Lightning Arrester plays a vital role in lightning protection of power system, and its grounding requirements and grounding resistance are directly related to lightning protection performance.
First of all, the grounding requirements of Lightning Arrester are very strict. Good grounding connection is the basis for ensuring the normal operation of Lightning Arrester. The grounding electrode should be made of suitable materials, such as galvanized angle steel, copper pipe, etc., which have good conductivity and corrosion resistance. The grounding electrode needs to be buried deep underground to a certain depth, generally not less than 0.6 meters, to ensure that there is enough contact area with the earth to form a stable grounding loop. At the same time, the grounding wire should have a sufficient cross-sectional area to carry the impact of lightning current without overheating and burning. For example, in high-voltage power systems, copper wires with large cross-sectional areas are often used as grounding leads. The connection must be firm and reliable to avoid looseness or virtual connection, otherwise it will seriously affect the discharge capacity of Lightning Arrester.
Secondly, the grounding resistance has a decisive influence on the lightning protection performance. The smaller the grounding resistance, the faster the lightning arrester can conduct lightning current into the earth when struck by lightning, thereby effectively limiting the overvoltage on the protected equipment. When the grounding resistance is large, the lightning current cannot dissipate in time after passing through the lightning arrester, which will generate a high voltage drop on the grounding electrode. This voltage drop and the residual voltage generated by the lightning current on the lightning arrester will act on the protected equipment after being superimposed, which may cause insulation breakdown of the equipment. For example, if the grounding resistance exceeds the standard, when lightning strikes the lightning arrester, the actual voltage borne by the equipment may far exceed its withstand voltage value, causing damage to the equipment and failing to achieve the purpose of lightning protection. Generally speaking, for power facilities of different voltage levels and importance, there are strict specified values for grounding resistance. For example, some important substations require that the grounding resistance does not exceed 0.5 ohms.
Furthermore, in order to reduce the grounding resistance, a variety of measures are often used. The number and length of grounding electrodes can be increased, and the total grounding resistance can be reduced by connecting multiple grounding electrodes in parallel. You can also fill the grounding electrode with a resistance reducing agent, which can improve the conductivity of the soil around the grounding electrode and increase the contact area between the grounding electrode and the soil, thereby effectively reducing the grounding resistance. In addition, the reasonable design of the shape and layout of the grounding grid, such as the use of a ring grounding grid, can also help to evenly disperse the lightning current and reduce the grounding resistance.
The grounding requirements of the Lightning Arrester must strictly follow the relevant standards, and efforts to reduce the grounding resistance are of great significance to improving the lightning protection performance of the Lightning Arrester and ensuring the safe and stable operation of the power system and equipment. In the design, installation and maintenance of the power system, the grounding link of the Lightning Arrester should be highly valued to ensure that it is in the best working condition.
