I’m actually not entirely sure how finding these videos began, but some shocking videos for your enjoyment:

• “Crazy man throws a wire on 110 kV power line” is about as accurate a title as they come. (Highly, highly not recommended!) It’s essentially the same deal as a lightning strike: one end of the wire is connected to ground, and when the wire makes contact with the 110,000V power lines, it shorts to ground.
• This one is even more absurd? Someone provides a translation of the Russian: they’re 500kV lines, and some idiots throw barbed wire (?!) onto the lines. You can’t see them throwing the wire, though, so there’s just a tremendous explosion as 500kV rushes to ground before, most likely, vaporizing the wire.
• This one is really bizarre to me. One description says they’re using “splicing technology,” and another explains that they’re “strengthening the lines.” Neither really gave any explanation to why there’d suddenly be a tremendous explosion and plumes of smoke from all of the insulators. It looks like they sent enough voltage on the lines to jump across the massive insulator. (Which is like a six-foot chunk of porcelain, chosen because it’s ridiculously non-conductive.) Rusty gave a good explanation: it seems that they’ve applied something-or-other on the lines, and are essentially “flash-welding” it on.
• Substations often have “air break disconnects,” which are essentially a big, metal, mechanical arm that they can “open” to keep electricity from flowing. The design wasn’t meant to to switch “hot” loads, though. Here’s a video of them opening the disconnect on a 230kV line, which… Well, just watch. (It shorts to another wire after a few seconds.)
• Here’s something sort of similar, except it appears that it’s more of a technical failure. It turns into somewhat of an accidental Jacob’s Ladder, before it burns itself out in a fantastic fashion.
• This is a neat compilation of various high-voltage “problems.” I actually saw a neat explanation somewhere of what happens in the first video… Something in a high-voltage transformer there shorts to ground, but nothing upstream ever tripped a circuit breaker. The transformer is filled with oil for cooling, before finally it becomes hot enough that it boils and starts spewing ‘steam’ (boiling oil) out its ’emergency’ valves, which makes things much worse, but is actually fortunate in that it blows up the incoming voltage, leaving firefighters with a simple de-energized power grid full of burning oil to deal with. The second is another case of them opening a mechanical “air break” disconnect, apparently in a deliberate test of a 500kV system. Then we see the same clip we saw earlier, and then… The most awesome thing ever. I have absolutely no clue what goes on, but it’s the most awesome fireball ever.