High-Voltage Direct Current (HVDC) technology plays a critical role in modern power transmission and applications such as X-ray systems and electric vehicles. Partial discharges (PDs) within insulation materials can lead to degradation and eventual failure of high-voltage equipment. This study focuses on streamer-type PD occurring in spherical cavities under HVDC stress. An adapted version of Niemeyer’s HVAC streamer discharge model is implemented for HVDC conditions, combining finite element simulations in COMSOL with a MATLAB-based numerical simulation and statistical analysis framework. The model investigates the relationship between discharge magnitude, repetition rate, and applied voltage and compares simulation trends with experimental data reported in the literature. The results provide insights into PD behavior under HVDC stress and contribute to the development of more reliable insulation systems.