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Author: search.filters.author.Pattanadech, N.Subject: search.filters.subject.Partial discharge

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    Analysis and Comparison of Characteristics for Offline PD Measurements in Turbo-Generators at Different Test Time Intervals
    (2022-01-01)
    Dorkmai, K.
    ;
    Pannil, P.
    ;
    Tattiwong, K.
    ;
    Maneerot, S.
    ;
    Suksawat, D.
    Partial discharge (PD) measurement is widely used for the condition assessment of high voltage equipments. It is a tool to detect the localized discharges occurring in the weakness point sites, which causes deterioration that can lead to failure. Hence, it is essential to diagnose the PD behavior to prevent the consequent failure which maybe takes place. This paper presents an analysis of the offline PD measurements performed on the stator winding insulation system of three turbo-generators which consist of a hydrogen-cooled generator rate of 211.75 MVA, 15.75 kV, and two air-to-water heat-cooled generators which the same rate of 50.8 MVA, 11.5 kV, which were located in the power plant. Firstly, the offline PD measurements of these generators have been energized to the star point side and the high voltage coupling capacitor is installed on the high voltage terminal side, according to IEC 60034-27-1. Additionally, the test voltages were applied to the test object with a step voltage profile. To analyze the PD behaviors of the stator winding insulation, the PD characteristics such as the PD pulses, PD magnitude, and phase-resolved PD (PRPD) patterns were monitored and recorded. Besides, the effect of applied test voltage-time, i.e., 1, 3, and 5 minutes, on such characteristics were reported and compared. Finally, the PD behavior of the stator winding insulation of these generators showed clearly different results for PD measured at different recording times. The highly fluctuating PD magnitude and PD pulse shape at the initial duration of the measurement, and then gradually decreases to convergence to a stable charge magnitude as the test-time increases.
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    A locating diagnosis of partial discharge on cross-bonding ground system
    (2021-05-19)
    Inwanna, W.
    ;
    Mongkolsatitpong, S.
    ;
    Chancharoensook, P.
    ;
    Pattanadech, N.
    At the present, Thailand has turned the attention to Underground Cable (UC) systems and trends to use it more to safety, stability and reliability of electrical system. However, one problem that can affect to this electrical system is the Partial Discharge (PD) problem. Most of PD problems are caused by incomplete installation, maintenance reason and insulation degradation on the weakest part, especially cable joint. This paper proposes a method of analysis to locate the PD source in UC systems with Cross Bonding (CB) focus on cable joints. This work has carried out in laboratory on CB system model using 50ohm R58 coaxial cable instead of underground cable. The PD detection technique according to IEEE 400.3 standard with a RFCT sensor to refer the appropriate signal. This work uses a PD diagnostic device that can filter noise from the PD groups and separate groups of PD for greater analysis accuracy. To determine which cable joint is PD source and to be able to fix it on the spot. The PD signal analysis are performed by using time of arrival method considered together with the characteristics and the polarity of the PD pulse.
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    Breakdown characteristics and partial discharge phenomena of gas-insulated system under slightly nonuniform electric field with floating object
    (2018-07-02)
    Chuayin, C.
    ;
    Chamnong, C.
    ;
    Sontayananon, N.
    ;
    Kachachaveevong, T.
    ;
    Nganpitak, T.
    The characteristics of breakdown voltage of air under slightly non uniform field with floating object was investigated experimentally. The sphere-plane electrodes with sphere diameter of 4.5 cm and plane diameter of 10 cm were used to study. The gap spacing between the sphere-plane electrodes was fixed at 3 cm. In this paper, the floating objects were divided into 2 types according to types of materials used, i.e., aluminum material represents a conductive particle and plastic material represents a nonconductive particle. The floating object position was varied between the sphere-plane electrodes in the test chamber. It was found that both types of floating objects clearly had negative effect on the breakdown voltage. Moreover, to more understand the effect of these floating objects, an ultra-high frequency sensor was used to detect partial discharge signal occurring during the experiment before breakdown occurred.
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    Experience of a partial discharge problem of electrical cables in power plant
    (2018-07-02)
    Kongdang, P.
    ;
    Nganpitak, T.
    ;
    Sontayananon, N.
    ;
    Chamnong, C.
    ;
    Chuayin, C.
    This paper represents a Partial Discharge ("PD") problem occurred in 6.6 kV electrical cable systems in a power plant. During annual switch gear and cable termination box inspection, some parts of electrical cables were identified as burned. Using electromagnetic and PD theory, the burned electrical cables were caused by the touching and pressing of different phase cables with inadequate clearance space. The initial solutions were rearranging the cables, using heat shrink tube for jacketing to improve the cable insulation. Inspection window was installed for PD measurement with Transient earth voltage method. Periodical PD monitoring has been performed to follow up whether new cable rearrangement can reduce the problem. The core of this problem could be better and deeper understood by Root Cause Analysis (RCA). Extension of busbar, enlargement of the cable box for better arrangement and addition of environmental control was later applied with a satisfactory outcome.
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    Dielectric properties of mineral oil compared with natural ester
    (2017-11-29)
    Jariyanurat, K.
    ;
    Nimsanong, P.
    ;
    Chaisiri, P.
    ;
    Maneerot, S.
    ;
    Kitcharoen, P.
    In this paper, dielectric properties of the mineral oil, ELECTROL A, and the natural ester, FR3, are comparatively investigated. AC breakdown voltages, dielectric dissipation factor, relative permittivity, partial discharge inception voltage and partial discharge of the mineral oil and of the natural ester are tested. In order to verify the capability in practical use of the mineral oil and the natural ester for transformer insulation systems, the impregnation of such liquids with pressboard insulation is performed. The impregnated pressboards are tested in the laboratory to measure the AC breakdown voltages. It is found that the natural ester shows superior dielectric properties to the mineral oil except the dielectric dissipation factor.
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    Corona phenomena of various high voltage shielding types
    (2006-01-01)
    Pattanadech, N.
    ;
    Potivetkul, S.
    ;
    Yuttagowith, P.
    This paper presents the corona phenomena of various high voltage shielding types. The 11 kinds of corona shieldings which were corona steering ring, 7 circular connected half-spheres, topping 2 rings, 4 connected spheres, barrel shape with 5 rings, decagon with 5 rectangles, 2 connected symmetrical rings, drum shape with 2 rings, spherical connected bowls, 3 connected bowls, and 5 connected donuts were designed, constructed and examined. The corona shields made of aluminum were designed for 50 kV rating. In the design process, the electric field distribution and its maximum value of the designed corona shielding were simulated using finite element program. Then the constructed corona shieldings were installed with the high voltage electrode and investigated in the topics of corona inception voltage and partial discharge values at the specified test voltages. The corona shielding characteristic test was carried out at various atmospheres. The tested results are composed of the corona phenomena pictures obtained from the corona camera and elliptical displays showing PD activity and the amplitude of corona discharge taken from the PD detector. The tested results show that the 5 connected donut corona shielding has the best performance. It reduced the corona phenomena of the tested electrode about 20 % after it was installed with the high voltage electrode. The trend of the data tested at 3 various atmospheres are relatively similar. Besides, the results obtained from the simulation program show good agreement with the tested results. © 2006 IEEE.