Series resonance protection is very important for GIS insulators. Once a flashover occurs, the capacitance changes abruptly, and the resonance conditions are immediately disrupted. The high voltage will collapse instantly rather than maintaining the arc, protecting the faulty point from being burned black, which is extremely beneficial for the later analysis of the fault cause. This is the "Secret Safety Skill" of the Series Resonant system.
The "Auto-De-Tuning" Effect: In a resonant circuit, the voltage is only maintained because L and C are in perfect harmony.
The Result: The moment a flashover (spark) occurs inside the GIS, the capacitance ($C$) changes instantly because of the arc path. This immediately destroys the resonance condition. The voltage crashes to near-zero in microseconds.
Protection: Because the voltage collapses so fast, the arc cannot "burn" or "carbonize" the surface of the resin insulator. Usually, the GIS can be retested after a short rest, whereas a traditional transformer might maintain the arc long enough to melt the metal and destroy the insulator.