i been watching rimstar's video on grounding/earthing
https://www.youtube.com/watch?v=zLW_7TPf310
as you know, ground wire is there so in case insulation on phase/live gets damaged and it touches the casing, electricity doesn't flow through you to the ground by through the ground wire which is connected to the neutral in the breaker panel.
what i don't understand, why not connect the neutral to the casing directly and lose the 3rd terminal.
what would be the difference. casing would still be at 0V and in case phase touches the casing current will flow to the neutral and not through you.
can anyone answer this
the difference? Suppose the neutral opens then what?the case rises to the hot and you get zapped good.
"Suppose the neutral opens" what you mean
i said why not connect casing directly to neutral, instead of connecting it to "ground" which connects to neutral in breaker box
Quote from: fritznien on August 31, 2020, 02:51:43 PM
the difference? Suppose the neutral opens then what?the case rises to the hot and you get zapped good.
Isn't that the story of Keith Relf?
Sometimes, there is a leak which goes round and round, causing
mains hum. If you cut the earth, it breaks the circle and the hum
goes away - but there is still a leak - and once the mike stand ended
up at mains voltage. I may be mixing up a couple of cases but Fritznien
is right. Don't do it.(p.s. please post smaller images, 800 max. it messes up the thread).
still no answer why not connect the casing directly to neutral
Quote from: nix85 on August 31, 2020, 05:59:43 PM
still no answer why not connect the casing directly to neutral
I did answer. if a break in the neutral happens anywhere between the case and the transformer on the pole,then the case will be connected to the hot line thru the load! Zap!am i clear enough? not all breaker boxes have the neutral and ground connected, depends on local code.we need the ground on the polepig because the primary has high voltage, mine is 18kv.
Quote from: nix85 on August 31, 2020, 05:59:43 PM
still no answer why not connect the casing directly to neutral
Hi Nix85. Actually fritznien answered your question already.
The ground wire is a backup pathway back to the ground lug in the panel and it should
be solidly grounded to earth ground at the panel, to ensure the metal case or chassis of an electric device
is properly grounded for safety. If the neutral wire opens up, a person could get killed if they
touch the metal case or metal parts of an electric device if the hot phase wire gets shorted to the
case or metal parts. The case or chassis being grounded with a separate ground wire ensures the case/chassis is
still at ground potential. As long as the mains neutral is properly grounded to the earth ground lug at the electrical panel,
the circuit breaker should still blow even if the neutral wire is open somewhere along the
neutral wire to the electric outlet or device. This gives backup ground protection in case there is a faulty neutral wire connection.
Somehow, however, I think you might still say no one answered your question... :)
Quote from: fritznien on August 31, 2020, 07:20:24 PM
I did answer. if a break in the neutral happens anywhere between the case and the transformer on the pole,then the case will be connected to the hot line thru the load! Zap!am i clear enough? not all breaker boxes have the neutral and ground connected, depends on local code.we need the ground on the polepig because the primary has high voltage, mine is 18kv.
my bad, didn't get what you mean at first. perfectly clear now. tnx
void, there was no need for your reply or emojis but it's ok.
There are many methods to apply safety to the ground circuit.
But on a technical level, the ground is our reference.
This is what determines the magnitude of every voltage in our systems.
The line in only 15-20k because the reference to earth is our "0".
The converted plug is at 120-240 because the earth is the "0" reference.
Rest assured, our planet is not "0" volts...
Electricity is relative. (moves at or close to c)
Because of this, it does not exist in the same time domain as we do,
and appears to be always out of phase with itself.
Change the perspective, change the potential.
Lose your reference, and you essentially disconnected one end of the "battery" or source potential.
Etheric pressure of infinite potential constantly rains on Earth and reflects back from it's core, tiny part of this netural spectrum you feel as "weight".
"earth is a vast reservoir of negative electricity" (he surely meant cold electricity)
nikola tesla, early 1900s patent on radiant energy
not to mention electric field between your head and ground is around 100v, but tapping into it is another thing
Hi sm0ky2,
You are very correct about the ground being our reference. And in the real world that reference is very imortant.
I once worked on a new automated storage and retrieval system. It had 4 aisles and each aisle had a robot that pulled or stored the parts. And each aisle had an operator and a PC work station where they put in the part number of the part which told the PC what to tell the robot so it would pull the right part.
