Experience with accumulated phase angle drift measurement for islanding detection

Distributed generation is increasingly likely to play a major role in electricity supply systems as recognition is made of its low carbon credentials. However, the integration of these units at distribution voltages is a major challenge for utilities. One particular issue is that generators may, unintentionally, continue to supply local demand when areas of the network are isolated from the main system. Reliably detecting this condition is regarded by many as an ongoing challenge as existing methods are not entirely satisfactory. This paper proposes a novel method based on accumulated phase angle drift that provides inherently enhanced stability without unduly sacrificing sensitivity. It is passive and thus requires no additional invasive hardware. Transient simulations have been used to demonstrate its performance [1]. The current paper presents further validation of the PAD method performance resulting from the field trial of a relay connected on the 38kV network at the interface to a 25MW windfarm in Ireland and also supplemented by the results of an on-going laboratory trial at the University of Strathclyde (UoS).