Risk of voltage escalation due to a single-phase fault on the ungrounded MV network of an industrial plant

• Published in: Electric power systems research Vol. 220; p. 109298
• Main Authors: Xemard, A., Deneuville, B., Girard, P., Uglesic, I., Filipovic-Grcic, B., Milardic, V., Stipetic, N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2023
• Subjects: EMT-like program; Insulated neutral; Permanent insulation monitor; Ungrounded MV network; Voltage escalation; Permanent insulation monitor; Voltage escalation; Ungrounded MV network; Insulated neutral; EMT-like program
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/j.epsr.2023.109298

•Risk of voltage escalation in ungrounded MEV networks.•Electromagnetic transient calculations.•Voltage transformers installed with permanent insulation monitors prevent voltage escalation. In an ungrounded electrical system, successive reignitions and extinctions of a single-phase to ground fault is known to potentially generate a voltage escalation phenomenon. This is the so-called arcing ground fault whose theory has been thoroughly described in literature, even though very few practical occurrences have been experienced in existing electrical systems due to the specific and rare conditions that cause its appearance. This paper studies the risk of appearance of voltage escalation in the 10 kV auxiliary system of an industrial plant. It describes the physical principles at the origin of voltage escalation and presents a study conducted using an EMT-like program. The results show that, thanks to the presence of a permanent insulation monitor (PIM) connected to the system through voltage transformers, the successive reignitions and extinctions of single-phase faults cannot cause severe overvoltages or voltage escalation. The paper ends with some general conclusions.