THHN/THWN copper cable (stranded 500, 600, 700 Kcmil, 600V) is a high-performance and widely used power transmission cable. With its unique structure and material, it plays an important role in various fields such as industrial, commercial and civil buildings.​ In terms of specification parameters, these three types of cables have their own characteristics. The 500 Kcmil cable has a cross-sectional area of approximately 253mm². The conductor is composed of multiple strands of copper wires, with a single copper wire diameter of about 0.5mm, and the overall diameter after stranding is about 16mm. At 20℃, the maximum DC resistance does not exceed 0.031Ω/km, and the current-carrying capacity when laid in air can reach 380A, which can meet the power demand of medium-power equipment. The 600 Kcmil cable has a cross-sectional area of about 304mm² and an overall diameter of about 18mm. At 20℃, the maximum DC resistance is no more than 0.026Ω/km, and the air current-carrying capacity is about 420A, which is suitable for higher-power power supply scenarios. The 700 Kcmil cable has a cross-sectional area of about 355mm² and an overall diameter of about 20mm. At 20℃, the maximum DC resistance is no more than 0.022Ω/km, and the air current-carrying capacity can reach 460A, which can cope with high-load power transmission tasks. All three specifications have a rated voltage of 600V, which meets the standards of low-voltage power distribution systems. The long-term operating temperature is 90℃, and the short-term operating temperature can remain stable in humid environments, which can adapt to temperature changes in different environments.​ In terms of materials, the conductor is made of high-purity multi-strand electrolytic copper with a purity of more than 99.95%, ensuring good conductivity and effectively reducing energy loss during current transmission. The high conductivity and thermal conductivity of copper enable the cable to dissipate heat quickly during operation, avoiding performance degradation due to overheating. The insulation layer is made of polyvinyl chloride (PVC) or cross-linked polyethylene (XLPE) materials. The insulation layer of THHN type cable is a thermosetting polymer, which has high heat resistance and mechanical strength; THWN type, on the basis of THHN, adds moisture resistance design, which is more suitable for humid environments. This insulating material not only has excellent insulation performance with a volume resistivity greater than 1×10¹⁴Ω·cm, which can effectively block current and prevent electric leakage accidents, but also has certain chemical corrosion resistance and weather resistance, and can maintain stable performance in complex environments.​ In terms of characteristic uses, 500 Kcmil cables are often used in power supply lines of medium-sized motors, large compressors and other equipment in industrial plants, and can also be used as the main distribution trunk of commercial buildings to provide stable support for the power system of the entire building. 600 Kcmil cables are suitable for power transmission of large industrial equipment, such as rolling mills in steel plants, reactors in chemical plants, etc. At the same time, in the power distribution system of high-rise buildings, they can be used as main lines to transmit power to multiple floors. Due to its large current-carrying capacity, 700 Kcmil cables are often used in main incoming cables of large data centers, auxiliary power supply systems of large power stations, and power supply for high-load equipment in heavy industries such as mines, which can meet the continuous power demand of high-power equipment.​ In addition, the multi-strand stranded structure of THHN/THWN copper cable makes it have good flexibility, which is convenient for bending and threading in complex wiring environments, reducing construction difficulty. Its moisture resistance (especially THWN type) makes it reliable in wiring in humid areas such as underground garages, bathrooms, and kitchens. At the same time, the insulation layer of the cable has certain flame retardant properties, which can delay the spread of fire in case of fire, buying time for personnel evacuation and fire rescue.​ In conclusion, THHN/THWN copper cable (stranded 500, 600, 700 Kcmil, 600V) has become an ideal choice in various power transmission systems with its reasonable specification design, high-quality materials and wide range of application scenarios, providing stable and safe power guarantee for industrial production, commercial operation and residents' lives.