Combined heating and power integrated energy system (IES) have gained increasing attention due to their high energy efficiency. However, the stronger coupling between subsystems also introduces the risk of cascading failures, which poses a significant challenge to their widespread application. To address this issue, this chapter employs dynamic simulation to investigate the fault propagation mechanism between heating and power systems, using pipeline leakage as a case study. Insights are provided from a simulation perspective to enhance the resilience of IES. First, this chapter introduces the equipment models, network operating conditions, and pipeline leakage models that account for both hydraulic and thermal effects under normal operating conditions. Next, a dynamic simulation framework for fault conditions in IES is proposed. This framework adaptively adjusts simulation strategies based on different fault scenarios and is applicable to common fault analyses in such systems. Finally, a case study of a 22-node IES is conducted to compare the impact of pipeline leakage on strongly coupled IES (SC-IES) and weakly coupled IES (WC-IES). Simulation results indicate that in SC-IES, the effects of pipeline leakage can propagate bidirectionally between the heating and power systems via combined heat and power (CHP) units, underscoring the critical role of coupling equipment conditions in enhancing system fault tolerance.