This study delves into the critical role of high-voltage underground cables in power transmission. These cables consist of multiple layers and conductors, typically made of copper or aluminum, and are insulated to endure various stresses. Insulation voids, bubbles, and defects within the material can cause partial discharge, impairing dielectric properties. Analyzing a cross-linked polyethylene (XLPE) high-voltage cable with copper conductor, this work employs numerical methods to investigate stress distribution. Finite Element Method (FEM) proves efficient for complex geometries, revealing how void size, location, shape, insulation properties, and operating voltage influence stress. Results show that void size affects maximum stress, while distance from conductor surface reduces stress. Cylindrical voids induce more stress than spherical or elliptical ones. Increasing insulation permittivity amplifies void stress, and higher operating voltages elevate stress, highlighting key factors for cable design and reliability assessment. The study underscores FEM's value in cable stress analysis, offering insights crucial for ensuring durable power transmission infrastructure.