With the increasing energy demand and tighter interconnection between systems, the loop flow problem should be solved for the purpose of reliable system operations. FACTS devices, such as UPFC, have the ability to control the power flow, which makes it possible for them to prevent loop flows in interconnected systems. For the Economic considerations, the FACTS devices can be installed in a suitable location in MV networks, instead of directly installed in HV network where loop flows occur. The modeling of UPFC in power flow calculation is introduced. A real case in South China, which focuses on solving loop flows by UPFC in MV network, is presented. Since the party benefiting from the interconnection is subjected to loop flows and takes on the network loss caused by loop flows, the Economic feasibility of implementing FACTS devices is discussed.