TalonNYC wrote: Electricity won't pass that "2cm gap" when it has a much easier path to ground (the 3rd prong).
Add numbers to your assumption. Let's say a trivial 100 amp surge is incoming to an appliance and protector. So that current will go back to a breaker box earth ground? 'Impedance' has been repeated often. Some numbers.
A 12 AWG ground wire maybe 50 feet back to the breaker box is less than 0.2 ohms resistance. And something like 120 ohm impedance. 100 amps times 120 ohms is something less than 12,000 volts. How does that current get back to a breaker box? It doesn't. It goes hunting for earth destructively via any nearby appliances. That appliance need not even be connected to the protector.
An NIST brochure puts numbers to this. That current is earthed 8000 volts destructively through a nearby TV. How is that protection?
Second, once that surge is all but invited inside, then nothing - especially not plug-in protectors - can 'block' or 'absorb' a surge. That is what an adjacent protector must do - either 'block' or 'absorb' that current. It can't.
Third, even open circuit breakers do not stop surges. Will a millimeters gap in a breaker, fuse, or switchl stop what 3 kilometers cannot? Of course not. Those are damning numbers.
Furthermore, circuit breakers take milliseconds or seconds to trip. Easily 300 consecutive surges could pass through that breaker or protector before any switch or fuse even thought about tripping. Nothing 'blocks' a surge. As in nothing. As made obvious by another term - current source.
A facility that cannot have damage always has a low impedance (ie less than 3 meters) connection to earth. So that a surge is nowhere inside. That is how protection from direct lightning strikes has been done over 100 years ago.
Fourth, failing protectors never do protection. Remember how electricity works. If a surge is incoming to that protector, then at the same time, that same current is outgoing into attached appliances. That current exists simultaneously everywhere in a path from a cloud, through the house, and maybe 4 kilometers through earth. Much later, something fails in that path. Nothing as in nothing blocks or stops that current. Effective protector with a low impedance connection to earth never tries to be so foolish.
Grossly undersizing a plug-in protector creates a "it failed to protect my CPAP" myth. A surge too tiny to overwhelm protection already inside a CPAP easily destroys that near zero joules protector. Then naive consumers recommend that ineffective and obscenely profitable device. Grossly undersizing a protector gets naive consumers to recommend it and buy more.
Informed consumers spend $1 per appliance for a 'whole house' protector (ie rated 50,000 amps). Then nobody even knew a surge existed. Even a protector is not damaged. Then protection remains functional for decades. Then one need not buy a new plug-in protector every year or so - and so many myths recommend.
Nothing useful is gains by an undersized (plug-in) protector. Again, how many joules does your's claim to absorb?
Grossly undersizing to create failures increases profits. Meanwhile, its fire risk is so great that cruise ships may confiscate that protector. Fire from near zero joules protectors is another major problem with protectors designed to fail on a surge.
What did that youtube video note?
https://www.youtube.com/watch?v=JvGw58w4rxg
Plug-in protectors do not provide effective protection without a 'whole house' protector. A 'whole house' solution is required to even protect plug-in protectors. The 'whole house' solution does 99.5% to 99.9% of the protection. Then plug-in protectors might do an additional 0.2%.
Did we mention the 15 million APC protectors now known to be so dangerous as to be removed immediately? And still some recommend these near zero protectors because advertising and another's insults said so.