Shortly after the system was starting to be used they discovered a problem. The PC's kept going crazy. They would lock up or restart themselves or even put bad info into the program. My boss asked me to check it out to see what was going on. To make a long story shorter I found that when the contractor put in the system they had installed a step down transformer to drop the 440 vac in the building to 120 vac to supply power for the PC's. The 120 vac was floating in reference to ground because they had not grounded either side of the secondary. Sometimes the secondary would be as high as 600 volts in reference to ground.
After I installed a ground connection to the secondary all the mysterious problems with the PC's went away.
Carroll
Nix85
Quote"earth is a vast reservoir of negative electricity" (he surely meant cold electricity)
nikola tesla, early 1900s patent on radiant energy
Try googling "atmospheric electricity" which is a very interesting subject and directly related to FE.
In effect, cosmic radiation induces a positive charge in our atmosphere and opposite charges attract therefore the negatively charged electrons always tend to be attracted to the surface of the Earth. So in fact it is a vast reservoir of negative charges as free electrons.
There are many inventors in the past who devised ways to harness the difference in potential between the Earth and atmosphere. Tesla has many lectures on this subject and he talks about using elevated and insulated antennas and a ground connection.
Regards
Quote from: onepower on September 01, 2020, 10:49:05 AM
Nix85
Try googling "atmospheric electricity"...
you are assuming i already didn't. i did and very deeply so. one of favorites is Roy J. Meyers' Absorber
but there are many. potential energy of the ionosphere is hundreds of gwh and that is just ordinary static electrcity.
in fact, most energy hides in usually non-observed spectrum, tesla and others learned how to harness.
this neutral, life energy passes through everything. it also has positive and negative, positive coming from the sun that manifests
light, heat and gravity
negative reflecting from earth to space at 1/3 higher frequency that manifests
darkness (and it's own spectrum of darkness colors), cold and levity...
earth besides being a vast reservoir of electrons, it is charged with negative electrcity (ordinary electrons being positive, hot electricity), of it's nature we don't know too much, but it is what floyd sweet tapped into when he observed that when he drew full power from his device (~1kw) the wires literally froze and it's weight became negative.
It's also helpful to understand what a difference in potential is.
In a battery we could measure 12 volts with a voltmeter however this is only a measure of the difference between two potentials. When I use my electrometer I measure a potential of negative 6 at the negative terminal and a potential of positive 6 at the positive terminal. The difference between -6 and +6 is 12, which is the difference between the two potentials.
The potentials are always equal and opposite discovered by Faraday I believe. Therefore the Earth cannot be at zero potential as shown in your diagram if all potentials are equal and opposite. So when we measure a potential difference of 100 volts around 1 meter above the Earth this means the Earth must be at a potential of -50 and the atmosphere at +50.
So a more accurate diagram would show a rising + potential as we move away from the Earth and also a rising - potential as we move towards the Earth, equal and opposite. Between any two different potentials we have a zero plane or point as negative cannot become positive without passing through or becoming zero. I once built an open battery to test this theory and in fact the electrolyte directly between the positive and negative plates was at zero potential. The potential became more negative as I approached the negative plate and more positive as I approached the positive plate as predicted.
It is amazing how much one can learn from the simplest things many of us take for granted. Many have overlooked and not questioned the fundamental nature of how things work all around us. There is a lot to learn.
Regards
In the past nobody ever responded when I showed the difference between a difference in potential which is Voltage and the individual potentials which constitute the difference. More so once I introduced the concept of the zero point or plane which divides the two equal and opposite potentials. It may have made them think too much.
Let's see how this goes... the two capacitor paradox and moving zero planes, or a ground as many call it.
I have one charged capacitor with +/- potentials and a difference of 10v. Now I connect an uncharged capacitor, they balance and both capacitors then have 5v on each but somehow I have lost 1/2 the energy... where did it go?.
Most say it was dissipated as heat or radiation but that's a weak explanation at best because it does not define the exact cause of how the energy was dissipated. When I did the experiment I found something quite amazing. We started with two +/- potentials at a difference of 10v with one zero plane dividing them however we ended with four +/- potentials and two zero planes over twice the surface area. So when we divided the energy into two distinct elements having twice the surface area the energy density must be 1/2 because the energy is dependent on the amount of electrical pressure per unit of area is it not?.
