Chang-Hyun Park

Development of a User-Friendly Application for Voltage Sag Analysis

This paper presents a windows application for voltage sag analysis and effective data visualization. The developed Voltage Sag Analysis Tool (VSAT) was designed by using the Object-Oriented Programming (OOP) concept and C++ programming language. The VSAT provides basic functions for voltage sag analysis such as power flow analysis, short circuit analysis and stochastic analysis. In particular, the VSAT provides effective data visualization through computer graphics and animation. Analysis results are expressed realistically and intuitively on geographical display. The Graphic User Interface (GUI) of VSAT was designed specifically for voltage sag analysis. In this paper, the development and implementation of VSAT is presented. In order to demonstrate the capabilities of VSAT, it is used to analyze the Jeju Island power system in South Korea.

Optimal Placement of Distributed Generation Units Considering Voltage Sags

This paper presents a method for determining the optimal placement of distributed generation units considering voltage sags. In general, the existing methods for distributed generation placement do not consider power quality problems such as voltage sags. In this paper, a novel method based on both genetic algorithm and voltage sag assessment is proposed for determining the placement of distributed generation unit. In the proposed method, the optimal placement is determined to minimize voltage sag effects and system losses.

Method to Estimate Expected Sag Frequency Considering the Operating Condition of Power System

This paper deals with the assessment of voltage sags regarding the variation of system operating conditions. In general, voltage sag assessment is performed by assuming the constant operating condition throughout the year. However, the assumption can lead to assessment errors in case of considerable changes of system operation condition. This paper presents a method to estimate ESF(expected sag frequency) considering the operating conditions according to the changes of power demand throughout the year.

Establishment of Preventive Measures against Faults Based on the Area of Severity to Voltage Sags

This paper presents an effective approach for establishing countermeasures against voltage sags based on the concept of area of severity. In order to apply preventive measures against faults such as lightning arrester, overhead earth wires and so on, it is important to find optimal points for installing the preventive measures. The optimal points can be determined by the calculation of the area of severity(AOS) to voltage sags and the expected sag frequency per unit length of line. In this paper, an effective method to find optimal points to apply countermeasures against voltage sags is addressed with case studies.

Method to Determine Areas of Vulnerability for Calculating Sag Cumulative Table and Sag Density Table

This paper presents a method to calculate a sag cumulative table and density table based on the area of vulnerability to voltage sags. The expected sag performance at sensitive load points can be easily assessed through the calculation of the sag cumulative table and density table. However, the calculation of the tables regarding large power systems is very difficult task. Therefore, an efficient method for calculating the tables is needed. In this paper, the improved method to determine the areas of vulnerability is addressed and the method to calculate the tables based on the area of vulnerability is also described. The proposed scheme can be efficiently used to assess the voltage sag performance at sensitive load points in large power systems.

Voltage Sag Assessment by using Voltage Drop Equation

This paper presents a simple method to determine an area of vulnerability to voltage sags by using voltage drop equation. In general, the stochastic assessment of voltage sags is performed by using the concept of an area of vulnerability. Therefore, in order to fast assess the voltage sag performance, the area of vulnerability should be fast and accurately calculated. The voltage sag assessment provides the expected sag frequencies at sensitive load points, and the assessment results can help to establish efficient planning for the mitigation of voltage sags. This paper describes how to determine the critical buses and lines for fast determining the area of vulnerability for given voltage thresholds.

Application of 3D Visualization to Power System Troubleshooting Guide

Abstract When power systems have troubles, inexperienced personnel have difficulty finding countermeasures and understanding the situation quickly. This paper presents an effective method to visualize power system Equipment in normal & abnormal condition using 3D graphic animations & virtual reality. It allows operators to understand what is going on with the equipment and the state variation of power system equipment can be represented using various methods. Additionally, this guide suggests suitable countermeasures to fix what happened in order to minimize effects of the incident by presenting a effective troubleshooting process.