Germany: Universal connection system for 66-kV inter-array cables

This can barely still be managed with the conventional 33 kV system. For this reason, the aim of the Offshore Wind Accelerator (OWA) promotion program is to upgrade the internal cabling to 66 kV. For this voltage level, the tried-and-tested cable-independent Connex connection system is available, which has recently been extended to include the offshore-standard HV-Connex joint.

The higher voltage of the 66 kV cables enables them to carry more power and with a smaller cross-section and lower amperage than conventional 33 kV cables. This means lower costs and less environmental impact, while at the same time offering higher performance and security of supply. In order to promote the necessary technical innovations for this, the industry and the British Department of Energy & Climate Change (DECC), with support from the international Carbon Trust organization, have initiated the Offshore Wind Accelerator (OWA) program. This is promoting the development of new 66 kV inter-array cables. To connect these cables, advanced connection solutions are required.

Vast offshore experience

Connex has been used in onshore systems with a maximum operating voltage of 72.5 kV since 1988. Due to this long experience in combination with the expertise of Pfisterer at all voltage levels, Connex was predestined for offshore use. It has been used in the inter-array cabling on the medium-voltage side for more than six years now.

With Connex, users can realize all cable connections in the towers of a wind energy plant: the internal connection between switchgear and transformers, as well as the connection of the external marine cable to the network cable inside the tower. This makes it possible to permanently join together HV cables that are either homogeneous or made of different materials. The interface is the new Connex connection joint, rated at up to 72.5 kV. It is dry pluggable, touch-proof, resistant to saltwater and UV radiation, and is submersible. Its integral longitudinal water barrier prevents any water that penetrates one cable, due to a cable fault, from entering the other connected cable. The offshore qualities of the Connex joint are certified by the world's largest shipping and offshore classification society, DNV GL.

Quick to install, gas-free, and zero maintenance

Connex simplifies the installation and the operation of wind energy plants, as the plug-in system is quickly installed or removed and is also maintenance-free. The solid-insulated, fully encapsulated cast resin joint requires no SF6 gas, eliminating the need for expensive gas monitoring. Even the testing for cable sheath faults becomes easier as it can be performed after installation of the joint without any modification of the connector system – with the aid of an insulated contact rail for the cable shielding.

The extensive Connex portfolio includes the only pluggable and touch-proof HV surge arresters available on the market for up to 145 kV, plus flexible test equipment comprising test cables, combined with the Connex joint. This means the Connex system has all the components necessary for performing universal connections for the future 66 kV networks in offshore wind farms.