Heat blockage of air gap for inner overheating of high-voltage power cable and delay of early detection

Early detection for inner overheating of high-voltage cable is important for safe power supply. A new radial heat transfer model is developed for a typical 110 kV cable with an air gap layer. Numerical analyses are conducted for dynamic temperature field in cable induced by hot copper core with different thicknesses of air gap. The results show that the air gap has an important heat blockage for the outward heat transfer in cable. The air gap causes the temperature inside the overheated cable to rise faster and the temperature outside slower. The air gap not only reduces the response sensitivity of the surface temperature on inner overheating but also induces the inner layers to heat up and even break down. Finally, the non-dimensional temperatures on cable surface indicate that the detection of inner overheating cable would be delayed if the air gap is not considered in calculation models.