Aiming to solve the problems that the 
electric power plant trips due to the ground fault for the strings under 
alternating current or 
direct current condition, and a plurality of accidents appear, for example, the device is damaged, the important 
relay coil with easy incorrect-
tripping is connected with a shunt 
resistor in parallel, the communication is carried out between the 
electric devices, and a rectification, insulating and 
tripping functional switch is installed on a direct-current power supply 
branch circuit, so that the influence on the fault source is reduced or isolated. The invention provides a novel 
direct current system design principle and a method, a special hall sensor for the unbalanced current is adopted, a 
grounding resistance-
capacitance loop is increased, the unbalanced current of the grounding 
branch circuit is increased, the sensitivity of measurement is improved, a distributed on-
site monitoring module finishes the 
data acquisition and the 
data transmission of the 
busbar voltage, the unbalanced current, the on / off state, and the like, the monitoring center finishes 
processing all the data and warning according to the logic of the design, the 
tripping command is transmitted to the fault 
branch circuit through the distributed on-
site monitoring module, and a switch with tripping function is used for shutting the fault branch circuit off in time after receiving the command. Therefore, the technical problem that the fault range is extended due to the 
short circuit and the ground fault for strings under the 
alternating current and the 
direct current condition is solved.