Detection Of Early-stage PVC Cable Fires Based On SnO₂ Semiconductor Gas Sensors

Electrical fires are the largest number of fire accidents in the total number of fire accidents in recent years,which can cause serious casualties and economic losses.Therefore,accurate detection and alarm in the early stage of electrical fires can help reduce the occurrence of such fires.However,the existing detection method of electrical fire mainly focuses on the monitoring of residual current,temperature,fault arc and other signals,which cannot satisfy the requirements of the early alarm of electrical fires and is prone to misreport and miss alarm.Moreover,the equipment costs of these detection methods are relatively high,so it is highly important to find a universally applicable detection method that can achieve rapid early warning.Studies have shown that when electrical fires occur,the insulation of cables such as PVC cables can volatilize a large amount of gases due to overload,while the semiconductor gas sensor can respond to the volatilized gases rapidly.However,due to the variety of cables and the complex volatile gas composition,the specific gas composition of various kinds of cable pyrolysis gas is not clear,which limits the development of targeted response semiconductor gas sensors and the improvement of detection sensitivity.Based on this,this paper analyzed different types of PVC cable insulation pyrolysis gas by TG-IR and GC-MS.Firstly,the weight loss behavior and infrared absorption spectrum of PVC insulation raised to 800? under the air atmosphere were analyzed to obtain the possible products and their chemical bond functional groups.Through GC-MS experiments,the gas components released from PVC insulation at heating temperatures of 150,170,and 200? were analyzed.Although the pyrolysis gas composition was complex and highly variable,all PVC insulation evaporated from low to high temperature for 2-ethylhexanol gas with a considerable concentration,thus 2-ethylhexanol(2-EH)can be regarded as the characteristic gas for the pyrolysis gas of test cables.In order to obtain semiconductor gas sensors which are sensitive to the characteristic gas,SnO2 nanofiber gas sensing material modified by Au was synthesized by one-step electrospinning.The response value of SnO2-1%Au to 100ppm 2-EH at 240? was 6.37,which was 1.72 times higher than pure SnO2 nanofibers.SnO2-1%Au sensor,ZnO nano flower gas sensor,commercial gas sensor TGS 822 and smoke detector were placed in the simulation container to simulate the cable overheating test.The gas sensor can generate warning response at a cable temperature of 130?.With the increase of cable overheating temperature,the alarm response of the gas sensor became faster and faster,and all alarm responses were earlier than the sound and light alarm of smoke detector.At the same time,the response to different concentrations of interference gas and other types of fires were tested with semiconductor sensor group.The response of the cable pyrolysis gas was well distinguished from the response of other gases,which was helpful to reduce the false alarm rate in practical applications.Finally,a summary of this thesis and prospects for the future research and development were presented.