Ablated Mass caused by the Arc in Plastic Tubes

Abstract

In expulsion fuses, load break switches, the electrical arc is formed in a wall made of organic materials during the switching period and the electrical arc induces ablation of these materials. Ablated mass of the organic material is entrained into the gas and arc flow. The estimate of ablated mass is important factor in the design of these devices, therefore, a number of theoretical and experimental investigations have been studied on high current arc in a narrow channel.
Ablation arcs in a cylindrical tube which has a pressure chamber at its one end have been investigated experimentally and theoretically. The ablation arc phenomena obtained experimentally are interpreted by the model consisting of four processes which are described by the relationship among the pressure distribu-tion, gas flow in the tube and the pressure in the pressure chamber . The estimate of ablated mass inside the tube under arc heating is essential for the theoretical construction of the ablation arc model. The data of ablated mass has been obtained by the experiment.
This paper describes the experiment and theoretical calculation about ablated mass of plastic tubes. Test samples are selected from the materials used for the arc chamber of switching devices such as load break switches for 6. 6kV distribution line and circuit breakers . The experimental data of ablated mass is obtained about three kinds of plastic tubes. The selected materials are OF (urea formaldehyde resin), POM (polyace-tal), PTFE (polytetrafluoroethylene). Theoretical calculation is made by means of an ablation model consid-ering absorption of thermal energy due to phase-change and heat conduction in the thin layer inside the tube wall. Theoretical calculation and measurement of ablated mass are in good agreement under the heat efficiency of 0.04_??_0.07 for the plastic tubes.