In an embodiment, the present invention provides an improved online, double-conversion UPS, an improved combined power supply and arc quenching device, an improved electrical appliance and an improved method of quenching a fault arc in an electrical appliance. In particular, the destructive impact of a fault arc can be reduced and hazards kept away from electrical equipment and personnel. Furthermore, long downtimes due to excessive damage to the equipment, such as electrical distribution panels, can be avoided.

In an embodiment, the present invention provides an online, double-conversion uninterruptible power supply (UPS) as defined in the opening paragraph, additionally comprising an override input, which when activated inhibits closing the bypass switch.

Furthermore, in an embodiment, the present invention provides a combined power supply and arc quenching device as defined in the opening paragraph, comprising an online, double-conversion UPS of the type above, wherein an output of the fault arc detection device is connected to the override input of the uninterruptible power supply in a way that the bypass switch is kept open if a fault arc is detected by the fault arc detection device.

Moreover, in an embodiment, the present invention provides an electrical appliance as defined in the opening paragraph, comprising a combined power supply and arc quenching device of the above type.

Finally, in an embodiment, the present invention provides an arc quenching method as defined in the opening paragraph, wherein a signal is sent from the fault arc detection device to the online, double-conversion UPS causing the bypass switch held open.