Design of a Single Wire Earth Return (Swer) Power Distribution System and Improvement of Its Voltage Profile Using Capacitors

Abstract

Access to safe, reliable and cost effective energy is essential for a country to make the economic growth of the population. It is well known that electricity is a service and a key input into economic development and household activities. The cost of extending the main grid to supply remote and rural area is extremely high. Rural areas which are characterized by low load density and scattered load requires a low cost electrification method; and electrification using Single wire earth return distribution has shown to be the most economic option . This is more important and more applicable for remote centers in different villages in Rwanda where people are living in settlements. In this research a settlement is considered as one load to be supplied by one distribution transformer. SWER system is, by definition a single wire earth return distribution system in which all equipment connected to it, is grounded to earth and the earth is used as a return path where the return current passes through. The purpose of SWER is to power relatively small but relevant loads over a long distance at the least possible cost; SWER is a low capital and maintenance cost distribution system which has ever been chosen and widely built in many parts of the world especially in remote areas where loads are scattered, light and far from the main grid. However,even if this system has shown to be most economical, it has shown challenges especially in terms of voltage regulation and losses that affect the system capacity and the quality of the power to the end users and there is a need to find a way of improving this distribution system and providing a reliable and sustainable power to remote rural areas. This research aims to improve the voltage profile of a single wire earth return distribution system. One of the sector located in rural area of Southern Province of Rwanda was selected, and its demand in electricity was estimated by taking into account several aspects such as type and number of consumers, equipment and expected time of operation for the appliance. After the network was designed a load flow calculation iv was performed using backward/forward sweep method to determine the system‘s voltage profile, the results from backward and forward sweep method were compared with the results from Direct load flow approach. Both results have shown a poor voltage regulation at all nodes except the starting node which is considered as the slack bus. To improve the voltage profile capacitors were proposed, These are usually used as reactive power compensators in electrical network. The main benefits of their utilization are to minimize the power losses, improve power factor and maintain best voltage regulations for all load buses. To determine the optimum size and siting of the capacitor, maximum power saving method were used. The findings has shown that the use of capacitor has improved the voltage profile, where voltage at all nodes are within the acceptable limits and both reactive and active losses were reduced.