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Power Quality Improvement Based on Active Harmonic Filter in 24 kV Liquefied Natural Gas Industrial Plant’s Photovoltaic System
(2026-06-01)
Pothisarn, Chaichan
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Patcharoen, Theerasak
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Lothongkam, Chaiyaporn
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Ngaopitakkul, Atthapol
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Lertwanitrot, Praikanok
This paper presents a case study demonstrating the power quality improvements in a 24 kV distribution system at a liquefied natural gas (LNG) industrial plant with variable speed drives (VSDs), the conventional capacitor bank, and a rooftop solar photovoltaic system. Solar photovoltaic (PV) inverters can supply harmonic currents to the grid, potentially affecting the system and causing maloperation of sensitive equipment in both the utility systems and neighboring industries connected to it. Therefore, the installation of shunt active power filters (APFs) in a 400 V system was proposed in this study. The installed locations were varied, and the corresponding power qualities were analyzed. The results were examined in terms of design and harmonic elimination. Simulations were conducted using the PSCAD/EMTDC software version 4.5. The power quality simulation and field measurement results after the APF installation were compared to demonstrate the effectiveness of the proposed solutions. The addition of APFs was found to improve the power quality. In addition to the mechanism analysis, the economic feasibility of the proposed approach was investigated. The costs of APF installation in various locations were analyzed. The results show that the proposed method can improve the power supply at a reasonable price. This work contributes to sustainable industrial energy systems by improving the reliability and power quality of photovoltaic-integrated electrical networks, thereby supporting higher penetration of renewable energy resources and stable low-carbon industrial operation.
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An Evaluation Study on Electric Appliance Characteristics and Load Patterns in Residential Buildings
(2026-01-01)
Thongsuk, Surakit
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Songsukthawan, Panapong
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Ananwattanaporn, Santipont
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Sottiyaphai, Chayanut
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Ngaopitakkul, Atthapol
Energy usage in residential buildings has been constantly increasing as work-from-home trends continue to maintain popularity. To improve energy efficiency, the load profile and electric appliances in households need to be established and analyzed. This study aims to evaluate the characteristics of electric appliances that are commonly used in residential buildings under various operating conditions. An experimental setup with household electric appliances was built, and power quality meters were installed to assess the patterns under various operating conditions. In addition, the usage patterns were used to construct the daily load profile and analyze the energy consumption in residential buildings. The results demonstrate that load patterns constructed from actual measurements can achieve an accurate depiction of energy usage in residential buildings. The obtained load profile can be used in load control to improve energy efficiency and the application of renewable energy in demand reduction.
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Transient Analysis to Distinguish Mechanically Switched Capacitors Using Discrete Wavelet Transform and Artificial Intelligence
(2026-01-01)
Thongsuk, Surakit
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Bunjongjit, Sulee
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Yoomak, Suntiti
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Ananwattanaporn, Santipont
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Jettanasen, Chaiyan
Capacitor banks are widely used in modern power systems for reactive power compensation and voltage regulation. However, switching operations of mechanically switched capacitors (MSCs) can generate transient phenomena, such as inrush currents, which may resemble fault currents and lead to misoperation of protection systems. Therefore, accurate detection and classification of transient events are essential for reliable system operation. This study proposes a hybrid approach for transient signal analysis and classification by integrating the discrete wavelet transform (DWT) with artificial intelligence (AI) techniques, including probabilistic neural networks and fuzzy inference systems (FIS). The DWT performs time–frequency analysis to extract multi-scale wavelet features from three-phase current signals. The proposed method enables both discrimination between inrush and fault currents and multi-class classification of transient events among six capacitor switching conditions, namely base case, pre-insertion resistor, pre-insertion inductor, current limiting reactor, 6% reactor, and synchronous closing. The methodology is validated using PSCAD/EMTDC simulations under isolated and back-to-back capacitor switching scenarios. The results demonstrate that the proposed DWT–AI approach achieves high classification accuracy exceeding 95%, outperforming conventional methods based on DWT alone and DWT combined with FIS. Furthermore, the proposed method improves protection system performance by reducing false tripping caused by transient inrush currents, while maintaining reliable fault detection capability. The findings confirm that integrating time–frequency signal processing with AI-based classification provides an effective and practical solution for transient event discrimination in MSC capacitor bank systems.
