Oil field harmonic concerns resulting from high impedance sources, multiple power converters and long cables

The paper presents an effective, robust and economical design solution for a severe power system harmonic problem. The case study examines an isolated power system at an oil field central processing facility supplied by on-site generators. Elevated harmonic distortion originates from the electronic adjustable speed drives installed on the well site submersible pump motors. The original design uses phase shifting techniques that achieve a significant reduction in harmonic current. Unexpectedly, even though harmonic current remained moderate, harmonic voltage distortion became excessive as the system grew in size. This unusual condition arose from a combination of high source impedance and distributed stray capacitances from long power cables that created many partial resonances throughout the system. Voltage distortion contributed to extensive equipment failures and system upsets over the years. The implemented solution is expected to provide considerable long-term improvement in the power system operation and availability.