Author N. Panklang, N. Phankong and K. Bhumkittipich
This research presents a design of transformer bushing insulation at high-voltage wire connection side. The bushing insulator is made from composite materials between natural rubber(NR) and high-density polyethylene(HDPE). HDPE has been used to increase a weather resistance properties of natural rubber such as ultraviolet resistance, temperature and heat resistance etc. The blend ratio of materials is natural rubber 60% and HDPE 40%. To study properties of insulator material, it is tested by using ASTM D2240, ASTM D412, ASTM D257-99 and ASTM D149-05 standard. The test results shown that the composite material has a tensile strength equal to 4.28 ±5.4 MPa, volume resistivity more than 2.14 × 1016 Ω – cm and surface resistivity about 5.56 × 1016 Ω/square. This insulation material can be withstanding a maximum AC power frequency voltage about 19.7 kV/mm. In additional to design, we used a finite element method(FEM) to analyze the electric field distribution around the bushing insulator. The highest electric field strength occurs at wire connector and equal to 0.95 kV/mm. Finally, the developed bushing insulator has been installed on 33kV distribution system at Saraburi province.
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