  We present the spectral analysis of Chandra/HETGS and NuSTAR observations of
the quasar PDS 456 from 2015, and XMM-Newton and NuSTAR archival data from
2013-2014, together with Chandra/HETGS data from 2003. We analyzed these three
different epochs in a consistent way, looking for absorption features
corresponding to highly ionized blueshifted absorption lines from H-like and
He-like ions of iron (and nickel), as well as of other elements (O, Ne, Si, and
S) in the soft band. We confirm the presence of a persistent ultra-fast outflow
(UFO) with a velocity of v_out=-0.24 - -0.29c, previously detected. We also
report the detection of an additional faster component of the UFO with a
relativistic velocity of v_out=-0.48c. We implemented photoionization modeling,
using XSTAR analytic model warmabs, to characterize the physical properties of
the different kinematic components of the ultra-fast outflow and of the partial
covering absorber detected in PDS 456. These two relativistic components of the
ultra-fast outflow observed in the three epochs analyzed in this paper are
powerful enough to impact the host galaxy of PDS 456 through AGN feedback.
