Dielectric strength of the vacuum interrupter sections after termination of the electric life

The dielectric strength of the vacuum interrupter (VI) sections is studied after termination of the electric life. It is shown the reduction of the electric life occurs in particular cases and its reason is the appearance of more low voltage breakdowns called as "slow" because of increasing almost by an order the time of the voltage drop to zero during breakdown (several microseconds against fractions of a microsecond for breakdowns in new vacuum interrupters). The conditions of occurrence of such "slow" breakdowns are considered.