Correlation and regression between the breakdown voltage and pre-breakdown parameters of vacuum switching elements

• The nondestructive method for determining the breakdown voltage of vacuum switching elements is shown.
• Correlation and regression between the breakdown voltage and pre-breakdown parameters have been examined.
• Observed pre-breakdown parameters were V-4, V-5 and V-6.
• The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts.

This paper considers the influence of switching operations on the characteristics of vacuum switching elements. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the pre-breakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10−4, 10−5, and 10−6 A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts.