SVC is used for dynamic reactive power compensation, which can significantly enhance the stability and security of the system. Load line fault caused by SVC protection malfunction, will exacerbate the operating conditions of the system. Based on the characteristics of several typical circuit faults, the TCR branch current voltage characteristic is analyzed, and the influence of the TCR DC component on the thyristor trigger conduction is analyzed during the fault period. It points out the deficiency of the current SVC under voltage protection, puts forward the adjusting scheme of SVC under voltage protection and the improvement direction of TCR branch fault setting, which can significantly improve the reliability of SVC protection. Combined with the actual case and the simulation, the effectiveness of the method is proved to be effective in improving the SVC protection setting.