Shore-side power supply of FSU/FSRU at Liquefied Natural Gas Terminal (LNG)

Profile

• What was needed: Heavy-duty energy chain for the offshore sector. Emergency shutdown system
• Requirements: Flexible energy supply due to the FSU often being in heavy motion, harsh environmental conditions required an emergency shutdown function for the whole system
• Industry: Shipping
• Success for the customer: State-of-the-art energy supply solution, low-maintenance and safe despite difficult environmental conditions

Problem

Liquefied Natural Gas (LNG) is one of the most important energy sources of the present and future, as it emits only very small amounts of greenhouse gases and is therefore considered an important fossil fuel. In Bahrain, the state authorities have set up a joint venture for the planning and construction of an LNG terminal, which has just gone into operation.
Due to security requirements, the terminal is located at sea, about three kilometres off the coast. The LNG tankers dock at the jetty and release the natural gas into a so-called Floating Storage Unit (FSU), which later pumps the gas via underwater pipelines to a regasification unit on shore.
Schneider Electric was responsible for the entire energy infrastructure in this project. In order to supply the floating storage unit with power, a connection had to be created between the terminal and the FSU. Here not only a distance of more than 30 m had to be bridged, but also the movements of the FSU due to loading and unloading, tides, waves and storms had to be considered. Further criteria were highest availability as well as smooth transmission – and without electromagnetic pollution.
Last, in an emergency – for example, a tsunami - the connection needed to be able to be disconnected in a planned manner so that the power is immediately and automatically switched off.

Solution

igus recommended the use of a heavy-duty energy chain, which turned out to be the perfect solution for the application.
The offshore energy chain is attached to the mooring post on the jetty side with a pivoting bracket and to the side of the FSU with a removable extender crossbar.
The robust and flexible energy chain system guides and protects two medium-voltage cables. The heavy-duty plastic chain impresses with its firmly screwed cable guide and interior separation, and is made of special plastics for extreme applications. All tensile forces are absorbed by the inner-lying ropes.  The use of this special energy chain allowed a passive design without the need for mechanical elements due to the continuous movement of the FSU.
The decisive factor was the controlled bend radius of the energy chain, which protects the cables from excessive bending even during a storm. The cables are equipped with special 3-phase medium voltage connectors. The most important safety element, however, is the emergency shutdown. Martin Tiling, Industry Manager Shore Power at igus, explains how it works: "In the event of an emergency, we measure the chain length. If the FSU drifts before it is disconnected from the system, the system will first send out an alarm and then initiate the emergency shutdown. After the power supply is switched off, the shore-side connection point of the energy chain can be pulled out of the special attachment point without the risk of an emerging arc.