Tracking and Ignition Phenomena of Polyvinyl Chloride Resin under Wet Polluted Conditions

This paper describes tracking and ignition phenomena of distribution cable and sheet specimens of polyvinyl chloride (PVC) resin on the basis of experimental results obtained by a test method conforming to the IEC tracking test method. Also, the processes of tracking associated with the ignition and combustion of PVC resin are discussed. In the tracking test using two kinds of F-Cables made of PVC resin, depending on the shape of the specimens, F-Cables may be ignited. From the results, it is found that a dry band is apt to form on the specimen and that tracking occurs by an arc across the dry band. The jacket is ignited by the arc under the test condition in which the deteriorated parts are always in contact with the open air. For the sheet specimens made of PVC resin, free carbon deposited by the heat of the scintillations forms a band, and the arc is produced between the carbon band and an electrode when the voltage gradient exceeds 14.2 kV/cm. The arc recurrence frequency is from 3 to 8 s-i just before ignition. The sheet specimens compounded with DOP, TCS, plus other mixtures are apt to produce an arc in comparison with the specimen compounded with only DOP and TCS, and the resistance to tracking and ignition is increased by including paraffin chloride and high melting point paraffin.