The paper investigates the potential challenges faced by conventional distance relays in case of thyristor controlled series capacitor (TCSC) compensated transmission systems. The mal-operations of back-up relays can trigger large scale cascaded outages. Detailed analysis on mal-operation of different zones of distance relay due to TCSC operation is carried out. The impact of TCSC on the relays of adjacent lines which provide back-up protection to the compensated line is observed. Finally, possible solutions to mitigate the problem associated with the impact of TCSC upon the conventional distance relays are discussed. The simulation studies are carried out on MATLAB environment. © 2016 IEEE.