There has been remarkable increase in the amount of decentralized wind farms (WFs) in sub-transmission grids. The high penetration of WFs causes complicated impacts on power flows and voltages. Therefore, WFs have to operate bus voltages of the sub-transmission grid continuously within a permissible range. Furthermore, WFs should transfer required amount of reactive power into transmission grid and/or absorb the necessary amount of reactive power in the sub-transmission considering the demand of transmission system operators (TSOs). In other words, reactive power requirements at connection points (CPs) where sub-transmission grids are connected to the transmission grids should be satisfied. Therefore, this paper presents a comparative analysis for reactive power management by WFs in subtransmission grids using both a novel linear programming (LP) approach based on voltage sensitivity and particle swarm optimization (PSO).