It's a chicken and egg dilemma, did the energy dissipate because it was flowing into the second capacitor or did the energy dissipate because it was flowing into the second capacitor which doubled the surface area decreasing the energy density by 1/2?. If the surface area did not increase the energy could not flow into the second capacitor but when it did it lowered the energy density so which mechanism caused the dissipation of energy?... exactly.
Contrary to popular belief the two higher potentials in the first capacitor sensing a path to a lower potential or greater surface area is the first cause not a current flow. As well the doubling of the surface area lowering the energy density by 1/2 is how the supposedly missing energy dissipated not the current flow. The current flow is an effect of the cause not the impetus which drives it.
Now the kicker, I have justified how a doubling of the surface area must reduce the energy density by 1/2 in the the two capacitor paradox which constitutes the cause of the dissipation of energy so if the conductor connecting the two capacitors dissipated energy as well ... then where did it come from exactly?.
You see we have to look at the bigger picture with respect to these problems because it is seldom cut and dry. The solution is actually quite easy so I thought I would throw this out as a brain teaser.
Regards
Quote from: nix85 on August 31, 2020, 08:05:53 PM
void, there was no need for your reply or emojis but it's ok.
Hi nix85. When I typed in my reply to you, fritznien had not made his second reply
to you yet. It just so happens he seems to have been replying to you at the same time
I was replying. Instead of thanking me for taking the time to explain to you further, you
reply with a very ignorant comment. Thanks for making it clear to everyone here that you are
just a clueless ignorant asshole.
What the hell is wrong so many people these days? More assholes than you can shake a stick at.
Many people seem to have completely lost all sense of manners and respect, etc.
I guess we have to blame their parents for not teaching their kids properly.
This does not bode well at all for the future of this world.
:o
Quote from: Void on September 02, 2020, 10:11:07 AM
Hi nix85. When I typed in my reply to you, fritznien had not made his second reply
to you yet. It just so happens he seems to have been replying to you at the same time
I was replying. Instead of thanking me for taking the time to explain to you further, you
reply with a very ignorant comment. Thanks for making it clear to everyone here that you are
just a clueless ignorant asshole.
What the hell is wrong so many people these days? More assholes than you can shake a stick at.
Many people seem to have completely lost all sense of manners and respect, etc.
I guess we have to blame their parents for not teaching their kids properly.
This does not bode well at all for the future of this world.
:o
calm your tits and look in the mirror. look at sarcastic ending of your first post and stupid emojis you use... your comment was posted after his, all i said is that it was not needed, especially the sarcasm.
i'm igorant? maybe compared to some 5D being, but to you, i am lantern of illumination, you poor ahole
Quote from: nix85 on September 02, 2020, 10:22:17 AM
call me your tits and look in the mirror. look at sarcastic ending of your first post and an stupid emojis you use...
i'm igorant? maybe compared to some 5D being, but to you, i am lantern of illumination, you poor ahole
you call me ignora
I rest my case.
Quote from: Void on September 02, 2020, 10:24:25 AM
I rest my case.
eng is not my first lang, you moron, i can misspell a phrase and correct it a second later all the while laughing how pathetic you are.
i rest my case.
let's review this once more. so to this..
Quotevoid, there was no need for your reply or emojis but it's ok.
mr nice manners replies with
Quote
Instead of thanking me for taking the time to explain to you further, you
reply with a very ignorant comment. Thanks for making it clear to everyone here that you are just a clueless ignorant asshole.
wow, so kind and sweet
QuoteWhat the hell is wrong so many people these days? More assholes than you can shake a stick at.
all those nasty assholes that do not show gratitude for his great contributions
then he goes on a rant about parents..
QuoteMany people seem to have completely lost all sense of manners and respect, etc.
I guess we have to blame their parents for not teaching their kids properly.
This does not bode well at all for the future of this world.
:o
thankfully, his parents taught him "nice" manners
Quote from: nix85 on August 31, 2020, 02:43:10 PM
i been watching rimstar's video on grounding/earthing
https://www.youtube.com/watch?v=zLW_7TPf310 (https://www.youtube.com/watch?v=zLW_7TPf310)
as you know, ground wire is there so in case insulation on phase/live gets damaged and it touches the casing, electricity doesn't flow through you to the ground by through the ground wire which is connected to the neutral in the breaker panel.
what i don't understand, why not connect the neutral to the casing directly and lose the 3rd terminal.
what would be the difference. casing would still be at 0V and in case phase touches the casing current will flow to the neutral and not through you.
can anyone answer this
Your casings and other stuff can produce lots of noise and phase shifted signals.