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Design and techno-economic evaluation of a nanogrid system for a small-scale public railway station building in Thailand
(2025-12-01)
Ngaopitakkul, Atthapol
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Songsukthawan, Panapong
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Bunjongjit, Sulee
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Sreewirote, Bancha
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Yoomak, Suntiti
In Thailand, numerous small-scale public facilities continue to rely on the electrical grid. The integration of renewable energy sources such as photovoltaic (PV) and wind power offers a sustainable alternative; however, their inherent intermittency necessitates advanced solutions such as nanogrid systems, which enable localized energy generation, storage, and management to enhance reliability and autonomy. This study develops a nanogrid-based energy management system for Hua Takhe train station, Thailand, by integrating photovoltaic (PV) panels, wind turbines, and battery energy storage systems (BESS). Using HOMER Pro, multiple configurations were simulated and evaluated across key financial indicators, including Payback Period (PB), Internal Rate of Return (IRR), Return on Investment (ROI), Net Present Value (NPV), and Levelized Cost of Electricity (LCOE). The analysis framework further incorporates economic feasibility evaluation, sensitivity and scenario analysis, and long-term performance and life cycle evaluation, thereby ensuring that both short-term financial viability and long-term sustainability are comprehensively assessed. Results show that PV-dominant nanogrid systems, particularly at larger scales, represent the most practical and cost-effective pathway for sustainable electrification of public facilities in Thailand. The 30PV Nanogrid achieves the most favorable balance between cost and performance, with a NPV of 23,925 USD, a LCOE of 0.04 USD/kWh, a PB of 7 years, an IRR of 13 %, and a ROI of 215 % under long-term life-cycle evaluation. In comparison, the 15PV Nanogrid proves economically marginal, with NPV falling to –9117 USD, PB extending beyond 20 years, IRR turning negative (–5 %), and ROI declining to –40 %, confirming that small-scale nanogrids cannot offset the costs of ESS and hybrid inverters.
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Reduction of Impact from Voltage Sags During Faults in Distribution System by Installing Neutral Grounding Resistor
(2025-01-01)
Phannil, Natthanon
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Ananwattanaporn, Santipont
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Pothisarn, Chaichan
This research focuses on a small power producer operating a cogeneration power plant that utilizes natural gas as fuel to generate electricity. The plant, with a capacity of 90 MW, supplies both electricity and steam to industrial customers within a designated industrial zone. Power is delivered to four feeder industrial customers and the Electricity Generating Authority of Thailand (EGAT) at voltage levels of 115 kV and 22 kV. The five customers connected to Feeder 4 at 22 kV experienced voltage sags caused by short circuits in the distribution system. These sags had a significant impact on their production processes, as the machinery in their factories is interdependent and requires high-quality power to function properly. Certain machines, being highly sensitive to voltage fluctuations, stop operating if the voltage drops outside their acceptable range. This disrupts the production process, as the halted machinery must undergo recovery and restart procedures, which are time-consuming. Consequently, this downtime leads to delays and lost revenue opportunities for the affected customers. This issue is a significant concern for factories in industrial estates. Therefore, to address this problem, this research focuses on studying methods to mitigate the impact of voltage sags by installing a Neutral Grounding Resistor (NGR). The study simulates the distribution system during a single line to ground fault. This research examines the effects of voltage sags to inform the design of NGR installations, including investment and cost-effectiveness for resistances of 0, 6, 13, 19 and 26 ohms. Simultaneously, the study also investigates the potential for voltage swell in the distribution system due to the installation of the NGR. The study is conducted using MATLAB Simulink simulations. The findings suggest that installing an NGR with a resistance of 13 ohms is the optimal choice, offering optimal voltage sag, voltage swell, and fault current performance. The budget for the NGR installation by a contractor is approximately 1,000,000 THB, while the total cost for replacing the surge arresters in the system would be 135,000 THB.
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Investigation and Study of High Voltage Capacitor Bank Techniques for Voltage Drop Improvement in 22-kV Distribution Line
(2025-01-01)
Thongsuk, Surakit
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Lertwanitrot, Praikanok
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Songsukthawan, Panapong
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Ananwattanaporn, Santipont
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Ngaopitakkul, Atthapol
Voltage drop in distribution lines contributes to power losses, leading to a decrease in the overall efficiency of the electrical power system. In this paper, we investigate methods to improve voltage drop through capacitor bank allocation techniques, specifically installation at the end of the distribution line, the 1/2-kvar rule, and the 2/3-kvar rule. In the case study, a 22 kV overhead distribution line in Thailand is utilized as a model to analyze voltage drop improvement. The study is conducted using PSCAD software to simulate and evaluate the effectiveness of various capacitor bank allocation techniques in enhancing voltage drop in the distribution line. In addition, the impact of capacitor bank placement and sizing on voltage drop mitigation in a distribution line is analyzed through a proposed mathematical framework. This analysis considers the interaction between reactive current compensation and impedance of a distribution line, ensuring an optimized approach for capacitor bank deployment to enhance voltage drop. The results emphasize that the capacitor bank installation at the end of the distribution line yields the most substantial voltage drop improvement. This is attributed to the utilization of larger capacitor bank capacities compared to the 1/2-kvar and 2/3-kvar methods. Furthermore, the mathematical analysis confirms that both the placement and sizing of capacitor banks play a crucial role in voltage drop mitigation.
