# A New Passive Islanding Detection Solution Based on Accumulated Phase Angle Drift
###### Abstract  
The existing passive methods for islanding detection are mainly based on the detection of voltage and frequency deviation after islanding, using protections such as voltage vector shift (VVS) and rate of change of frequency (ROCOF). Although there are reported issues with these passive methods such as inherent non-detection zones and nuisance trips, utilities prefer the passive methods due to the low cost and simplicity of deployment. In this paper, one composite passive islanding detection method is presented. It tracks the voltage phase angle, the system frequency, and ROCOF every power cycle. If three phase voltage vectors shift in the same direction and the rotated angle values are balanced, the calculation of the accumulated phase angle drift (PAD) will be initiated. This calculation continues until the ROCOF measurement is below the ROCOF setting threshold. If the accumulated phase angle drift reaches the set angle threshold, the condition for islanding is claimed. The performance of this composite method is verified under different scenarios based on Matlab Simscape multidomain physical systems and practical waveforms recorded from sites. Although there are still non-detection zones, this composite PAD solution has better sensitivity than existing VVS and ROCOF methods and is stable under external system faults. islanding detection; loss of main protection; voltage vector shift; rate of change of frequency +  
measurements. Some other passive methods based on wavelet design [3], fuzzy rules [4], and artificial neural networks [5] are also proposed. A passive islanding detection using an accumulated phase angle drift has been proposed [6] where the phase angle drift calculation is based on the estimation of the main grid frequency, but the related field tests demonstrated that this method cannot ensure stability under system frequency fluctuation [7]. Another new passive method has been proposed which defines the three phase voltage indexes as the main discriminative quantity based on the high sampling frequency [8]. Although the performance of this islanding detection method is good during simulation tests, it is difficult to apply the proper voltage index setting in practical applications. Active methods normally require the continuous interaction with the output of DG. These methods inject small signals into the distribution system or force the DG to a slightly abnormal status. The connected network and islanded network have different response characteristics to these active disturbances from the DG. With low frequency current injection, the active rate of change of frequency ROCOF relay for islanding detection is proposed by Reference [9]. Among these active methods, reactive power variation based the islanding detection method is one of the effective ways of drifting frequency during islanding [10]. However, the active methods are only used for inverter-based DG. The fast development in communication technologies makes the wide-area information exchange possible [11]. The communication-based methods apply the communications between the utility grid and the DG, such as direct transfer trip or phasor measurement unit. The communication-based methods are most reliable and NDZs can be reduced to zero, but the cost is expensive when a dedicated communication channel is required. The direct transfer trip solution is complex when there are many devices upstream which can switch and cause islanding [12]. Islanding detection based on the phasor measurement unit is proposed [13; 14]. It mainly applies the frequency difference and change of angle difference to detect islanding. The main problem of the solutions in References [13; 14] is the time delay caused by the phasor report latency. Although there are inherent non-detection zones, the passive methods do not affect the normal operation of the DG system and are easy to implement. Due to the trade-off between accuracy and cost, passive methods, such as ROCOF and voltage vector shift (VVS) relays are normally used for islanding detection [15; 16].