Classification by Voltage Level
Power cables can be classified by voltage level into medium- and low-voltage cables (35 kV and below), high-voltage cables (above 110 kV), extra-high-voltage cables (275–800 kV), and ultra-high-voltage cables (1000 kV and above). Additionally, they can be classified by current type into AC cables and DC cables.
Classification by Insulation Material
1. Oil-impregnated paper insulated power cables: These cables use oil-impregnated paper as insulation. They have the longest history of application and are safe, reliable, durable, and cost-effective. Their main drawback is that installation is limited by elevation differences (drop height). The development of non-draining impregnated paper insulation resolved this limitation, allowing oil-impregnated paper cables to remain in widespread use.
2. Plastic insulated power cables: These cables feature an insulation layer made of extruded plastic. Common plastics used include polyvinyl chloride (PVC), polyethylene (PE), and cross-linked polyethylene (XLPE). Plastic cables have a simple structure, are easy to manufacture and install, are lightweight, and are not restricted by elevation differences during installation. Consequently, they are widely used for medium- and low-voltage applications and are trending toward replacing viscous oil-impregnated paper cables. Their primary disadvantage is the phenomenon of "treeing" (electrical treeing) leading to dielectric breakdown, which limits their use at higher voltages.
3. Rubber insulated power cables: The insulation layer consists of rubber mixed with various additives; this compound is thoroughly mixed, extruded onto the conductor core, and then cured (vulcanized) under heat. These cables are flexible and elastic, making them suitable for applications requiring frequent movement or installation with tight bending radii.
Common rubber compounds used for insulation include natural rubber/styrene-butadiene rubber (SBR) blends, ethylene-propylene rubber (EPR), and butyl rubber.
Classification by Voltage Level
1. Low-voltage cables: Suitable for fixed installation on AC 50Hz power transmission and distribution lines with a rated voltage of 3 kV or below.
2. Medium- and low-voltage cables (generally referring to 35 kV and below): Includes PVC insulated cables, PE insulated cables, XLPE insulated cables, etc.
3. High-voltage cables (generally 110 kV and above): Polyethylene cables, cross-linked polyethylene (XLPE) insulated cables, etc.
4. Extra-high-voltage cables (275–800 kV).
5. Ultra-high-voltage cables (1000 kV and above).