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(abridged) We present VLT/X-shooter spectroscopic observations in thewavelength range 3000-23000A of the extremely metal-deficient blue compactdwarf (BCD) galaxy PHL 293B containing a luminous blue variable (LBV) star. Wedetermine abundances of N, O, Ne, S, Ar, and Fe and study the properties of theLBV from the fluxes and widths of broad emission lines. We derive aninterstellar oxygen abundance of 12+log O/H = 7.71+/-0.02, which is inagreement with previous determinations. The observed fluxes of narrow Balmer,Paschen and Brackett hydrogen lines correspond to the theoretical recombinationvalues after correction for extinction with a single value C(Hbeta) = 0.225.This implies that the star-forming region observed in the optical range is theonly source of ionisation and there is no additional source of ionisation thatis seen in the NIR range but is hidden in the optical range. For the LBV starin PHL 293B we find broad emission with P Cygni profiles in several Balmerhydrogen emission lines and for the first time in several Paschen hydrogenlines and in several HeI emission lines, implying temporal evolution of the LBVon a time scale of 8 years. The Halpha luminosity of the LBV star is by oneorder of magnitude higher than the one obtained for the LBV star in NGC2363=Mrk 71 which has a slightly higher metallicity 12+logO/H = 7.87. Theterminal velocity of the stellar wind in the low-metallicity LBV of PHL293B ishigh, ~800 km/s, and is comparable to that seen in spectra of someextragalactic LBVs during outbursts. We find that the averaged terminalvelocities derived from the Paschen and HeI emission lines are by some ~40-60km/s lower than those derived from the Balmer emission lines. This probablyindicates the presence of the wind accelerating outward.

VLT/X-shooter observations of the low-metallicity blue compact dwarf galaxy PHL 293B including a luminous blue variable star