Simulation of Capacitively Graded Bushing for Very Fast Transients Generated in a GIS during Switching Operations

In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) aregenerated due to switching operations and ground faults. These fast transients are associated with high s of MHz. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420 kV graded bushing for high frequency pulses of rise time 1 to 50 ns, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with diferent equivalent layers has been considered. The effect of influence of coper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients. In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) aregenerated due to switching operations and ground faults. These fast transients are associated with high s of MHz. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420 kV graded bushing for high frequency pulses of rise time 1 to 50 ns, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with diferent equivalent layers has been considered. The effect of influence of coper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients. KCI Citation Count: 1