Compact Vacuum Interruption with Microsecond Accuracy

A new bellows free compact vacuum interrupter has been developed which can interrupt fault current with an accuracy of 39 us, without commutation by thyristor. The system has been tested at fault currents of up to 9 kA and is designed to be retrofitable onto low-voltage AC networks. The low latency and high precision of the point-on-wave system permits opening the breaker close to current zero, thereby substantially reducing contact erosion, and extending the vacuum lifetime. During a chaotic fault with a reduced confidence prediction of current zero, custom designed tungsten-carbide radial magnetic flux and axial magnetic flux contacts have been tested to control the vacuum arc until the first current zero, without reignition.