Very fast transients in GIS

Abstract

Different types of very fast transients (VFTs) are classified and their characteristic parameters are summarized based on measurements in a 800 kV SF/sub 6/ gas-insulated pilot installation and 420 kV GIS (gas-insulated switchgear) in service. The electromagnetic field between the enclosure and earth results in a transient enclosure voltage of up to some 10 kV and at the same time in a radiated electromagnetic field from the enclosure with amplitude of some 10 kV/m. The electromagnetic wave guided by the overhead line results in an overvoltage with a multifrequent oscillation of some 10 to 100 kHz, depending on the parameters of the overhead line and the adjacent equipment, e.g. the transformer. The transient enclosure voltage and measures to reduce it are analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>