Vacuum circuit breakers — Promising switching technology for pumped storage power plants up to 450 MVA

Vacuum as switching medium has been established widely in the distribution systems for more than 30 years. Well known for its outstanding and reliable interrupting capability of fault and load currents of all possible nature, the vacuum switching technology is now dominating the medium voltage level up to 52 kV. Technical advancements in the field of vacuum physics in last decades made it possible to implement vacuum switching technology also for generator applications. Well known for their demanding requirements on interrupting devices such as high fault currents with high degree of asymmetry or higher and steeper transient recovery voltages, the standards IEC/IEEE 62271-37-013 (2015) & IEEE C37.013 (1997) were introduced to address such requirements on circuit breakers used in generator applications. Circuit breakers employing vacuum technology fulfil all defined requirements to be qualified as Generator Circuit Breakers (GCBs) according to the above mentioned standards. Especially for Pumped Storage Power Plants (PSPPs), the Vacuum Generator Circuit Breakers (VGCBs) in compared with GCBs with gas quenching medium offer distinctive advantages such as fast dielectric recovery strength that eliminate the need of surge capacitors for switching duties, significantly higher number and frequency of possible switching operations, lower maintenance cost and environmental-friendly (GWP is 0). The VGCBs, due to their design flexibility & interrupting capabilities, are ideal for PSPPs for both motor and generator operation, back-to-back starting which are typical in such plants. A case study on a typical pump storage power plant is presented here by simulating various fault scenarios showing that a VGCB is fully suitable due to their reliability and economic profitability.