Modeling, Analysis, and Verification of a Weld-Breaking Mechanism for Automatic Circuit Recloser Applications
Date of Award
Master of Science (MS)
The automatic circuit recloser (ACR) is responsible for protecting electrical distribution grids in the event that high voltage power lines come in contact with ground. In order to prevent damage, ACRs break the electrical continuity of the circuit through the use of a vacuum interrupter and a weld breaking mechanism. Vacuum interrupters consist of two metallic contacts in an air-tight ceramic housing. Due to the electrical interactions that take place during the interruption process, unintended welds are formed between the contacts. These welds have the ability to impede or completely stop the interruption process, thus rendering the ACR inoperable. In order to ensure that the ACR can interrupt current even when welds have formed, a mechanism is used to complement the opening force and impart an impact load on the weld. This mechanism is generally designed based on rules of thumb and engineering judgment. This thesis develops a dynamic model of an ACR, which acts as a blueprint for the further development and optimization of the weld-breaking motion. The dynamic model consists of four main submodels: the dynamic motion of the masses, the dielectric breakdown model, the contact bounce model, and the weld-strength model. The dynamic motion and the weld-strength model are developed based on first principles, while the dielectric breakdown model and the contact bounce model are determined based on experimental data. The overarching dynamic model is compared to performance data and shows good agreement.