ABSTRACT
The chapter describes power distribution systems, how these systems are deployed and operated, components and characteristics and the power distribution in the context of smart grids. Transmission systems end-up at substations, which distributes power through distribution networks to load centers and to all customers. Distribution systems effectively are the grid section delivering electricity to residential, commercial or industrial loads. In power distribution, electricity is distributed through two key steps: transforming electricity to required voltage levels and fanning out electricity to each consumer. Power distribution networks are the most exposed grid sections to the public, having the most challenging safety and supply security issues. Electric services, feeders, panel-boards and protection are critical components of power distribution. To cope with today's power system issues, such as environmental impacts, supply diversification and security, reliability, faster service restauration or consumer participation, there are major trends to use local energy sources, energy storage and dispersed generation. Moreover, high-distributed generation penetration is one of the smart grid attractive features, aside from being reliable, robust and efficient. However, this comes with challenges, such as new voltage and reactive power control methods, new protection methods, needs for two-way communication, power system instabilities and additional local power losses. Higher renewable energy and storage uses or higher demands for power quality, system reliability and resilience are changing the way power distribution is planned and operated. To achieve such new and more intelligent power distribution, emerging technologies need to be used, e.g. smart metering, sensing and monitoring, two-way communication and advanced energy management.
Power distribution networks are very large and extensive systems consisting of hundreds of thousands of nodes that can generate huge data volumes. However, the existing power distribution systems as a whole are often poorly monitored and the availability of required real-time measurements is impractical due the massive system size and associated costs. In order to provide affordable, reliable and sustainable energy, a modern grid needs to become smarter and more efficient. The major characteristics of distribution assessment are: reliability, efficiency, voltage regulation, cost and safety, environmental and esthetic impacts. Moreover, power distribution design and operation present a multitude of complex and often conflicting objectives. For example, reliability, efficiency and safety must be maximized for asset protection, while minimizing the costs and customer disturbances. These conflicting objectives impact the type, choice and structure of the power distribution assets, substation topologies, locations, feeder design, feeder and substation protection, control and other significant technical decisions. Transitioning from conventional power distribution to smart power distribution requires a paradigm shift in the design, management and operation. This shift is due in part to the increased use of distribution management systems, demand side response and more significant is the burgeoning of distributed energy resources. Massive underway DG deployment is expected to increase in the near future. The smart distribution systems must be designed, so that rapid service restoration, improved safety and reliability are implemented. It is envisioned that smart distribution systems will increasingly migrate to networked configurations, especially in the high load density areas. Rapid service restoration can accomplish several objectives, including reduction of the average interruption duration and frequency, or the minimization of unserved energy to loads. A highly reliable, reconfigurable and fault-tolerant distribution system must contain multiple redundant paths. However, more important than multi-connection paths are the smart strategies for the fault detection, isolation and reconfiguration (FDIR) to manage the distribution redundancy.
