Establish a 110 kV system protection mechanism. During the operation of the line, the CPU line protection device must be effectively designed and applied to gradually protect the overall operation of the line and to reflect and detect grounding and phase-to-phase in a timely manner - phase faults. The action value of the device can be determined in system operation. It is mainly used in ultra-short circuits. It can be oscillated and blocked, whereby the internal and external errors of the oscillation are effectively protected and can be found and found in good time and deal with the related errors in the line operation.