Changes in electrical insulation properties of fire resistant cables during a fire incident

This paper is focused on the comparison of the behavior of two low fire hazard cables of different construction under fire conditions. The fire barrier of the first one was created by glass and glass mica tape while the second one was protected by ceramifible silicone insulation. The insulation resistance between insulated cores of cables was measured and periodically recorded. The fire test was done according to IEC 60331, the whole test took 90 minutes of a burning and 15 minutes of cooling. The results show interesting changes in insulation properties of the cable in the first few minutes when the insulation resistance decreases by several orders of magnitude. On the other hand, during cooling the insulation, the state of cables is almost restored to its initial values.