Multiple earthing systems for offshore production platforms

Fixed offshore integrated oil and gas facilities will generally comprise accommodation, utilities, production and drilling facilities supplied from on-board centralised power generation via a fully integrated electrical distribution system. In such applications the selection of appropriate methods of system earthing is a key factor in achieving safe and reliable operations whilst meeting the sometimes differing requirements of the topsides and drilling operations. This paper considers the types of electrical power system configurations encountered on major offshore platforms and in particular considers the earth fault tolerance requirements of drilling operations to ensure supplies are maintained whilst moving towards make-well-secure conditions. The benefits and limitations of various options are discussed in relation to operation under both normal and emergency conditions and particular account is taken of achieving safe operations under life support and drilling make-well-secure conditions. The paper also discusses the differing practices worldwide and provides recommendations for achieving a comprehensive and effective integrated power system configuration.