Optimal Vegetation Maintenance Scheduling of Overhead Electric Power Distribution Systems

Vegetation maintenance involves trimming or removing trees and brush near the overhead conductors to reduce the number of tree related outages and maintain system reliability. This paper reports a maintenance scheduling algorithm that determines the optimal location and time for performing vegetation maintenance on overhead distribution feeders. A vegetation failure rate model is developed that quantifies the impact of the maintenance schedule on the reliability of a distribution system. Using this reliability model and a predictive reliability assessment algorithm, the maintenance scheduling algorithm is formulated as a combinatorial optimization problem that considers different objective functions and constraints. After experimentation with several heuristic search techniques, a hybrid genetic algorithm-hill climbing technique consistently found the highest quality maintenance schedules. The results from applying the maintenance scheduling algorithm to a real distribution system are also presented. It is shown that the new maintenance scheduling algorithm can find lower cost and more reliable schedules as compared to standard fixed interval schedules.