Non-detection zone (NDZ)

The effectiveness of the Islanding Detection Methods (IDM) is usually depends on the NDZ which relies mainly on the amount of local loads connected to the DG [10]. The closer the active power consumed by these loads is to the active power supplied by the DG, the higher the probability to form an islanding.
In the same way, as the resonant frequency of the local load approaches the local grid nominal frequency the potential formation of the islanding also increases. There are two kinds of representation methods up to now as follows: Power Mismatch Space Representation (PMSR), Load Parameter Space Representation (LPSR) [11].
PMSR uses the amount of active power flow (DP) and reactive power flow (DQ) to the grid. After islanding occurs, the islanding voltage and islanding frequency goes to the new operating point for the power balance between PV generation and local load consumption [12]. Under the local passive AIMs, the quantitative NDZ of PMSR can be analyzed as Eqs. (1) and (2) and this NDZ zone is described in figure 2.
\begin{equation} {\text{\ \ \ }\left(\frac{V}{V_{\max}}\right)}^{2}-1\leq\ \frac{\text{ΔP}}{P}\ \leq\left(\frac{V}{V_{\min}}\right)^{2}-1\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (1)\nonumber \\ \end{equation}\begin{equation} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1-\left(\frac{f}{f_{\min}}\right)^{2}\ \leq\ \frac{\Delta Q}{P}\ \leq 1-\left(\frac{f}{f_{\max}}\right)^{2}\ \ \ \ \ \ \ \ \ \ \ \ \ \ (2)\nonumber \\ \end{equation}