This article introduces the 0.6/1kV NYY-J series cables, which include two specifications: 3×50mm² and 4×50mm². Both belong to low-voltage power transmission cables and are widely used in scenarios such as building power distribution, industrial equipment connection, and outdoor laying. The rated voltage of this series of cables is 0.6/1kV, where "0.6kV" refers to the rated power frequency voltage between the cable conductor and the ground, and "1kV" refers to the rated power frequency voltage between conductors. They are suitable for power transmission in fixed laying in low-voltage distribution systems and can meet the daily electricity needs of residences, commercial buildings, factories and other places. In terms of structure, both specifications of cables use high-purity copper as conductors. Copper conductors have excellent electrical conductivity and mechanical strength, which can effectively reduce losses during current transmission. The outer layer of the conductor is wrapped with a polyvinyl chloride (PVC) insulation layer. PVC material has good insulation performance, chemical resistance and weather resistance, which can ensure electrical isolation between conductors and between conductors and the outside world, avoiding potential safety hazards such as short circuits or electric leakage. "Double sheathing" is a prominent feature of this series of cables, that is, an additional two layers of PVC sheathing are provided outside the insulation layer. The inner sheath mainly plays a role in further insulation and buffering, protecting the insulation layer from mechanical damage; the outer sheath enhances the overall protection capability of the cable, enabling it to adapt to different laying environments, such as buried, piped or exposed to the air, and also has certain wear resistance, ultraviolet resistance and impact resistance. The "NYY-J" in the model represents the specific type and structure of the cable. Among them, "N" usually indicates PVC insulation, "Y" indicates PVC sheathing, and "J" may represent a specific structural or application improvement (the specific meaning needs to refer to relevant standards or manufacturer definitions). The difference between 3×50mm² and 4×50mm² lies in the number of conductors. The 3-core cable is suitable for three-phase three-wire circuits, while the 4-core cable includes a neutral wire, suitable for three-phase four-wire circuits, which can be selected according to the needs of the actual distribution system. In general, the 0.6/1kV NYY-J 3×50mm² and 4×50mm² PVC insulated and double sheathed cables, with their reliable electrical performance, solid structure and wide adaptability, have become an ideal choice in the field of low-voltage power distribution, providing safe and stable power transmission guarantees for various electricity usage scenarios.