Overcurrent Protection Response of a Hot Rolling Mill Filtering System: Analysis of the Process Conditions

This paper reproduces the abnormal operating conditions of a hot strip mill during different switching contingencies that may take place in the filtering system of the installation. Moreover, the evolution of the main electrical variables is predicted considering different characteristics of the steel to be milled. Within this work, the response of the overcurrent protection of the different filtering banks is analyzed along with different scenarios that could lead to switching operations in those filters. The analysis of the voltage stability and distortion at the point of common coupling (PCC), the evaluation of reactive power flows upstream of the PCC, the prediction of harmonic currents, and the study of the new operating conditions of the filters and the rolling stands under the said contingencies are assessed. The methodology described in this study provides the operator with important information on the expected electrical variables that can be extremely useful in deciding if the hot rolling mill can ride-through unexpected switching states of the filter banks. This forecast can avoid a good number of unscheduled stops, which could result in a significant reduction of production and economical losses.