4. Igniting Experiments of Flat-type Cables by Dropping Saline Solution on their Damaged Insulation

T. Hagiwara, Y. Hagimoto; J. of Japan Association for Fire Safety and Engineering (JAFSE), Vol. 37, No. 5, (170), 1987

Abstracted by translator

This flat-type cable is used very popularly as the wiring behind the ceiling in Japan. It has two copper wires of 2.0 mm in diameter. Each wires are covered with flexible PVC insulation and they are covered again with the same insulating material. Concentration of salt in the distilled water was changed from 0% to 15% (0%, 1%, 2%, 3%, 5%,7%,10% and 15%). Load of 10 connected in series limited the maximum short current within 10 Amps. Main results are as follows:

a) Much longer time was needed to ignite the cables when the concentration of the solution was decreased below 5%.

b)Although insulating material has self-extinguishing characteristic, the insulating material continued to burn for about 20 minutes while an electrical arcing was generated. This burning was considered to be enough to ignite combustibles nearby.

c) The copper wire with arc marks was analysed by EDX and copper oxide was detected in its surface. ( This is not new and quite natural.)

d) Insulating materials carbonised showed high electrical conductivity. It was also analysed by EDX and chloridized copper was detected. ( This is also natural.)

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