Hard drives, like any electronic devices, need electricity to function. But they can also suffer a lot of damage if they’re exposed to too much electricity. For your phone, your TV, your computer, etc. an electrical surge is a bit like choking on a glass of water—or drowning. There’s a reason we invented surge protectors.
The job of a surge protector is to kick in when it detects a spike in voltage and (hopefully) prevent any serious damage to your electronics. Think of it as a sippy cup for your electronic devices. And surge protectors do a very good job most of the time—but sometimes, like all human inventions, their efforts fall a little short.