Effect of Short Circuit Currents on Thermo-mechanical Properties of Insulated Cables

Cables are expected to have the ability to safely carry the rated short circuit current during abnormal dynamic conditions, such that a through fault does not damage the whole cable. For XLPE insulated cables, the maximum temperature during short circuits should not exceed 250 degrees C. This temperature must not adversely affect the conductor or the lead sheath. However, the effect of the thermo-mechanical stresses generated on the speed of degradation of the insulation system is of great importance. This paper analyses the influence of short circuit current on the interface between the cable sheath and insulation. Based on the theory of elasticity, a finite element thermomechanical model is proposed of a single core cable, incorporating temperature-dependent properties. The model demonstrates the importance of the mechanical properties of the insulation material, which plays a critical role in understanding the internal thermomechanical stresses within a cable.