Abstract
by electrical heating. Presently 42 km is the longest pipeline supplied with DEH (Direct Electrical Heating). The main limiting factor is the power cables operational voltage, which limits the heated length to approximately 60 km depending on heating requirements. Increasing the voltage level is therefore required and this needs further qualification work. However, the variations of the heat input to the pipeline versus distance will be more pronounced with increasing pipeline length. This is a disadvantage that may limit the feasible length to around 100 km. Hence, heating above 100 km as a continuous heated length will be far beyond any experiences at the moment.
In order to avoid comprehensive verification issues it is proposed to design the electrical heating system as a sectioned heating system. I.e. the pipeline will be heated from a power supply system feeding a number of sections. The sections can be fed by separate power cables to each section or each section can be galvanically separated by a subsea transformer and fed from a common power cable. If the first section is powered from shore, which may be the case for Arctic regions, an alternative heating system to DEH can be selected to avoid problems related to grounding and stray currents. Alternatives such as induction heating (IHS) and pipe in pipe (PiP) heating systems are considered. For Arctic regions the landfall part may need special measure for protection against icebergs.
In order to avoid comprehensive verification issues it is proposed to design the electrical heating system as a sectioned heating system. I.e. the pipeline will be heated from a power supply system feeding a number of sections. The sections can be fed by separate power cables to each section or each section can be galvanically separated by a subsea transformer and fed from a common power cable. If the first section is powered from shore, which may be the case for Arctic regions, an alternative heating system to DEH can be selected to avoid problems related to grounding and stray currents. Alternatives such as induction heating (IHS) and pipe in pipe (PiP) heating systems are considered. For Arctic regions the landfall part may need special measure for protection against icebergs.
