SIMULATION AND MEASUREMENT OF VERY FAST TRANSIENT OVER VOLTAGES IN A 245KV GIS AND RESEARCH ON SUPPRESSING METHOD USING FERRITE RINGS

Very fast transient over voltages are generated during the switching of disconnections in gas insulated substation. Such over voltages can cause malfunctioning of protection circuits and control circuits and also initiates faults and influence on other components such as transformers. The suppression of VFTO (Very fast transient over voltage) is very important in GIS systems. There are some deficiencies in the existing suppressing methods. In this paper new idea for the suppressing VFTO by ferrite is put forward and the computer simulations were conducted on 245KV GIS models with and without ferrite rings and the results are verified with the experimental results. The simulation test results are closely matched with the experimental results so the use of magnetic rings to suppress VFTO is distinctly efficient.