# Islanding and Anti-Islanding Protection

Islanding is the dangerous condition in which a grid-tied inverter keeps energising a section of the network after the utility supply has failed. Anti-islanding protection is the mandatory function that detects this and disconnects the inverter within a fraction of a second.

Source: https://inverterdata.com/en/glossary/anti-islanding/
Site: InverterData (inverterdata.com) — open technical specification database
Last updated: 2026-08-24
License: free to quote with attribution to inverterdata.com

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The hazard is concrete: a line crew expects a de-energised circuit, and an inverter still feeding it could injure them, while reconnection out of phase can damage equipment. Detection combines passive monitoring of voltage and frequency limits with an active method that gently perturbs the output and watches whether the grid pushes back. The practical consequence for homeowners is the one that surprises them most — a standard grid-tied system stops producing during a blackout even in bright sunshine. Backup requires a **hybrid** or off-grid inverter with a transfer arrangement that isolates the house first.