Mobile Laser Scanning (MLS) systems have been used for power line inspection in a fast and precise fashion. However, manually processing of huge LiDAR point clouds is tedious and time-consuming. Thus, an automated method is needed. This study proposes a machine learning-based method for automated detection of power lines from MLS point clouds.  The proposed method consists of three main steps: pre-processing, line extraction using Support Vector Machine (SVM), and post-extraction. In the pre-processing step, noisy and low-height points are eliminated after sectioning the collected point clouds. This step considerably reduces the volume of point clouds by 90%. Then, the point features including linearity, planarity, verticality, and the largest component of Principal Component Analysis (PCA) are used as the best-fitted descriptors for power line detection. After training the SVM by a small section of points, SVM properly classified the point clouds with about 97% and 98% accuracies regarding precision and recall, respectively. In the final step, a post-extraction is required to eliminate false points in the power line class. This step improved the recall from 98% to 99.4% and decreased slightly the precision accuracy from 97% to 95.5%. The results demonstrated that the proposed method works rapidly, about 14 seconds per section with an average of 5 million points in each section.