Something to protect cords

I'm wondering if anyone knows of something that you can cover electrical cords with to keep a new puppy from chewing them?
Of course we keep an eye on her and pen her when we are not home, but still she is sneaky. To be honest, she seems really dumb. :(
I have had dogs that were just really bright from the get go, but this one just doesn't seem to be that type. She's young though, so maybe there is hope... I hope!
Anyway so far we had two cords chewed a little, one we replaced and the other wasn't so bad. That happened when my daughter didn't get the latch tight on her pen and she apparently invited herself out to party all night in the house and no one knew. Yeah, that was a mess...