Effect of sectionalizing switches malfunction probability on optimal switches placement in distribution networks

Sectionalizing switches (SSs) are installed in distribution networks to provide ring and maneuver points, thereby increasing service reliability. These switches are either manual switches (MSs) or remote controlled switches (RCSs). The switches are usually assumed to be fully reliable. However, in practice, their performance is not always ideal. Actually, the switches may sometimes experience malfunction, which reduces their ability to enhance system reliability. The present study proposes a model to consider the malfunction possibility of the switches in their optimal placement problem. The model helps to minimize the total costs of SSs as well as the interruption costs incurred by interrupted customers. In order to calculate the malfunction probability of the switches, historical data on operation of the switches and their repair time are obtained from an electric power distribution company in Iran. The discrete Markov chain model is used to obtain the malfunction probability under different modes. The placement problem is then modeled in mixed integer linear programming (MIP) which can be easily solved to obtain the global optimal solution. The effectiveness of the proposed model is revealed by means of multiple case studies and sensitivity analyses. The studies show how the results of the placement problem are affected by the uncertainty caused by the probable malfunction of the switches and how overlooking this uncertainty can lead to deviation of the expected profit from the actual one.