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Author: search.filters.author.Inwanna, Woranan

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    The Study of Partial Discharge of a Decommissioned 11kV Rotating Machine
    (2024-01-01)
    Waiwicha, Supisara
    ;
    Monkolsatitpong, Suriya
    ;
    Inwanna, Woranan
    ;
    Vanijkirati, Parada
    ;
    Jeenmuang, Siwakorn
    Over time the insulation system of the stator winding in machinery will gradually lose electrical and mechanical strength due to factors such as thermal, electrical, ambient, and mechanical stressors. At a certain point, the material will deteriorate significantly to the extent that the insulation breaks down or cracks under normal operating voltages, due to transient electrical or mechanical situations. This paper presents a study of the stator winding insulation system of a decommissioned 11kV motor with the removed rotor, using offline PD measurement. The measurement results revealed PD signals in all three phases. The PRPD patterns indicate internal delamination discharge and discharge at stress control coating(S/C) and stress control grading which is occurring simultaneously. When the test voltage is increased to a certain point, the electric field stress in the stress control grading area becomes high enough to cause a gap-type discharge pattern, occurring between the press finger and the stress control grading area. Visual inspections also revealed spark discharge.
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    Partial Discharge and Dissolved Gas Analysis on 22kV MV Oil-type Transformer - Case Study
    (2024-01-01)
    Inwanna, Woranan
    ;
    Waiwicha, Supisara
    ;
    Vanijkirati, Parada
    ;
    Monkolsatitpong, Suriya
    ;
    Chumpiboon, Komin
    Detecting faults leading to potential failure of important power distributing transformers in the power system before an occurrence is an important attribute. Various inspection methods are available, however online PD and oil analysis remain the most preferred method. The methods mentioned do not require equipment shutdown. This paper introduces a case study of the 22kV transformer with online PD and DGA results indicating signs of problems in the insulation. The PD group found initially had an increase in density of signals during the three months and the magnitude shows an upward trend. DGA results found H2 and CH4 gas, the latter is a key gas indicating PD. Results show an increasing trend of almost three times as high during the latter half of the year. In addition, CO, CO2, and C2H6 gases were also found to be higher than average. Virtual inspection was conducted after the transformer was shut down. The surface is found to be uneven around the bus bar, causing high temperatures in the transformer which then impacts the insulation performance.
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    Partial Discharge Characteristics of MV Switchgear Using TEV and HFCT Sensors
    (2024-01-01)
    Kingkham, Sukanya
    ;
    Smerpitak, Krit
    ;
    Inwanna, Woranan
    ;
    Jeenmuang, Siwakorn
    ;
    Buranaaudsawakul, Techatat
    This paper presents partial discharge (PD) experiments for a medium voltage (MV) switchgear. Various types of defects were simulated i.e., corona discharge, surface discharge, and floating discharge inside the simulated MV switchgear. The transient earth voltage (TEV) was employed as a PD sensor to acquire the PD signals generated by the simulated PD defects. The TEV sensors were installed on the simulated metal enclosures MV switchgear to detect electromagnetic (EM) pulse radiated through such metal housing. Besides, high-frequency current transformer (HFCT) sensors were also used for a purpose similar to that of a TEV. Based on laboratory test results, it was found that when the external structural material and internal partition wall of the MV switchgear have greater insulation properties, some of the PD signals detected by the TEV sensor tend to exhibit a significant decrease in signal magnitude. The detected PD results of the simulating PD sources inside the MV switchgear will be presented in this paper. Moreover, the field test PD experiment for the MV switch gear is also reported.