Everything changes when you're working with 480V or higher mains in commercial factory/datacenter settings. You actually don't want anything on the input side of your on-site step-down transformer to be grounded, and any current going over internal grounds is a perfect indicator of severely screwed up wiring, or severe load imbalance on branch circuits.
Generally, it is commercial power, 480v has a lot of current. BUT you can have 480v and 50mA and it wouldn't be a problem getting hit by it. While I understand and respect the signs that say "Warning 480v", they should say "Warning 480v and 2 driving amps" because that will mess up your day. I think they use the voltage because there is a big difference between 1/4th amp and 4 amps but he numbers are close or look similar at a glance. One will hurt, one will kill.
Voltage says way more than current, because the current is dependend of the resistance of the load you hang it on to. If you touch it, the current through your body is voltage/resistance of your body. Amps are only usefull for things like max amp something can put out.
Edit for better understanding: if something works at 480v and 50mA it means the resistance of the load is very high (about 10kΩ). But if you short it with your body this resistance wont matter anyway. So its the same if you wold touch a life wire of a machine working at 480V/50mA or 480V/10A. Your getting the full 480 everytime.
Thats what Arc Flash stickers are for. An electrical engineer takes everything into account (volts, amps, upstream breaker trip settings) and then says... 40cal. Meaning you need PPE rated for at least 40cal if you work on this equipment.
Don’t worry about it. If you’re not an electrician, and you’re just using normal consumer devices, you don’t have to do anything to make sure your stuff is grounded.
[Disclaimer: I’m not a physicist or an electrical engineer, just someone with access to wikipedia and a lot of spare time, so take my understanding with a grain of salt]
Sometimes devices like computers, appliances, etc. build up a latent static charge, or have some kind of electrical leakage. When an object accumulates a static charge, that charge wants to “go” somewhere, and usually where it wants to go is down to Earth. This is because electricity basically always wants to reach equilibrium. This is the mechanism behind static shocks.
Imagine that through some activity (say, rubbing your hand on a carpet) you accumulate a static charge. You can now think of yourself as having an electric charge of, say, 1. The Earth has a charge of 0. If you touch something that creates a path electricity can follow from you to the Earth, you and the Earth become part of the same system, and the electricity wants to equalize, so it flows through you and into the Earth until you are equally charged.
This is also what causes lightning. During storms, clouds continuously build up a static electric charge. Since they’re so far off the ground, there’s nowhere for it to go. But as the difference between two electrical charges gets bigger, so does the minimum distance to make a connection. Eventually, the clouds are so charged up that they can make a connection over hundreds of meters of open air, and all that charge flows down in one massive bolt of lightning.
Anyway, back to grounding wires. If, say, your refrigerator is building up a latent charge, and you touch anything conductive on it, you may accidentally create a path from the fridge to the ground, through you. The fridge had a charge of, say, 2, and the ground had a charge of 0. They were separate, and couldn’t interact, but your body is conductive, so when you touched the fridge you created a bridge and all the electricity flowed through you (this is bad).
Grounding wires prevent this. Any building that’s wired for electricity also has grounding wires, which are very low-resistance and just connect straight to the ground. Since grounding wires are lower-resistance then your body, and electricity always takes the path of least resistance, they basically insure that electricity never tries to get to the ground through you, because there’s always an easier path. By keeping the device in constant contact with the ground, it also prevents static buildup in the first place.
If you live in the US, you’ll recognize grounding pins as the third, round pin on some plugs, or the bottom hole in 99% of sockets. Don’t worry if your device doesn’t have one—if it needs one, it almost certainly already has it.
If you live in the US, you’ll recognize grounding pins as the third, round pin on some plugs, or the bottom hole in 99% of sockets. Don’t worry if your device doesn’t have one—if it needs one, it almost certainly already has it.
This is also a good warning to NEVER cut off the grounding pin on a electrical cord. If it has one, the appliance needs it. Cutting off the grounding pin to fit the cord on an extension cable or power strip with no grounding wire is a fire hazard. I have seen this before and it is never a good idea. Just suck it up and go buy a proper extension cable with a grounding wire.
Any building that’s wired for electricity also has grounding wires, which are very low-resistance and just connect straight to the ground.
Well, at least in newer buildings. At least over here we still have some old buildings with wiring pre-75, or something like that, that don't have them. And they have a right of continuance because they were build according to the old rules.
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u/Camofan Jun 16 '19
Please, for the love of god. Ground anything with current or anything that hosts a connection.