Abstract: The urban lifeline system refers to the key infrastructure system necessary to maintain the normal operation of the city and ensure the basic life of residents and the continuous development of social and economic activities, mainly including subsystems such as electricity, transportation, and gas. This type of system has the characteristics of spatial interweaving, functional dependence and implicit transmission of accidents, and is the basic support for the safe operation of the city. Aiming at the problem of cross-system coupling accident propagation and chain break control between power transmission and distribution network, gas supply network and traffic network in the lifeline system, this paper takes the uncontrolled transfer of energy as the driving mechanism of lifeline anomalies, and takes the leakage and explosion of LPG transport tank trucks as the typical scenario of damage to power grid facilities. Based on the case analysis, this paper carries out a quantitative analysis of the cascade failure evolution and consequences of the cross-system coupling accident chain composed of hazardous chemical leakage, explosion, road interruption, power grid function failure, etc., identifies the spatial and functional vulnerability points of the lifeline system, and puts forward suggestions for the control of the broken chain for urban spatial heterogeneity, which provides support for the refined analysis and emergency decision-making of urban lifeline cross-system coupling accidents driven by physical laws.

Key words: risk analysis, urban lifeline system, energy out of control, coupling risk, power grid