In power transmission and distribution systems, cables are the crucial link connecting energy sources and end-user equipment. Depending on the application and voltage level, cables are generally classified as low-voltage cables and high-voltage cables. Understanding the core differences between these two types is essential for ensuring the safety, reliability, and economy of the power system.

Voltage Level Definition

The most fundamental difference between high and low voltage cables lies in their applicable voltage levels. Typically, the voltage level is the core factor determining the complexity of the cable's insulation structure.

Low-voltage cables are generally used in power systems of 1kV and below. For example, common 0.6/1kV rated voltage cables are widely used in building power distribution, industrial equipment power supply, and urban low-voltage power grids. These cables are responsible for transmitting electrical energy from the distribution box to the final consumer equipment.

In contrast, high-voltage cables are used for transmission scenarios with higher voltages. Taking 110kV as an example, these cables are mainly used in urban main power grids, incoming and outgoing lines of large substations, and long-distance power transmission. 110kV falls under the high-voltage category, designed to achieve high-capacity, low-loss power transmission.

Differences in Structure and Materials

Due to the vastly different voltage levels they bear, high- and low-voltage cables exhibit significant differences in their internal structural design and material selection.

1. Conductor and Insulation Design

Taking a typical flame-retardant low-voltage cable as an example: Flame retardant LV Low Voltage Cable 0.6/1kV CU/XLPE/STA/PVC Class C power cable. This cable uses copper conductors (CU) and cross-linked polyethylene (XLPE) as insulation material, with a rated voltage of 0.6/1kV. For low-voltage cables, the main function of the insulation layer is to prevent phase-to-phase short circuits and ground leakage; the structure is relatively simple and the insulation thickness is thin.

High-voltage cables are completely different. Taking a 630mm² High Voltage Cable 110kV Electric Single Core Copper Water Proof Resistant Power as an example, although it also uses copper conductors and cross-linked polyethylene (XLPE) insulation, the insulation layer thickness of the 110kV high-voltage cable is much greater than that of the low-voltage cable. More importantly, high-voltage cables typically have conductor shielding layers and insulating shielding layers inside and outside the insulation layer. These shielding layers are made of semi-conductive materials to uniform the electric field and prevent partial discharge (PD). Under high voltage conditions, the electric field stress is highly concentrated; without a proper shielding structure, the cable will be damaged by breakdown in a very short time.

2.Armor and Sheath 

Low-voltage cables often require a certain level of mechanical protection to adapt to complex laying environments. The aforementioned low-voltage cable uses steel tape armor (STA) with an outer polyvinyl chloride (PVC) sheath and C-class flame retardant properties. This design allows it to withstand certain mechanical stress and is suitable for direct burial, conduit installation, or indoor environments requiring flame retardant safety.

High-voltage cables place greater emphasis on waterproofing and radial mechanical protection. The aforementioned 110kV high-voltage cable is a typical single-core high-voltage cable structure, typically using a corrugated aluminum sheath or polyethylene (PE) sheath and featuring a water-blocking structure. Since high-voltage cables are often laid underground or underwater, moisture intrusion can lead to insulation dendrite growth, ultimately causing insulation breakdown; therefore, its waterproof performance is of paramount importance in structural design.

Application Scenarios and Installation Requirements

Due to differences in structure and materials, high-voltage and low-voltage cables have different requirements for installation and use.

Low-voltage cables have a wide range of applications, from power supply trunk lines in residential buildings to equipment wiring in factory workshops. Because of their relatively small bending radius (e.g., the minimum bending radius of the aforementioned low-voltage cables is 12D to 15D, where D is the cable's outer diameter), they offer high installation flexibility and require relatively fewer construction tools.

High-voltage cables are mainly used for main power transmission lines. 110kV single-core cables have stricter requirements for bending radius during laying. Furthermore, because single-core cables generate alternating magnetic fields during operation, they typically require clamps made of non-magnetic materials for fixation, and the arrangement must be considered to reduce eddy current losses. In addition, the manufacturing process for intermediate joints and terminations of high-voltage cables is extremely complex, usually requiring operation by specially trained professionals. The installation quality directly affects the operational safety of the entire power grid.

Summary

In conclusion, both low-voltage and high-voltage cables are indispensable components of modern power systems. Low-voltage cables prioritize convenience and safety in terminal power distribution, while high-voltage cables focus on stability and efficiency for large-capacity, long-distance transmission. When selecting cables, it is essential to accurately choose products that meet the standards, based on the rated voltage of the actual project, the laying environment, and the electrical performance requirements. Only by fully understanding the fundamental differences between high- and low-voltage cables can we ensure the safe and reliable operation of the power system from source to end.