VFT is mainly characterized as very fast transient overvoltage on GIS bus-bar bushing, and as the raise of transient earth voltage on GIS enclosure, and as transient electromagnetic field ( TEM ) around the GIS. 主要表现为:GIS母线套管上的快速暂态过电压和GIS壳体上的暂态地电位升高以及GIS周围空间产生暂态电磁场。