Observations from study of pre-islanding behaviour in a solar PV system connected to a distribution network

Unintentional islanding is a more relevant issue today due to rising penetration of solar photo voltaic systems on distribution grids. As the smart grid matures, better techniques for mitigating this problem have to evolve. Commercially available, inverter-resident, islanding detection based methods are aplenty and a lot others are being developed at research level. This work is oriented towards trying to understand the distributed-generation system dynamics that build up to the island forming situation. It is felt that inverter dynamics along with power system transitory events can provide a clue to an impending unintentional islanding event. Approaches resulting from such a study can train the system with predictive intelligence with regards to the possibility of an unwanted islanding condition. The study also results into interesting observations regarding the impact of capacitive reactive power present on the network, in excess of load requirement, on the grid-side current in the load-containing phase of the islandable feeder section. Arcing current inside the island and distortion in this current before islanding are the effects that are recorded.