The structure and principle of bridge differential unbalanced protection capacitor bank are introduced. A kind of fault location method based on relative current detection is proposed to solve the problem of fault location for bridge differential unbalanced protection capacitor banks. A new type of fault location device is designed. In case of damage fault of capacitor element of capacitor bank

the minor and symmetrical fault can be identified by way of capturing sudden change of relative current and the fault area can be judged in 1/4 area of H bridge. The H-bridge model is set up for simulation and analysis and it is thought that the method can achieve above functions.