An on-line monitoring technology of metal oxide arrester(MOA)degradation based on the particle swarm optimization algorithm is proposed for on-line aging monitoring of MOA. PSO algorithm is employed to compute the aging parameters,α、k and c of the MOA equivalent model for monitoring the degradation of MOA. In addition,the simulation by the MATLAB to analysis the impact of the voltage harmonic in the power grid to the algorithm in this paper. Simulation shows that PSO algorithm can fit the calculated leakage...