Summary of Distributed Resources Impact on Power Delivery Systems

TLDR

Traditional distribution systems assume a single source, so connecting distributed resources creates operating conditions not seen in conventional systems. The paper examines the system issues that arise as distributed resources penetrate distribution networks. The authors analyze voltage effects and interactions with capacitors, voltage regulators, and LTCs, protection challenges such as fuse coordination, fault feeding, interrupting ratings, fault detection, ground source impacts, single‑phase interruption on three‑phase lines, recloser coordination, and conductor burndown, as well as loss‑of‑grid vulnerabilities, overvoltages from islanding, reclosing coordination, and restoration and network issues.

Abstract

Because traditional electric power distribution systems have been designed assuming the primary substation is the sole source of power and short-circuit capacity, DR interconnection results in operating situations that do not occur in a conventional system. This paper discusses several system issues which may be encountered as DR penetrates into distribution systems. The voltage issues covered are the DR impact on system voltage, interaction of DR and capacitor operations, and interaction of DR and voltage regulator and LTC operations. Protection issues include fuse coordination, feeding faults after utility protection opens, impact of DR on interrupting rating of devices, faults on adjacent feeders, fault detection, ground source impacts, single phase interruption on three phase line, recloser coordination and conductor burndown. Loss of power grid is also discussed, including vulnerability and overvoltages due to islanding and coordination with reclosing. Also covered separately are system restoration and network issues.