81
votes
Accepted
Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?
simulate this circuit – Schematic created using CircuitLab
Figure 1 and 2. showing the danger of earthing through neutral.
In the first example the Lunatic 'Lectrician has 'grounded' the lamp ...
- 159k
75
votes
Accepted
Can a bird, previously at earth potential, get electrocuted by landing on a powerline at high-enough voltage due to the initial "equalization charge"?
Assuming the bird still is at earth potential when entering in contact with the wire (say, it jumped right on it from the pole).
There are lots of unknowns in this problem but let's try to fill some ...
- 9,682
72
votes
Why are consumers located near high-voltage lines typically not connected to those lines but instead are connected through a lower high-voltage line?
HV (66kV - 500kV) is... difficult to deal with.
I will rattle off reasons I can think of from the top of my head.
All figures that follow (weights, dollars) are order-of-magnitude guesstimates.
...
- 8,691
64
votes
What is this object found on transmission lines?
The are called aeolean vibration dampers, or Stockbridge dampers. They aren't rigid weights: the weights vibrate on the ends of the centre-clamped bars.
You can see the wavelength that they are ...
- 3,918
41
votes
Accepted
Why do condors get electrocuted by power lines?
Wingspan. Condors are large birds and can easily bridge the gap between the divided power lines. Pigeons, Crows, etc, are tiny. The only way to get shocked is by completing a circuit after all.
Which ...
- 70.7k
41
votes
Why does power dip during a lightning storm?
Janka comes close, but there are are several more details. (Note, recalling from EE classes about 45 years ago.)
On many high voltage lines there are arc electrodes at various points. When ...
- 753
37
votes
Accepted
Why three-phase power? Why not a higher number of phases?
In addition to PlasmaHH's answer, industry uses almost exclusively three phase power since an induction motor needs at least a three phase supply to start and run in a known direction. Single phase ...
- 4,075
33
votes
Accepted
Do electricity meters contain inverters?
There is no conversion going on because it isn't needed.
The 400 V is the voltage between two phases of the 3-phase 380V grid.
The 230 V is the voltage between one phase and neutral.
Read more at: ...
- 78.7k
33
votes
Accepted
When a wind turbine does not produce enough electricity how does the power company compensate for the loss?
This is correct. When the demand exceeds supply, voltage will sag and frequency will drop (which can risk equipment failure and is certainly an undesirable situation). The operators of power grids ...
- 13.6k
32
votes
Accepted
What is this device attached to a high-voltage power line?
These seem to be optical fibres.
Figure 1. Close-up of fibres branching onto each of the lightning protection wires.
Thanks to your high-res photo we can see the fibres at (1) and (2). Note that ...
- 159k
32
votes
Why does power dip during a lightning storm?
Lightning brownout procedure:
When lightning hits an overhead power line, there is overvoltage at first, for about 100 milliseconds.
This overvoltage creates an arc at a nearby pole.
The arc works as ...
- 13.1k
30
votes
Accepted
Why 3 phase and not 1 phase power transmission?
Why not three lines all in the same phase?
Because then there is no return path.
Because single phase has no "rotation". Three phase makes it very simple to make a rotating motor with phase sequence ...
- 159k
30
votes
Accepted
Using DC in transformers?
Transformers are AC only.
Running DC through a transformer basically gives you a heater.
Critically, transformers work through the fact that a change in magnetic field induces a voltage in a wire. ...
- 31.5k
29
votes
What happens to excess energy fed into the power grid?
This is, as you might imagine, not something that has just one solution and the problem in itself is pretty complex as well. Let's break it down.
The power grid as it exists now in most civilized ...
- 8,018
29
votes
What is the speed of "electricity"?
For most of the copper wire and traces you see, about 60% the speed of light in a vacuum. The energy is the signal so they are the same.
The speed of electrons is much slower...slower than walking ...
- 45.9k
26
votes
How can energy "physically" be fed back into the grid?
I cannot comprehend how, for example, multiple homes can feed their ... energy into a grid using the lines of the public utility.
That's the way the power stations do it, so why not? All that is ...
- 159k
25
votes
Why three-phase power? Why not a higher number of phases?
When you have single phase power distribution, you need one phase and one return, both carrying the same current.
If you now instead use symmetrical three phase power, you use three phases with a ...
- 6,309
23
votes
Can a bird, previously at earth potential, get electrocuted by landing on a powerline at high-enough voltage due to the initial "equalization charge"?
I mostly agree with Andy Aka explanation. I'll give a more detailed theory though (of course I might be overlooking something).
A body doesn't have a capacitance by itself, as it always needs the "...
- 2,175
22
votes
Why are the power transmission/distribution systems AC and not DC?
There are several reasons. One: power loss in a wire is I^2 * R. Therefore it is better to transmit power at very high voltage and low current. AC is much more easily boosted to high voltage (no ...
- 24.2k
22
votes
Why do condors get electrocuted by power lines?
Wingspan, most likely.
Figure 1. The condor, monotypic genus, is the largest bird in the Western Hemisphere with a wingspan of up to 3.5 m.. Photo by Colegota on Wiki Commons.
Figure 2. Typical ...
- 159k
20
votes
What is the speed of "electricity"?
(added) The wave speed ratio of electricity v/c is limited by the relative permetivvity, \$ε_r\$ of insulation around the conductor for the speed, v relative to speed of light, c in a vacuum. It is ...
- 133k
18
votes
Why three-phase power? Why not a higher number of phases?
Three is the lowest number of phases which are equally spaced around the circle, and which can be used to create a rotating magnetic field in a given direction.
Any more phases just require more ...
- 19.3k
15
votes
What happens to excess energy fed into the power grid?
In Germany this May, the price paid for renewable energy actually swung negative, as they had too much of it. In other words, they were charging producers to take the excess energy. So they dealt with ...
- 327k
15
votes
Why three-phase power? Why not a higher number of phases?
Addition to other answers:
The main purpose is that having at least three phases allows your motor to start in expected direction. For one-phase induction motors some workarounds are necessary (like ...
- 499
14
votes
Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?
While usually neutral wire and earth wire are at the same potential, and can therefore be effectively swapped from a purely electrical point of view, the way they are connected makes them very, very ...
- 15.6k
13
votes
What is the speed of "electricity"?
You need to separate two slightly different concepts.
There is the electron drift velocity which is the speed at which the charge carriers in the wire move due to the electric field (and is ...
- 16k
13
votes
Accepted
Australia–ASEAN Power Link - why not build the solar farm near Singapore?
The land area required is unavailable in Singapore.
The land area is potentially available in Malaysia or Indonesia.
Land in the Australian outback is available and generally of low cost relative to ...
- 142k
Only top scored, non community-wiki answers of a minimum length are eligible