What is the Most Efficient Power Transmission System?
Within the Subsea Oil and Gas Production Control System (PCS) sector, the majority of the system electrical distribution architectures utilise single phase AC, 50/60Hz or DC at voltages up to 1.2kV for the power transmission across the main umbilical. There are, of course, a few exceptions to this that include three phase at up to 3kV.
Can electrical distribution architectures be developed to support higher power demands and increased offsets?
Viper Innovations has conducted a study supported by in-depth performance analyses covering a range of power transmission techniques and umbilical cable designs. Simulations were performed on over two thousand different systems with a range of supply configurations, cable characteristics, offset distances, and consumer loads.
The simulated system distances ranged between 50km to 500km, with system operating voltages ranging between 1kV and 33kV.
For each supply voltage, analysis was undertaken on the following system configurations:
|· DC Monopole (2 Wire)
|· AC 50Hz Three Phase (3 Wire)
|· AC 50Hz Single Phase (2 Wire)
|· AC 16.7Hz Three Phase (3 Wire)
|· AC 16.7Hz Single Phase (2 Wire)
Both electro-hydraulic and all-electric loads were included in the study to allow a comprehensive evaluation of the different technology types. Cables with Cross-Sectional Area (CSA) ranging from 16mm2 up to 95mm2 were selected. These larger CSAs are not directly suited to SPCSs currently used within the subsea industry; however, CSAs >16mm2 allowed for requirements to be met for significantly longer offsets, larger loads, and the medium voltage cables.
Study results showed that the optimum supply characteristics for any given system are dependent upon the specific characteristics of the transmission cable/umbilical and the power levels required at the load. However, findings also identified that the relationship between the parameters did not necessarily fit within the normal assumptions and rules that would generally apply. i.e.:
- An increase in system voltage will not necessarily result in an increase in the offset capability;
- An increase in the cable CSA will not necessarily result in an increase in the offset capability;
- An increase in system voltage will not necessarily result in an increase in the system efficiency;
- An increase in the cable CSA will not necessarily result in an increase in the system efficiency.