Abstract: The influence of phase controlled reactors of a large capacity SVC on the low voltage DC power supply of a power substation can be very serious. In order to understand this influence, field measurement of SVC is carried out in a substation. Furthermore, a three-dimension electromagnetic field simulation model is established for SVC and its adjacent area. A full-scale model is established in the laboratory to verify the equivalence of the simulation results through comparison with the field measurement. An analysis is made on the improvement of DC power quality brought about by different shielding materials and related problems. The results show that the influence of phase controlled reactors of a large capacity SVC on the low voltage DC power supply of a power substation has exceeded the allowable value stipulated by relevant code, and the layout optimization of silicon steel sheet, aluminum plate and iron plate can effectively reduce the interference, and the resulting inductance change and heating are acceptable.