The reliable and good operation of grounding and neutral devices is of great significance for ensuring personal safety. During its installation, operation, inspection and maintenance process, attention should be paid to meeting the following safety technical requirements:
1. It is necessary to ensure the continuity of conductivity between the electrical equipment and the grounding body or between the electrical equipment and the neutral point on the low-voltage side of the transformer, without disconnection. The connection between the natural grounding body and the artificial grounding body must be reliable. When welding between grounding devices, the length of the flat steel lap welding should be twice the width, and at least three edges should be welded. The length of the round iron lap welding should be six times its diameter. When using other connection methods, it is necessary to ensure good contact and the grounding resistance value should meet the requirements of the regulations.
2. The grounding body should be made of galvanized steel components, with the welding joints coated with asphalt oil and the exposed ground parts painted. In highly corrosive soil, grounding bodies made of copper plated or galvanized components should be used, and their cross-sectional area should be appropriately increased to ensure that the grounding body has sufficient mechanical strength and anti-corrosion performance.
3. When using protective grounding, the neutral wire should have sufficient conductivity to enable the protective device to quickly operate in the event of a short circuit. Without using natural conductors as neutral wires, the conductivity of the protective neutral wire should not be less than half of the phase wire. The grounding device of a high grounding current system should be checked for thermal stability when single-phase grounding occurs.
The distance between the grounding body and the building should not be less than 1.5 meters, and the distance between the grounding body of the independent lightning rod should not be less than 3 meters. In order to improve the reliability of grounding, the working grounding, protective grounding, and lightning protection grounding branch lines (or neutral branch lines) of electrical equipment should be separately connected to the grounding main line or grounding body, and there should be two connection points.
In addition, the upper end of the grounding body is generally buried at a depth of not less than 0.6 meters and below the frozen soil layer. The grounding wire or neutral wire should be installed in a place that is not easily accessible to people to avoid accidental damage, but it must also be in a prominent location for easy inspection and maintenance.