I am trying to add power lines in the map as a layer. I am using leaftlet for making this webapp. is there any possibility to add this info as a layer into the map. Or any example regarding this?
Yes, it is possible, but not trivial. The optimal solution will depend on the amount of data you are willing to process (i.e. do you need power lines for a small city, or for a whole continent?).
The process will probably involve extracting the power line data from a OSM planet dump (do read http://enipedia.tudelft.nl/wiki/Extracting_Power_Data_from_OpenStreetMap !), and then rendering that data as plain vector data (smaller sizes), raster tiles (backend work), or vector tiles (several approaches).