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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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Partial Discharge Detection beyond the Frequency Ranges of IEC 60270
(2024-01-01)
Rajakrom, Asawin
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Cheechang, Chayapitch
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Laochu, Prechapol
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Nimsanong, Phethai
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Yutthagowiht, Peerawut
Due to the high background noise encountered during on-site partial discharge (PD) detection of power cables, calibrating PD detection systems at low PD levels becomes challenging, resulting in low sensitivity of PD detection systems. Achieving a 1-nC PD charge within the frequency range recommended by IEC 60270, which is lower than 1 MHz, is often difficult in practice. This paper presents an analysis of PD pulse currents in the frequency domain and proposes an alternative approach for PD detection during on-site testing of power cables. In the proposed method, the center frequency for PD detection is shifted to frequencies exceeding one megahertz, which lies outside the recommended frequency ranges of IEC 60270. Typically, the center frequency falls within the range of 1.5 MHz to 2.5 MHz, with a frequency bandwidth of several hundred kilohertz. By utilizing such frequency ranges, the signal-to-noise ratio of the PD pulse current significantly increases compared to the standard approach. Despite falling outside the standard-recommended frequency ranges, this adjustment allows for calibration using a 50-pC PD charge.
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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 Assessment of Moisture Content and Degree of Polymerization in Power Transformers via Dielectric Response Sensing
(2023-10-01)
Kunakorn, Anantawat
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Pramualsingha, Sarawuth
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Yutthagowith, Peerawut
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Nimsanong, Phethai
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Kittiratsatcha, Supat
Power transformers are essential apparatuses used to transfer electrical energy from one voltage-level circuit to another. For reliable systems, preventive maintenance of the transformers is required to ensure good services of all mechanical, electrical, and insulation parts. Oil-immersed paper is most often used for transformer insulation. To ensure such good insulation performance and for assessing insulation conditions, advanced transformer sensing, monitoring, and effective assessment techniques are required. This paper introduces an effective technique for assessing the insulation conditions in power transformers, which are crucial for ensuring reliable energy transfer. The method utilizes advanced transformer sensing and monitoring, focusing on oil-immersed paper insulation commonly used in transformers. The technique employs dielectric response sensing, obtained from frequency-domain spectroscopy tests, to estimate degrees of polymerization (DP) and percentages of moisture content (PMCs) in the oil-immersed paper insulation. These parameters are well-known indicators of insulation performance. The approach is based on the weighted k-nearest neighbor regression, using a database of dielectric loss factors at low frequency and oil conductivities. To overcome limited data availability, linear interpolation and extrapolation techniques are applied to enlarge the database. Experimental verification and comparison with a previously developed method demonstrate the proposed technique’s superiority in accuracy and complexity. The maximum deviations of DP and PMC in the validation cases are 6.2% and 18.7%, respectively. In addition, to evaluate the validity of our proposed method in the case of a real power transformer, a comparative analysis of the DP and PMC values determined by the proposed method with those obtained through a previously developed and complicated approach was performed. The predicted results indicate that the DP and PMC values of the oil-immersed insulation fall within the ranges of 800 to 1000 and 1.5 to 2.0, respectively, which agree with the results determined by the complicated approach and closely align with real conditions. By offering a reliable and advanced means of assessing insulation conditions, this technique contributes to the preventive maintenance and overall efficiency of power transformers.
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Determination of Dielectric Models Based on Effective Multi-Exponential Fittings
(2023-06-01)
Raxsa, Jedsada
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Nimsanong, Phethai
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Mai-Eiam, Thanatorn
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Yutthagowith, Peerawut
In high-voltage (HV) transmission and distribution systems, HV apparatuses are subjected to electrical, thermal, and mechanical stresses that deteriorate the insulation performance. The polarization and depolarization current (PDC) measurement is an effective tool used for evaluating insulation performances. The depolarization current represented by the summation of the discharge currents with the different time constants can be utilized for the development of the dielectric model based on the extended Debye’s model (EDM). This paper presents effective techniques for determining the dielectric model. Iterative approaches with predetermination of the time constants and least squares methods (either linear ordinary or percentage ones) were utilized to fit the depolarization current in the form of multi-exponential functions. The fitting parameters determined by the proposed method with the linear ordinary least squares (OLLS) method and provided by commercial software agree very well only in the high current and beginning range. Application of the linear percentage least squares (PLLS) method shows better accuracy than that of the OLLS method, and the deviation from the measured one in the low current range and the late measuring time were reduced significantly. The fitted current by this proposed technique with the PLLS method agrees well with the measured current throughout the whole recording time, even in the low current and late time range. From the accurately fitted currents, the dielectric model and the dielectric loss factors can be determined precisely, and the insulation condition of HV equipment can be evaluated properly.
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The Study of the Voltage Frequency Effects on Partial Discharge Characteristics
(2023-01-01)
Marukatat, Nattapon
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Mai-Eiam, Thanatorn
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Chaisiri, Punyavee
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Raxsa, Jedsada
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Nimsanong, Phethai
In this paper, the partial discharge (PD) characteristics under the voltage at frequencies in the range of 20 Hz to 300 Hz are studied. Three main types of PD being corona, surface and internal discharges are simulated by an arrangement of electrodes in test cells. The effects of voltage frequency on the PD characteristics in terms of PD inception voltage (PDIV), PD extinction voltage (PDEV), and phase-resolved PD (PRPD) patterns have been reported from the experimental results. It is found that in the frequency range of 20 Hz to 300 Hz there is no frequency effect on the PD characteristics (PDIV, PDEV, and PRPD) found in cases of corona and surface discharge. However, the frequency effects are found in the case of the internal discharge representing the higher frequency increase the higher PDIV and PDEV are.
