This paper describes the electrical power infrastructure including high voltage and low voltage powerrntransformers, switchboards, distribution units and their associated connection and protection systemsrnrequired to power a subsea EHTF installation. It discusses the options considered for both topsides andrnsubsea electrical power infrastructure, their integrity monitoring and methods of fault protection.rnThe low power EHTF PiP system, developed by Subsea 7 and ITP InTerPipe, typically requires arnsubsea supply operating voltage of 1kVrms phase to neutral at the flowline start and the requirement tornsupply multiple heating wires arranged in subsets of three phase circuits, typically 12. This voltage sitsrnat the challenging intersection of normal industry low voltage (＜1kV) and high voltage standardsrn(＞1.8kV) and thus relevant clauses have to be selected to fit the qualification purpose of the full EHTFrnPiP system.rnThis voltage can be supplied from either local or remote topsides facilities bringing with them thernoption of multiple power circuits direct from topsides to subsea or alternatively using a subsea distribution/rnsplitting system. The electrical power system needs to be able to either adjust the applied voltage, therntime applied or the number of heating elements in order to control the power required by the pipelinernheating system for different production scenarios and redundancy purposes. It also needs full integrityrnmonitoring and appropriate fault clearance facilities that can operate for the local and remote topsidesrnsolutions and operate successfully on long umbilicals and EHTF lengths up to ca. 30 km from a singlernpower feed. There may be multiple power feeds on longer lines (Cherkaoui 2016).rnInstead of complex phase control systems, a simple heating control, using contactors on individualrncircuits in the local topsides option provides sufficient EHTF heat control. Whereas the addition of subsearnfuse modules and/or solid state relay modules (SSR) in the remote topsides option can provide individualrnsubsea circuit isolation and protection.rnThe benefits and drawbacks of different power transformer arrangements are reviewed with availablerntopsides electrical network (power balance / voltages / redundancy). Integrity monitoring and faultrnprotection for local and remote topsides options are reviewed; specifically, the application of linerninsulation monitoring systems and residual current protection devices.
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