This chapter specifies the impact of time delay on regulating flexible loads to provide emergency resources involved in accidental outages. First, in order to analyze the dynamic regulation process of power systems in accidental outages, the power system model in a faulty condition is reconstructed to obtain the regulation power from well-running generators. On this basis, flexible loads are modelled and integrated into the novel reconstructed power system model as an alternative method of making up for the fast regulation capacities. Considering that the inevitable communication time delay probably leads to the slowdown of response speed and endangers the system security, an adaptive time-delay control (ATDC) scheme is proposed and integrated into the control process of aggregated flexible loads. In this manner, the regulation speed of flexible loads can be accelerated, the control precision of response capacities can be improved, and the power system frequency deviations caused by time delay can be decreased. Finally, the proposed models and methods are verified by numerical studies. The results in the test system show that the frequency deviations can be decreased effectively in accidental outages by using the ATDC scheme of flexible loads.