Technology progress in high-voltage gas-insulated substations

In the last two decades, the evolutionary development of gas-insulated substations/switchgear (GIS) has resulted in higher integration of a number of new technologies to enhance performance and reliability by reducing defects, having more compact designs, and reducing maintenance intervals and costs. Incremental improvements are continuing in interrupter technology, such as self-extinguishing features at medium voltage (MV) and resistance interruption at extra- and ultra-high voltages (EHV and UHV). In addition, sulfur hexafluoride (SF₆) gas technology for circuit breakers, zinc oxide (ZnO) for arresters, radio communication for condition monitoring, and a choice of porcelain or polymer composite for the full range of equipment are also some of the technologies integrated or innovated by GIS manufacturers in recent years. Recently, ac GIS ratings have reached up to 1,100 kV rated voltage and 50{kA_rms}rated short-circuit breaking current. In addition, 1,200-kV ac GIS are going to be visible very soon. Moreover, 500 kV dc GIS for dc transmission systems have become available.