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Development of a Rogowski Coil-Based Lightning Current Measuring System with Wide Frequency Bandwidth for Wind Turbines
(2026-01-01)
Pramualsingha, Sarawuth
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Yamamoto, Kazuo
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Yutthagowith, Peerawut
Accurate monitoring of lightning currents is critical for incident assessment and the implementation of protective measures in wind turbines. Owing to the complex geometry of turbines, direct measurement is impractical, making indirect approaches, such as the Rogowski coil, a promising alternative. The Rogowski coil provides galvanic isolation, fast transient response, and high current capacity; however, achieving broadband performance with a very low cut-off frequency remains a significant challenge. This article proposes a broadband Rogowski coil-based lightning current measuring system (RLMS) with an exceptionally low cut-off frequency. The system comprises a Rogowski coil, hybrid integrator, and digital filter. The coil was designed and optimized using transmission line theory and a distributed parameter model. The hybrid integrator, which combines the Sallen-Key and T-feedback topologies, ensures effective compensation, whereas the digital filter suppresses high-frequency noise. The feasibility of the RLMS was confirmed by a frequency response analysis in the frequency domain and time-domain comparison of lightning current waveform measurements against the reference system. The experimental results confirmed the effectiveness of the system for lightning current measurements. This demonstrates the strong potential for integration into wind turbines to enhance the accuracy of lightning detection and protection strategies.
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A Simple Mathematical Expression for Nonlinear Resistive Characteristics of Metal Oxide Elements in Lightning Surge Analysis
(2025-06-01)
Yutthagowith, Peerawut
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Baba, Yoshihiro
Accurate simulations of transient phenomena in electric power systems with metal oxide varistors (MOVs) or lightning arresters (LAs) using the finite-difference time-domain (FDTD) method for solving Maxwell's equations require simple and accurate representations of MOVs or LAs. By representing a small cell within a MOV or LA with resistivity (ρ) dependent on electric field (E), these components can be modeled in three dimensions and seamlessly integrated into FDTD simulations. Achieving computational efficiency in FDTD simulation necessitates avoiding iterative computations for ρ from E. Hence, there is a significant need for a simple and accurate mathematical expression of ρ in terms of E. This study presents a methodology for deriving a three-coefficient exponential function from experimental data. By using integration properties, this method transforms nonlinear characteristics into linear ones without iterative processes or uniform data sampling. It also incorporates data weighting and outlier discrimination for enhanced accuracy. Comparative analysis with previous methods based on the ordinary least squares method and experimental data, using an applied current with a rise time of approximately 8 μs, confirms high accuracy and effectiveness in computing residual voltages resulting from impulse current injection using the FDTD method.
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An Effective Approximate Mathematical Expression for Non-Linear Resistance Characteristics of Metal Oxide Elements
(2025-06-01)
Yutthagowith, Peerawut
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Baba, Yoshihiro
A metal oxide varistor (MOV), manufactured from a blend of zinc oxide and other metal oxides, undergoes changes in resistance or resistivity depending on changes in applied voltage or electric field strength. Typically, the nonlinear resistive characteristics of MOV elements are determined through experimental measurements of voltage and current. This article introduces a mathematical expression comprising two power functions and a constant term with five adjustable coefficients. It is utilized to describe the voltage-current or electric field-current density characteristics across a wide range of current or current density, spanning from microamperes to several tens of kiloamperes or from several hundred A/m2 to a few hundred of kA/m2, respectively. This expression accurately reproduces the observed nonlinear resistive behaviors of several low-voltage MOV elements. A noniterative fitting method is developed to determine the expression’s five coefficients, using integration to linearize nonlinear characteristics without requiring iterations or uniform data sampling. Through comparison with a previously proposed expression and experimental data, the proposed technique demonstrates remarkably high accuracy. Furthermore, the proposed technique is applied to accurately estimate the parasitic inductance of an MOV and its lead wires during a residual voltage test conducted with an 8/20-microsecond impulse current.
