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Differences Between High-Voltage and Low-Voltage Cables--Shanghai Shenghua cable Group Co,.Ltd
Differences Between High-Voltage and Low-Voltage Cables--Shanghai Shenghua cable Group Co,.LtdWhile the names might suggest that the primary difference lies in voltage levels, the distinctions between high-voltage and low-voltage cables are actually substantial, encompassing initial design concepts, material selection, and application scenarios. Let's explore these differences together.Application ScenariosLow-voltage cables are primarily used for "end-point power supply," connecting the low-voltage side of transformers, distribution boxes, and electrical equipment. They are common in residential buildings, commercial complexes, and small factories. Transmission distances are short (typically tens to hundreds of meters), and voltage levels are low (mainly 220V, 380V). They do not require complex supporting systems; simple protective switches are sufficient for safe control.High-voltage cables, on the other hand, undertake "medium to long-distance power transmission" tasks. They are used for power transmission from power plants to substations and between substations themselves. Applications include urban power grids, cross-regional transmission, and offshore wind farm grid integration. Transmission distances can range from several kilometers to tens of kilometers, with voltage levels varying from 10kV to 1000kV. Due to the high transmitted power and voltage, high-voltage cables require complex supporting systems, including equipment like lightning arresters, instrument transformers, and grounding devices, to monitor operational status, limit overvoltage, and ensure safe grounding during faults. The entire system's design, operation, and maintenance must adhere to strict standards.Insulation StructureLow-voltage cables (typically referring to 1kV and below) have relatively simple insulation requirements. Most employ a single-layer insulation design, commonly using materials like Polyvinyl Chloride (PVC) or Polyethylene (PE). Due to the low transmission voltage, the insulation's main role is to prevent leakage and short circuits. The insulation layer is relatively thin (generally a few millimeters), and the structure is often a simple combination of "conductor + insulation + sheath." Some low-voltage cables may even omit the sheath for use directly in dry indoor environments.High-voltage cables (typically 10kV and above) face extremely high electric field strengths. A single insulation layer cannot withstand the risk of high-voltage breakdown. Therefore, they adopt a "multi-layer composite insulation" structure. The core insulation layer uses materials with superior dielectric properties, such as Cross-Linked Polyethylene (XLPE) or oil-impregnated paper, with thicknesses reaching tens of millimeters. Additionally, "semiconducting screens" (conductor screen and insulation screen) are added to evenly distribute the electric field and avoid localized field concentration that causes insulation aging. Some extra-high-voltage cables are also equipped with an "insulation cushion layer" and "water barrier layer" to further enhance insulation reliability and service life. This multi-layer design is like putting "body armor" on the cable, providing all-round protection against the erosion of high voltage.Conductor DesignLow-voltage cable conductors focus on "efficient conductivity." They are typically made of copper or aluminum cores, with a round cross-sectional shape. The number of strands is relatively low, and the manufacturing process is simpler. As they transmit high currents (low-voltage supply requires high current over short distances), the conductor cross-sectional area is flexibly adjusted based on load requirements, focusing primarily on reducing resistive losses without excessive consideration for electric field effects.High-voltage cable conductor design must balance the dual needs of "conductivity" and "electric field control." Besides using high-conductivity copper cores (aluminum cores are less common in high-voltage applications due to oxidation issues at joints affecting insulation), the conductor surface undergoes "compaction treatment" to reduce burrs and gaps, avoiding electric field concentration on irregular surfaces. For extra-high-voltage cables, a "segmented conductor" structure might be used, dividing a single thick conductor into multiple insulated thinner strands to reduce losses caused by the skin effect. Furthermore, selecting the conductor cross-sectional area for high-voltage cables considers not only current capacity but also thermal stability and mechanical strength.Protective PerformanceLow-voltage cable protection design follows the principle of "suitability for常规 environments." For outdoor use, a PE sheath might be added for moisture resistance. When installed in conduits, non-armored cables can be used. The protection focus is on preventing mechanical damage and slight corrosion, with a relatively low safety margin. For example, BV wires (PVC insulated copper core wires) used in home decoration rely solely on the insulation layer and a thin sheath to meet the needs of dry indoor environments.High-voltage cable protection emphasizes "adaptation to extreme environments" and "safety margins." As they are often used for outdoor burial, aerial installation, or submarine laying, they must withstand soil corrosion, external force impact, temperature changes, and other challenges. Therefore, high-voltage cables are equipped with an "armor layer" (steel tape armor, steel wire armor) to enhance mechanical strength and prevent crushing or piercing during installation or operation. The sheath uses materials with better weather ability and corrosion resistance (e.g., polyolefin sheath, lead sheath). Buried high-voltage cables also incorporate "water-blocking tapes" and "metallic screens" to prevent moisture ingress that could lead to insulation breakdown. Additionally, the protective design must consider safe isolation during faults to prevent accident escalation.Joints and AccessoriesFrom Simple Connection to Precision SealingLow-voltage cable joints and accessories (like terminal blocks, junction boxes) have simple structures. Their core function is to connect conductors and ensure electrical continuity, with relatively low requirements for insulation and sealing. For instance, household terminal blocks only need tightening and wrapping with insulating tape to meet insulation needs, offering low cost and easy installation.High-voltage cable joints and accessories are "core safety components" with extremely high technical requirements. Under high electric fields, the insulation transition and electric field control at joints are critical weak points; improper handling can easily cause breakdown accidents. Therefore, high-voltage cable accessories (e.g., straight joints, terminations) often use "prefabricated" or "cold shrink" structures, incorporating screens and insulation components to ensure a uniform electric field at the joint. Connection requires strict cleanliness control to avoid impurities affecting insulation, along with precision sealing to prevent moisture and dust ingress. Some EHV cable accessories are filled with insulating oil or gel to further enhance insulation performance. Moreover, the materials for high-voltage accessories must be compatible with the cable insulation, having matching coefficients of thermal expansion to avoid seal failure due to temperature changes.The above outlines the key differences between high-voltage and low-voltage cables.Shenghua Cable Group, founded in 1954 and ranked among the top 500 machinery manufacturers in China, is a highly capable wire and cable manufacturer. Its product range encompasses hundreds of thousands of types, including but not limited to: KVVP shielded control cables, ZR-YJV22 armored power cables, ZR-BVR/RVS/RVV PVC insulated sheathed household wiring cables, YJLHV aluminum alloy cables, BTTZ mining cables, aerial cables, and fire-resistant specialty cables. All products are manufactured in compliance with national standards, ensuring guaranteed quality. For reliable cables, choose Shenghua Cable.
