Paralle l passive filters are used for decrease of harmonic co mponents of load currents. In electrical distribu- tion systems, over voltages such as switching and lightning over voltages are applied to the parallel passive filters. Th is paper analyses the behaviour of parallel passive filter employed to decrease the load harmonic currents under travelling wave conditions. The parallel passive filter is vulnerable to lightning surges. Therefore, protection of it against lightning surges is necessary. Equipment protection against lightning surges is usually done by gapless surge arrester. This paper presents important points of gapless surge arrester to protect parallel passive filters. A lso an algorith m is presented to select gapless arrester under harmonic conditions in this paper. The presented algorithm is based on the IEEE standards C62.22 and 1531. Finally the simulat ion results are provided to verify the presented algorithm.