The development of wide-area measurement system(WAMS)has provided a new method for solving inter-area oscillation problems in large interconnected power grids

but the time-delay and data-loss appearing with it exerts a negative influence on system stability. The damping torque analysis(DTA)is an important method to analyze small signal stability problems for its clear physical meaning. This paper describes the practical handling method of time-delay and data-loss. Then data-loss is turned from a probabilistic event into a precise numerical value by calculating its expected value. Thus the sampling model including time-delay and data-loss is deduced in both the time and frequency domain. On this basis

a DTA-based unified model considering time-delay and data-loss is developed. The model is applied to power system stabilizer(PSS)design drawing on the phasor method. Finally

the correctness and feasibility of the unified DTA model considering time-delay and data-loss is verified by actual examples.