How do we stay safe with electrical failures? We’ve covered a bit about how grounding is essential. When there is an excess of electrical power, send it to ground. This is not the end of the problem. If there is a physical fault or a problem with the incoming power supply, we need to cut off power altogether.
These are in many ways, the first line of defense. Surge protectors work mainly to protect equipment. In the event of electrical shorts, they may not protect you. There are numerous protection mechanisms inside. Some surge protectors use resistors, some have gas discharge tubes, others use special diode systems, dump the charge to ground, and more.
The important thing to always keep in mind with surge protectors is that many surge protectors are power strips, but not all power strips have surge protection built in. In fact, surge protection exists as a whole corner of the industry all its own. There are large-scale surge protectors that can be built directly into buildings. These devices arrest and mitigate surges before they can cause damage and before a breaker or other safety device would have time to react.
Ground Fault Circuit Interrupters
There should be as much current, as many amps coming back into an AC Outlet, as leave it. If the current coming back into an outlet is significantly less than the outbound current, that energy must have gone somewhere. Running your appliances won’t generally reduce the current going back to the outlet. An electrical short however, could discharge vast amounts of current to a ground connection. If you’re touching an energy piece of metal, you may become that ground connection. All the current is going to go through you.
This electrical short needs to be stopped as quickly as possible. The first place to do that reliably is in the electrical outlet itself. Newer homes and offices use GFCI outlets. These are generally required in kitchens and bathrooms by building code, and they’re a good idea for the entire building altogether. When a short is present, the outlet will shut itself off and stop the flow of electricity.
These GFCI outlets generally work with an electrical transformer and a comparator circuit. Generally if the input and output are off by more than 5 Milliamps, the comparator will open a contactor and cut all power to the outlet. These outlets are readily recognizable by their Test and Reset buttons. Additionally, these GFCI outlets are thicker than their standard counterparts.
The next line of defense is the circuit breaker. Homes and offices will likely have just one breaker panel. Larger facilities will have multiple breakers for different areas and equipment. The average breaker can be tripped two ways: sudden current draw and too much current draw. This relies on a magnetic tripping system and a thermal tripping system. Sudden currents will create a massive magnetic field that trips the mechanism. Pulling too much current will heat a metal element that pushes another tripping mechanism.
The flaw in this protection is that it reacts far slower than a GFCI outlet. The breaker will run business as usual until more current comes through than it’s rated for. You could be killed with ten amps, a thirty amp breaker won’t trip unless there is a surge or constant draw near that 30 amp limit.
With some digging, we found someone actually testing a breaker to demonstrate how these work. It goes without saying, “DO NOT TRY THIS AT HOME, AT WORK, or ANYWHERE.” Take a look.
As fast as the breaker trips in the video, it’s important to remember that not all incidents will trip that quickly, not all incidents will even trip, and in terms of damage, that is incredibly slow. In the few fractions of a second it takes the breaker to respond, there is already a massive current blasting down the wires.
Things get interesting when you move up to utility-scale equipment. At this point, everything needs to be insanely robust. Failure in this area basically isn’t an option. This equipment might always work, but it’s also going to be slower to act. Small hiccups have to be ignored. Someone being shocked to death in a house is “too small” an event for a utility breaker to detect. These are devices that are going to detect when too much power is flowing and cut the output current. In some cases this may be a fuse on the utility pole, in others it could be a 30KV interrupter. Learn more in the video below.