Abstract Magnetic controlled shunt reactor is widely used in new energy transmission, and its special operation characteristics provide dynamic reactive power compensation for the power system, while the reactive power capacity can be continuously adjusted, solving the problem that conventional fixed reactance cannot be applied to reactive power demand fluctuations. This paper briefly introduces the structure and working principle of a magnetic controlled shunt reactor, analyzes the relationship between core magnetic saturation and control current in a magnetic controlled reactor under different DC bias conditions, and the reliability of interturn protection under different working conditions is studied and a feasible scheme is proposed, provides a certain reference for the design and operation and maintenance of magnetic controlled shunt reactor.