Detection and identification of high impedance faults in single wire earth return distribution networks

Single Wire Earth Return (SWER) system is an inexpensive method for extending power to remote areas in scantly populated countries such as Australia. SWER network introduces several challenges to the conventional methods for protection relays. This paper focuses on the protection aspect of the SWER network and investigates the effectiveness of the existing conventional protection mechanism in detecting and suppressing common fault conditions including High Impedance faults (HIFs). While the existing SWER distribution network protection system can detect HIFs, it may be often taken as a normal step load increase due to the low fault current levels. The persistence of the HIFs compromises safety of people within the vicinity of the fault and also increase risk of fire, therefore, a new protection strategy for the detection and identification of HIFs to mitigate the risks is necessary. This paper presents a new algorithm based on mathematical morphology, called the Decomposed Open-Close Alternating Sequence, (DOCAS) for the detection and identification of any power system disturbances in SWER systems. The effectiveness of the proposed method in the detection and identification of the High Impedance Fault and differentiate with other conditions such as Single line-to-ground (SLG) fault and step load increase is demonstrated. The simulation results show that the HIFs can be clearly distinguished from the other conditions by analysing the transients generated by the HIFs.