Investigation Into the Detection of Polyvinyl Chloride Pyrolysis Particles in 10-kV Switchgear Using a Laser Particle Sensor

Polyvinyl chloride (PVC) is extensively utilized in medium-voltage (MV) switchgear and is recognized as a fundamental material that contributes to switchgear fires. Currently, there is a notable deficiency in effective technical methods for the early detection of fires within MV switchgear. This study proposes a novel detection method for the incipient stages of fire and overheating defects in switchgear by monitoring the concentration of solid particles generated from the thermal decomposition of PVC materials using a laser particle sensor (LPS). This paper elaborates on the pyrolysis mechanism and process of PVC, analyzing the characteristics of both particles and gases produced during pyrolysis. Based on thermogravimetric–mass spectrometry (TG–MS) test results, gases such as HCl, CH₄, and CO are identified as characteristic gases. This study compares experimental results from corresponding gas detection sensors and LPS under varying temperature conditions. The results confirm that the detection of PVC pyrolysis particle concentration using LPS exhibits a faster response time and greater sensitivity compared to the detection of characteristic gases. Furthermore, this paper details the development of a PVC pyrolysis particle testing platform in the laboratory using the membrane weight method, and further validates the feasibility and accuracy of LPS for detecting PVC pyrolysis particle concentration through on-site testing. The experimental results demonstrate that the method proposed in this paper holds significant promise for the early detection of fires in MV switchgear.