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Determining Optimum Location and Number of Automatic Switching Devices in Distribution Systems
Ying He, G¨ ran Andersson and Ron N. Allan o Royal Institute of Technology, Stockholm, Sweden
 

Abstract: Nowadays consideration is being given to increasing the level of automation of distribution system. Automatic switching devices are important in automated distribution networks. This paperpresents an approach for determining optimum allocation of automatic switching devices in distribution systems considering investment constraints and taking into account dynamic network configuration changes by using an inhouse developed computer program RADPOW. A number of application studies of the approach are performed to show the effect of network and investment constraints on the optimalallocation of such devices. The results of application studies are presented in the paper.

can increase the system reliability by rapid restoration of supply, and can provide substantial cost savings to companies in which switching events are normally performed manually [3, 5]. The degree of improvement in system reliability is sensitive to the locations and the number of automatic switching devices.Some methods have been developed for placing switching devices [5, 6, 7], but they mainly deal with non-automated or low level automated distribution systems. Therefore, there is a need to develop methods that determine where to place automatic switching devices in order to achieve maximum benefit. Determining optimum locations and number of automatic switching devices is a complex procedure andinvolves a number of factors and constraints. This paper presents an approach to determine optimum allocation of automatic switching devices in distribution systems considering investment constraints and taking into account dynamic network configuration changes by using an in-house developed computer program RADPOW [1], A series of case studies were performed in order to show the effect of the networkand investment constraints on the optimal allocation of switching devices. The results of the application studies and the importance of considering the network and investment constraints are also discussed in the paper.

Keywords: distribution, reliability, automation, switching device, optimal allocation.

I. INTRODUCTION
One of the main ways of improving the reliability of power suppliesis to reduce the outage duration once the interruption has occurred [1]. In order to ensure rapid restoration of supply, consideration is being given to increasing the level of system automation. The implementation of system automation is presently very different at different levels of a power system. At the transmission level, a large investment has been made to provide automation, while at thedistribution level, switching of the network has predominantly been achieved manually [2]. Therefore, it is believed that there is great potential to improve automation in distribution networks. Investigations and experiments have shown that reliability indices and the customer outage cost can be improved monotonically as automation is increased and/or extended [3, 4], and this improvement becomesmore transparent when automation is added on non-automated or low level automated distribution systems. Automatic sectionalizing switches are important in automated distribution networks. Feeder switch automation
Also associated with the Manchester Center for Electrical Energy, UMIST, England as Professor of Electrical Energy Systems. Paper BPT99-24-17 accepted for presentation at the IEEE PowerTech’99 Conference, Budapest, Hungary, Aug 29 - Sept 2, 1999.
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II. CONCEPTS AND TECHNIQUE APPROACH
Automatic switching devices are located in primary distribution systems for various purposes, e.g., to improve reliability, to isolate component failures and faults, and to reconfigure the network, etc. In general, determining optimum location and number of automatic switching devices is a...