If you use neutral for grounding you introduce all that garbage back to network,
and soon your network will not have clean sine wave but garbage.
How many casings are just in one city?
The reason to use ground is to try to keep clean network,
and remove garbage signals to the ground.
Quote from: v8karlo on September 03, 2020, 12:12:31 PM
Your casings and other stuff can produce lots of noise and phase shifted signals.
If you use neutral for grounding you introduce all that garbage back to network,
and soon your network will not have clean sine wave but garbage.
How many casings are just in one city?
The reason to use ground is to try to keep clean network,
and remove garbage signals to the ground.
good point, all that stray capacitance
Yes, and with stray capacitance emerge reactive power as well.
Network will become source of noise and sensitive electronics on user end will be fried very quickly,
while power companies will be having headiche.
ofc, like you said, phase shifting voltage and current
Quote from: v8karlo on September 03, 2020, 12:12:31 PM
Your casings and other stuff can produce lots of noise and phase shifted signals.
If you use neutral for grounding you introduce all that garbage back to network,
and soon your network will not have clean sine wave but garbage.
How many casings are just in one city?
The reason to use ground is to try to keep clean network,
and remove garbage signals to the ground.
i been thinking about this again, this argument makes sense at first but
in most usual case where ground is connected to neutral
in the box, what is the difference, metal casings and other stuff
is still connected to the main circuit, no big difference if it's connected
right at the plug or few meters away in the box and still
"casings and other stuff can produce lots of noise and phase shifted signals"
i still dont see a single valid reason for existence of the 3rd hole
the third prong ....
In a home wiring system, if a hot wire contacts the outer body
of an appliance, it is a dead short to the breaker. The appliance
body cannot conduct a large current if it is wired to the third prong.
An undesired current available through the appliance body becomes a source
of current through any person's body that completes an electrical circuit from that
appliance body to a grounding point.
... ... ... ... ... ...
The actual earth grounding rod at the electric service points, are / is for lightning
strikes.
In RF ranges and earth grounding there are other things to consider.
let's first dispell the "hot wire" nonsense
there is no such thing as "hot wire", or "phase and neutral"
voltage is same on both terminals with only difference being that
"neutral" is USUALLY (not always) earthed.
MCBs are used for overcurrent protection
RCDs for earth leakage human protection
i know earthing is used mostly for lightning and static build up drain
again, what is the difference if casing of an appliance is connected
to neutral in the appliance or 2 meters away in the breaker panel
"again, what is the difference if casing of an appliance is connected
to neutral in the appliance or 2 meters away in the breaker panel"
In short (pun intended) the third wire is for redundancy.
Current flows between a hot wire and a common wire only after an appliance is used
on that pair (hot and common).
Current never flows between a hot and a ground unless something is wrong.
The ground wire is for safety only, never to be used as common, always out of the
circuit unless something is wrong. It is to provides a dead short to the breaker.
Breakers help prevent fires.
Current never flows between a ground wire and a common wire unless something is wrong.
They are supposed to have the same resistance and voltage potential.
Common and ground have parallel paths to the common terminal.
The common is connected to earth ground at the main breaker box.
Down the line, it does not have the same potential to earth ground as does a hot wire.
The ground wire is connected to earth ground at the main breaker box.
Down the line, it does not have the same potential to earth ground as does a hot wire.
Common wire or ground wire, it will always dead short a hot wire, because it leads to the center
tap of the line transformer. But also they short a hot wire because they are earth grounded.
Common is supposed to connect to a hot wire only with current that has passed through
the electrical resistance of an appliance. That connection is to both the transformer and to
earth ground.
When an appliance draws a large current, it is because the appliance has a low
electrical resistance.
In respect to an earth ground (buried plumbing), an appliance that draws a large current
( low resistance) may still have a considerable voltage potential to that earth ground even
after the load.
If a path is provided, voltage and current will divide between an earth ground
and the common wire (according to the resistance differences).
If the common wire is connected to the body of an appliance and a person's body connects the appliance to an earth ground, that person becomes part of that divided circuit.
