The HVDC transmission system is becoming ever more complex, further, demand for reliable supply of electricity is growing, increasing the need for a higher level of system reliability. A probable solution might be to incorporate controllable power components within the system. One such important is smoothing reactor or DC reactor. In this paper the effect of failure rate and repair time on expected capacity level or power transmission capacity of smoothing reactor at different inductance values with one, two and without spares is analyzed and compared. And also effect of number of spares on expected capacity level is presented.