Revealing the mechanism of pipeline-failure-induced cross-system fault propagation in hydrogen-blended integrated gas-electricity systems through transient analysis

Hydrogen blending in integrated gas-electricity systems can elevate pipeline failure risk, increasing the chance that localized disturbances propagate across interconnected systems and trigger cascading consequences such as large-scale outages. The existing literature mainly focuses on steady-state post-fault performance metrics, with limited attention to how faults evolve across interconnected subsystems. This omission hinders the comprehensive understanding of cascading mechanisms and the development of effective mitigation strategies. To address these gaps, this study systematically investigates the mechanism of pipeline-failure-induced fault propagation in hydrogen-blended integrated gas-electricity systems (HIGES). A novel fault-state transient simulation framework that integrates time-dependent failure evolution, heterogeneous dynamic gas flow, and power-system frequency response is proposed, with an iterative algorithm designed to resolve the temporal disparity. Case studies show that (i) the multi-stage propagation pathway is verified: pipeline failures generate pressure and composition fronts that disrupt hydrogen-blended electric-driven gas sources (HEGSs) and gas-fired units (GFUs), causing power deficits and frequency drops, while grid-side protection actions may in turn trigger re-escalation on the gas side; (ii) two distinct fault propagation regimes induced by hydrogen blending are identified, either pressure-transient-dominated or composition-transfer-dominated, depending on the failure location and gas source configuration; (iii) higher hydrogen blending and more severe pipeline failures accelerate fault propagation and cascading consequences: raising hydrogen from 0 to 90% reduces the propagation time from 897 to 271 s, while enlarging the leak reduces it from 5572 to 732 s. These results provide practical and theoretical guidance for fault isolation and resilient operation of HIGES.