The invention concerns a protection arrangement (18) for a multiphase uninterruptible power supply system comprising a vacuum circuit breaker (S1a, S1b, S1c) connected in series with an inductive element (14), where the inductive element comprises, for every phase, two series-connected magnetically coupled windings (L1a, L2a, L1b, L2b, L1c, L2c) separated by a tap point (Ta, Tb, Tc). The protection arrangement (18) comprises one first group of protective components per phase, each first group comprising a first protective component (SA1a, SA1b, SA1c) having a first end connected to a link between the vacuum circuit breaker (S1a, S1b, S1c) and the inductive element (14) and a second end connected to a corresponding tap point (Ta, Tb, Tc), where at least one protective component in each first group is a surge arrester.