Impact of Power Regulations on Unwanted Islanding Detection

The contribution of decentralized generators in the provision of ancillary services, such as voltage and frequency regulations, is currently growing in many power systems. The impact of these new regulations on islanding detection is generally investigated by calculating the nondetection zone (NDZ) of the protective relay located at generator level. This subject has already been studied in the literature, but has been generally treated by means of steady-state calculations only. As demonstrated in the present paper, the analysis yields very different results when the entire time-evolution of the system is taken into account. It is shown that the impact of the studied regulations, i.e., the P(f) and Q(U) controls, on a standard test system is to reduce the NDZ which goes against the conclusion of several previous works based on steady-state calculations. Then the generalization of this result to other loads and generators is investigated. At last, the impact of the dynamics of the grid and the dynamics of the regulations is further investigated through a parametric study which shows that, if the power regulations dynamics are slow enough compared to the voltage and frequency dynamics, then the NDZ is necessarily reduced by the addition of the new regulations.