INVESTIGATIONS ON THE INFLUENCE OF CURRENT INTERRUPTION OPERATIONS ON THE ON-SITE MEASUREMENT OF THE INTERNAL PRESSURE IN VACUUM INTERRUPTERS

Summary

From various pressure measuring principles, only the magnetron method, using a vacuum interrupter (VI) as its own gauge, was identified in previous investigations to be suited for a quantitative on-site assessment of the vacuum inside a sealed VI. The application of this pressure measuring principle, however, requires a disconnection of the vacuum circuit breaker (VCB) and thus, an electrical switching operation, influencing the internal pressure and the residual gas composition inside the VI. Due to the impact of the arcing on the high purity surfaces and the bound residual gases, the pressure measured after disconnecting the VCB can be different from the initial pressure before the VCB has been disconnected. Hence, the influence of current interruption operations on the internal pressure and consequently, on the interpretability of the result of the on-site vacuum assessment is addressed in this contribution. An experimental test setup for investigating the internal pressure in VIs immediately after current interruption is developed. Based on the magnetron method, a non-intrusive analysis of the internal pressure inside the VI is possible. First investigations with vented and baked-out VIs show that the arcing during the interruption operation leads to a limited increase of the internal pressure, in case a significant quantity of gas molecules was bound on the metallic surfaces inside the VI before arcing (e.g. as a consequence of the venting). For lower interruption currents with diffuse arcing, the observed pressure increase can be proven to be caused by a release of bound residual gases. In case of contracted arcing, the pressure increase results from erosion of the contact surface, leading to a release of enclosed residual gases. The results show the general applicability of the magnetron method for the non-intrusive investigation of the internal pressure in VIs after current interruption operations.

Additional informations

Authors

COSTER, Dessouky Sobhy Serry, Giussani Riccardo, van de Ploeg