As leader of a consortium, Siemens LLC, Dubai, has secured an order from the Abu Dhabi Gas Liquefaction Company Ltd. (ADGAS) to modernize and extend the power supply and distribution equipment of the gas liquefaction plant on the island of Das. The scope of this project also includes a new medium voltage switching substation and a new power distribution network. That will improve supply reliability. An additional gas turbine with an output of 20 megawatts will also be installed. These improvements will provide ADGAS with power reserves for expanding the gas liquefaction plant in the future. The order is worth 40 million U.S. dollars. Modernization of the power supply is scheduled to be completed by the end of 2005.
The island of Das, about 160 kilometers north-west of Abu Dhabi in the Arabo-Persian Gulf is the center of the United Arab Emirates' offshore oil industry. The island provides an export terminal for the liquid gas of ADGAS and for petroleum from the offshore fields of the Abu Dhabi Marine Operating Company (ADMA OPCO), both of which belong to the Abu Dhabi National Oil Company (ADNOC) Group. The gas liquefaction plant is the only one in the world able to process both natural gas as well as the petroleum gases that arise when oil is extracted. Every year an average of eight million metric tons of liquid natural gas, liquid propane, pentane, and liquid sulfur are produced.
Growing power needs and the planned expansion of the plant made thorough modernization of the power network necessary. Three generators driven by gas and steam turbines
provide electrical energy for the network of ADGAS via the 11 kV switching substation L1. Moreover, the L1 links the ADGAS network to the 11 kV switching substation of ADMA, to which three gas turbine generators are also connected.
Siemens will disassemble station L1 and erect it again at another location. The main energy distribution will be assured in future by a 33 kV and 11 kV medium-voltage network, at the heart of which lie 33 kV 8DA10 gas-insulated and NXAir air-insulated switchgear. These substations have been developed especially for hostile environmental conditions and are modular, which means they can guarantee fast recovery. Moreover, the explosion-proof compartments provide a high level of resistance to accidental arcs. The vacuum circuit-breaker is designed for up to 10,000 operating cycles. Under normal operating conditions, that will result in maintenance intervals of around 10 years.
The Siemens substations are protected by Siprotec protection relays, which combine protection, control, communications, operating, and monitoring functions in a single device. An integrated transient recorder monitors and logs all operating states around the clock. This ensures a high degree of reliability and safety. An intuitive user interface and the easy-to-parameterize protective relays support the personnel with operation. Digital interfaces permit connection to data buses such as Profibus DP. That means that the substations can be easily integrated into the central power management system "Castomat", which is also responsible for load shedding. Simatic PCS7 is the process control system chosen for this solution.
The 11 kV network will be further enhanced by additionally equipping another station with new air-insulated NXAir switchgear. ADMA's existing 11 kV network will be kept and then connected to the 33 kV main distribution board using 33 kV/11 kV distribution transformers. In total, around 60 kilometers of medium voltage and more than 400 kilometers of low-voltage cables and data lines will have to be laid. Modernization of the entire power distribution equipment will be carried out while the plant is in operation. Besides supplying and installing all components, Siemens is also responsible for all project management, engineering, erection, and commissioning.