The GE contribution
Grid Solutions, a business of GE Renewable Energy, has a rich GIS development history through its ancestor companies, Delle-Alsthom, Sprecher & Schuh, GEC and AEG.
Delle-Alsthom France started GIS development in 1958 and in 1966-1967 delivered a world first with its “Fluobloc” at 245 kV in several Paris substations, demonstrating the benefits of underground GIS to supply bulk power close to city users. Achievements in the higher voltage ranges were subsequently marked by the deliveries of the first substations for 420 kV in 1976 and for 550 kV in 1977. Another “world first” was the completion of AEP’s 800 kV GIS in Joshua Falls in 1979.
Sprecher & Schuh studied compact metalclad installations as early as 1954 with oil insulation systems, but soon came to the conclusion that SF6 gas insulation offered greater advantages. Their first GIS for 220 kV was delivered in 1970 and the 145 kV, 40 kA in 1971. The original circuit breakers with double pressure SF6 systems (220 kV, 50 kA), developed together with ITE USA, were operated by the well-known Sprecher motor-wound spring operating mechanisms, which contributed to the success of subsequent GIS families. The exclusive third-generation FK mechanism today serves all Grid Solutions' GIS products on the world market.
AEG in Germany has also long been involved in GIS and SF6, with its first GIS substation delivered in 1971.
Meanwhile, GEC in England was collaborating with Siemens, and their first GIS was a 145 kV substation in London in 1982. As GIS systems developed and their extensive use in HV networks grew, Grid Solutions became the manufacturer of complete GIS ranges of 72.5-800 kV in which single-phase and three-phase encapsulation is used.
Clearly, the most significant development factor was the adoption of SF6 as an insulation medium. This boosted the development of smaller switchgear requiring less operating energy and reduced materials and resources, leading to higher performance. So far 420 kV, 63 kA with a single break is possible with the spring mechanism.