In order to ensure the normal operation of the power system and equipment to achieve a grounding
The grounding of power system and electrical equipment can be divided into working grounding, protective grounding, grounding and repeated grounding.
4) repeat grounding: in the low voltage three-phase four wire system (380V/220V), which is directly grounded in the neutral point, in addition to the working connection at the power supply, it is necessary to re connect the ground at the other place of the zero line. To ensure the safety and reliability of the zero line. It is simply to say that one or more points on the zero line are grounded again.
2) protection of grounding: is the electrical equipment in normal circumstances, such as metal parts, such as metal shell, structural frame and the earth to make metal connection. In order to ensure personal safety.3) security is zero: is the electrical equipment in normal circumstances without the metal part of the system and the zero line connection to avoid the risk of electric shock. For three-phase four wire system of electrical equipment, must adopt the method of security zero.
1) work: grounding is to ensure electrical equipment in normal or accident conditions reliably, the neutral point directly or through special equipment (such as Petersen coil, reactor, resistance, breakdown insurance, etc.) do metal and earth connection.
