Experimental Study on Thermal Decomposition of Polyvinyl Chloride Outer Sheath of 110 kV High Voltage Cable

The state of the polyvinyl chloride (PVC) outer sheath of cable before combustion has not been fully clarified, especially in relation to thermal decomposition gas research. To further establish the cable fire warning technology based on thermal decomposition gas, the author of this paper sets up an experimental platform for thermal decomposition of high voltage cable outer sheath. The objective is to investigate the thermal decomposition characteristics of 110 kV high voltage cable PVC outer sheath in oxygen-free and oxygen conditions. The thermal decomposition behavior of PVC outer sheath in nitrogen and air atmospheres were studied by Fourier Transform Infrared (FTIR) spectroscopy. The characteristic gases produced by thermal decomposition were revealed by infrared spectroscopy. The effects of heating temperature and heating time on these characteristic gases were investigated. The results showed that the thermal decomposition gases of the PVC outer sheath of 110 kV high voltage cable in two atmospheres were mainly H₂O, CO₂. Also found were small amounts of alkanes, as well as dioctyl phthalate (DOP) and 2-ethylhexanol (2-EH). The peak absorbance of DOP was influenced by the heating temperature and heating time, while that of 2-ethylhexanol was almost not influenced by the heating temperature. The experimental results of this paper will provide theoretical and technical support for the early warning of cable fires.