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Variable speed ac drives are finding their way into all types of industrial and commercial power system applications. Their application to the load (motor) generally is reasonably well selected - at least within heavy industry. However, there are many line (source) design parameters learned in the 1950's and 1960's which are now being frequently overlooked. This paper represents many years of experience doing power quality investigations. The authors combined this experience with recent technology and discuss some of the areas of concern which frequently result in serious performance or power quality problems. Finally, basic design guidelines are given to greatly minimize system problems - especially as newer technologies are intermixed with old.

This paper addresses electrical distribution system problems that affect the reliability of power to oil-field pump motors and support loads. An off-shore oil facility is used as an example. Field measurements at numerous platforms were conducted and subsequently analyzed to evaluate power quality concerns. A power system study was completed off-site to provide computer simulation of the electrical system under numerous operating conditions. Electrical considerations include fault current calculations, protective relay coordination, load flow, harmonic analysis, transient stability, and motor starting. The principal results of this work were a series of recommendations involving operations changes and/or adding conventionally available hardware borrowing from other industry experiences. Index Terms--Coordination, grounding, load flow, motor failures, motor starting, off-shore electrical distribution, power quality, transient stability.