HelWin1

HVDC HelWin1 is a high-voltage direct current transmission link designed to transport offshore wind power to the German mainland's power grid. The project is part of Germany's Energiewende (Energy Transition) program and forms a crucial component of the HelWin cluster, named after the German island of Heligoland.

Project Overview

The HelWin1 link has a total length of 130 km, consisting of 85 km of subsea cable and 45 km of underground land cable. It uses Voltage-Sourced Converters (VSC) with a power rating of 576 MW and operates at a DC voltage of ±250 kV. The project's unique feature is that one of its two converter stations is built on a platform in the North Sea.

Technical Specifications

The converter stations, manufactured by Siemens, employ Modular Multi-Level Converter technology in a symmetrical monopole configuration. Each station is equipped with two three-phase transformers in parallel, rated at 425 MVA offshore and 422 MVA onshore. The converter valves use 4.5 kV IGBTs as switching elements and are equipped with 50 mH dry-type valve reactors.

Offshore Platform

The offshore converter is located on the HelWin Alpha platform, which was constructed by Nordic Yards in Warnemünde. The platform's topside is a float-over type, designed to be transported to the installation site and jacked up onto a submerged supporting structure. It weighs 12,000 tonnes and measures 75 m x 50 m x 23 m high.

Cable System

The cable system, supplied by Prysmian, consists of two 250 kV cables with extruded Cross-linked polyethylene insulation. The sea cables come ashore near Büsum and continue as underground land cables to the onshore converter station at Büttel.

Construction and Commissioning

The HelWin1 project was ordered in 2010. The HelWin Alpha platform was installed on August 26, 2013. Commissioning was completed in January 2015, and the project was handed over to TenneT, the transmission system operator, in February 2015. At the time of handover, 288 MW of wind power was connected to the converter station.

Connected Wind Farms

HelWin1 transmits power from two offshore wind farms:

1. Meerwind Süd | Ost (288 MW)
2. Nordsee-Ost (295.2 MW)

Significance

The HelWin1 project plays an important role in Germany's offshore wind energy infrastructure. It enables the efficient transmission of renewable energy from offshore wind farms to the mainland grid, supporting the country's transition to cleaner energy sources. By providing a low-loss transmission of generated wind power, HelWin1 contributes to powering over 700,000 homes in Germany with renewable energy.