Determining the breaking capacity of vacuum interrupter chambers according to the failure criterion using a method of nondestructive testing

Аннотация

During research tests of vacuum interrupter chambers (vacuum interrupters, VIs), their breaking capacity is determined by bringing the chamber to a thermal failure, i.e., to a situation in which a VI is already unable to switch a current off and a safety switch of the test bench interrupts the current. Thus, the highest short-circuit current is defined, which can be interrupted by an opening switch with a VI under prescribed standard conditions. This current is characterized by the effective value of its periodic component and the fraction of the aperiodic component in the current curve. However, if in the case of a failure, some elements of the VI (or the chamber as a whole) are destroyed, this will impede analysis of the cause of this failure. This paper describes a test method in which the development of a failure is not allowed, and the risk of a failure is established on the basis of its primary features. It is shown that such features are a considerable burning-arc duration before the first arc-current zero and arc reignitions even at a low transient restoring voltage. It is also established that, for VI chambers with contacts that create an axial magnetic field, the rated breaking current can be determined using the failure criterion, for which the critical value of the electric charge, which is transferred through the vacuum arc before the first current zero, is adopted. This failure criterion makes it possible to reduce the number of tests that are needed for determining the rated breaking current. The calculated data for determining the values of the critical charge and the rated breaking current are presented.