic field. A set of test system is built to verify the measurement model based on10kV switch board. According to fitting analysis on acquired data

two factors that can affect the precision of measurement are found: magnetic sensor placement and measurement range. Through optimizing installation site of the sensor

the optimum place

show that the TMR magnetic sensor has excellent precision which can meet the measurement requirements.