Measurement study of very fast transient overvoltage in GIS

In power system, pulse voltage is measured by both the circuit and the electric field. The special measure of VFTO is determined by non-alterable equipments of GIS. In this paper, external transient voltage is measured by electric spherical probe which means it is not necessary to access any equipments to the system. According to actual space between three phase external lead wire in GIS, we built the model, demarcated the system and imposed pulse voltage, the result of which indicated the feasibility. In addition, sphere probe improved measurable frequency range in the measuring system. From the experiment, we get transformation properties of electric spherical probe, and put forward two methods of rebuilding transient voltage of line based on transient voltage measured by spherical probe.