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Applying HF and VHF/UHF partial discharge detection for distribution transformer
(2019-01-01)
Maneerot, Sakda
;
Kando, Masaaki
;
Pattanadech, Norasage
This paper represents application of high frequency (HF) and very high frequency/ultrahigh frequency (VHF/UHF) partial discharge (PD) detection for a distribution transformer. A capacitive sensor is used to detect the HF electric field caused by charge transfer inside oil–paper insulation due to PD at the defect site, and an electromagnetic sensor or antenna is used for detecting electromagnetic PD transients in the air outside the investigated transformer in the near-field region. Three types of artificial PD sources in air and insulating liquid, which are corona discharge, surface discharge and air void discharge in pressboard, were investigated. Three identical distribution transformers were rated at 22 kV, 400 V and 50 kVA, and were designed and constructed. The first transformer was filled with mineral oil, the second was filled with natural ester and the third was filled with palm oil. The PD generated by the air-filled voids in the insulating papers and pressboards of these transformers with five different conditions were investigated, i.e., non-impregnated paper, impregnated paper for 3 hours, 6 hours, 9 hours and 12 hours. The impregnation process was done with 65<sup>◦</sup>C liquid temperature, and the pressure in the oven was around 5 mbar. From the experimental results, it can be concluded that the electromagnetic PD transients radiated from the corona discharge of both high-voltage (HV) and low-voltage sides in the air are in the VHF range, and surface discharge frequency is extended up to the UHF range. For the PD in the insulating liquid, the phase resolved PD (PRPD) pattern in the HF range is a valuable tool to characterize the PD sources. The PD in an air-filled void inside the insulating paper of the mineral oil transformer is obviously different compared with those of the natural ester transformer and the palm oil transformer. For the manufacturing of distribution transformers in this research, it is found that after the paper insulation is dried out, the impregnation process for a period of 9 hours is suitable for improving the oil–paper insulation with an acceptable PD level. This paper is the cross-field application by applying the antenna and communication theory for detecting the discharge problems in HV equipment.
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Wideband antenna performance evaluation for ultra wideband communication system
(2018-07-02)
Ruethorn, Issaree
;
Promwong, Sathaporn
The transmission loss in modern wireless communication systems is usually evaluate by Friis' formula. However, ultra wideband communication systems cannot apply its directly because the transmission waveform for the ultra wideband is difference from the other wireless communication systems. In this paper, the performance of the ultra wideband antenna with the measurement data of the transmission waveform based on Friis' formula and correlation receiver are presented. This scheme used to evaluate formula for the transmission waveform of the ultra wideband communication system. The distortion will be consider the receiver waveform and antenna should be known. Since the ultra wideband transmission waveform are pulse-shaping by the antenna, difference parameter of the antenna is investigated, especially the effect of the antenna performance and waveform template.
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Multi-reconfigurable band-notched coplanar waveguide-fed slot antenna
(2018-01-01)
Lertwatechakul, M.
;
Benjangkaprasert, C.
This paper proposes an antenna design concept to achieve a multi-reconfigurable band-notch antenna by using a set of microswitches. The proposed idea was proved by the design of the coplanar waveguide (CPW)-fed slot antenna. The sample design gives a wideband antenna the impedance bandwidth of which covers the frequency ranged from 1.9 GHz to 6.55 GHz. The antenna could be configured to work either in single-band mode or in one of the defined dual-band modes.
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3D finite element analysis for varicose vein therapy by using microwave ablation
(2012-12-01)
Prasantamrongsiri, S.
;
Phasukkit, P.
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Pintavirooj, C.
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Tungjitkusolmun, S.
;
Sanpanich, A.
This paper presents three-dimensional finite element method for analyze a varicose vein microwave ablation. Varicose vein can contract by using heat from microwave ablation. Because of varicose vein patients have leg pain from long time standing, and do a lot of activities. Symptoms have influenced the daily life of patients. We study method for varicose vein therapy by using microwave ablation. Because of this method is easy to use for varicose vein therapy. In this research work, we propose simulation varicose vein that varicose vein is inserted with antenna into blood vessel. Simulation method delivers microwave to antenna inserted in varicose vein. For this reason, varicose vein is contract. Finite element analysis can apply in treatment planning and show temperature distribution and specific absorption rate (SAR) distribution for contract of varicose vein characteristic by using microwave therapy. And the doctor can be use the data for treat in future. ©2012 IEEE.
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Performance evaluation scheme of ultra wideband impulse radio transmission
(2010-07-30)
Sereewattanapong, Thawatchai
;
Promwong, Sathaporn
Ultra wideband transmission waveform is investigated by using extended Friis' transmission formula baseded on experiment data. This paper, we consideration the performance system design on ultra wideband impulse radio (UWB-IR) system for personal area networks. The received signal and isotropic template receivers are considered based on Friis' transmission formula. In this experimental study, the biconical antennas are uesd as the transmitter (Tx) and the receiver (Rx) antennas. The rectangular passband, which is satisfied the full band of UWB signal definition and Federal Communications Commission (FCC) indoor and outdoor limit spectral masks, is used as the transmitted UWB signal. The channels are measured in an anechoic chamber by using a vector network analyzer (VNA). The relative gains of received signal and isotropic template receivers are shown and compared in results.
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Waveform distortion and transmission gain on ultra wideband impulse radio
(2010-01-01)
Promwong, Sathaporn
;
Supanakoon, Pichaya
;
Takada, Jun Ichi
A waveform of an ultra wideband impulse radio (UWBIR) system can be extremely distorted through a channel even for free-space transmission because of antenna dispersion. This highly degrades the link budget performance. Therefore, the understand of antenna characteristics, which effects on waveform distortion, is necessary. This paper studies the waveform distortion due to antenna in free space transmission in UWB-IR system. The link budget is usually evaluated by using the Friis' transmission formula. However, it is not directly applicable to the UWB-IR transmission system. The link budget evaluation formula attended from conventional Friis' transmission formula that takes into account the transmitted waveform, its distortion due to the antennas, the channel and the correlation receiver is proposed. Since the antenna is significant pulse-shaping filters in UWB-IR system, the example kind of the log-periodic dipole antenna (LPDA) is experimentally examined, especially focused on the effect of the template waveforms. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers.

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