Experimental Investigation of Aging Effects on the Combustion Performance of the Tunnel Cable

Abstract

Cables are laid tightly in the tunnel, which are an important part of modern power transmission infrastructure. Large power transmission and cable aging can cause cable fires easily, and high fire smoke temperature threatens the stability of tunnel structure, meanwhile smoke toxicity causes evacuees poisoning in the tunnel. The combustion performance including the ignite time (TTI), heat release rate (HRR), critical heat flux, fire performance index (FPI), fire growth index (FGI), and smoke production about ZR-Y44JV cable used in tunnels are investigated by cone calorimeter and multifunctional flue gas analyzer. The cable aging time and temperature in experiments are determined based on the thermal aging mechanism of cable sheath and cable insulation. The increase of aging time leads to flash ignition and the increase of ignition time and changes the HRR curve, wherein the plateau stage occurs after the second heat release peak, and the initial peak PHRR1 decreases firstly and then increases. Due to the early pyrolysis, the mass loss of cable combustion changes earlier than the initial HRR change point. The occurrence time of the peak mass loss rate (MLR) is delayed firstly and then advanced with the increasing cable aging time, and the maximum MLR peak time is earlier than that of the unaged cable. It is verified that the aging ZR-YJV cable is still suitable for the hot thickness material model. The fire performance index and fire growth index of the cable are calculated and show that the fire hazard decreases firstly and then increases.