As the load on building cable systems continues to increase, the performance requirements for cables used in electrical construction are becoming increasingly stringent. To meet market demand, numerous cable manufacturers are continuously developing new cable products to deliver high-quality, high-performance building cables. Let’s take a closer look at the performance and applications of mineral-insulated cables in cable systems.

　　Mineral-insulated cables used in cable engineering are primarily made from magnesium oxide, a non-combustible material that does not emit toxic fumes or other harmful substances when exposed to high temperatures. Consequently, cables that use magnesium oxide as the insulating material between the copper conductors and the copper sheath exhibit superior performance and numerous advantages.

　　1. High insulation.

　　Under normal conditions, as long as the moisture content of the cable is maintained below 0.4% in cable engineering applications, the insulation resistance of magnesium oxide insulation will be significantly higher than that of conventional insulating materials, thereby endowing mineral-insulated cables with superior insulation performance.

　　2. The cable project exhibits excellent heat resistance.

　　At high temperatures, neither the conductor core nor the copper sheath undergoes significant oxidation. Because the cable insulation has a low oxygen content, oxidation of the conductor core is relatively mild. However, the cable jacket, being exposed to ambient air, experiences severe oxidation, and the higher the temperature, the more pronounced the oxidation. When the temperature of the copper jacket exceeds 250°C, rapid oxidation sets in, leading to the formation of an oxide layer that reduces the jacket thickness. At 250°C, the jacket thickness decreases by 0.25 mm over approximately 240 years; at 1000°C, the same reduction occurs in just 2.87 hours. Therefore, the permissible normal operating temperature should be 250°C or lower. Moreover, when the copper jacket thickness is 0.5 mm, it can withstand operation at 1000°C for only 6.79 hours.

　　3. The cable project allows for a high current-carrying capacity.

　　Magnesium oxide-based materials exhibit high thermal conductivity and exceptional overload resistance, enabling fire-resistant cables to handle high current densities—particularly in small-cross-section cables. In cable installations, for cables of the same cross-sectional area, fire-resistant cables can carry a higher current than other types. Comparative studies show that small-size cables experience an approximately 30% increase in current-carrying capacity, while large-size cables see an increase of about 10%. Moreover, their superior overload capability is unmatched by other cable types.

　　4. Mechanical Properties.

　　Fire-resistant cables exhibit excellent mechanical properties and can maintain their operational performance even after undergoing significant deformation.

　　5. Excellent fire-resistant properties.

　　An investigation and analysis of the causes of electrical fire incidents in China’s building sector reveal that such incidents are predominantly triggered by cable self-ignition due to excessive load or short circuits, or by external ignition sources coming into contact with cables and causing them to ignite. In either case, the root cause is the poor fire-resistant performance of the cables themselves. By contrast, mineral-insulated cables are highly resistant to self-ignition and combustion because they are made from magnesium oxide, which has a melting point as high as 2,800°C and is inherently difficult to burn. Consequently, mineral-insulated cables offer excellent fire protection in cable installations.

　　6. The cable project exhibits excellent corrosion resistance and radiation resistance.

　　Due to the excellent corrosion resistance of copper sheaths, additional protective measures are generally not required. However, when cables are used in environments with severe chemical corrosion (such as acidic or alkaline conditions) or significant industrial pollution, fire-resistant cables with polyvinyl chloride sheaths should be selected. In addition, the copper sheath serves as a shielding layer, thereby providing radiation-resistant properties as well.

　　7. Cable systems have a longer service life and are safer and more reliable.

　　Because mineral-insulated cables consist of a copper conductor and an insulating sheath, forming a sealed, integral structure, the materials are highly resistant to oxidative degradation by atmospheric oxygen, thereby extending the cable’s overall service life. In addition, the copper sheath possesses inherent characteristics that enhance the cable’s grounding performance. Consequently, effective lightning protection and grounding measures can be implemented, ensuring the safe and reliable operation of electrical circuits.