Series resonant overvoltages due to the neutral grounding scheme used in petrochemical power systems

This paper describes the transient overvoltages caused by the neutral grounding connection of the generators and transformers during phase to ground failures in some Mexican petrochemical plants. Examples of this type of overvoltages generated during phase to ground failures are shown, it can be seen that severe damages to the generators and other electrical equipments is produced. Unfortunately, these problems occur rather frequently and produce outages with great economical impact. A solution to this problem was proposed, by permanently connecting the neutral of all generators with a high resistance scheme using a grounding transformer. This solution has been presented to petrochemical plants and it has been accepted and finally introduced in one Mexican plant. Simulation and practice show that no overvoltages are presented by applying this solution.