Point of common coupling

The point of common coupling (PCC) is the precise location in an electrical power system where a consumer's electrical circuit connects to the utility grid. It serves as a crucial demarcation point, defining the boundary between the public utility network and the customer's private electrical installation. This is where the utility's responsibility for power delivery ends and the consumer's responsibility for their internal power quality begins. The PCC is typically located at the electrical meter, the service transformer secondary terminals, or the main service entrance. The conditions and characteristics of the electrical supply, such as voltage, frequency, and power quality, are measured and monitored at this point to ensure compliance with grid codes and regulatory standards.^[1]

In the context of Distributed Energy Resources (DERs) and microgrids, the PCC takes on added significance. It is the point where locally generated power—from sources such as solar panels^[2], wind turbines, or combined heat and power (CHP) systems—is either injected into the main grid or drawn from it. The behavior of these systems, including their power sharing capabilities in both grid-connected and islanded modes, is critically evaluated at the PCC. The design and operation of DERs must ensure that their interconnection does not negatively impact the grid's stability or power quality. The PCC also plays a vital role in the protection and safety of the electrical network, as it is the location where protection devices are installed to isolate the customer's system from the grid during faults or other abnormal conditions.^[3]

Power quality issues, such as harmonic distortion, voltage sags, and voltage swells, are frequently analyzed at the PCC.^[4] These issues can arise from either the utility side or the customer side and can have detrimental effects on sensitive equipment and overall system reliability. For this reason, standards such as IEEE 519^[5] and others provide guidelines for the limits of harmonic current and voltage distortion at the PCC. Adhering to these standards is essential for maintaining a reliable and stable electrical grid. The PCC is thus not merely a physical connection point but a critical interface for ensuring the safe, stable, and high-quality transfer of electrical power between a consumer and the main grid.

See also

• Active power filter