As a typical and critical configuration in power systems, the flame interaction among multiple conductors arranged in parallel significantly influences flame spread behavior. In this work, two types of polyethylene-insulated wires (with copper core diameters of 6 and 8 mm and an insulation thickness of 2 mm) were selected. By controlling a comprehensive set of spacing parameters, defined as S1 (0, 3, 6, 10, 12, 15, 18 mm) and S2 (3, 6, 10, 12, 15, 18, 20 mm) with the condition S1<S2, the flame spread and merging characteristics of triple wires under unequal spacing conditions were systematically investigated across a wide spectrum of configurations to understand their integral flame behavior. The experimental results revealed that the three flames exhibited distinct asymmetric characteristics due to the different spacing. Specifically, flame 1 and flame 2, located on the side with the smaller spacing (S1), demonstrated a higher flame merging probability (Pm) and greater flame height (Hf) than flame 3. Moreover, it was observed that the average flame width (Wf) increased significantly in the transverse direction. Thermal analysis further showed that the heat feedback among the three flames varied considerably depending on the spacing. Due to the strong thermodynamic coupling effect between flame 1 and flame 2, their gas phase heat transfer exceeded that of flame 3, resulting in a faster flame spread rate for the closely spaced pair. As the spacing between the wires was systematically increased, all previously noted asymmetric flame characteristics gradually diminished until there was no interaction between flames. Finally, a heat transfer model of flame spread was established, which accurately predicted the flame spread rate, and the prediction error was within ±20%. This study can provide corresponding wiring spacing designs for multi-wire energy systems and enrich the flame spread theories, both of which hold significant practical importance.