Testing AC Shore Power

[GordMay]

Professional Boatbuilder magazine (on-line) Issue 100 April/May, page 56:

”Ground Fault, Interrupted” ~ By Nigel Calder

http://www.proboat-digital.com/proboat/200604/

So, if I read that right, measuring between the nuetral and hot leads should not read 220volts, and if I stick the end of a flourescent bulb in the water next to the dock it should not light up?
Just kidding. Good article. Nice common sense tests.Truth be told, it would be scary to check the shore power in this marina. I did that once. We go through zincs really fast in this harbor.

[Alan Wheeler]

I don't get the joke Kai. I have 230V between hot and neutral and how the heck do you think we get under water lighting effects around our boats here.

I forgot, you Kiwis have BIG power over there. No measly 110volt for you In all seriiousness, we have reall problems with the shore power here. ON several occasions when diving on the boat I have gotten zapped by the conduit that runs along the dock when climbing out. I have taken to using the inflatable as a dive platform even when working in the slip. THe harbor's side of the game is that if anyone complains they will kick everyone out until repairs are made. I have my own ace in the hole. Just waiting to get ticked off enough to use it.

[CaptainK]

I have one question.

Why is it that England and Kiwiland has such high voltage in their electrical outlets?

What's the big main advantage over the US's 110V electrical outlets?

[Alan Wheeler]

We're "Real blokes" is why K.
There are advantages and disadvantages in what ever system. We have here in NZ a system called MEN. Multiple Earthed Neutral. I do think this system is one of the most stable and safest of all. But it's only a small part of the overall generation and distribution system we have here in NZ. And waay to complex and long winded for this board.
But to your main question,
Having a higher voltage also means lower current, so we can run longer distances and use smaller cabling. Wall sockets and appliance plugs have much smaller pins making them smaller and lighter. We are also 50Hz as against your 60Hz system. This also makes a difference. Transformers in electrical equipment have to be much heavier in core material, which makes them heavier in weight, bigger in size and of course more expensive.
Just why the 110/115/120/220/230/240 around the world, I don't have a clue.

For world Cruisers, here is a handy page of info.
http://Kropla.com/electric@.htm

[Boracay]

I'd be very careful swimming round a marina.
Check out :-
http://www.ecmweb.com/mag/electric_case_hot_marina/
and
http://www.mikeholt.com/newsletters....36#addComments

[coot]

Originally Posted by Alan Wheeler

Just why the 110/115/120/220/230/240 around the world, I don't have a clue.

The choice of 120 or 240 volt AC power is arbitrary, as is the choice of 50 or 60 Hz. But if you are installing one of the first electrical distribution systems, you have to pick something. Higher voltages mean thinner wires for the same amount of power, but then why 240 instead of 500 volts? There are tradeoffs to be made, you pick something, and design around your choice. A hundred years later, somebody wonders why you didn't make the same choice as the guy 5000 miles away.

Typically, conventions like this follow political alignments. For example, many former British colonies use the 240 V 50 Hz power. I expect this is because they sent people to study in the UK and bought UK equipment. If they bought stuff from the US, they would have 120 volt 60 Hz. Some countries do have both.

In the US, we have 120 volts 60 Hz pretty much everywhere, but that was not always the case. For example, San Francisco originally had 50 Hz power until sometime in the 1930's (IIRC). A 50 Hz clock would run 20% fast on 60 Hz power. At the transition, the city would either fix your clock or let you trade it in for a new one if they couldn't fix it easily enough. They dumped tens of thousands of useless 50 Hz clocks in the bay.

You can see that changing is disruptive, but at the time it was considered an advantage to use the same standards as the rest of the country. Now, we have such a large installed base of equipment that it would be prohibitively expensive to change, so we just keep doing what we've been doing...

I guess I am glad I am in salt water. It is amazing what electricity can do. Subtle but deadly. It is interesting, the people that are responsible for our shorepower are not marine electricians. They do have basic electrical knowledge, but boats are a special case as is shown in these two links. It just goes to show when you put non boat people in charge of boating safety issues, bad things happen. I know a number of union electrician who do not know ohms law.

Coot, it is interesting that in this age of snesitive electical components such as computers, even the cycle rate is not consistant. I find it interesting that computers built all over the world, to work all over the world are able to be adapted to the differences. run a computer monitor designed around 60 cycles on a 50 cycle system and see what happens. A true formula for epileptic seizures.

[Alan Wheeler]

That was the basis for the Switchmode power supply being designed into most cosumer electronics. It meant that TV and Stereos could be made for any market.
Coot, most british colonies, NZ being one of them, did indeed use British equipment. Early in our colonial history, most all industrial equipment was brought in from England. All the power generaters for instance, were all made in England. We had no access to American trade at all way back then. The same for Australia. I can't say if the same were true for other Countries that were under British control.