Practical Guidelines For Oil & Gas Plant Design Against Sub-Synchronous Torsional Interaction Phenomena

Abstract

Variable Frequency Drives (VFDs) are widely used in the Oil&Gas industry to enable variable speed operation of motors. These drives use power electronic devices, which produce current and voltage harmonic distortion. They can also interact with other units connected to the same electrical grid (i.e. turbine-generators) via a phenomenon called Sub-Synchronous Torsional Interactions (SSTI). This can lead to a restriction of plant operation, and in the worst case, to major damage of machinery. This paper provides a comprehensive evaluation of the SSTI phenomenon and gives practical guidelines to enable the following: a proper design of the plant and the system, an optimization of plant operability, and a strategy for mitigation of potential problems. Field test results and simulation analyses are presented, emphasizing the importance of a proper SSTI evaluation and management in the early engineering phase.