Effects of Dynamic Electromechanical Stress on Electrical Tree Characteristic in Epoxy Resin

Epoxy resin insulation is widely used in high-voltage power equipment, where they endure complex electromechanical stresses. This study examines the effects of dynamic electromechanical stress on electrical tree growth in epoxy resin under simultaneous AC voltage and cyclic stress. The results show that under high cyclic stress, tensile stress promotes residual stress release, thereby enhancing tensile strength and suppressing electrical tree propagation. In contrast, compressive stress induces fatigue damage, leading to strength reduction and accelerated tree growth. Under low cyclic stress, fatigue striations contribute to improved mechanical strength; however, tensile stress facilitates defect extension and tree initiation, whereas compressive stress inhibits treeing via defect closure. Reverse trees arise under compressive stress due to high resistivity in forward channels. Tensile stress produces wider, slower-growing trees with higher partial discharge amplitude, fewer counts, and narrower phase ranges, while compressive stress leads to narrower, faster-growing trees with lower amplitude, more counts, and broader ranges. These behaviors result from stress-induced dielectric variations that reshape local field distribution and partial discharge activity, ultimately governing tree evolution. This study provides new insights into electromechanical stress-driven insulation degradation and informs epoxy insulation design for long-term reliability in high-voltage equipment.