Considering a class of networked control systems with long time delays, the fault detection is carried out with
the presence of control delays and data packet dropout. Firstly, a modeling approach of the system is presented, and the
fault observer is modeled as a stochastic switching discrete-time linear system with delay. Then, based on Lyapunov stability
theory, a linear matrix inequation gives the stability condition of this observer. When the system is normal, if the given
inequality condition is satisfied, the observer is stable. When a fault is present, the observer residual can change rapidly and
detect the occurrence of the fault. Finally, an illustrative example shows the effectiveness of the proposed method.