ABSTRACT
As the GIS of 1,000 kV substation switches on/off the un-loaded busbar, gas breakdown and restrike generally occur between contactors due to the slow movement of contactors and the weak arc extinguishing capacity of the switch. Every breakdown will have a very steep traveling wave, and refraction and reflection will occur as the traveling wave encounters the mismatched point of wave impedance, resulting in Very Fast Transient Overvoltage (VFTO) with high-frequency oscillation. As the traveling wave arrives at the outlet bushing from GIS, electromagnetic leaks will occur and induce Transient Earth Voltage (TEV) at GIS enclosure. The space electromagnetic field and TEV will be coupled into the secondary equipment port by means of induction and conduction, and the traveling wave on the busbar will also pass directly to the secondary side via the potential transformer and the current transformer. During the commissioning of the expansion project of the UHVAC
equal to the ratio of the breakdown voltage and GIS wave impedance, the amplitude of switching transient of 1,000 kV substation is higher. In addition, because on-line monitoring devices scattered in the switch yard and some protection and control equipment increase and get closer to the source of disturbance, the EMC problem tends to occur.