If an appliance is one that draws a lot of power (low resistance), the voltage and current to
earth ground which is still available after the appliance load can be substantial.
If the common wire becomes disconnected from its terminal at the breaker box,
It has become disconnected from both the transformer center tap and the earth ground.
The appliance body is now completely live in respect to an earth ground, (after the
appliance load).
This is of course less live, than if the hot side of the load were directly connected to the
appliance body (before the appliance load).
Both the common and the ground wire are neutral to earth ground (ideally).
The "common" wire is hot in common, to either side of the transformer.
The "common" wire is neutral to the ground wire and to an earth ground.
The hot wires are hot to both, the earth ground and to the common (transformer).
Again the third wire is for redundancy.
also
Common and ground wires share the same terminal at the mains breaker box.
In general, in a sub panel connection, there is no local connection present between common
and ground wires.
The common bar is not connected to the box / body.
A separate ground bar is connected to the sub panel box / body.
The common and ground wires are connected to the same bar only at the mains box.
There are exceptions to this generalization.
Quote from: nix85 on April 27, 2021, 03:04:18 PM
let's first dispell the "hot wire" nonsense
there is no such thing as "hot wire", or "phase and neutral"
voltage is same on both terminals with only difference being that
"neutral" is USUALLY (not always) earthed.
MCBs are used for overcurrent protection
RCDs for earth leakage human protection
i know earthing is used mostly for lightning and static build up drain
again, what is the difference if casing of an appliance is connected
to neutral in the appliance or 2 meters away in the breaker panel
we have been thru this,any fault in the neutral will let the case rise to full voltage and ZAP!what are you trying to do here?you want to cheap out on the cord use non conductive cases.no the ground in a house wiring is not remotely able to handle lightning but it will keep metal safe to touch if there is a fault. telephone equipment has very stringent grounding systems but compared to a toaster the equipmentin a phone system is very delicate.
Floor that is all that is common knowledge most of it is already mentioned,
or perfectly assumed.
here is a video explaining all those basics nicely
https://www.youtube.com/watch?v=P-W42tk-fWc
you might just have simply written redundancy
also "Both the common and the ground wire are neutral to earth ground (ideally)."
this is often not the case cause there is potential between remote and local earth
which will trip the RCD if "neutral" is earthed.
sometimes it's even possible to power small appliances between neutral and ground
https://www.youtube.com/watch?v=BF0CS8aY1CY
again, there is no such thing as "phase" and "neutral", these are nonsensical terms
that just confuse the public.
in your american split phase system you have 3 wires coming from the pole transformer
2 of which might be called "common" cause one of your two 120v phases is common wire of the 3 phase transformer and your household "common" is common for two sides of that single phase winding.
the ONLY difference is that so called neutral/common is often but not always earthed.
Jerry Volland, all you wrote is basics all of us know
fritznien no, goal is not to be cheap on wire but to clear this up.
yea "any fault in the neutral will let the case rise to full voltage and ZAP"
but no zap happens in that scenario if you have RCD which you surely do
hopefully one with less than 500mA tripping current.
you might as well think of similar scenario where fault happens in the ground
wire and again casing is live, thankfully RCD again saves you
also i did not say ground wire is to handle lightning but earthing, that is, metal rod on your roof connected to the rod in the ground
i will accept redundancy as an answer
So I see at least two scenarios. One in which neutral and ground are connected at load, but only the neutral is connected to rcd. In this case rcd will trip when load is connected. The other scenario is where neutral and ground are connected at load and also at rcd. In this case the rcd will not trip. Now suppose there is short to the case but it is perfectly isolated. In this case the rcd would not sense a fault, correct. You now come along and touch the device and provide a path to ground. As I see it the rcd will trip but you might feel a brief shock. But if case is grounded separately the rcd hopefully trips before you make contact with the faulty device. Does anyone else see it the same way or am I way off.
it makes no difference if casing is connected to neutral in the appliance
or few meters away in the breaker panel
in any case if "live" touches the casing MCB will trip cause of short circuit,
not RCD. in a case MCB fails for some reason and casing is live
and grounded person touches it small current will flow through
a person but only for 25-40ms. now we come to sensitivity of your
RCD
"To prevent electrocution, RCDs should operate within 25–40 milliseconds with any leakage currents (through a person) of greater than 30 mA, before electric shock can drive the heart into ventricular fibrillation, the most common cause of death through electric shock."
we for example have 500mA RCD so it is questionable would it save a person
this whole grid is shit and requires this overcomplex protection,
with greater potential for failure.
we should be using say 30v instead of 120 or 240 at cost of thicker conductors
but no danger of shock.
