In this paper we have analyzed the various algorithms used for reactive power optimization (RPO). The objective of an optimal power flow (OPF) algorithm is to find the steady state operation point which reduces the generation cost, loss etc. Reactive power supply plays an important role in the power system. A properly designed optimal power flow solution provides the best and the most optimum practical solution to achieve improvement in a single or multiple hierarchical objectives based on the various constraints on the system. The main aim of RPO is to minimize the system losses and to maintain the voltage profile according to the constraints. Considering the voltage security, power systems are provided with a lot of voltage controlling devices such as generators, tap changing transformers, shunt capacitors/reactors, synchronous condensers, and static VAR compensators etc. A real time control employing those controlling devices is required to solve the problems. Traditionally, classical optimization methods were used to solve this problem, but due to its various limitations, modern methods have been proposed in this paper for the optimization of the reactive power. The purpose of this paper is to present a comprehensive survey of various reactive power optimization methods.