Since 2:00 p.m. on Wednesday, September 16, Heligoland has been disconnected from its regular power link to the mainland. The submarine cable was shut down to connect a newly laid section near St. Peter-Ording. Consequently, diesel generators have been supplying the North Sea island with all its electricity since Wednesday afternoon. An additional disruption is occurring today, Thursday, September 17: regular internet, mobile, and landline connections are scheduled to be interrupted for approximately ten hours between 8:00 a.m. and 8:00 p.m. Residents, businesses, and visitors should therefore anticipate issues with card payments. However, emergency calls are expected to remain possible.
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Heligoland disconnected from mainland power supply due to submarine cable modification
The modification became necessary because the connection joint on the beach at St. Peter-Ording had been repeatedly exposed by the tides. Consequently, SH Netz is relocating the transition point between the submarine and land cables approximately 700 meters further inland. The new cable section is also buried about three meters deep in the ground.
The grid operator had already completed preparatory work prior to disconnecting the island from the mainland power supply. Since Wednesday, technicians have been installing new connection joints and integrating the section into the existing grid. However, the timing of specific work steps depends on the tides.
Diesel generators power the entire island grid
Heligoland remains supplied with electricity during the switchover, despite being disconnected from the mainland. The local utility company is operating its diesel generators to power the entire island grid. The island had already tested this backup supply system in January during a planned blackout simulation.
However, the submarine cable carries more than just electrical energy; it also houses a fiber-optic line for telecommunications. Consequently, internet, landline, and mobile services are expected to go down largely simultaneously today, Thursday.
Card payments and digital services may be unavailable today
The disruption therefore affects hotels, restaurants, shops, and other businesses. Without a regular data connection, many internet-dependent systems may temporarily cease to function. FRS Helgoline had previously advised visitors to bring sufficient cash.
Tourists should also expect disruptions to Wi-Fi, messaging services, and other online offerings today. However, Deutsche Telekom plans to provide limited backup connectivity via satellite links, even though the regular data connection to the mainland will remain interrupted while the work is underway.
Heligoland to operate in island mode without mainland power until Friday
Before connecting to the mainland, Heligoland generated all its electricity on the island itself. The subsea cable link—spanning more than 50 kilometers across the North Sea—did not go into operation until 2009. Since then, the existing diesel generators (and those added later) have served as a backup for outages and maintenance work.
Island-mode operation is scheduled to continue until 2:00 p.m. on Friday, September 18. Until then, the island will remain independent of the mainland grid and rely entirely on its own power generation. Afterward, the subsea cable is expected to resume the regular transmission of electricity and data between the mainland and the island.
Author: Blackout News
Sources: teltarif (15.09.26) – Die Zeit (14.09.26)