Economics, design and emergency control of electrically-interconnected offshore gas/oil installations

In order to improve the load factor of generating plant on offshore platforms it is economically advantageous to electrically interconnect platforms, one or more of which may be without generation capability. Furthermore, the practical distances between platforms and the amounts of power to be transferred have meant that an economical interconnection voltage can be as high as 33 kV using step-up/step down transformers. The authors examine the economics, design and emergency control features of a typical 3-platform arrangement. In particular the advantages of a power management system are discussed including the importance of its co-ordination with individual protection relays in order to ensure plant stability following system disturbances including faults and loss of generation. With regard to the latter, specialised techniques are described for the accurate system simulation during long term disturbances. These are additional to the transient stability analyses carried out to determine acceptable fault clearance times