A Study on the Effect of Distributed Generation on Short-circuit Current and Voltage: Validation and Case Studies

Distributed generation (DG) resources defined as small, medium, or large grid-connected or stand-alone electric energy sources can show many advantages such as improving reliability (e.g., decreasing the failure frequency and duration), the emergency supply of power (e.g., islanding operation), or peak power reductions (e.g., peak demand reduction at peak hours). However, these DG resources are in nature an electric energy source, so they can affect the short-circuit current of the system to which they are connected. Thus, the objective of this study is to present several case studies on the effect of DG on a change in short-circuit current and voltage. For this purpose, Part 1 presented a method of accurately calculating short-circuit current caused by DG working as a current source, which was defined as the current injection method. As an extended study, Part 2 of this study presents an example of calculating short-circuit current and voltage in detail. As a result of case studies, this study verifies the proposed method and examines the effect of DG on short-circuit current and voltage after a single line-to-ground fault. The case studies show that as the capacity of DG increases, DG can also increase the short-circuit current, but with a slight change rate (e.g., up to 17.44% in the simple 5-bus power system), and DG may cause a slight overvoltage problem during or after the fault. Copyright © The Korean Institute of Electrical Engineers.