The power market is to be in highly competitive environment because of power deregulation. The electric power companies have raised business efficiency to reduce the number of employee and centralize the business establishments. Furthermore, an installation of photovoltaic generation (PV) will increase because of energy policy. However, electric power companies must maintain power supply reliability. Therefore, to reinforce the reliability in distribution systems is one of significant problem. In this paper, we propose an optimal placement of distribution section switches to maintain the power supply reliability under such a situation and exhibit the simulation result in the original distribution system using genetic algorithm.