ECN Forum Forums General Topics of the Trade General Discussion Area An ideal system

I'm going to make you put on your thinking caps now. Suppose you were setting out to design an electrical system from scratch.

You have a completely free hand. You're not tied to using any type of connectors for compatibility, or using certain voltages because of existing equipment.

Yes, I know that's not very practical with the millions of installations already in use, but just pretend you were given the job of devising distribution systems for the first permanent Martian colony or something..!!!

What systems would you use for residential services? 3-wire at about the current 120/240V level? Would you prefer that even small appliances run on a higher voltage and maybe adopt a 3-wire 200/400 to 250/500 system so that each house only needed a 2-wire service for 200-250 volts?

If you were sticking with lower voltage, how about 3-ph 120/208 for residential? Would you rather see a British-type system where distribution is 3-ph 240/415V and houses just get one phase? Would you adopt some other standard supply voltage entirely: 175V? 300V? 2 What about commercial supplies?

Frequency: The current 50 or 60Hz standards or something different? Why? (I can't imagine anyone suggesting going back to a DC system, but if you want to, let's hear a good reason!)

Grounding arrangements: Would you like to stay with the current American system, or adopt something different? How about a separate ground wire back to the xfmr and the neutral grounded only at the xfmr? Or perhaps some other arrangement.

You get the idea. Any & all suggestions for devising the ideal system.

Well Paul,
how absolutley and uninhibitedly innovative you've allow us to be! To actually be so unrestrained of the all the powers that be leaves me somewhat at a loss here....
My choices are;
volatge
phase arangement
frequency
grounding configuration

My first concern and choice would be what interfaces best with alternatively contrived systems, and NOT with what the 'grid monger'junkies would have me do

For residential, I quite like the sound of a system they used in parts of Scandinavia (not sure if it still exists).
They had all 220-volt equipment fed from a 1-ph xfmr with a center-tap ground. In other words, very much like a U.S. residential arrangement but without any 120V circuits.
I'd keep what is now your neutral to the xfmr tap and use it solely as a grounding conductor.
As I see this proposed system;
Advantages: 220V power with only 110v to ground at any point. With no neutral as such, a N-G short couldn't go undetected; a short on either line to ground would trip a breaker. No need to worry about polarized plugs (equipment would have to be suitably designed, of course - Most already is, and many European countries don't have polarized plugs anyway).
Disadvantages: Cost of having double-pole breakers for every branch circuit. Awkward to do from a 3-ph distribution system. Any others?
What do you reckon?

[This message has been edited by pauluk (edited 10-02-2001).]

Well, the isolated or singular point of grounding at the X-former ( vs. our dual-usage N&G )would certainly end much squabble here.

A higher voltage would solve some V-drop problems, probably lessen conductor sizes a tad....

I can't figure a good reason for a different frequency???? Higher= more skin effect, lower= possible visual recognition.

Higher frequency = smaller transformers, but it would have to be much higher to make a significant difference (think of switch-mode power supplies), and then there'd be a whole load more problems.
50 or 60 Hz is probably about right. Or am I just being trapped by years of accepting this as the norm?
I'd like to see American/Continental type dedicated circuits for all major appliances, and I wouldn't use the British ring circuit. Too many complications.
.
P.S. Have you ever seen the German "Schuko" plug?

[This message has been edited by pauluk (edited 10-03-2001).]

One reason to dump 60HZ would be that it just happens to be in the range the really messes with the human heart. Higher frequencies, I understand, don't send the heart into ventricular fibrillation(<spelling?( ) as easily.
Nick

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[This message has been edited by Nick (edited 10-03-2001).]

Good point Nick. I remember hearing that too, though I'd forgotten about it for the moment.

Do you happen to know what sort of frequency we'd need to go up to in order to get out of the range most likely to cause fibrillation?

the German "Schuko" plug?

nope, ain't seen one...but knowing thier engineering it probably works better than it sounds..

the V-fib thing sounds interesting.

Along the same lines,I like the idea of a GFI main for safety, but not for nuisance trips, etc. I would prefer some sort of monitoring/notification system, with shutdown time proportional to the level of ma lost.

My vote would be similar to what is used on aircraft and shipboard systems--400 Hz 3 phase.

Primary advantages:

Smaller, lighter transformers/motors.

No visible flicker from fluorescent lighting.

Higher ripple frequency means smaller, lower cost filtering components (chokes and capacitors) in AC/DC power supplies.

The above mentioned cardiac fibrilation issue.

3 phase power available to residences would allow the use of lower cost motors for things like furnace blowers and well pumps, as well as doing away with failure-prone start/run capacitors and centrifugal switches. Also makes for easy reversal of rotation.

The standard US 3 phase voltage of 208Y/120 seems fine to me, but the plugs/receptacles would have to change. The German Schuko would be a good starting point. I also like the British "fuse in the attachment plug" idea for appliance protection.

A GFCI main breaker set at around 100 mA would provide primary protection against "bolted" ground faults, with 20-30 mA units (in the breaker panel) handling individual branch circuits as needed for personnel protection. Individual single-phase branch circuits protected at 10, 20, or 30 amperes for lighting, general receptacles, or special purpose receptacles. Circuits for large appliances (ranges, A/C, etc. would be 3 phase.

Breaker panels would have a combination of gas tube and MOV surge protection right at the service entrance, where it can do some good.

No. I looked for info but came up empty so far. I can't remember where I heard this. I'll keep looking and if I find something I will post it.