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Author: search.filters.author.Pattanadech, NorasageSubject: search.filters.subject.Complex capacitance

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    Frequency Domain Spectroscopy Analysis of the Water Tree XLPE Cable
    (2022-01-01)
    Sawatdimongkol, Whichakorn
    ;
    Chancharoensook, Phop
    ;
    Sawatdimongkol, Worachai
    ;
    Taylim, Alisala
    ;
    Luangpol, Amata
    Water tree is one type of insulation deterioration occurring in polymeric cables such as polyethylene, ethylene-propylene rubber, and cross-linked polyethylene (XLPE) caused by the existing impurities in the bulk insulation or imperfection of the semiconductive surface. Moreover, the water tree phenomenon affects the cable's overall lifetime and can be developed into an electrical tree, leading to the failure of the cable. Because of this, the evaluation of water trees becomes one of the most important factors in the condition assessment of the cable. This paper presents the comparison of the dielectric properties of 22 kV XLPE underground cable between aged and new (unused) cables. Furthermore, the water tree was detected in the aged cable. Besides, the evaluation of aged and new cables was performed by frequency-domain spectroscopy (FDS), which measures the insulation's complex capacitance and dissipation factors in the frequency domain. Then, the aged and new cables' complex capacitance and dissipation factor were compared. The test result found that the dissipation factor and imaginary part of the complex capacitance of the aged cable have a higher value than these of the new cable. More or less, the results show that FDS is one of the non-destructive testing methods suitable for assessing the condition of the cable insulation, which deteriorated by water tree.
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    The aging of the insulation system of large rotating machines in frequency domains
    (2019-07-01)
    Phloymuk, Natthawut
    ;
    Pattanadech, Norasage
    The insulation of stator winding in a rotating machine consisted of mica and epoxy resin materials. The structure was also composed of junctions, so, a diagnostic monitoring condition of this insulation was taken into consideration. First, the results of the polarisation and depolarisation current measurement (PDC) of the test sample (stator winding rate of 13.8 kV) were investigated, as an experiment in the laboratory. The conditions of the experiment were conducted under different thermal stresses of 25°C and 100°C. The test sample was full stator bar. As found, the trend of the temperature of the winding rise if the current of the polarisation and depolarisation was increased. Second, the results of the PDC were calculated from the time domain to the frequency domain. The aim found that the aging point of the insulation system should take into consideration the results of the calculation of the frequency domain. The aging of the insulation system was a variant by the thermal stress, which was an effect from the complex capacitance and polarisation losses in the insulation winding system. Finally, this identified the phenomenon of the aging of the machine insulation system.
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    The investigation of insulation performance evaluation of the large electrical rotating machine in frequency domain
    (2019-01-01)
    Phloymuk, Natthawut
    ;
    Kando, Masaaki
    ;
    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<sup>◦</sup>C (the room temperature) and 100<sup>◦</sup>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.