Suggested Guidelines for Assessment of Distributed Generation Unintentional Islanding Risk

The report, Suggested Guidelines for Assessment of Distributed Generation Unintentional Islanding Risk, offers guidance for interconnection studies.

Technical Report

Suggested Guidelines for Assessment of Distributed Generation Unintentional Islanding Risk (Michael Ropp and Abraham Ellis 2013)
The guidelines in this report are widely used in interconnection studies to evaluate the risks of unintentional islanding for specific installations and to help determine the appropriate mitigation for those risks. The content has a focus on photovoltaic systems but could be applied to any distributed energy resource (DER).

Topics Covered

  • Background on how and where unintentional islands can form
  • Types of anti-islanding detection methods
  • Scenarios in which unintentional islanding risk is considered low or nonexistent
  • Scenarios which may require additional study
  • Summary of the risk assessment methodology

Key Takeaways

Conditions for a potential unintentional island can arise at any location along the distribution line if the normal power flow from the utility source is interrupted.

There are a variety of passive and active anti-islanding detection mechanisms built into inverters that are designed to shut down the inverter if an unintentional island is formed. 

There are a set of conditions under which unintentional islanding is exceedingly unlikely to form. If such conditions exist, no further study is required.

DER deployments include scenarios that could present challenges for on-board anti-islanding techniques. A set of guidelines have been developed to help identify the risk of unintentional islanding under these scenarios.