Catenary is generally done as a spline that's placed over the tracks. The process can be tedious, but the results are worth it in the end. There are issues that you'll run into such as with complex track, grades, and height. You may find an awesome catenary, but the pantographs never reach the bottom of the wires, or the end up pushing through them. This is a combination of the various heights found throughout the world and also the pantographs used by the content creator. Some are overall too high no matter what while others are meant for a different model and were used. It's also an animation thing based on the scripts. The more realistic pantographs will be adjustable for the wire heights while some go full up no matter what and push through the wires.
The catenary comes in two flavors. There's the simple spline that's dragged point-to-point just like roads. You basically center the spline point in the middle of the track and the poles are generated by the splines. These have the advantages when it comes to long stretches where there's not a lot of complex tracks and curves. There are some variations on this with poles that are track-objects that "clip" to the tracks like signals. You still have to place spline "wires" above and align the spline points with the insulators that are attached to the poles. This can become a pain when there's a lot of tracks and splines due to the number of visible spline points. The other kind of catenary is a fixed track scenery object that's clipped together one after another. This type is common amongst the Eastern European and Russian modelers. And finally, there are also some really, really detailed kinds that go as far as to include the infinite connectors, insulators, clips, and arms which are placed either as track-objects, or as scenery-objects that the spline wires attach to.
The thing is you need to choose what's going to work for you including the style you want to use.
