Grounding question

[nix85]

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

[nix85]

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.

[fritznien]

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!

[nix85]

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