Priority is claimed to British Patent Application No. GB 1812016.2, filed on Jul. 24, 2018, the entire disclosure of which is hereby incorporated by reference herein.

The invention relates to an online, double-conversion uninterruptible power supply (UPS), comprising a UPS input, a rectifier, which with its input is connected to the UPS input, an inverter, which with its input is connected to an output of the rectifier and a UPS output being connected to the output of the inverter. Furthermore, the online, double-conversion UPS comprises a bypass switch between the UPS input and the UPS output and a control unit for closing the bypass switch in case of excessive output current and/or excessive voltage drop and/or excessive power demand at the UPS output. Furthermore, the invention relates to a combined power supply and arc quenching device, comprising a fault arc detection device. Moreover, the invention relates to an electrical appliance, which comprises a grid connection to a power grid, a combined power supply, and arc quenching device, wherein a UPS input is connected to the grid connection, an electrical consumer is connected to the UPS output and a circuit breaker is arranged between the grid connection and the consumer for disconnecting said consumer from the power grid a) in case of an excessive current flowing over the circuit breaker and/or b) by means of a fault arc signal from the combined power supply and arc quenching device being connected to said circuit breaker. Finally, the invention relates a method of quenching a fault arc in an electrical appliance, wherein a fault arc is detected by means of the fault arc detection device.