Power quality enhancement, energy losses reduction as well as transmission efficiency improvement are pivotal for the sustainable expansion of power distribution networks. Generally, reactive power optimization is essential for the stable and efficient functioning of distribution networks. Regarding this issue, in this study the impacts of reactive power load, transformers, generators, capacitors, and static var compensators are comprehensively evaluated. For this purpose, an improved genetic algorithm is adopted, by refining key components such as the coding framework, initial population, and adaptation mechanism, along with crossover and mutation strategies. The IEEE-118 bus system is used for simulation experiments. The results confirm the merits of the applied improved genetic algorithm.