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Author: search.filters.author.Thungsook, Kittisak

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    The Response of Natural Esters when Being Under a Direct Current Electric Field for a Long Time
    (2024-01-01)
    Thungsook, Kittisak
    ;
    Manger, Rene
    ;
    Zink, Markus H.
    ;
    Kobus, Maja
    ;
    Pattanadech, Norasage
    This study examines the dielectric behavior of natural esters exposed to a DC electric field over an extended period of time. The dielectric response was investigated by using polarization and depolarization current measurements. The natural ester sample was subjected to a DC electric field of 0.1 kV/mm, 0.5 kV/mm, 1 kV/mm, 1.5 kV/mm, and 2 kV/mm, respectively. Besides, the moisture content of natural esters was also controlled using a natural method. The test results showed that after being exposed to an electric field for an extended period of time of the natural ester, different forms of charge accumulation might be found partly depending on the initial condition of the investigated natural ester.
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    Online PD Measurement by Detecting the Pulsed Compensating Current in High Voltage Equipment
    (2022-01-01)
    Srinangyam, Chissanupong
    ;
    Pannil, Pittaya
    ;
    Nimsanong, Phethai
    ;
    Chuayin, Chaitawat
    ;
    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
    ;
    Pannil, Pittaya
    ;
    Thungsook, Kittisak
    ;
    Promwong, Sathaporn
    ;
    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 on-site UHF Sensor for Partial Discharge Measurement
    (2022-01-01)
    Thungsook, Kittisak
    ;
    Promwong, Sathaporn
    ;
    Pattanadech, Norasage
    Partial discharge is the main problem that can lead to insulation failure or breakdown of high voltage equipment. An important and widely accepted process that can determine or ascertain partial discharge (PD) phenomena is the ultra-high frequency (UHF) method applied for monitoring HV apparatus and appraisal. This research explains the bandwidth verification of the on-site UHF sensor for partial discharge measurement. The researchers used a vector network analyzer for measuring the reflection coefficient (s11) of the UHF antenna compared to the voltage of the incident wave. In this research, 16 UHF sensors were used in the experiment. The reflection coefficient value and relevant parameters of high-frequency signals detected indicate the sensitivity and bandwidth of the antenna applied for PD detection in HV equipment. The reflection coefficient will be used as a criterion for selecting a UHF sensor type for partial discharge measurement.
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    The Bandwidth Verification of VHF Antenna and Apply for Partial Discharge Measurement
    (2022-01-01)
    Thungsook, Kittisak
    ;
    Pattanadech, Norasage
    ;
    Nimsanong, Phethai
    ;
    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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    The Reflection and Attenuation of High-Frequency Signals in a Distribution Transformer
    (2021-04-01)
    Thungsook, Kittisak
    ;
    Promwong, Sathaporn
    ;
    Pattanadech, Norasage
    This paper explains and demonstrates how to measured high-frequency signals in a distribution transformer. The high-frequency signals tend to suffer attenuation while propagating within a transformer to a detection device. In order to understand the propagation and attenuation characteristics of the high-frequency signals within the transformer, the highfrequency signal simulation in the transformer is essential. In this research, the reflection and the attenuation characteristics of high-frequency signals amplitudes as well as the frequency components of the high frequency while propagation through transformer winding and a core of transformer were examined both in the time domain and frequency domain measurement. The detail of high-frequency signals, including methods of detection device and material properties, are described in this paper. The infallibility of the experiment results was also evaluated.
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    Polarization and Depolarization Current Characteristics of Thermally Stressed Stator Coils
    (2020-10-25)
    Thungsook, Kittisak
    ;
    Phumipunepon, Natnaree
    ;
    Worthong, Tehneht
    ;
    Methavithit, Winai
    ;
    Vittayakorn, Wanwilai
    When the motor is exposed to thermal stress more than its limit, its insulation characteristic degrades and/or deteriorate. This paper presents the characteristic of stator coils under thermal stress by analyzing the polarization and depolarization current (PDC) characteristics. This research used a slot part of stator coils, which were obtained from a synchronous motor rated 6.6 kV with class F (155°C) insulation. Twelve test samples of motor stator coils were divided into four groups depending on the stress temperature levels, 100°C, 140°C, 180°C, and 220°C. Each specimen was heated at the specified temperature for four cycles (6 hours per cycle). To analyze the insulation characteristic of the tested specimen, PDC measurement was performed. It was found that the PDC magnitude decreased related to the number of thermal cycles and temperature levels, as described in this paper.