NANOSECOND SWITCHING TRANSIENTS RECORDED IN A MINING TRANSFORMER INSTALLATION

Tests carried out on a mining transformer supply system to determine t he severity of the switching transients developed with a range of syst em and plant conditions are described. Results obtained with vacuum an d SF6 circuit-breakers are presented and indicate that very fast trans ients with wavefront durations as short as 10 ns are frequently produc ed. An examination of the transients is made and the system and plant parameters that lead to the production of very fast transients are ide ntified. Wavefront duration is mainly governed by system parameters an d wave amplitude by type of circuit-breaker. The relevance of the resu lts to other types of transformer supply systems is indicated.