Study on VFTO Suppression in 220  kV GIS Based on a Dynamic Synchronous Parallel Resistor Model

Very fast transient overvoltages (VFTO) in GIS during disconnector operation are strongly influenced by repeated breakdown and arc reignition. Conventional parallel‐resistor models usually apply time‐controlled switching and may not coincide with the actual arc state, leading to biased suppression assessment. This paper proposes a dynamically synchronized parallel‐resistor model implemented in ATP‐EMTP via the MODELS module, where the resistor is inserted and withdrawn in real time according to the instantaneous arc condition. A segmented arc model covering pre‐breakdown, steady arcing, and extinction is established using a hyperbolic function, a constant low resistance, and a simplified Mayr model, together with breakdown and extinction criteria, enabling full‐process reproduction of stepwise VFTO waveforms. Simulation on a 220 kV GIS substation verifies that the proposed scheme effectively reduces VFTO amplitude, wavefront steepness, and oscillatory components, while mitigating restrike development and trapped charge. By sweeping the parallel resistor from 100 to 800 Ω, the recommended range is 300–400 Ω; at 400 Ω, VFTO amplitude and breakdown steepness at the load side are reduced by 29.36% and 64.49%, respectively. A normalized impedance‐scale index R / Z tr is further introduced ( Z tr ≈ 70 Ω), yielding a recommended range of 4.3–5.7 for the studied system. © 2026 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.