To address the growing severe arc fault challenges in distribution networks, the research of efficient arc fault detection technology has become important to maintain grid safety and operational reliability. This study develops an arc fault detection strategy for three-phase AC power networks through instantaneous reactive current, which reduces the risk of electrical fires caused by arcs and ensures the stability and reliability of distribution networks. Firstly, an experiment environment is constructed for three-phase AC low-voltage distribution networks to simulate the arc fault phenomenon in real scenarios. Subsequently, through the application of instantaneous reactive power theory, the coordinate transformation technique is utilized to convert the three-phase current signals into instantaneous reactive current components, and the identification of arc faults is realized by monitoring the dynamic change characteristics of the instantaneous reactive current components. Finally, the experiment results validate the method's superior performance in both transient response and fault signature discrimination, which provides an effective technical support in arc fault detection for AC power distribution systems.