The distribution grid is the infrastructure that transports electrical energy generated by large plants that are long distances away to the final user. A typical distribution grid consists of High-to-Medium Voltage (HV/MV) transformation centers; the MV grid; Medium-to-Low Voltage (MV/LV) transformation centers; and the LV grid, both three-phase and single-phase. Residential and commercial customers are mainly connected to the LV, while large industrial facilities are connected to the MV.

The business of distribution system operators is rapidly evolving as the distribution grid is hosting more distributed energy resources. Technology for monitoring, control, and protecting the grid is progressively pervading the lower segment of the network. These changes require a performing communication infrastructure to enable data exchange among the control centers of the grid. The 7th Framework Program European Project INTEGRIS proposes a hybrid infrastructure-based on broadband power line (BPL), Wi-Fi, and fiber optics (FO)-to enable services for grid management. This mix of technologies provides a balanced tradeoff between investments and benefits, meeting most of the requirements of the smart grid. This paper investigates the technologies that could be adopted and describes the experimental assessment performed in an operational environment in Italy. Using this installation, transfer time, time synchronization accuracy, dependability, and throughput are evaluated and analyzed over a long-term campaign. Results show that the FO is the best communication media, able to provide a two-way latency of 3 ms (95 percentile), whereas BPL has a two-way latency of 57 ms (95 percentile -4 hops). Those results confirm that a careful selection of the technologies is required to satisfy requirements of smart grid.

The IEC 61850 standard allows for a structured grid automation system where critical tasks like grid protections, renewable energy sources management, synchronized measurements, and monitoring applications share the communication network. So far, the use of IEC 61850 has been mainly limited to the primary substations, but more interesting could be the coordinated actions between primary and secondary substations in order to quickly react to faults and to reduce service downtimes for final customers. Unfortunately, the communication networks between primary and secondary substations are today only partially deployed. Considering this context, the broadband power line over medium voltage grid (MV-BPL) could be a suitable solution for closing the communication gaps between substations that use IEC 61850. The main objective of this paper is to present the outcomes of the first phase of a project whose final goal is the implementation in real grids of distribution grid automation based on IEC 61850. A new and comprehensive set of experiments on a real (and in service) medium voltage grid in Italy has been designed and carried out. The practicability of IEC 61850 communication over the distribution grid is assessed comparing the time characteristics of the MV-BPL against the transfer time classes of the IEC 61850, determining which IEC 61850 services may be transported over MV-BPL. The experimental long-term analysis highlights that more than 90% of the service requests are transferred on the network with a round-trip time lower than 40 ms even in the case of four hops, a time which is compatible with the IEC 61850 fast automatic interactions on MV grid.

Power quality in LV distribution networks is already a concern in many European countries especially where there is a strong presence of renewable energy generation. Therefore there is a growing interest in new solutions able to improve the power quality level of such a system. Among them, an interesting solution is represented by the open unified power quality conditioner (Open UPQC) proposed within the present work. The system consists of a single or three-phase ac/dc power converter installed at customer's premises and a main single or three-phase ac/dc power converter in the MV/LV substation. The paper discusses the design, simulation and implementation phases related to an Open UPQC installed in a real LV distribution grid in the city of Brescia (Italy) within the smart domo grid project, co-funded by the Italian Ministry of Economic Development. Results from the field installation show the effectiveness of the proposed solution to face power quality issues in distribution networks.

Traditionally, distribution network monitoring has been focused on primary substations (i.e., high voltage/medium voltage level), whereas low voltage (LV) network has not been monitored at all. With rapid growth and penetration of distributed energy resources in LV grids, there is growing interest in extending the real-time monitoring to LV level. The framework program FP7 European Project INTEGRIS proposes an integrated real-time LV network monitoring solution and implements it in a cost-efficient way. This solution integrates smart metering data with secondary substation measurements to get a more accurate and real-time view about LV grid, uses “decentralized” distribution management architecture to optimize data flow, and uses International Electrotechnical Commission 61850 Standard-based interfaces to improve interoperability. This paper focuses on information and communications technology perspective, explains the implementation details of this monitoring solution, and presents its functionality/performance testing results from two distribution system operator field trials and from real-time digital simulator laboratory.