什么是零序电流、什么是剩余电流、零序电流保护（What is the zero sequence current, what is the residual current and zero sequence current protection）.doc

什么是零序电流、什么是剩余电流、零序电流保护（What is the zero sequence current, what is the residual current and zero sequence current protection） What is the zero sequence current, what is the residual current, zero sequence current protection and residual? In order to avoid personal contact between electricity and power distribution lines due to various reasons caused by damaged, fire and other accidents, ensure the thermal stability of equipment and lines, the relevant rules of our country, the construction of electrical design are put forward in the low voltage distribution line to ground fault protection settings. In the national standard GB5005495 low-voltage power distribution design standard article 4.4.10 pointed out the ground fault protection of two kinds of method, zero sequence current protection and residual current protection (also known as the RCD). The basic principle of the two current protection is the same, but the scope of application, installation and other requirements are different. Zero sequence current protection concrete application in the three-phase transmission lines are respectively provided with a current transformer (C.T), or let the three-phase conductor through a sequence of C.T, also can install a sequence C.T in neutral line N, and to detect the current vector phase using these C.T, the zero sequence current Io, IA+ IBIC=IO, when the three-phase load balance on the line completely (no grounding fault, without considering the leakage current circuit and electrical equipment), IO=0; when the line three-phase load imbalance, IO=IN, the zero sequence current unbalance current of IN; when one phase ground fault occurs. Must have a single-phase grounding fault current is Id, the zero sequence current detected at IO=IN+Id, is a vector and three-phase unbalanced current and single-phase grounding current. The specific practices of residual current protection is measured in the three-phase guide line and neutral N are respectively provided with a C.T, or let t