The Houat and Hoëdic islands

ERDF is testing out a ground-breaking solution in Brittany to increasethe security of the power supply on the islands of Houat and Hoëdic, off the coast ofMorbihan. These two islands are connected to the continent by an underwater powercable. In case of failure of the cable, ERDF has put in place an innovative fall-backsolution which averts the effects of power cuts by dispatching the available energy.This solution thus lets customers on the two islands benefit from electricity and avoidinvestment into an additional generator.Project background and scopeThe islands of Houat and Hoëdic are supplied bytwo medium voltage underwater cables. The firstone links the continent with Houat; the second oneconnects Houat with Hoëdic.Before this project was rolled out, and in case of anincident on the first cable, island residents could experience power cuts lasting several days.Indeed from 4 to 8 weeks are necessary to repairthe underwater power cable and it takes at least 48hours to install emergency generator sets.Three solutions have been combined to securethe power supply between the two islands1. A generator on the island of Hoëdic. It is remotelycontrolled from the regional dispatch center locatedin Rennes. Thus, if the undersea cable fails,it can supply supply power to Hoëdic or to bothislands.2. Remote controlled sensors / devices on the mediumvoltage grid of the two islands, enabling theregional dispatch center to control them remotely.3. Ground-breaking smart grid functions, takingadvantage of the Linky smart meters installedin the homes of both islands’ residents. Thesemeters are operated remotely, allowing the adaptationof the maximum power level according tothe capacity of the generating set