Application Verification of Fireproof Mud in Flame-Retardant Class A Power Cables

Four cable specifications (WDZA-YJY 3×50 mm²+1×25 mm², 2×95 mm², 4×120 mm²+1×70 mm², and 3×185 mm²) were focused on to address the instability in combustion performance of 0.6/1 kV flame-retardant Class A power cables. Shortcomings of conventional structure (non-compacted stranded round copper conductor + cross-linked polyethylene insulation + polypropylene filling rope + wrapped high flame-retardant tape + tube-type extruded sheath) were analyzed, and three rounds of optimization were conducted to enhance their combustion performance. First optimization: replacing the conductor with a compacted profile copper conductor and the filling rope with a flame-retardant material; second optimization: increasing the number of high flame-retardant tape wrapping layers to 4 and changing the sheath extrusion method to semi-extrusion; third optimization: introducing a fireproof mud extruded oxygen barrier layer to replace traditional filling rope and partial tape structure. Test results showed that pass rate of conventional structure in combustion tests was only 20%, with carbonization heights generally exceeding 2.1 m. After optimization, all cables exhibited carbonization heights below 0.9 m, successfully passing flame-retardant Class A combustion test on the first attempt with a 100% pass rate. Performance-cost ratio analysis indicated that the third improved structure had extremely high cost-effectiveness. The study demonstrated that composite structure of the fireproof mud oxygen barrier layer and high flame-retardant tape significantly suppressed flame propagation through synergistic effects of expansion-induced oxygen isolation, heat absorption cooling, and physical fire resistance, providing a technical template for the design of flame-retardant Class A cables. However, attention must be paid to derivative issues such as increased outer diameter and decreased current-carrying capacity to balance comprehensive performance.