Quote Originally Posted by OldF View Post
One thing I almost forgot about is the resistivity. Maybe it has something to do with that it’s almost 40 years since I was studying electrical engineering.

However here have been talks about the resistance of water but water, as any other conductor, water don’t have a specific total resistance but the resistance (or impedance) depend on what kind of water (the resistivity of the conductor) and how much water is in question (the length and area of the conductor). The more water the less resistance.

With a cable it’s more simply because with a cable the electricity come in (usually) from one end and go out from the other end and the resistivity, length and area of the cable is known. With water it’s more complicated because in a case of an accident the circumstance varies a lot i.e. the type of water, the length and area of the water conductor.

The resistance is:

R (ohm) = resistivity of the conductor (ohm meter) * length of conductor (m) / area of conductor (m2)

As you can see in a case of electrical accident in water it can be difficult to assess the length and area of the water conductor and also with the resistivity if the type of water is not known.

Interesting article about bath tube accidents with self-testing (crazy). Nothing to do directly with hybrid cars but however with electricity and water.

http://www.powerlogic.com.au/Attachm...iegelmeier.pdf

As said in the summary the path electric source – human in – human out – water – ground or other terminal is more dangerous than the path electric source – water - human in – human out – water – ground or other terminal.




The case with my example was mainly to show that how a small fraction of the total current can be lethal to a human if a human body is in parallel with any other low level resistance.

In the picture below the human is in parallel with the load of the electric system. Imaging that the dotted line is water and the minus terminal is in water, the body and the water would be in series and parallel with the load. Now the question is: What is the probability for this kind of accident to happen. Luckily the bird is safe.



http://www.allaboutcircuits.com/text...-current-path/


Btw, idiots always exists. It seems that a very common electrical accident is when some idiots are climbing on the roof of a train.

http://www.tukes.fi/tiedostot/sahko_...nunen_2013.pdf
The incident with the train is fairly easy... in that case the human is the only conductor connecting the power to earth and the super high voltage (16 kv in sweden... don't know what finnish train systems run) can actually arc the air to human due to the high voltage and conduct to earth. Just a shame that railway operators have to be responsible for these idiots... let them burn I say!

In the case of the rally car, we still have to conclude that both poles have to be earthed through the water for this to work. It is true that different kind of water conduct differently... distilled fresh water is the worst conductor and salt water the best (due to the ions and free electrons etc etc). We know that we need a relatively high voltage to create any current in a human person.

This is why 12v and 24v systems can be touched and nothing happens...

We also know that voltage in a system of resistances distribute over the highest resistor with the greatest voltage and the lesser resistors with lesser voltage when in series.

We also know that the most current pass "the path of least resistance".

Below is a very simplified diagram of the situation. In reality it is endlessly more complicated but it is a simple map to help us understand what happens.



As seen in the diagram (where I have lied a bit and connected the left hand of human to the minus pole... but hey, resistors are addable in series so), the voltage over human is distributed over water 4 (I named the waters differently but in reality as it is just one big body of water so we could all have named them the same but for understanding, better like this) and then human... so it won't be many volts over human as the body of water 4, even in salt water, have resistance per meter and cable area...

Now if human really was in series with water only and was touching the minus pole, 100% of the current would pass through human... but that is not the case because there is earth, water and body shell also in parallel and they are much preferred path of the current to take so the current passing through human will be microscopic... at best.

Quote Originally Posted by OldF View Post
I’m far from an expert but after reading http://electronics.stackexchange.com...-as-a-resistor this maybe it’s the wrong way to measure the voltage just to put the small probes of a volt meter in the water. Maybe what you said (voltmeter across two points) was just an expression. As I said I’m not an expert in this case but as I understand to get the true value of the voltage/current (or measuring the resistance) true the water is to have electrodes covering the whole area of the water where current/voltage is applied to the water (+ terminal of a battery or the “hot” wire of a house case) and electrodes covering the whole area of water where the current goes back to the source, i.e. path from terminal to terminal in a battery case or a path from “hot” wire to ground in a house case or vice versa. (- terminal of a battery or the ground in a house case).
You need to remember that there is no ground in a battery system of a car (other than the bodyshell which is used as a common 0 of sorts... I guess you can regard that as ground but it is important to remember that it is not the ground you stand on).

The reason why trains and all other land based electricity is dangerous is because it returns through ground (yep, that is right, the 0 cables (blue) of almost all land based equipment today, including high voltage transformers etc etc, are earthed and return the current through ground... and yet you don't get fried when you put a shovel in the ground... same thing as the rally car in the water really). When you touch any live electric bit, it always wants to return to earth... which is exactly why the bird in your chart is fine even if it were to sit on a live wire where the insulation is gone... the bird does not touch earth.

Quote Originally Posted by OldF View Post
No, we didn’t do such drastic laboratory works. And I won’t try it at home by putting the three phases of our sauna heater in the water.
I don't think your fuses would survive it and you probably have an earth fault breaker as well... so go ahead Ok no probably not, unforseen things will probably happen, but theoretically you'll be fine!

Generator tests are done without fuses and other safety equipment hahahaha, but there is a safety parameter... mostly because the pahses are live and bare and not because of the water... it is very interesting to watch