Enhancement protection coordination for distribution networks connected with PV using preset-time method

Abstract

,In the modern era, electricity is the lifeblood. There is almost no practice without electricity in daily life. Distribution systems are the most important parts of the electrical system because they deal directly with the consumer, and any problems with them will reduce the quality of the electrical system and thus reduce its reliability. At a time when the global warming problem is emerging, the demand for and promotion of renewable energy is increasing. The spread of photovoltaic (PV) within the distribution networks has become widely spread in many countries. Despite the advantages provided by PVs, they cause negative effects on the distribution networks. One of the most significant negative effects that PVs cause on the distribution networks is the significant impact on the protection system. The high penetration of PVs can lead to the destruction of important parts of the distribution network due to the loss of coordination between the protection relays or increase the operating time (ROT) of backup relays when a main relay does not respond for any reason during faults. Most of the studies concerned with reducing the negative effect of PVs on the protection systems followed two basic strategies: either reducing the current coming from the PVs during the fault or modifying the curve characteristics of the protection relays. Both strategies have satisfactory results in reducing the harmful effects of PVs during faults. However, both strategies followed in most studies either require equipment to be added to the electrical network, such as current limiters, or use advanced and modern relays through which the characteristics of the curves of the protection relays can be modified. In this study, a method called Preset-Time is used to enhance the performance of the protection system during faults at high PV penetration within the radial distribution networks. The method aims to achieve the lowest possible ROT for the backup relays in the event of a failure of the main relays. The database of a radial distribution network (11.5 kV) located in western Iraq is used as a test system for the proposed method. To ensure the correctness of the Preset-Time method, the performance of the protection system in the conventional setting with and without PVs is analyzed; the Preset-Time method is implemented at full and zero penetration of PVs at various locations on the test system; the performance of the Preset-Time method is evaluated for different operating conditions of PVs; and finally, the effectiveness of the Preset-Time method is validated by comparing it with the conventional and Max PSM methods. The Etap19 software is used for modeling, while the genetic algorithm is used to calculate TMS. The Preset-Time method has proven its quality and effectiveness in reducing the ROT of the backup relays for the whole test system compared with the conventional and Max PSM methods alike at an initial critical time interval (CTI) of 0.3s.