Surge Protection for Ladle Melt Furnaces

摘要

Vacuum circuit breakers (VCBs) are commonly applied to the primary circuit to switch Ladle Melt Furnace (LMF) transformers in melt shop applications that support rolling mill operations. Because of the well documented phenomenon of switching transients induced on the line of the furnace transformer due to the opening and closing of the vacuum circuit breaker, most LMFs in this application also have surge protection applied at the transformer terminals. This paper contains an analysis of one such location with two identical LMFs, each fed by a VCB where the LMF transformer terminals were equipped with primary surge protection consisting of surge arresters and snubbers. Recently, high transient counts and increased levels of combustible gasses in oils samples raised concerns and led to a field investigation, measurements, electromagnetic transient program (EMTP) simulations, and evaluation of the surge protection of both LMFs. Power quality measurements identified the transients experienced by the surge arresters at the transformer terminals. EMTP simulations reproduced the transients, determined a worst case switching event, and proper surge protection for each LMF transformer.