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

Abstract

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.

Assessment and Planning of the Electrical Systems in Mexican Refineries by 2014

“…Boletín IIE julio-septiembre-2012 Artículo de investigación 6) If a generator is out of service, there will be capacitors banks which can supply the necessary reactive power to keep 0.9 power factor in bound accomplishment. There are many other benefits mentioned in references (García et al, 2008;. Table 3.…”

“…In the other hand, because of the new requirements NRI has presented new action schemes, like migrate from 13.8 kV to 35.5 kV, and to 115 kV in some cases (García et al, 2008). Moreover, there are operative limitations which generate non programmed shutdowns, for example: between 2005 and 2006 there were three non programmed stops because of "the generation sources floating neutral" (García et al, 2008;(García et al, 2005).…”