High levels of distributed energy resources (DER) are causing reverse power in distribution systems. A key indicator is relative generation-to-load ratios that are typically increasing as more DER is interconnected. Reverse power can dramatically change daily load profiles and often involves substation transformers including reverse power into the transmission system.

Technical concerns with reverse power include voltage regulating equipment and feeder automation misoperation, increased potential for unintentional islanding, power frequency overvoltages, and equipment loading impacts. Each of these can negatively impact distribution reliability, safety, and power quality.

There is currently industry debate regarding the need to derate substation transformers when reverse power flow exists and research findings will be shared that address this concern. This session will also bring utilities — National Grid and FirstEnergy — together to share their experiences related to reverse power.