The smart grid project was initiated to reduce the amount and duration of power outages and improve service continuity in the medium-voltage secondary distribution in the city of Rome. To reach these goals, new technological solutions are deployed to ensure the continuity of electricity distribution, reduce energy losses and improve the overall load capacity in the grid, as the amount of distributed generation increases.
In this large-scale project, two primary substations and 76 secondary substations have been upgraded and a total of 70 km of new medium-voltage lines were drawn to distribute electricity to about 1,200 households and seven industrial plants in the region of Malagrotta-Ponte Galeria in the Italian capital. The medium-voltage lines have been connected to four distributed generation plants (one photovoltaic and three gas turbine plants).
ABB's smart power distribution solutions improve the reliability of the power distribution system through advanced automation and logic selectivity using the IEC 61850 standard for power system automation. The solution relies on horizontal GOOSE-based communication technology to improve data acquisition and gain seamless communication between substations, and from substations to the control center. GOOSE (Generic Object Oriented Substation Events) is part of the IEC 61850 standard for power system automation. The communication between the intelligent devices and substations up to the supervisory control and data acquisition (SCADA) system is over a wireless network.
ABB’s advanced REC615 protection relay is used for control, monitoring and protection of the cable feeders and offers superior fault detection and location. To improve reliability and to reduce the duration and frequency of power outages, ABB’s solution is built on logic selectivity between the protection relays, as this is an effective approach to reduce the area affected by a fault. Another benefit is the flexibility to apply different levels of automation for different areas in the network.
Further, to improve selectivity in the grid – and thus ensure continuity of the electricity distribution and reduce energy losses - high accuracy current and voltage sensors provide the protection relays with very precise measurements.
The customer also set very high requirements for compactness of the solution, because of the difficulty of performing maintenance activities and replacing equipment in the narrow spaces in the existing substations. To meet this challenge, ABB saw that a new type of secondary substation recloser, which integrates a circuit breaker and a disconnector in the same device, would make an ideal fit. In this exceptionally compact solution, which is based on UniSec switchgear and equipped with multi-function HySec apparatus, the circuit breaker panel is only 500 mm wide and still fits all the protection, communication and automation equipment needed.
As a result of the successful implementation of this solution, Areti (previously ACEA Distribuzione) chose to deploy the same solution for their entire secondary distribution network.