Transient Recovery Voltages in Vacuum Circuit Breakers Generated by the Interruption of Inrush Currents of Large Motors
The switching of medium voltage electrical motors is typically realized by means of vacuum circuit breakers (VCBs) essentially in view of their elevated number of switching cycles. As known, switching of VCBs generates important transient recovery voltages (TRVs) that need to be properly evaluated for both VCB sizing and insulation coordination. As large medium voltage electrical motors are installed into plants typically controlled by means of Supervisory Control And Data Acquisition (SCADA) systems, maneuvers that involve the motor inrush followed by its sudden de-energization (due to the intervention of an automatic diagnostic function), results into important TRVs. The paper aims at investigating the TRVs due to this specific type of VCB switching by means of a model that has been developed for the purpose, and has then been implemented in the EMTP-RV simulation environment. The validation of the implemented models makes reference to a real plant, and is obtained by comparing the simulation results with some experimental transients provided by the plant data fault recorder. The paper finally discusses the adequacy of different countermeasures by analyzing their effectiveness for the TRVs limitation.
Record created on 2012-06-14, modified on 2016-08-09