Grounding methods, functions, and other issues

Grounding is divided into instrument grounding (working ground) and protective grounding. For specific methods, you can refer to the grounding standards. Remember one thing: single-point grounding.

Agree with what was said above; for work-related grounding, single-point grounding is generally used, while for protective grounding, multiple points are preferable

1. Function of the grounding system: ① Protecting equipment and human safety； ②Suppress interference. Automatic grounding is divided into protective grounding and working grounding according to its different functions. The function of protective grounding is to protect equipment and human safety ； The function of working ground is to ensure the accurate, reliable, and proper operation of instruments. It includes signal circuit grounding, shielding grounding, and intrinsically safe instrument grounding. The principle for working groundings is single-point grounding; different types of groundings must be strictly separated to avoid any mixing. 2. The grounding system consists of two parts: the grounding connection and the grounding device. ① Ground connections include: ground wires, ground busbars, ground branch lines, ground collection plates, and ground main lines. ② The grounding system includes a main grounding plate, a grounding main conductor, and grounding electrodes. The grounding connections for instruments and control systems should be organized in categories and then connected to the main grounding plate. 3. Methods for grounding connections of instruments in the control room: ① In the automatic control equipment installed with instruments in the control room (instrument cabinets, consoles, panels, racks, and boxes), protective grounding busbars, signal and shielding grounding busbars, and intrinsically safe grounding bars should be installed separately by category. ② The protective grounding terminals of various instruments and equipment, as well as the signal and shielding grounding terminals, are connected to the protective grounding busbar and the working grounding busbar respectively through their own grounding wires. Various types of grounding busbars are connected to the protective grounding collection board and the working grounding collection board via their respective grounding branch lines. ③ Each bus bar (mounting rail) of the Zener-type safety barrier can be connected to the working ground assembly plate using two separate grounding branches. ④ The protective grounding assembly board and the working grounding assembly board are connected to the main grounding plate via their respective grounding trunks. ⑤ Connect the ground plate and the grounding electrode using a grounding main trunk. 4. Grounding requirements for automatic control systems: ① The sum of the resistances of the conductors and connection points from the grounding terminals of the instrumentation equipment to the main ground plate is referred to as the connection resistance, and this value should not exceed 1Ω. ② The ground resistance is defined as the sum of the resistance of the ground electrode to the ground, and the resistances at the connection points of the main grounding electrode, the main grounding conductor, and both ends of the main grounding conductor. Requirements for the grounding resistance of the instrumentation system: The grounding resistance without an intrinsically safe ground shall be less than 4Ω ； There is a low value of less than 1Ω in milliamps. 5. The specifications for the grounding connection wires are as follows: The wires in the grounding system should be insulated copper wires or cables with multiple strands; the required wire diameters are as follows: grounding connection wires ≥ 1 mm2, grounding branch wires ≥ 4 mm2, grounding main wires ≥ 10 mm2, and grounding main trunk wires ≥ 16 mm2. The grounding collection plates and main grounding plates should be made of copper plates, with a thickness of not less than 6 mm. The length and width are determined as needed. 6. Requirements for grounding connection structure: ① All grounding connection wires must be properly insulated before being connected to the grounding busbar; all grounding branch wires must be properly insulated before being connected to the grounding assembly plate, and all grounding main wires must be properly insulated before being connected to the main grounding plate. ②Ground busbars, ground collection plates, and main ground plates should be fixed using insulated brackets. Do not touch other conductive media. All connections in the grounding system must ensure good electrical conductivity. The connections between grounding wires, grounding branch lines, grounding main lines, and the main grounding conductor, as well as those with the grounding busbars and grounding collection plates, should be made using copper connectors and galvanized steel or copper bolts. Anti-loosening and anti-slipping devices should also be used, or copper welding can be employed to ensure firm and reliable connections. ③The materials that can be used for the grounding electrodes include flat steel of 25×4, round steel with a diameter of ø20, equilateral angle steel of 50×50×5, and steel pipes with a diameter of ø57×3.5, among other steel-based materials. If the grounding resistance does not meet the requirements, copper materials can also be used. ④The connection between the main grounding conductor and the grounding electrode should be made by welding, and anti-corrosion treatment should be applied after welding (by applying protective paint). When lap welding is used for the main grounding conductor and the grounding electrode, the lap length must be twice the width of the flat steel or six times the diameter of the round steel. ⑤The grounding system should be equipped with durability markings.