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Designing HV Reactor With Multiple Air Gap Structure Based on Fringing Flux Factor
(2024-01-01)
Yutthagowith, Peerawut
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Raxsa, Jedsada
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Leelachariyakul, Banyat
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Khumpho, Juthathip
This paper introduces an experimental approach to determining the fringing flux factor (F), representing the leakage flux within the air gap of the magnetic core, for the design of high-voltage (HV) reactors. The formula for determining F was developed from the AC excitation experimental data using curve-fitting techniques on the proposed reactor's reduced-scale model, which features a CC shaped magnetic core with six air gaps. The significant configuration of the model includes an iron core and coil windings. The test conditions for the reduced-scale model are based on the number of turns in the winding, 85 and 300 turns for each coil winding and the length of the air gap, 2 mm. and 5 mm. for each gap. Based on experiments with the reduced-scale model, the developed formula for F demonstrates effective results, exhibiting an absolute error lower than 20 %. This F formula provides a promising guideline for designing HV reactors, with a lower absolute error value.
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Design of Narrowband and Wideband UHF Antennas for Partial Discharge Detection on High Voltage Equipment
(2024-01-01)
Yutthagowith, Peerawut
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Mai-Eiam, Thanatorn
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Nimsanong, Phethai
This paper presents designs for ultra-high-frequency (UHF) electromagnetic sensors based on printed circuit board (PCB) antennas for partial discharge (PD) detection in gas-insulated substations (GIS) applications. The sensors were designed to meet the requirement of narrowband/wideband UHF measuring systems for the UHF PD detection in GIS. The PD signals in the physical characteristic of the high-frequency electromagnetic (EM) wave were detected using the designed UHF antennas, which include the inset-fed rectangular microstrip patch (IFRMP) antennas, known for their narrowband characteristics that offer high interference signal rejection to improve signal-to-noise ratio and the two arm Archimedean spiral (TAAS) antennas, recognized for their broadband frequency spectrum capability. Because UHF PD signals are typically detected using various field sensor designs, both IFRMP and TAAS antennas were designed for three different models under calculation and simulation using MATLAB to apply in different operating frequency bands within the UHF range of PD detection (300 MHz-3 GHz). The designed UHF antennas have very characteristics, i.e. portable, lightweight, and attractive for practical applications with a low fabrication cost. Additionally, they are more convenient to install on the insulating flange compared to some types of external antenna sensors. In terms of antenna performance, they exhibit parameters like return loss (parameter S11) less than -10 dB and voltage standing wave ratio (VSWR) less than 2 within a close range of the designed operating frequency. Using the designed antennas, the phase-resolved PD (PRPD) patterns, the statistical magnitudes and waveforms of detected UHF signal have been obtained from laboratory testing for the sensitivity verification to help users in the effective application of the UHF PD detection.
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Design and Construction of Tesla Transformer for testing on Suspension Type Insulator Class 52-3
(2024-01-01)
Paophan, Busayapol
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Marukatat, Nattapon
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Yutthagowith, Peerawut
This paper presents the design and construction of a Tesla transformer used for an electrical flashover test of a suspension insulator. The testing waveform of the Tesla transformer is contained based on the resonance circuit. Tesla transformer circuit uses inductive coupling of a primary voltage inductor of 3.75 μH, primary voltage capacitor of 109.4 nF, secondary inductor of 8.106 mH, and high voltage capacitor in the form of toroid and suspension insulator. The simulation and experimental results of the Tesla transformer present the appropriateness of the main design parameters. The rated voltage and frequency of the developed are 250 kV and 200 kHz, respectively. The insulators under test are suspension type ANSI 52-3. It is found that the Tesla transformer can generate high voltage with a frequency of about 200 kHz (160 to 220 kHz) and make flashovers on the insulators according to the ANSI C29.1 standard.
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A System for PD Pulse Generating, Monitoring, and System Characterization
(2024-01-01)
Chaisiri, Punyavee
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Paophan, Busayapol
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Yutthagowith, Peerawut
This paper introduces a system for generating and measuring pulse signals used in calibrating and evaluating the performance of partial discharge detection systems. A LabVIEW-based software program has been created to control a digital oscilloscope and an arbitrary waveform generator. The program functionality includes pulse signal generation, measurement of partial discharge (PD) pulse current and charge, and characterization of PD measurement circuits in accordance with standards such as IEC 60270 and IEC 60885-3. This system can generate accurately calibrated pulse charges ranging from 2 pC to 100 pC. Additionally, it can generate a double pulse with an adjustable interval time between pulses ranging from 0.2 μ s to 100 μ s, with the frequency of the calibrated charge signal also adjustable. Test results demonstrate that the developed system can generate calibrated pulse signals meeting standard requirements, with a charge generation tolerance of approximately 2%. Furthermore, this system offers a cost-effective alternative compared to commercial solutions. Its implementation in the High Voltage Laboratory enhances its capability to conduct partial discharge calibrations and accurately assess the characteristics of partial discharge measurement systems.