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Polarization and Conduction Characteristics of Mineral Oil and Natural Ester Mixed with Nanoparticles
(2022-01-01)
Maneerot, Sakda
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Pattanadech, Norasage
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Kittikhuntharadol, Yannaphol
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Nimsanong, Phethai
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Bunlaksananusorn, Chanin
Mineral oil (MO) has been widely used in transformers because of its reasonable price and acceptable properties. Currently, alternative liquid insulations have been proposed with some excellent properties. Therefore, the mineral oil characteristics need to be enhanced for high performance to compete with such alternative liquid insulations. This paper aims to study the power frequency dielectric dissipation factor (tanδ) along with polarization and depolarization current (PDC) characteristics of the mineral oil-based nanofluid and natural ester (NE)-based nanofluid. Besides, Fourier-transform infrared spectroscopy (FT-IR) measurement of the test specimen was performed. Titanium dioxide (TiO2) and zinc oxide (ZnO) with 0.01% and also 0.03% volume concentration were used to mix with the unmodified liquid to create liquid insulation-based nanofluid. Then, unmodified mineral oil, unmodified natural ester, mineral oil-based nanofluid, and natural ester-based nanofluid were comparatively investigated. Tanδ at power frequency and the PDC characteristics of such liquids were examined. For PDC measurement, TiO2 clearly affected the polarization current and conduction loss factor, whereas ZnO evidently impacted the depolarization current and polarization loss factor. In the case of FT-IR test results, there was no significant change when the modified insulating liquid was compared with those of the unmodified insulating liquid.
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Online PD Measurement by Detecting the Pulsed Compensating Current in High Voltage Equipment
(2022-01-01)
Srinangyam, Chissanupong
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Pannil, Pittaya
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Nimsanong, Phethai
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Chuayin, Chaitawat
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Thungsook, Kittisak
This paper discusses the pulsed compensating current caused by partial discharge (PD) phenomena that flows inside the electrical equipment installed in the power system. Such electrical equipment like to be the capacitive coupler in the partial discharge test circuit. In order to study the pulsed compensating current of the PD measurement, artificial PD source such as corona, surface, and internal was used in this experiment. The electrical equipment like surge arrester combined with HFCT sensor utilized to detect the PD pulse current. Furthermore, this proposed technique has been applied for online PD measurement in substations. It was found that the surge arrester could compensate for the pulse current arising from the PD source. This study will be helpful information for online PD measurement.
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The Verification of HF Signal Transmission via Grounding System for Online PD Measurement
(2022-01-01)
Srinangyam, Chissanupong
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Pannil, Pittaya
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Thungsook, Kittisak
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Promwong, Sathaporn
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Nimsanong, Phethai
This paper discusses signal transmission in the grounding system. During online partial discharge (PD) measurement for the high voltage (HV) apparatus, various PD pulse currents recharge the dielectric of HV apparatus when a PD occurs. One of the noise typologies that affects PD patterns is called the cross-talk, that is, discharges that appear in the measured point due to coupling from another point. In order to study the cross-talk signal, the two PD measuring circuits which are circuit no.1 and circuit no.2, on the same grounding system in the HV laboratory were performed. The distance between two PD measuring circuits is about 20 meters. The artificial PD models were utilized to generate the PD signal injecting to the test circuit no.1, while the cross-talk signals were investigated in circuit no.2. The HFCT sensors were used to measure the PD signal in circuit 1 and the cross-talk signal in circuit 2. The measurement results found that the cross-talk signal transmission in grounding systems provides a bipolar PRPD pattern, and the pulse waveform shows an oscillation shape. Moreover, onsite PD measurements of the generator steam turbine were studied. It is noticeable that the knowledge about cross-talk phenomena in grounding systems can help the PD verification and location for online PD measurement.
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The Bandwidth Verification of VHF Antenna and Apply for Partial Discharge Measurement
(2022-01-01)
Thungsook, Kittisak
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Pattanadech, Norasage
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Nimsanong, Phethai
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Srinangyam, Chissanupong
This research explains the bandwidth verification and application of the VHF antenna for partial discharge measurement. Three different VHF antennas were used for the experiment. In the research, the measuring bandwidth of such antennas was evaluated using a network analyzer. The antenna properties such as return loss and voltage standing wave ratio were analyzed. Then, the partial discharge in the air was simulated using the surface discharge model. The physical phenomena of PD occur like pulse current transients and electromagnetic waves. The pulse current transients were detected using a coupling capacitor and HFCT sensor, while the electromagnetic wave was detected using a VHF antenna. five test positions of the VHF antenna were designated for partial discharge measurements namely 1, 2, 3, 4, and 5 meters away from the partial discharge source. The PRPD pattern, PD magnitude, and waveform obtained from the VHF antenna were compared with coupling capacitors and HFCT sensors and presented in this paper. It is found that the VHF antenna, which has higher return loss and lower voltage standing wave ratio, provides high performance to detect the electromagnetic wave of partial discharge.

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