Subsea Cable Applications in Offshore Oilfield Facilities

Abstract

Abstract The increase in use of variable frequency drives (VFDs) in oilfield facilities, especially for some offshore platforms, often leads to a significant percent of VFDs in total load demand. The VFDs provide many advantages for facility operation, but also produce harmonic contents to electrical power systems. Subsea cables are widely used in offshore power distribution systems. There are two typical applications for subsea cables: 1) transmitting power from the power generation to loads on remote platforms (involving line-side harmonics of a VFD); 2) transmitting power from the output of a VFD to remote electrical submersible pump (ESP) systems (involving load-side harmonics of a VFD). The combination of VFDs and subsea cables in power systems could introduce harmonic resonance, which, if not properly mitigated, amplify certain harmonics and cause significant damage to the electrical equipment in the facilities. An investigation was conducted for the two typical applications in offshore oilfield facilities considering harmonic resonance conditions. The first application involved parallel harmonic resonance and line harmonics, which will amplify harmonic currents. The second application involved harmonic resonance and load harmonics, which will amplify harmonic voltages. Computer simulation software programs were used to develop solutions using line-side and load-side harmonic filters to mitigate harmonics and attenuate resonance; these solutions were verified to be effective in case studies