Surges Induced in Secondary Circuits Due to Very-Fast Transients in Primary Circuits: Experimental Study Using a Test Platform

In recent years, numerous digital devices have been implemented as control and protection relay circuits in substations. Prior research raised concerns regarding failures in secondary circuits due to switching-induced surges, which occur during the operation of a disconnector in gas-insulated switchgear (GIS). These surges are characterized by very-fast transients (VFTs) and manifest as inner surges in the MHz range, resulting from multiple reflections within the GIS. To devise effective mitigation strategies, the characteristics of these surges need to be determined. Moreover, the effectiveness of the potential countermeasures should be assessed via measurements or numerical simulations. Unfortunately, there is a scarcity of data and studies that thoroughly examine these characteristics. In this study, the characteristics of VFT-induced surges are experimentally quantified using a test platform that simulates the primary/secondary circuits of a GIS substation. Furthermore, we evaluated the effectiveness of surge-reduction techniques such as surge-absorbing capacitors, which are typically applied against lightning-induced surges and ferrite cores designed to address higher frequency surges. The findings provide general insights into the nature of induced surges.