Optimization method for voltage sag monitor placement in power system

Abstract

Voltage sag is one off the severe power quality issues and may cause huge losses to industries. Voltage sag happens frequently and might be caused by random and unpredictable factors. To monitor voltage sag, Voltage Sag Monitoring (VSM) system has been currently implemented to the whole power system. However, implementation of VSM at all buses is not economical. Therefore, the objective of this study is to evaluate the optimal number and placement of voltage sag monitors in IEEE 30-bus system. First, the concept of monitor reach area is used. In this study, voltage sag is represented by balance and unbalance fault with fault impedance, Zf equal to 0Ω. To obtain fault voltage on each bus, IEEE 30-bus system was constructed using PowerWorld software. Then, monitor reach area matrix is formed by comparing fault voltage with selected voltage threshold, α. After that, monitor reach area is analysed by using branch and bound method to evaluate the minimum number and the possible arrangements of VSM. Finally, to optimally place the identified number of VSM, all possible combinations of VSM in the power system were evaluated using sag severity index. To show the effectiveness of the proposed method on the optimal voltage sag monitor placement in power system, the proposed algorithm was implemented and tested on the IEEE 30-bus test system. The proposed method was tested with two different α; i.e. 0.55 p.u. and 0.80 p.u. respectively. The proposed method successfully found the optimal number and its placement for monitoring the whole IEEE 30-bus system with respective α value. Based on the results, for α equal to 0.55, VSM need to be installed on bus 6, 17, 25 and 30 in order to monitor voltage sag on IEEE 30-bus system; and for α equal to 0.80 p.u., VSM are only required to be placed at bus 25 respectively.