Development of a Simplified Calculation Tool for Voltage Drop Caused by Transformer Inrush in Distribution System

It is well known that a voltage drop due to inrush current at an energizing transformer may at times interrupt electrical equipment. Generally, the voltage drop is calculated by using a sophisticated tool such as EMTP, so that the transformer saturation phenomenon has been properly represented. However, it is not practical for distribution system engineers to calculate the voltage drop with transformer inrush by using EMTP, because there are many network access requests needing such calculations with many kinds of transformers. Therefore, in this paper, a simplified and easy‐to‐use calculation tool for voltage drops caused by transformer inrush in a distribution system is developed. In order to understand the voltage drop by inrush current during the planning stage, it is formulated by considering the transformer saturation/unsaturation periods in each winding type. The newly developed tool is based on versatile spreadsheet software such as Microsoft Excel ýO.R. It can be used with accuracy similar to that of EMTP. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(1): 36–47, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22394