Pannil, Pittaya

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Pannil, Pittaya
Alternative Name
Pannil, P.
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Email
pittaya.pa@kmitl.ac.th

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    Item type:Publication,
    AC Breakdown Characteristics of Different Moisture Content Pressboards Impregnated with Natural Ester
    (2021-04-01)
    Pattanadech, Norasage
    ;
    Kittikhuntharadol, Yannaphol
    ;
    Pannil, Pittaya
    Biodegradable materials are necessary for saving the environment. Natural ester is alternative liquid insulation that can be biodegraded and used in a transformer. Insulation system in a transformer, liquid insulation cooperates with solid insulation such as cellulose. Pressboard is the main kind of cellulose used in the transformers. Normally, the characteristics of solid insulation can be investigated and analyzed by diverse methods. This paper represents the study of AC breakdown voltage of non-impregnation, 8-hours, and 16-hours impregnated pressboard with natural ester with different moisture content. To vary the moisture content of the pressboards, they were heated at 100 degrees Celsius for 12 hours and 24 -hours in a vacuum oven. After that, the Coulometric Karl Fischer method was used to determine the moisture content. Before impregnation, the natural ester was heated at 100 degrees Celsius for 12-hours in another vacuum oven. To investigate AC breakdown voltage, electrode configuration and test circuit were set-ups according to IEC 60243-1. From the test result, higher' moisture content caused clearly lower AC breakdown voltage of the pressboards.
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    Item type:Publication,
    Overload Duration Analysis of Mineral Oil and Natural Ester in Retrofilled Distribution Transformers
    (2025-01-01)
    Pongpitak, Siriwut
    ;
    Pannil, Pittaya
    ;
    Pattanadech, Norasage
    Natural ester fluids such as FR3 provide higher fire safety, better biodegradability, and extended insulation life compared with mineral oil. Retrofilling existing transformers with FR3 offers a practical means to enhance safety and environmental performance without redesigning the unit. This study evaluates the thermal performance and overload endurance capability of a 160 kVA distribution transformer before and after retrofilling from mineral oil to FR3. Results show that steady-state temperature rises increased modestly after retrofilling (+1.3-4 K for top oil and windings) but remained within IEC limits. Under 1.5 p.u. normal cyclic loading, the mineral-oil unit reached its 120 °C hot-spot limit after 5 hours and 20 minutes, whereas the FR3 unit stabilized near 126 °C and did not reach its 140 °C limit within 10 hours. Under 1.8 p.u. long-time emergency loading, FR3 extended the time-to-limit to 5 hours and 20 minutes, compared with 4 hours and 30 minutes for mineral oil (18.5% increase). Overall, FR3 trades slightly higher temperature rises for a wider operational safety envelope and longer overload endurance, supporting safer peak-shaving and contingency operations in retrofilled assets. These findings provide actionable insights for utilities considering FR3 retrofilling as a cost-effective transformer upgrade strategy.