Smart Switch for Solar Renewable Sources at the Point of Common Coupling (PCC) in MV and LV Networks

Abstract

The escalation in power usage of green energy globally and the demand for green energy sources has necessitated the growth of distributed renewable energy generation in an effort to reduce greenhouse gas emissions. The ever increasing electricity tarriffs in South Africa has given rise to a rapid rollout of renewable energy and subsequently has led many household to self generate instead of relying on the power utility only. Solar is the most popular distributed renewable energy that is used by many households in South Africa. Solar energy generation pattern is highly predictable and has a high coincidence factor nearly 100% in a given small area. Because of high coincident factor of solar, low vltage (LV) networks are therefore prone to thermal overload and overvoltage in residential areas during the mid day. To avoid overloading and overvoltages on LV residential networks customers on shared transformer are limited to generate 25% of their individual load capacity as per statutory requirement in NRS097. Many of the household have installed renewable generators without complying to the 25% requirement and it is difficult for the utility to manual monitor all customers whether they comply or not. In this paper, we propose a smart switch that address this challenge and we outline the parameters to consider in relation to the NRS 097 as per grid codes in South Africa. This then enables us to devise a smart and automated interface between the renewable solar power generator and the public utility grid with the capability of having real-time intelligence to active/reactive power as well as the voltage produced by means of IEC 61850 communication protocol interface