Electrical Tree Growth at Various Needle-Plane Distances under Constant HVDC Voltages in Flexible Epoxy Resins

<p> In high-voltage systems, electrical insulation is essential for safety operation including isolation from ground potential, and its failure will cause the entire high voltage system to fail. Metallic protrusions in the insulation concentrate the electric field strength and provide conditions for electrical tree initiation and growth, which may lead to unexpected premature insulation failure. In this work, electrical treeing growth in flexible epoxy resins has been investigated using controlled geometry metallic protrusions in the form of needles cast in epoxy resin. The electrical tree experiments were conducted with a constant High Voltage Direct Current (HVDC) voltage without any repetitive interruptions in the HVDC supply or superimposed AC waveforms. The influence of variations in the pin-plane distances on the electrical tree inception and growth were examined. The magnitude of partial discharges with respect to the time of inception and tree growth duration were measured and analyzed. The partial discharge measurements were matched to superimposed photographs of the electrical trees growth to aid understanding of the electrical treeing progress under HVDC applied stresses.</p>