83
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 ...
- 170k
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 ...
- 72.6k
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 ...
- 752
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 ...
- 4,145
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: ...
- 80.2k
33
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 ...
- 13.9k
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 ...
- 18.1k
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 ...
- 170k
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 ...
- 170k
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. ...
- 32k
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 ...
- 54.9k
28
votes
How to ramp up a factory consuming a lot of energy?
I'm not an electrical engineer but I am involved in specifying some pretty large rotating equipment, up to 2MW - specifically, combustion air fans for industrial furnaces and hydrogen plants (steam ...
- 941
27
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 ...
- 170k
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 ...
- 6,498
25
votes
Accepted
How to ramp up a factory consuming a lot of energy?
The classic case of users managing their demands was at the JET fusion facility, where they could call on the grid for only some of their required power, but had to install a ginormous flywheel + ...
- 159k
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 ...
- 170k
20
votes
Accepted
What is the reason for these utility poles with a 6-sided hole in the middle for conductors
It appears the reason for these pylons is due to limited right-of-way (ROW) when the line was built. There was only a 50ft wide strip through which the line was allowed to be built on, so a narrow ...
- 63.8k
19
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 ...
- 19.9k
18
votes
Accepted
Why does a delta/wye transformer make 30 degrees phase shift ?
Let's call the 3 phases A, B and C and let's say we notionally have a neutral wire. Neutral is basically 0V in the system.
The "A" phase voltage (to neutral) is my chosen reference that all other ...
- 437k
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
15
votes
How to ramp up a factory consuming a lot of energy?
I know that a paper mill on start up would demand power from the grid and this was planned for by phoning the grid people.
Once started, the mill had sufficient power to run itself and supply excess ...
- 6,407
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 ...
- 16.1k
14
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 ...
- 17.3k
14
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 ...
- 148k
13
votes
How can energy "physically" be fed back into the grid?
The way I see it is that a utility is able to send 3 phase electricity over multiple lines, for example, 1 phase per line, for a 3 phase power supply. Most homes only need one phase, and therefore one ...
- 18.7k
12
votes
Why three-phase power? Why not a higher number of phases?
Three phase has a very important property: if you look at power (V^2/R) across all three phases and sum them, that power is CONSTANT across the entire cycle. This means 3 phase motors can drive at a ...
- 2,896
12
votes
What is this device attached to a high-voltage power line?
It may be a splicebox for optical fiber. Many power lines carry fiber inside one of the wires for telemetry and control.
- 8,881
11
votes
Accepted
Why are twisted pair cables used in electric power distribution systems?
After nearly 2 years, I found the answer to my question.
I recently walked past an electric utility's storage yard and noticed this reel of twisted pair cable.
The manufacturer is Southwire ...
- 605
Only top scored, non community-wiki answers of a minimum length are eligible