Towards the Flexible Distribution Networks Design Using the Reliability Performance Metric

At present, the entire world is moving towards digitalization, including in the electric power industry. Digitalization is in its heyday and a lot of articles and reports are devoted to this topic. At the same time, the least digitalized of the electrical networks are distribution networks that account for a very large share in electric power systems. The article proposes a methodology for creating a flexible distribution network based on the use of digital technology. Additionally, we elaborate a methodology with the identification and collection of the necessary information to create digital networks, develop ways to adapt the required equipment, and suggest methods of recognition of some short circuits. Furthermore, we address the issue of reliability of the information obtained from digital devices, develop a technique for arranging the devices to cover the entire network as required to improve the power system protection of electrical power distribution networks. The above measures make it possible to ensure the flexibility of the active distribution network, as well as to adjust the parameters of the actuation of power system protection depending on changes in external conditions and in the event of emergencies. We propose a technique for controlling the distribution network, based on the factoring-in of the type of damage during an emergency in real time, as well as a technique for arranging the measuring devices and the creation of an information and communication network. We provide recommendations for the design and operation of electric power distribution networks with digital network control technology.

Analysis of Distributed Generation Accommodation in Flexible Distribution Networks

This work proposes a method to analyze distributed generation (DG) accommodation in a flexible distribution network (FDN). Firstly, the DG-load matching degree is proposed to quantitatively describe the power balance degree of DG and load in a distribution network. Secondly, the accommodation ratio of DG is proposed and divided into a DG-load accommodation ratio and DG-network-load accommodation ratio, to distinguish whether the index takes the network operational constraints into account. We derive the DG-load accommodation ratio directly from the matching degree and propose the simulation model of sequential production to solve the DG-network-load accommodation ratio. Finally, the cases of FDN under the scenarios of different matching degrees are studied and compared with those of the traditional rigid distribution network. The results show that the improvement of the accommodation ratio by upgrading the rigid distribution network to an FDN is conditional, which is related to not only the matching degree of the whole network but also that of each local network. The DG-network-load accommodation ratio will tend to the DG-load accommodation ratio if proper planning or optimization measures are taken. We find that the capacity of branches adjacent to the DG bus mainly limit the DG accommodation in the FDN, and it is recommended to relocate the DGs and enlarge the capacity of those branches.

Long-Term Trends of Planted Loblolly Pine Diameter Distribution Characteristics

Diameter distributions are fundamental characteristics of stand structure. It is widely assumed that unthinned plantation loblolly pine (Pinus taeda L.) diameter distributions are unimodal and slightly skewed. In this work, the assumption of unimodality is formally tested and confirmed using 413 long-term permanent plots representing three generations of genetics and silviculture across the native range of loblolly pine in the southeastern United States. Approximately 96% of plot measurements had no significant evidence to reject the hypothesis of unimodality. While levels often significantly differed, similar developmental trends of skewness, kurtosis, and estimated Weibull parameters were observed despite the advances of genetics and silviculture. The results of the study indicate the continued need for a flexible distribution for characterizing diameter distributions in plantation loblolly pine. Study Implications Knowledge of diameter distribution helps inform management activities. Further, assessing monetary or ecological value requires an understanding of a stand’s diameter structure. Using three long-term research studies established across the native range of the loblolly pine, this investigation confirms the assumption of slightly skewed, unimodal distributions. Additionally, long-term trends in skewness, kurtosis, and fitted Weibull parameters across the three generations of genetics and silviculture represented in the studies are presented. The results of this work confirm the need for a flexible distribution model form and indicate that managers can expect similar trends in diameter distribution structure in both vintage and contemporary stands at least until first thinning.