A new test method for the assessment of the arc tracking properties of wire bundles in air, oxygen enriched atmospheres and vacuum

摘要

Damage to the cable insulation in an aircraft or spacecraft network can lead to a high current arc burning between metal conductors of damaged cables. This high current arc can develop or is sustained as long as no self-extinguishing process is begun or as long as the system protection is not engaged. Neighbouring cables of a bundle can be damaged as a result of the high temperature of the arc finally leading to the arc propagation. After the arc extinction, the phenomenon may reappear if the system is re-energised. Many different processes are included in the arc-tracking or arc propagation failure and therefore many test methods have been developed to assess the consequences of these phenomena. At least 25 methods and standards covering different aspects of arcing and arc-tracking have been identified. For the specific spacecraft conditions (e.g. vacuum and oxygen enriched atmosphere, DC network) no regular are tracking tests of cable bundles have been performed. The paper presents the concept of a new arc tracking test of wires for space application. Furthermore, the test procedure, test equipment and the results of the investigations of the arc behaviour on the cable bundles in air, oxygen enriched atmosphere and vacuum have been shown. The results indicate that the damages caused depend strongly on the kind of insulation material, the cable size and construction, the test current value and the environmental conditions. For certain wires the arc tracking effects are increased at higher oxygen partial pressure and significantly increased under vacuum.