Distribution grid codes: Opportunities and challenges

Traditional distribution networks were not originally designed to accommodate power generation facilities. The installation of distributed generation (DG) units with significant capacity in these passive networks can cause reverse power flows which will result in some conflicts with the operation of the existing protection system. In this context, utilities around the world have started establishing requirements to ensure safe and reliable interconnection of generators in low- and mediumvoltage networks. Grid interconnection is presently one of the most important issues involving DG. This paper presents a critical review of the requirements adopted by distribution companies in selected countries such as the USA, the UK, Germany and Australia to facilitate the connection of DG. Critical issues such as voltage regulation, islanding operation, dynamic interactions among DG and loads are discussed to identify a few points where attention is still needed to improve the reliability of distribution systems.