Substations in a DER-Heavy Grid: DERMS, FLISR, and Grid-Enhancing Technologies

The substation was originally designed to manage power flowing in one direction, from generation through transmission and into distribution feeders that carried it to passive customers. That assumption no longer holds. Rooftop solar, community battery storage, electric vehicle charging, and small-scale distributed generation now push power back through the same feeders the substation was built to manage outward only. Substation engineering and the technologies operating inside the substation fence have had to adapt accordingly.

The Hosting Capacity Problem

Before a utility can approve a new interconnection request for solar or storage, it has to answer a deceptively difficult question: how much additional distributed energy resource capacity can this feeder and this substation absorb without violating voltage, thermal, or protection limits. This is the hosting capacity question, and it has become one of the most common engineering studies performed on substations today.

Hosting capacity analysis typically requires detailed feeder modeling combined with substation-level data on transformer loading, voltage regulation equipment, and protection coordination. Where this analysis once happened occasionally, for unusually large interconnection requests, it is now a routine part of distribution planning at substations serving any feeder with meaningful DER penetration. The substation’s instrumentation, particularly its ability to provide accurate, granular load and voltage data, directly determines how confidently a utility can answer the hosting capacity question without resorting to overly conservative limits that needlessly restrict legitimate interconnections.

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https://online.electricity-today.com/electricity-today/q2-2026/