Sandia Frequency-Shift Parameter Selection to Eliminate Nondetection Zones

The Sandia frequency-shift (SFS) method is one of the active islanding detection methods that possesses small nondetection zones (NDZs). The effectiveness of the SFS depends to a great extent on its design parameters ( cfo and k). In this letter, a formula is derived to aid protection engineers to determine the optimal parameter setting for the SFS islanding detection method. It is concluded that the parameter (k) has a significant effect on the NDZ and a modified version of the SFS is proposed that relies only on this parameter.