The day-to-day increase in electric energy demand with increasing population and urbanization is causing transmission facilities to transfer load at their upper limits; therefore, the probability of failures of these facilities increases. One of the ways of mitigating failures is by constructing more transmission lines; which would serve as alternatives to reduce the transmission line utilization levels (TLUL). However, there are constraints in adopting this method; therefore, the use of Interline Power Flow Controller (IPFC) has been suggested by many researchers; but very few of these studies proposed the IPFC that has capability of handling operating constraints (IPFCthC) in solving power transmission systems issues. Some of the studies that proposed the IPFCthC use trial and error approach in identifying the optimal location for its injection in multi-buses power grid. Also, some of the studies that proposed the IPFCthC do not employ it to investigate its capability in reducing TLUL. In order to reduce the TSUL in the multi-bus grid, this paper therefore proposes optimal location for the injection of IPFCthC using Transmission Line Performance Index (TLPI) and Transmission Line Reactive Power Loss (TLRPL) in Newton-Raphson Load Flow (NRLF) algorithm. The proposed algorithm was tested on IEEE-30 Test-bed in Matlab environment. The results obtained reveal that the TLUL of each of the transmission lines of the Test-bed that is not connected to PV bus is reduced averagely by 4.00 % each, with the injection of the IPFCthC in an optimally location established by the proposed algorithm.