(yea, theoretically even 24v can kill you if you are wet but still)
grid of the future is no grid
i am looking at these high voltage long distance dc transmission lines
gaining popularity lately and transmission lines in general
such monstrosity, obsolete for 150 years
Quote from: nix85 on April 29, 2021, 07:42:06 AM
it makes no difference if casing is connected to neutral in the appliance
or few meters away in the breaker panel
in any case if "live" touches the casing MCB will trip cause of short circuit,
not RCD. in a case MCB fails for some reason and casing is live
and grounded person touches it small current will flow through
a person but only for 25-40ms. now we come to sensitivity of your
RCD
"To prevent electrocution, RCDs should operate within 25–40 milliseconds with any leakage currents (through a person) of greater than 30 mA, before electric shock can drive the heart into ventricular fibrillation, the most common cause of death through electric shock."
we for example have 500mA RCD so it is questionable would it save a person
this whole grid is shit and requires this overcomplex protection,
with greater potential for failure.
we should be using say 30v instead of 120 or 240 at cost of thicker conductors
but no danger of shock.
(yea, theoretically even 24v can kill you if you are wet but still)
grid of the future is no grid
it makes every difference where the neutral is connected. in the panel the ground is tied to earth,
no matter what goes on in the appliance and neutral the ground line will remain safe.call it redundant if you like it is safe. your RCD breaker will kill somebody. at 500ma you are going to be standing there with smoke coming out your ears 6 months later when they cut off your power for non payment. also i have one GFI in my house, i'm sure many are similar. i bet there are service panels in my countythat still have fuses. would you trust your life to a 30 year old RCD?
grounding is not complicated, run the ground wire to every metal junction box where you have connections.it is also the law as it is required by code.
Quote from: fritznien on May 02, 2021, 03:41:47 AM
it makes every difference where the neutral is connected. in the panel the ground is tied to earth,
no matter what goes on in the appliance and neutral the ground line will remain safe.call it redundant if you like it is safe. your RCD breaker will kill somebody. at 500ma you are going to be standing there with smoke coming out your ears 6 months later when they cut off your power for non payment. also i have one GFI in my house, i'm sure many are similar. i bet there are service panels in my countythat still have fuses. would you trust your life to a 30 year old RCD?
grounding is not complicated, run the ground wire to every metal junction box where you have connections.it is also the law as it is required by code.
there is no difference if neutral is connected to the casing
in the appliance itself or few meters away in the box
as shown in the diagram below
again, if "live" came into contact with the casing you would have a short
and MCB would trip near instantly. it is highly unlikely person would
touch the casing at that very instant and if they did RCD trips.
but let's say neutral is damaged (no "return path")
and "live" comes into contact with the casing. now nothing happens
until a person touches the case and if there was not for RCD you would
possibly get killed. but now that small current passes through you and back
to neutral through earth bypassing the RCD it detects the difference in current
between two wires and trips the switch and you are saved.
hopefully it is clear how extremely unlikely the second scenario is.
you would need a socket with broken "neutral", that is, a dead
socket you did not notice it's dead. then you would need
an appliance in which isolation broke on "live" and managed to
touch the casing. then you would also need bare feet and "hopefully"
wet floor to make good "return path". and even if all that happens
RCD is still there to protect you.
i agree 500mA is potentially dangerous as i said myself
but you're not gonna be "standing there with smoke coming out your ears"
it is unlikely you would actually get killed by 500mA for 30-40mS
but if current passes through your heart you just may.
do you know when they electrocute criminals it sometimes takes
20 minutes to kill them at much greater current. i don't even wanna go there.
it would be far better if it was closer to 30mA, but they say 30mA
trips too easily when air is bit humid, like in bathroom
if i was designing the installation i would sure use RCD closer to 30mA
here is another puzzle for you. i mentioned it before.
my father says sometimes when he was doing electric work
in other houses, when he earthed the neutral RCD tripped
he ascribed this to difference of potential between local earth
and that in transformer station
but does that really make sense. first of all that voltage difference
is small, few volts at most, and considering the great resistance
of earth that current would probably be below tripping current
maybe not https://en.wikipedia.org/wiki/Soil_resistivity#Corrosion
secondly, if neutral is earthed correctly, after the RCD looking from
the perspective of the house, then circuit between two earths
does not pass through the RCD.
