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In order to prevent the possible AC interference to the buried metal structures, reduce the possible harm to the structures, and avoid the electrical hazards to the relevant operators, some effective protection devices and measures can be adopted, such as installing DC decoupling device on the grounding body directly connected with the buried structure.
Electrical shielding generally uses the shell, mesh or other objects as shielding materials, which are installed on one side of the affected structure, so as to fully weaken the electric field influence of the electrical device or circuit on the affected structure. Electrical shielding is often used to protect buried structures from the influence of the arc in the ground generated by AC power system, so as to reduce the possibility of the structure's anti-corrosion coating and even the structure itself being broken down under impact.
Grounding pad is a bare conductor system installed on the ground or under the ground, also known as gradient control pad. These bare conductors are usually made of metal plates or grids, which are arranged and connected to each other to provide an equal potential over the step distance. The so-called grounding grid is a number of bare conductors buried in the ground, which are interconnected to form a grounding electrode system to provide common grounding. No matter what material the grounding pad is made of, it must be bridged with the structure, preferably at several locations at the same time. If the cathodic protection of the structure is difficult to operate due to grounding, a DC decoupling device can be installed.
Independent structure grounding means that if any metal structure installed is not connected with the existing grounding structure, an independent grounding device shall be installed there. This grounding system can be composed of all or more grounding electrodes and their connecting wires. All components of the grounded structure shall be properly connected.
The existing structure bridging is an effective method to reduce the induced AC voltage on the structure. It uses the cable with appropriate cross-section area and DC decoupling device to connect the affected structure with the grounding device of power system. In the case of a fault, the voltage and current of the affected structure will increase significantly during the fault due to the jumper connection. If the affected structure is located on the ground or well insulated from the ground, a significant high potential will be generated and propagated along the length of the structure to be bridged.
Distributed anode is a protective measure that uses sacrificial anode as a part of grounding system to reduce AC potential between structure and earth. When using distributed anode, the sacrificial anode should be installed close to the protected structure and away from the power grounding system. It is better to connect the anode directly to the structure without using test connection in the middle, so as to reduce the number of contact points in the connection system, provide the shortest path to the ground, and reduce the contact opportunities between personnel and structures.
The bushing can be used to reduce the resistance of the structure to ground under surge conditions. It is to connect bare steel casing or poorly coated casing to the structure with anti-corrosion coating by DC decoupling device carefully, which can not only reduce the resistance of structure to ground under surge State, but also avoid the arc between structure and casing.
The insulated joint is used to insulate the protected structure or the protected section from the unprotected section in the cathodic protection project, so as to ensure that the cathodic protection current is limited in the protected section.
Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services.
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