Publications
Suggested guidelines for anti-islanding screening
As increasing numbers of photovoltaic (PV) systems are connected to utility systems, distribution engineers are becoming increasingly concerned about the risk of formation of unintentional islands. Utilities desire to keep their systems secure, while not imposing unreasonable burdens on users wishing to connect PV. However, utility experience with these systems is still relatively sparse, so distribution engineers often are uncertain as to when additional protective measures, such as direct transfer trip, are needed to avoid unintentional island formation. In the absence of such certainty, utilities must err on the side of caution, which in some cases may lead to the unnecessary requirement of additional protection. The purpose of this document is to provide distribution engineers and decision makers with guidance on when additional measures or additional study may be prudent, and also on certain cases in which utilities may allow PV installations to proceed without additional study because the risk of an unintentional island is extremely low. The goal is to reduce the number of cases of unnecessary application of additional protection, while giving utilities a basis on which to request additional study in cases where it is warranted.