Electromagnetic disturbances in gas-insulated substations and VFT calculations

This paper is focused on the oscillating frequencies of very-fast transients (VFTs) generated by disconnector and circuit breaker operations in gas-insulated substations (GISs) related to electromagnetic disturbances (EMDs). Test results of the VFT amplitudes and oscillating frequencies are summarized, and the measured results have shown that there is no significant difference of the frequencies in the high-voltage main circuits and the low-voltage control circuits in the GISs. Modeling of GIS elements for VFT simulations by EMT-type software are explained, and simulation examples are demonstrated in comparison with test results. Also, FDTD (finite-difference time-domain) computations are performed, and the calculated results are compared with EMTP simulation results. If proper modeling is adopted, EMTP and FDTD results show a reasonable agreement.