Impact of Capacitor Banks on Voltage Profile and Power Losses in Medium Voltage Power Systems

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International Journal of Research and Scientific Innovation (IJRSI) | Volume VIII, Issue VIII, August 2021 | ISSN 2321–2705

Impact of Capacitor Banks on Voltage Profile and Power Losses in Medium Voltage Power Systems

Nguyen Thi Thanh Thuy
Electrical Faculty, Thai Nguyen University of Technology, Thai Nguyen, Viet Nam
Corresponding author

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Abstract— This paper studies the impact of capacitor banks on voltage profile and power losses in medium voltage power systems. Corresponding to compensative levels, some case studies are considered to evaluate the effect of capacitors to power systems such as no capacitor bank, a capacitor bank at a bus and some capacitor banks in whole system. A simple power system is consider to analyze values of bus voltage, power losses and power flows. The Newton-Raphson method is also made more detailed in case studies of having the participation of capacitor banks at any bus in complex systems. ETAP software is used to simulate and determine all parameters and evaluate the meaning of capacitor banks. Carried out by ETAP, voltage quality and power losses can be improved very much corresponding to the high value for capacitor banks at some buses. To have higher quality for values of bus voltage and smaller power losses, capacitor banks must be combined with other distributed power sources.

Index Terms—Capacitor bank, compensation, ETAP software, power losses, reactive power, voltage quality.


Power sources in power system are designed to meet many different requirements of loads and transmission lines. There are many types of power sources, such as power plants, renewable sources, capacitors,… These sources can generate only active power, only reactive power or both active and reactive powers. In these sources, a parallel capacitor is considered as a reactive generator that helps to regulate bus voltage and power flows in whole system [1].
The voltage deviation of all buses in power systems must be limited in an acceptable range. In Vietnam, its range is from 0.95 pu (95%) to 1.05pu (105%) for medium voltage power systems [2]. At time having high load levels, values of bus voltage can be out of above range and cause much power losses. A solution to overcome this problem is that uses parallel capacitors with continuous adjustment [1] or multi-level adjustment [3], [4], [5]. Continuous adjustment uses devices in FACTS (Flexible AC Transmission System) and requires high technique to regulate. Multi-level adjustment uses circuit breakers to switch on/off branches in capacitor banks. With multi-level adjustment, individual capacitor bank will be added in case of having lower voltage value than minimum threshold or released in case of having higher voltage value than maximum threshold. Multi-level compensation is suitable for medium voltage power system with low cost, easy to execute in acceptable efficiency. So, multi-level compensation will be main object in this study.