HOW TO OPERATE EAF SYSTEMS SAFELY USING VACUUM TYPE FURNACE BREAKERS

摘要

Switching of furnace transformers using vacuum circuit breakers always necessitates surge protection devices that include RC elements and surge arresters. Only then it is possible to prevent the insulation of all the electrical equipment, mainly of furnace and step-down transformers as well as series reactors (if available), from overstressing due to effects called "multiple re-ignitions" and "virtual current chopping." There are a number of influencing factors to be taken into account when evaluating an appropriate protection system/scheme to ensure safe plant operation for all the system conditions and over a long service life. Although it appears that different plants look quite similar, each system is unique. The bus routing between furnace breaker and transformer can have a significant influence on the damping behavior of RC elements which cannot always be located as desired or as would be ideal from the electrical point of view. Unfavorable changes of system conditions can result in failures causing plant outages and correspondingly high economic losses. The expense for studies makes up a fraction of such losses and provide reassurance of a reliable system, if performed in the planning stages. As can be concluded, it is not possible to standardize such protection systems. It is therefore left to specialists with comprehensive knowledge and years of experience to design such equipment.