The benefits of reactive power compensation depend greatly on the placement and size of the compensators. STATCOM is a shunt compensator and one of the important members of the Flexible AC Transmission Systems (FACTS) family that are increasingly being used in long transmission lines in modern power systems. The FACTS devices placement problem is commonly solved using heuristic optimization techniques which are diverse and have been the subject of ongoing enhancements. This chapter, in the first stage, presents a survey of the literature from the last decade that has focused on the various heuristic optimization techniques applied to determine optimal placement and sizing of the STATCOM. In the second stage, the application of the global harmony search (GHS) algorithm as a new meta-heuristic optimization method for determining the optimal location and size of STATCOM in a transmission network is presented. The algorithm is easy to be implemented and capable of finding multiple optimal solutions to the constrained multi-objective problem, providing more flexibility in making decisions about the location of STATCOM. Power system loss reduction, bus voltage profile improvement, voltage stability enhancement and device size are employed as measures of power system performance in the optimization algorithm. The proposed multi-objective GHS algorithm is validated on 57 and 118-bus transmission networks.