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Accurate Mathematical Parameter Determination for Double-Exponential Impulse Waveforms with Specified Parameters
(2024-01-01)
Yutthagowith, Peerawut
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Baba, Yoshihiro
A double-real-exponential function is extensively utilized in high-power electromagnetics, encompassing research on high-altitude electromagnetic and ultrawide-band pulses, lightning, and high-voltage tests. There is a substantial demand for converting pulse waveform parameters such as rise time, full width at half maximum, fall time, front time, time to peak, time to half peak, and peak value into the first- and second-time constants and a peak factor of a mathematical function. The article introduces an accurate method named the time normalization technique for mathematically generating impulse waveforms with a set of waveform parameters, including: the rise time, the full width at half maximum, and the peak value and the front time, the time to half peak, and the peak value. The validation of the proposed method reveals that estimation errors below 10-6% can be achieved. Using the results obtained from this method, expressions for mathematical parameter estimation in a wide range of time parameters are developed, which yields estimation errors below 0.02% for converting the rise time, the full width at half maximum, and the peak value to the first- and second-time constants and the peak factor, and below 0.01% for converting the front time, the time to half peak, and the peak value to the first- and second-time constants and the peak factor. Additionally, the utilization of these expressions for waveform generation to evaluate the measurement uncertainty of a voltage measuring system is demonstrated.
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Development of a Simple Dielectric Equivalent Circuit Model from Polarization and Depolarization Current Measurements
(2024-01-01)
Yutthagowith, Peerawut
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Nimsanong, Phethai
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Baba, Yoshihiro
Assessing insulation performance is vital for sustainable energy systems, which aim to minimize visual impact while ensuring reliability and resilience against weather-related disruptions. With increasing reliance on renewable energy sources, the importance of insulation performance becomes even more pronounced. Regular evaluations of insulation performance are critical for maintaining the safety, reliability, and resilience of electricity networks. By promptly identifying risks such as insulation degradation, utilities can improve maintenance practices, prioritize repairs, and enhance the integration of renewables, thereby boosting overall infrastructure performance. This paper introduces a straightforward and precise technique for determining the equivalent circuit parameters of insulation systems in high-voltage equipment. The proposed method facilitates the accurate determination of the dielectric loss factor from the equivalent circuit. To validate this approach, test cases were utilized to demonstrate its effectiveness. The results obtained through this method were then compared with those obtained using commercial software. The comparison reveals that the proposed approach results in a lower number of depolarization current branches compared to the commercial software. Also, it provides almost the same relative root mean square error and the lower root mean square relative error of the depolarization current. These findings underscore the appeal and effectiveness of the proposed method for determining the equivalent circuit of the dielectric model.
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Accurate Loss Tangent Determination in Damped Alternating Voltage Tests
(2024-01-01)
Yutthagowith, Peerawut
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Chaisiri, Punyavee
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Paophan, Busayapol
Underground cables are crucial for sustainable energy systems due to their minimal visual impact, reliability, and resilience against weather-related disruptions. As reliance on renewable energy sources rises, their importance grows. Regular evaluation of these cables is essential for ensuring safety, reliability, and resilience of electricity networks. By promptly identifying risks like insulation degradation, utilities can optimize maintenance, prioritize repairs, and bolster the integration of renewables, enhancing overall infrastructure performance. Loss tangent is the most significant value used for evaluation of the cable condition. This paper presents an alternative method for estimation of loss tangent in comparison with a conventional approach in damped alternating current voltage (DACV) tests. In the loss tangent estimation, the equivalent circuit of the DACV test system and a damping factor of the measured test voltage are utilized in the loss tangent estimation. From simulation experimental results, it is found that the conventional method is not accurate in loss tangent estimation in cases of low loss tangent measurement in the range of 0.1% which is a typical value of the new and used underground power cables. However, the accuracy of the proposed method is still in the acceptable range for estimation of the loss tangent in the range of 0.1%

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