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The Comparison of DGA Interpretation Techniques Application for Actual Failure Transformer Inspections Including Experience from Power Plants in Thailand
(2022-03-01)
Jongvilaikasem, Korraya
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Pattanadech, Norasage
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Wattakapaiboon, Wilasinee
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Kando, Masaaki
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Maneerot, Sakda
Dissolve gas analysis (DGA) is a diagnostic test technique applied for transformer condition evaluation. The interpretation of the dissolved gas results is a significant procedure to classify the incipient fault types in transformers. A variety of dissolved gas interpretation methods utilized for the same investigation case may give different fault type results. This paper investigates the performance of dissolved gas interpretation methods, including Doernenburg Ratio, Roger Ratio, IEC Ratio, Müller-Schlliesing and Soldner Method, Duval Triangle, and Duval Pentagon. The twenty-four failure transformer cases are used to evaluate the performance of the dissolved gas interpretation methods. The test result shows that the Duval pentagon interpretation technique shows the highest consistency interpretation. Besides, the Duval pentagon method demonstrates the ability to identify a normal aging problem of the transformer insulation.
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The investigation of insulation performance evaluation of the large electrical rotating machine in frequency domain
(2019-01-01)
Phloymuk, Natthawut
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Kando, Masaaki
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Pattanadech, Norasage
The insulation structure of winding in a large electrical rotating machine consists of epoxy resin and mica material. The insulation structure is composed of many junctions. The insulation problems generate different kinds of signals, such as electromagnetic waves, which may get released from the non-perfect characteristics of the enclosure. This signal may interfere with the functioning of other nearby electronic devices. Therefore, maintaining an excellent condition of the insulation system of the machine is very important. For a condition monitoring of this insulation as proposed in this research, it is taken into consideration the results of the polarization and depolarization current (PDC) measurement of the test sample, and the stator winding rated 13.8 kV was investigated. The experiments were conducted under different thermal stresses, i.e., 25◦C (the room temperature) and 100◦C (the operation temperature). The test samples were divided into three types: I. haft-overhang, II. overhang and III. full stator bar. From the PDC measurement data record, the complex capacitance and polarization losses (ion migration polarization, slow relaxation polarization and interfacial polarization) were calculated. It was found that the aging of the insulation related to the complex capacitance and polarization losses can be contributed for research in future wireless technology.
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Applying HF and VHF/UHF partial discharge detection for distribution transformer
(2019-01-01)
Maneerot, Sakda
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Kando, Masaaki
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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◦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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An improved Current Voltage Transferring Device for high current high frequency measurement
(2018-10-01)
Pattanadech, Norasage
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Kando, Masaaki
This paper represents the characteristics of the improved Current Voltage Transferring Device (CVTD) for high current measurement including lightning impulse currents. The improved CVTD has been developed from the prototype CVTD to provide exceptional characteristics for high current with high frequency measurement. The improved CVTD in h-shaped configuration is made of copper and aluminium. The relationship between input current and output voltages of the new CVTD was investigated with short and long duration lightning impulse currents to establish the empirical formulas. The typical impulse current generator was used to generate 8/20 μs lightning impulse current with the amplitude of 940 A while the impulse generator with crowbar elements was utilized to generate 10/350 μs lightning impulse current with magnitude of 30.2 kA for the experiment. The lightning impulse current measurement characteristics of the CVTD and Rogowski coil were examined. From the experiments, the new improved CVTD shows the superior characteristics to measure the impulse currents with very fast rise time. Besides, nanosecond pulses superimposed on the lightning impulse currents were detected by only the improved CVTD. According to the experiments, there is no doubt that the new improved CVTD is a superior one for high current with high frequency measurement especially lightning impulse currents.
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A Direct Current Circuit Breaker With the Grid Method
(2018-02-01)
Pattanadech, Norasage
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Kando, Masaaki
This paper describes the developed direct current circuit breaker with the grid method (DC CBG). The simplified DC CBG was designed and constructed. It comprises the third electrodes, as the grid of a triode, installed between the main contact electrodes. Moreover, the special-designed transformer (SDT) was designed and constructed to supply a damping high-voltage pulse to the grid electrode for suppressing the arc current. The experiment was conducted to verify the performance of the designed DC CBG. Experimental results show that the amplitude of the arc current was significantly reduced by approximately 94% after the damping high-voltage pulse generated from the SDT was applied to the third electrode. Therefore, the proposed DC CBG has the ability to be developed for practical use in the future.
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New electrical shunt with two rectangular holes in a copper plate
(2015-11-01)
Kando, Masaaki
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Pattanadech, Norasage
A new concept of an electrical shunt with two rectangular holes in a copper plate (ESRP) has been developed to be used for measuring a large current with a short-duration steep wave in a high-voltage field. The ratio of the input current to the output current is 106, as obtained from a DC voltage test circuit. The electrical shunt has a special configuration. To verify the shunt current ratio of ESRP in a real application, the shunt current was connected to a sphere-to-sphere electrode breakdown test circuit with a 10 mm gap to measure the large damping current (8.4 kA) of a DC breakdown voltage. The voltage signal from the shunt was transmitted to excite two light-emitting diodes (max. 50 mA, 4 V), which were reverse-connected in series. The light-emitting diodes operated properly and were illuminated, which validated the capability of the newly designed electrical shunt.
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New current-voltage transferring device with different metals
(2015-09-01)
Kando, Masaaki
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Pattanadech, Norasage
A new concept of an electrical shunt with different materials (aluminum and copper) has been developed to be used as an alternative current measurement device. The device provides better current measurement characteristics compared with the conventional current measurement devices such as a shunt resistor with an ammeter or the multiple shunts consisting of molybdenum having a low temperature coefficient and a Rogowski coil with an integrated circuit. The currents in several electrical circuits have been measured using the developed current-voltage transferring device (CVTD) as voltages between the aluminum and copper elements. The measured voltages (V<inf>m</inf>) are proportional to measuring currents (I<inf>m</inf>), which is shown as the following the experimental equation V<inf>m</inf> [mV] =kI<inf>m</inf> [A], in which k is a coefficient depending on the configuration of the CVTD.
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Design procedure of common-mode filter for induction motor drive using butterworth function
(2007-10-01)
Khun, C.
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Tarateeraseth, V.
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Khan-ngern, W.
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Kando, Masaaki
This paper presents improved and simplified methods to design passive EMI filter of the common-mode noise mitigation complied with CISPR 14 or EN 55014; Conducted <700 W, Motors. The proposed design procedure of commonmode (CM) filter uses approximation function based on highorder Butterworth function to achieve not only the complied conducted noise but also the transfer function of the filter. This procedure is also based on the knowledge of the base-line of CM filter. The high frequency (HF) current probe is used to measure the conducted noises. Furthermore, this method makes possible a simplicity and fast design of the EMI filter with an arbitrary number of states. Design examples are given and the results are experimentally verified. © 2007 IEEE.
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