Quote from: nix85 on May 02, 2021, 08:34:45 AM
there is no difference if neutral is connected to the casing
in the appliance itself or few meters away in the box
as shown in the diagram below
again, if "live" came into contact with the casing you would have a short
and MCB would trip near instantly. it is highly unlikely person would
touch the casing at that very instant and if they did RCD trips.
but let's say neutral is damaged (no "return path")
and "live" comes into contact with the casing. now nothing happens
until a person touches the case and if there was not for RCD you would
possibly get killed. but now that small current passes through you and back
to neutral through earth bypassing the RCD it detects the difference in current
between two wires and trips the switch and you are saved.
hopefully it is clear how extremely unlikely the second scenario is.
you would need a socket with broken "neutral", that is, a dead
socket you did not notice it's dead. then you would need
an appliance in which isolation broke on "live" and managed to
touch the casing. then you would also need bare feet and "hopefully"
wet floor to make good "return path". and even if all that happens
RCD is still there to protect you.
i agree 500mA is potentially dangerous as i said myself
but you're not gonna be "standing there with smoke coming out your ears"
it is unlikely you would actually get killed by 500mA for 30-40mS
but if current passes through your heart you just may.
do you know when they electrocute criminals it sometimes takes
20 minutes to kill them at much greater current. i don't even wanna go there.
it would be far better if it was closer to 30mA, but they say 30mA
trips too easily when air is bit humid, like in bathroom
if i was designing the installation i would sure use RCD closer to 30mA
you miss the point. ground is earthed at the panel and at the transformer center tap.it is your safety. without the ground line a fault can put hot to a metal case.with neutral hooked to the metal case any fault with the neutral puts the case to hot.that fault could be a clean break or an intermitant or resistive it don't matter.
your RCD trip point is 500ma so you could be there for the rest off your life at 400ma.what if there is no RCD? is every breaker in your panel an RCD? none of mine are.what about an old house with fuses?no one has said you can not have an RCD, but do you? bigclive on utube shows all kinds of equipmenttaken apart to show how it works or not, one he did had a fake breaker switch!
Quote from: fritznien on May 04, 2021, 12:46:12 AM
you miss the point. ground is earthed at the panel and at the transformer center tap.it is your safety. without the ground line a fault can put hot to a metal case.with neutral hooked to the metal case any fault with the neutral puts the case to hot.that fault could be a clean break or an intermitant or resistive it don't matter.
your RCD trip point is 500ma so you could be there for the rest off your life at 400ma.what if there is no RCD? is every breaker in your panel an RCD? none of mine are.what about an old house with fuses?no one has said you can not have an RCD, but do you? bigclive on utube shows all kinds of equipmenttaken apart to show how it works or not, one he did had a fake breaker switch!
"ground is earthed at the panel and at the transformer center tap.it is your safety."
you are repeating what i already said and what everyone knows
ground is just a second neutral, they meet at the panel where they are
earthed, "neutral" is also earthed at the central tap of the transformer as
both diagrams i posted show. i even talked about potential difference
between two earths
"without the ground line a fault can put hot to a metal case"
again, i said this since the first post and everyone knows this
i'm not missing the point, you are focusing on extreme scenario of no RCD at all.
i am assuming every modern household should have an RCD/MCB
(RCBO or GFCI breaker) and i believe great majority does
i already agreed ground should be there as redundancy"your RCD trip point is 500ma so you could be there for the rest off your life at 400ma"
that can't happen. i got RCD+MCB (RCBO)
if "live" touched the case, MCB trips instantly.
without RCD, if you happened to touch the case at the moment it
became "live", do you really think a fuse would save you.
"The operating time is not a fixed interval but decreases as the current increases.
Fuses are designed to have particular characteristics of operating time compared
to current. A standard fuse may require twice its rated current to open in one
second, a fast-blow fuse may require twice its rated current to blow in 0.1 seconds,
and a slow-blow fuse may require twice its rated current for tens of seconds to blow."
fast RCD is a must