Mitigation of transient ground potential rise in gas insulated substations during very fast transient overvoltage

Abstract

• The paper proposes PEEC based a simulation technique the allow to take into account the complex 3D structure and the various electromagnetic coupling phenomena that take place between the metallic structure of a complex GIS and the associated earthing system during VFTO events. • The proposed GIS modeling and simulation technique is applied in case of 110 kV GIS in order to identify the grounding grid area that mostly effect the clearance of VFTO fault. • A mitigation procedure is show cased for the identified grounding grid area in order to accelerate the clearance of VFTO faults. This paper is focused on the assessment and mitigation of the transient response of a Gas Insulated Substation's (GIS) grounding grid to the fault due to voltage breakdown using the Partial Element Equivalent Circuit (PEEC) numerical approach. The adopted analysis methodology considers the magnetic induction by quantifying the electromagnetic couplings generated within the metallic components contained by the GIS configuration. The Transient Ground Potential Rise (TGPR) and transient current are computed and analyzed at several locations inside of GIS housing. With the aid of 3D graphical representation, the maximum amplitudes of the TGPR across the substation are illustrated. The mitigation efforts are considerably optimized by assuming the grounding grid sub-system is responsible for high frequency fault energy clearance based on identification method. By adopting several simplifications of the earthing system during the computational process, from a step-by-step analysis, it has been discovered that the grid located beneath the GIS enclosure will mostly attenuate the TGPR across the GIS building. Based on the aforementioned findings a successful mitigation technique is implemented.