  It is known that most of the electrical cables use as insulation compositions
based on polyvinyl chloride. Like most polymers, the latter is quite sensitive
to thermal aging, which is not without reason, to be one of the main causes of
the various types of faults in the polymeric insulation, leading eventually to
a short circuit and fire. On the example of the most common polymer
insulator-PVC subjected to preliminary partial thermolysis, simulating the
process of accelerated aging, we for the first time show that in this case as a
result of the aging process, the electrical conductivity of PVC can acquire
abnormal (not obeying Ohm's law) character. In this case, transitions from a
state with normal (low) conductivity of PVC into the state with an ab-normally
high conductivity was clearly observed, being spontaneous uncontrollable
process. Es-pecially the large-scale nature of these changes allowing easily
transferring polyvinylchloride from a state of typical dielectric (insulator)
in a class of conductors attracts attention.). Thus, an-other one of the most
important features of a short circuit in the PVC insulation is opened. It is
noted that the reduction of fire hazards in this case (by the maximum possible
elimination of the phenomenon of short circuit due to thermal aging of
polymeric insulation) should be preventive in nature, as the most effective,
simple and convenient way.
