The Power Xpert PX8000 meter is used to monitor power quality, schedule VFD maintenance, and increase electrical system integrity. (Image courtesy of Hess Corp.)

When a Hess Corp. floating production, storage, and offloading vessel (FPSO) working offshore Equatorial Guinea in West Africa began encountering problems in the form of subsea electrical connector and multiphase pump failures, the company teamed with Eaton Electrical Inc. to find a solution.

Together, the companies designed and installed a unique permanent power quality monitoring system to collect key electrical parameters and high-speed electrical transients from variable frequency drives on the FPSO.

Eight variable frequency drives (VFDs) on the vessel, each rated at 1 MW, operate subsea multiphase pumps 4.3 miles (7 km) away. A series of electrical failures suggested power quality problems/excursions emitting from one the VFDs. Conventional portable power metering equipment could not be used for power quality diagnostics because the VFD operating range is 50 to 85 hertz with a maximum VFD output voltage of 690 volts. And a laboratory power meter was not robust enough for repeated measurements in an offshore installation. A permanent power quality meter and instrument quality current transformers were required to continuously capture high-frequency waveforms and voltage transient data for detailed analysis.

The result was a permanently installed power metering system that has since been used on the C5B multiphase pump VFD. The Power Xpert PX8000 meter obtained high-frequency waveforms, harmonic spectrums, and transient data that implied power quality problems within the VFD as a result of component failure.

Hess is moving forward with seven additional permanent metering systems following the successful installation on the C5B pump. The systems will be used to monitor power quality, schedule VFD maintenance, and increase electrical system integrity.

The companies anticipate the power quality monitoring strategy will increase pump run time, increase VFD maintenance awareness, and enhance the overall integrity of the subsea electrical system.

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