When a malfunction occurs in the power grid, in a short amount of time, it can lead to catastrophic damage. Because of this, to minimize the risk of failure, transmission line insulators need to be inspected. In the past, manual inspection was shown to be not fast enough for it to be effective. For these analyses, speed is of the essence. To ensure power grids are working properly and the inspection is fast enough, image segmentation techniques are utilized for analyzing transmission line insulators. In this paper, we employ multilevel thresholding techniques to analyse transmission line insulators. The Particle Swarm Optimization (PSO) algorithm is used to determine the optimal threshold values, while Kapur’s and Otsu’s entropy methods are applied to select the best threshold values across all iterations. These two entropies are one of the most widely used entropies for image segmentation. They show different performance in terms of speed and accuracy.