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electrofelon said:
Is one of the conductors of the system connected to Earth? That is what system grounding is.
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Yes if there is a fault. The distribution system for domestic residences starts at 11V and drops to 400/230V. The earth is at the distribution point in normal circumstances the earth doesn't conduct current. If a fault occurs then current will flow into the earth. I don't know if I can make it any clearer........
 
Besoeker3 said:
Yes if there is a fault. The distribution system for domestic residences starts at 11V and drops to 400/230V. The earth is at the distribution point in normal circumstances the earth doesn't conduct current. If a fault occurs then current will flow into the earth. I don't know if I can make it any clearer........
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So the secondary wye point of the transformer is grounded/earthed? Is an overhead service drop just two conductor for single phase?
 
So the secondary wye point of the transformer is grounded/earthed? Is an overhead service drop just two conductor for single phase?
Normally we have 3-phase oil filled local units
 
What about rural areas without 3-phase distribution?
I imagine they have something like this

earthing2_tt.png
or this
earthing_tt.png
 
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CoolWill said:
Except you haven't. You have danced all around it. If you don't know just say you don't know. You'll look less foolish.
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Yes I don't understand why he doesn't answer the question or just won't say he doesn't know or doesn't want to answer...

Does anyone else know? Okay so my understanding is this: low voltage is basically 230Y/400. Commercial gets three phases and a neutral, residential generally just gets single phase, a line and the neutral. Correct?

Questions:
1. Is the wye point grounded? If so where? At the pole and also at the building like we do here in the states?

2. So is a single phase service drop just two conductors? Is the neutral a bare messenger with the single line conductor wrapped around it?

3. I assume three phases distribution is not run everywhere and that there must be single-phase distribution perhaps in rural or residential areas. So in that case it is just a single phase 230 volt transformer with one end grounded? (Relates to question #1 of course).
 
The IEC has standardized types of grounding systems in 60364-1, when doing any kind of comparison its helpful to take a minute and understand IEC terminology in terms of the NEC and then whatever country your working in or discussing etc;
It translates to NEC terminology like this,

Start at the secondary of a distribution transformer (utility side or a separately derived system)

The First Letter (I or T) indicates the relationship of the distribution transformer to ground.
T = direct connection of one point to earth.
I = all live parts isolated from earth, or one point connected to earth via a high impedance.

The second letter indicates the relationship of all exposed-conductive-parts and any equipment grounding conductors to a grounding electrode system.
T = direct electrical connection to a grounding electrode system independent of any other grounding electrode system.
N = direct electrical connection of the neutral point or a line conductor to the grounding electrode system and thus the equipment grounding conductors.

Subsequent letter with a dash - (if any) and describe the arrangement of neutral and equipment grounding conductor
S = Grounds and neutral (or grounded phase) are run separately all the way from the distribution transformer.
C = neutral (or grounded phase conductor) and equipment grounding provided by the same conductor

So what we typically have here under the NEC is called TN-C-S
T) Because at the secondary we have a direct connection of one point to ground;
N) We have direct electrical connection of the neutral point or a line conductor to the grounding electrode system and thus the equipment grounding conductors.
Then for the conductors
-C The utility neutral is combined with the equipment grounding conductor until the service disconnect.
-S After the service disconnect they are separate

Under the NEC a ungrounded system with ground detectors would be a IT system.

electrofelon said:
Does anyone else know? Okay so my understanding is this: low voltage is basically 230Y/400. Commercial gets three phases and a neutral, residential generally just gets single phase, a line and the neutral. Correct?

Questions:
1. Is the wye point grounded? If so where? At the pole and also at the building like we do here in the states?
Click to expand...
The main earthing systems in the UK TN-C-S,
but they also allow and have are TN-S and TT
TN-S is that Mtnelect fells dream, the neutral is bonded once at the secondary then everything is separate after that.
So for a 208/120 three phase service you'd have 5 wires from the utility.
TT is when a the neutral or one of the phases on the secondary is grounded to a ground rod at the pole but then that's it, its ran insulated after that, then at your house you establish a GEC connect all your equipment grounds to it but don't bond the neutral,
I am fairly certain this is how they do it in Japan.

electrofelon said:
2. So is a single phase service drop just two conductors? Is the neutral a bare messenger with the single line conductor wrapped around it?
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In areas with allot of underground distribution the service lateral looks like our MV cable, a concentric coax type, for a TT system the neutral is insulated or what we call covered.
electrofelon said:
3. I assume three phases distribution is not run everywhere and that there must be single-phase distribution perhaps in rural or residential areas. So in that case it is just a single phase 230 volt transformer with one end grounded? (Relates to question #1 of course).
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See my diagram in post #53 the only diagram I am unsure of is if there are old TT systems where at the pole center-tap is grounded.
I am fairly certain you can find 240/480 split phase in rural Scotland, and probably 220/440 in old parts of mainland EU and all the way east.
Rural parts of Australia and NZ also have 240/480.
But hopefully others will chime in and correct me as I probably missed something.
 
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