Effective factors on the very fast transient currents and voltage in the GIS

According to reports that had been published in many papers, switching operation in gas insulated substation (GIS) lead to malfunction in the substation equipments. These improper functioning contain of malfunction electronic equipments and deformation of transformer winding and bushing failures. The reason of malfunction of electronic equipments is due to coupling voltages on data and control cables. The reasons of these problems are travelling waves which is generated during switching operations in a gas-insulated substation (GIS). To evaluate these cases, it must be performed an accuracy analysis on the wave shape and level of the very fast overvoltage (VFTO) and very fast transient currents (VFTC). In this paper the effective factors on the wave shape and level of the VFTC and VFTO is investigated and the beneficial approaches for the industry to finding the optimum approaches for VFT mitigation, is presented. These factors are included trapped charge, entrance capacitor, compensation resistor, hybrid compensation L and T types and variation of arrangement of switchgear. As variation of switchgear arrangement is included variation of lengths, branches (bypasses) and series capacitor (disconnectors opened).