Distributed generation is gaining popularity around the world as consumers opt for reliable and locally generated power. However, the integration of distributed generation with the utility network poses challenges for anti-islanding schemes. These schemes detect islanding conditions and trip the distributed generation system.
The formation of an unintentional island represents a failure to detect a loss-of-connection to the utility. Unintentional islanding ,even if it lasts a short period of time, is something that the utility should avoid in its system operation due to the following risks:
Safety hazards for both line crews and the public resulting from exposure to energized conductors
Transient overvoltage caused by ferroresonance and ground fault conditions
Out-of-phase reclosing, leading to potential damage to distributed generation systems, customer loads, and utility-owned equipment
Increase in restoration time-this may reduce reliability.
Therefore, it is suggested that all distributed generation systems, including photovoltaic inverters, have anti-islanding controls fitted.
As the distribution generation market grows, protection specialists will need to invent robust technologies to avoid unintentional islanding.
One such company, GridEdge Networks Inc., a provider of advanced smart grid communications solutions, has announced the commercial availability of a new grid protection system for distributed generation facilities. The Distributed Generation Transfer Trip Protection (DG-TTP) system is required for most utility scale energy generators (e.g. solar, wind) that directly attach to the distribution grid.
Power Line Communications (PLC) technology has been specifically customized for this application to provide a sustainable and cost effective solution for the protection of the distributed generation facility.
The technology provides state of the art protection in situations of unintentional islanding, by detecting the islanding condition and disconnecting the energy generation facility within two seconds as required by the criteria established in the IEEE-1547 regulatory standard.
Benefits of this solution are the relatively low lifecycle costs and its fast installation process. Furthermore, the technology can be installed on the existing energized primary lines and requires very little maintenance. It also helps to reduce the utility’s operating costs.
Nachum Sadan, President & CEO of Grid Edge Networks, says: “DG-TTP fills a real need in a new and fast growing market, and will be beneficial to other utilities as well. I believe the low cost and ease of installation will enable more renewable energy generation projects to be completed.”
To support the development of distributed generation and its integration to the grid, it is essential for utilities to adopt technological solutions that will protect the connection between the grid and the distributed generation source.