  In this study, the problem of fault zone detection of distance relaying in
FACTS-based transmission lines is analyzed. Existence of FACTS devices on the
transmission line, when they are included in the fault zone, from the distance
relay point of view, causes different problems in determining the exact
location of the fault by changing the impedance seen by the relay. The extent
of these changes depends on the parameters that have been set in FACTS devices.
To solve the problem associated with these compensators, two instruments for
separation and analysis of three-line currents, from the relay point of view at
fault instance, have been utilized. The wavelet transform was used to separate
the high-frequency components of the three-line currents, and the support
vector machine (using methods for multi-class usage) was used for
classification of fault location into three protection regions of distance
relay. Besides, to investigate the effects of TCSC location on fault zone
detection of distance relay, two places, one in fifty percent of line length
and the other in seventy-five percent of line length, have been considered as
two scenarios for confirmation of the proposed method. Simulations indicate
that this method is effective in the protection of FACTS-based transmission
lines.
