Pushing GIS limits to new horizons
To meet the tough duties of 420 kV/63 kA gas-insulated substations (GIS), Alstom teams have developed a new single-chamber, double-motion circuit breaker. It demonstrates major improvements in size, cost and environmental impact.
High voltage circuit-breaker (CB) technology has advanced greatly since its introduction. Several interrupting principles have been developed to enhance performance and reduce operating energy. Among the various CB technologies Alstom has in its portfolio, gas-insulated substations (GIS) offer several advantages compared with air-, oil- or vacuum-insulated approaches. One is compactness, which explains why GIS are often chosen when space is limited and land is costly. As this becomes more significant with population growth and the trend of urbanisation, equipment compactness has become a key factor. “When dealing with high voltages such as 245 kV, the solution was originally to
use 2 breaking chambers in series, each chamber taking half of the voltage. Then we developed a single chamber, but with high operating energy,” explains Jean-Baptiste Jourjon, Alstom’s GIS R&D group manager. “Advances in design then made possible the use of a single SF6 chamber or ‘single break’, but with a low energy operating mechanism.” Subsequently, the same principles were extended to even higher voltages such as 420 kV, i.e. beginning with 2 chambers in series and then, to improve compactness, moving to a single chamber via the ingenious “double-motion” technology. This permits a drastic reduction in the operating energy of the opening mechanism (see sidebar -
box 4), allowing the adoption of a commonly used spring mechanism.