As we all know, the small current grounding line selection device can accurately find the fault line and upload the information to the background through alarm relay and communication. In the small current grounding system, there are two kinds of grounding protection, one is non selective grounding protection, the other is selective grounding protection.

      Non selective grounding protection basically uses the change of three-phase to ground voltage when single-phase grounding fault occurs in small current grounding system to judge the grounding phase and grounding degree. The voltage change at the opening triangle of auxiliary winding of the bus voltage transformer is used to start the voltage relay to alarm and inform the operator to carry out manual search. This kind of protection has fewer small outgoing lines Current grounding system, more applicable, for the system with more outgoing lines, it is more inconvenient.

The small current grounding line selection device can selectively carry out the grounding protection of the small current grounding system, which makes good use of the characteristics of the grounding fault current when the system is grounded, and realizes the protection function.

Small current grounding line selection is a selective protection based on the characteristics of large zero sequence current at the beginning of the fault line. It is generally used in the line with zero sequence current transformer installed. It is suitable for the system with more outgoing lines. The fault line can be directly pointed out, which is also the advantage of small current grounding line selection device installation.