Distributed generation impact on reliability and power quality indices

Properly sited distributed generation (DG) can increase the feeder capacity limit, but this does not necessarily produce an improvement in system reliability or power quality, as quantified by standard indices. The DG may have a positive impact on reliability through faster system restoration following a fault. The DG can also improve reliability for the owner, and may reduce the severity of voltage sags near the DG. Indices normalized to the number of customers dilute these positive benefits. The DG often has a negative impact on reliability indices through sympathetic tripping, required changes to utility overcurrent device settings, and increased fuse blowing. The utility cannot assume DG automatically improves system reliability, and action may be required to ensure that reliability does not actually degrade for other customers.