Series and Shunt Reactors in Power system

Shunt Reactor are used for reactive compensation:
During normal operation of an electrical power system, the transmission and distribution voltages must be maintained within a small range, typically, from 0.95 to 1.05 pu of rated value. Due to the load variations, shunt reactors and capacitors have been applied in
power systems to compensate excess reactive power (inductive for heavy load conditions, and capacitive for light load conditions). Shunt reactors are commonly
used to compensate the capacitive reactive power of transmission and distribution systems and thereby to keep the operating voltages within admissible levels.

Series Reactor for limiting the fault current.


Reference:
http://www.ritzusa.com/pdf/TECH%20NEWS_SHUNT_71665.PDF