Insulation Structure and Electric Field Control Technology of Medium and High Voltage Cables and Their Important Role in Power Transmission Backbone Networks

As core components of power transmission backbone networks, medium and high voltage cables demonstrate a precise understanding of the demands for high-voltage, high-capacity transmission through their insulation structure and electric field control technology. From an insulation structure perspective, medium and high voltage cables typically employ a three-layer co-extruded structure consisting of a conductor shielding layer, an insulation layer, and an insulating shielding layer. The conductor shielding layer wraps around the conductor, eliminating electric field concentration caused by uneven conductor surfaces. The insulation layer, made of cross-linked polyethylene, possesses excellent electrical and heat resistance properties and is the main body for the cable to withstand voltage. The insulating shielding layer, located outside the insulation layer, forms an equipotential surface with the metal sheath, limiting the outward extension of the electric field. This multi-layered structure ensures a uniform distribution of the electric field within the insulation layer, effectively improving the cable's withstand voltage and service life.

Electric field control technology for medium and high voltage cables is crucial for their safe operation. When the cable operates under high voltage, a complex electric field distribution forms within the insulation layer, potentially leading to electric field concentration at the conductor surface, the interior of the insulation layer, and the interface of the shielding layer. By optimizing the material properties and geometry of the conductor shielding layer and the insulation shielding layer, the electric field distribution can be effectively improved, and the maximum field strength reduced. Using a smooth shielding surface and appropriate shielding thickness can prevent localized electric field distortion. For higher voltage cables, stepped insulation or capacitor cone structures can be used to further optimize the electric field distribution. The application of these electric field control technologies enables medium- and high-voltage cables to operate stably for extended periods under higher voltage gradients, improving material utilization and reducing cable size.

The crucial role of medium- and high-voltage cables in the power grid is reflected in their function as the backbone of urban power grids and industrial power distribution. In urban construction, overhead lines are gradually being replaced by underground cables, and medium- and high-voltage cables bear the heavy responsibility of transmitting electricity from substations to various urban areas. In industrial parks, medium- and high-voltage cables connect main substations and distribution rooms in various workshops, ensuring a reliable supply of electricity for production. In large industrial and mining enterprises, medium- and high-voltage cables are used to power high-voltage motors, electric furnaces, and other equipment, meeting the demands of large-capacity loads. In the new energy sector, medium- and high-voltage cables are used as collection and transmission lines for wind power and photovoltaic power generation, transmitting green electricity to the power grid. Through advanced structural design and electric field control technology, medium and high voltage cables can meet the stringent requirements of the power backbone network for safety, reliability, large transmission capacity, and long service life.