In LT system(say 415 V) ,CTs will be located in the Main Power Distribution panel.CT connection and potential connection will be given to Automatic Power factor correction relay.(APFC relay ) this relay willbe of 4/6/9/12 stages).supposing 4 stages means there will be 4 banks of capacitors located in the Capacitor panel and controlled by a contactor.The contactor will be located in the same panel.The contactor will get signal from APFC relay for switch on /off depending on the PF of the load.
For HT system the method would be same, but instead of Contactor controlling unit would be VCB or sf6 breaker.the capacitors will not be located in the same switch gear panel.CT and PT will be located else ware for giving detailed current and voltage input to APFC
TCSC , thyristorised control Series Compensation, a circuit where switching of capacitors are thyristorised controlled. Normally used in transmission line. You can check web site to learn more on this topic.