AC power generation and transformers

[Agriias]

Hi guys,

I have a question.

When electricity is generated how is it determined which side of the coal in the generator is the hot and which side is the neutral? Since AC fluctuates in polarity wouldn't both leads be essentially electrified?

With that said, if the hot path was severed from the return and creating an open circuit, would any load that is electrified before the open circuit still be powered? Would this also apply on the return side?

Another example, if I unplug an outlet in my house and touch the neutral wire, will I get a shock?

Thanks,
Agriias

 

[BobK]

The side that is connected to ground is neutral the side that is not is hot. It is arbitrary and indeed must be because there is not difference between the two.

If you touch the neutral wire only, you would not get a shock. If you touch the hot wire only it depends on many other factors. If you are well isolated from the ground, you will not get a shock. If you hold neutral in one hand and hot in the other, you are probably dead.

Bob

 

[Agriias]

Ok makes sense thanks.

I'd imagine the amount of grounding needed for a power generation plant or even large transformers must be very deep to keep it safe.

Also, when they are running how large can the electromagnetic field be? I wonder how many feet away you would need to be to not get fried through inductance.

 

[Arouse1973]

The magnetic field is a fact of life, but the electricity company would want to reduce this as much as possible. Without power factor correction this is wasted energy so they would want to keep the inductance to a minimum.
Adam

 

[jbelectric777]

let me clear something: if the grounded conductor (neutral) is not connected to the panel bus bar and say the circuit feeds from the breaker through a few light bulbs and back to its break between its bar and its conductor, and you get between it, your in for the shock of your life! Im a master electrician and inspector in NJ & PA (30 yrs) the reason is say your bodys resistance is 100k then add the resistance of the bulbs and any other loads the circuit happens to have connected will flow through your body and most likely hurt real bad or worse. also ac power goes back and fourth with a midpoint of zero, you MUST ground one side or equipment will not work, unlike DC, AC is not polarized until that equipment ground is connected in the transformer marked with a midpoint zero marked "XO", also its ungrounded conductor not "hot" Just wanted to help, Im here to learn electronics. which from line voltage is night and day. Jim B (ps, I learned as an apprentice many yrs ago to respect electricity at any voltage, a car battery can kill under the right conditions)

 

[jbelectric777]

The magnetic field is a fact of life, but the electricity company would want to reduce this as much as possible. Without power factor correction this is wasted energy so they would want to keep the inductance to a minimum.
Adam

adam, so long as the poco is getting your money they don't care about your owner owned equipment, just their poco owned equipment.

 

[jbelectric777]

clearance distances are in the NEC codebook but I never trusted them, I worked highline and airfield which is all hi volt and if your grounded or the buckets grounded it will jump, its called "tracking" the largest I worked on was yearly up keep, so they shut it down (60kv 60,000 volts) ground all phases to each other and ground then release the capacitance!!!!! when they let that capacitance go holy friggin hanna!!!!! its like a gun goin off in your ear!!!!!

 

[Arouse1973]

clearance distances are in the NEC codebook but I never trusted them, I worked highline and airfield which is all hi volt and if your grounded or the buckets grounded it will jump, its called "tracking" the largest I worked on was yearly up keep, so they shut it down (60kv 60,000 volts) ground all phases to each other and ground then release the capacitance!!!!! when they let that capacitance go holy friggin hanna!!!!! its like a gun goin off in your ear!!!!!

Fair point JB, didnt think of it like that.
Adam

 

[Bluejets]

Any hv cabling I've ever had anything to do with, in Aus at least, there is a strictly controlled method to discharge the capacitance.
This is before works commence or during test proceedures.
Just shorting out seems a very dangerous approach to me and in this day and age with workplace health and safety in every conceivable nook and cranny, I have a feeling it would be frowned upon to say the least.

 

[KrisBlueNZ]

At the company I used to work for, we would sometimes get sent out onsite with power company electricians, and I've heard a few good stories, like the time an air break switch started to open (or close; not sure which) on a live line! The linesman's advice is "if you see me cover my ears and run, you do the same!"

 

[chopnhack]

Any hv cabling I've ever had anything to do with, in Aus at least, there is a strictly controlled method to discharge the capacitance.
This is before works commence or during test proceedures.
Just shorting out seems a very dangerous approach to me and in this day and age with workplace health and safety in every conceivable nook and cranny, I have a feeling it would be frowned upon to say the least.

Do they discharge through a large load resistor before grounding?

@KrisBlueNZ - reminds me of the bomb squad technician ;-)

 

[hevans1944]

Ok makes sense thanks.

I'd imagine the amount of grounding needed for a power generation plant or even large transformers must be very deep to keep it safe.

Not too deep, maybe ten feet or so, and bonded to buried-in-concrete rebar grid.

Also, when they are running how large can the electromagnetic field be? I wonder how many feet away you would need to be to not get fried through inductance.

Good question, but I don't have a definitive answer. Some folks believe it is unsafe to live under or near high-voltage power lines, even if no immediate physical effects are apparent. It is probably safe to walk under a high-voltage transmission line because the wires are far overhead, but I personally would avoid doing this unless paid big bucks and covered by company-paid insurance.