4.2.2. Phase Jump Method

The aim of the phase jump (PJ) method is the detection of a "jump" between the PVS inverter current and voltage [78]. The PJ technique represents one of the first anti-islanding methods and it is based on the use of synchronization systems extracting information about the current and the voltage phase. However, considering the present availability of fast PLLs and the development of high performance current controllers, voltage and current synchronization could be achieved also during islanding operation. Consequently, the detection of the islanding phenomenon based on this technique could fail.

## 4.2.3. Rate of Change of Frequency Method

The ROCOF islanding detection method measures the rate of change of frequency *df*/*dt* in a set time window. When the grid is disconnected, the power mismatch between generation and load causes frequency variations. The PVS is tripped when *df*/*dt* exceeds the threshold value [91,92]. The threshold setting is the main issue of this method since it is necessary to distinguish islanding from load changes. Besides the ROCOF exhibits a wide NDZ combined with slow dynamics.