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An Approach for Voltage Drop Improvement in Distribution Line Using High-Voltage Capacitor Bank
(2025-01-01)
Songsukthawan, Panapong
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Ananwattanaporn, Santipont
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Thongsuk, Surakit
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Phannil, Natthanon
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Bunjongjit, Sulee
Distribution line voltage drops cause power losses and a general decline in the efficiency of the electrical power system. In this study, PSCAD software is used to evaluate the elements that impact the voltage drop in the distribution line, including distribution line length, electric load power factor, and electric load capacity, both with and without capacitor bank installation. The 22-kV overhead distribution line in Thailand served as the basis for the simulation model’s creation. It has been suggested to install capacitor bank-based techniques to increase voltage on distribution lines. The findings show that the voltage drop is significantly influenced by the distribution line distance, electric load power factor, and electric load capacity. The voltage drop can be minimized to the greatest extent by properly arranging capacitor banks.
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Impact of Rising Number of Electric Vehicle Charging Points on Electrical Utility
(2025-01-01)
Chiradeja, Pathomthat
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Lertwanitrot, Praikanok
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Songsukthawan, Panapong
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Yoomak, Suntiti
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Ngaopitakkul, Atthapol
This paper presents an investigation of the impact of a rising number of electric-vehicle charging points on an interconnected distribution system. Using the PSCAD 4.6 software, this study simulates an electric-vehicle charging station consisting of a charging unit with 2 DC charging and a maximum power of 100 kW. The station receives power from a 23 kV substation through a step-down transformer at 400 V and provides power through the charging unit. The unit regulates the voltage level at 500 V and has a maximum charging capacity of 50 kW each. In addition, the study replicates an actual distribution system of the Provincial Electricity Authority (PEA) in the section spanning the Si Samrong to Sawankhalok substations in Sukhothai Province, Thailand. The effects of the following study conditions on the power quality are observed in the simulation: 1) variable location of charging panels, 2) variable number of charging panels, and 3) additional sets of charging panels in the distribution system. The results show that the charging-panel installation location and number of charging panels are significant factors that affect the power quality, including the voltage level. Therefore, optimizing the design of EV charging stations should consider the location and number of charging panels as important factors.
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Development of overcurrent relay based on wavelet transform for fault detection in transmission line
(2024-12-01)
Ananwattanaporn, Santipont
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Lertwanitrot, Praikanok
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Ngaopitakkul, Atthapol
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Pothisarn, Chaichan
This study proposes a protection relay using a microcontroller to detect and classify faults in transmission lines based on the wavelet transform. An experimental model was constructed from an actual 115 kV transmission system prototype. The current signal was observed based on the fault type, phase, and position. Clark’s transform and the discrete wavelet transform (DWT) were applied to transform signals for analysis. Moreover, the performance of fault detection based on the output signals of Clark’s transform (alpha sequence, beta sequence, and zero sequence current) was compared to the performance of the alternative proposed fault detection method, which is based on the combining factor between alpha and beta sequence current. In addition, the influence of DWT level on fault analysis is also considered and is used to confirm the accuracy of fault detection. Results show that the proposed method is efficient for fault detection and classification. This finding allows the researcher to choose the appropriate analytical method. Moreover, it can also be used as the basis for overcurrent relay algorithm design in the effort to develop more advanced technologies.
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An approach to improve grounding resistance characteristic in existing 115 KV transmission towers
(2024-12-01)
Pothisarn, Chaichan
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Kulwongwit, Wiwat
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Lertwanitrot, Praikanok
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Bunjongjit, Sulee
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Ngaopitakkul, Atthapol
Effective grounding can attenuate fault currents and reduce damage to power system equipment, making the grounding system a crucial protection scheme. Generally, the ground resistance is set to a value less than 10 Ω. However, in practice, it is difficult to achieve this in certain areas, such as mountains, plains, and swamps. To address this problem, this study analyses the (1) actual footing resistance, (2) ground resistivity, and (3) ground length of transmission towers located in specific areas. Non-linear factors, impedance, and coupling effect are considered instead of traditional variables. A grounding design algorithm is proposed based on the ATPDraw program. Simulation results are applied to the 115 kV real-world system of the Electricity Generating Authority of Thailand. The grounding system exhibits a satisfactory performance improvement, as evidenced by comparisons between simulation and actual measurements. The findings are useful for implementing future improvements in grounding protection schemes.

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