The point of common coupling (PCC) is the electrical boundary where a user, plant, or substation connects to the wider power network. It is the main reference point for measuring voltage quality, current draw, and harmonic distortion, because problems seen at the PCC are no longer just local—they can affect other connected equipment and the utility grid.
In power engineering, standards such as IEEE 519 use the PCC to judge whether a facility is injecting too much distortion. In cyber-physical security, the PCC matters because it is often where monitoring, protection relays, and metering can detect abnormal behavior from compromised drives, inverters, or converter stations. Attackers who manipulate industrial loads or grid-connected electronics may create unusual harmonics, voltage swings, or switching patterns at this boundary. Defenders use PCC measurements to spot tampering, verify compliance, and isolate a problematic site before it spreads instability across the network.