Current Progress in Research on Very Fast Transient Overvoltage(VFTO)
The operation of disconnectors in gas insulated switchgear(GIS)generates very fast transient overvoltages(VFTO),which pose significant threats to both the GIS and the disconnectors themselves.This paper reviews the current research on VFTO,including its generation mechanisms and associated hazards,basic parameters,and the breakdown characteristics of related gaps.It also discusses the influence of operating speed on VFTO,VFTO withstanding testing of disconnectors,and methods for VFTO suppression,modeling,and calculation.Additionally,a method is proposed for estimating the breakdown characteristics of disconnector contact gaps using residual voltage measured on-site at a substation.This method is applied to a 750 kV GIS,with the aim of providing a basis for insulation coordination design.
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