Switching the mains to DC

[Gyro]

Problem breaking DC? What problem? 

[Sorama]

And the wires that would be used for domestic appliances would be rather thin.

[Marco]

You could ameliorate it a bit by going the UK way and taking it further. Plug? Fuse. Then also, socket? Fuse. Switch? Fuse. Every accessible node gets a fuse.

[tooki]

You could ameliorate it a bit by going the UK way and taking it further. Plug? Fuse. Then also, socket? Fuse. Switch? Fuse. Every accessible node gets a fuse.

That’s affordable to do for AC fuses.

DC-rated fuses are larger, more complex, and much more expensive.

[Siwastaja]

You could ameliorate it a bit by going the UK way and taking it further. Plug? Fuse. Then also, socket? Fuse. Switch? Fuse. Every accessible node gets a fuse.

When fuses for DC are more expensive, then the actual result would be the opposite, put fewer of them, not more. Or accept a significantly more expensive system, which is what OP wasn't anticipating.

[Zero999]

You could ameliorate it a bit by going the UK way and taking it further. Plug? Fuse. Then also, socket? Fuse. Switch? Fuse. Every accessible node gets a fuse.

When fuses for DC are more expensive, then the actual result would be the opposite, put fewer of them, not more. Or accept a significantly more expensive system, which is what OP wasn't anticipating.

That would be less safe.

Also DC has will produce more of an arc flash which increases the fire risk.

[jonpaul]

Old arguments:

see 1890s War of the Currents:

Thomas Alva Edison: DC (Pearl St NYC first)

Nikola Tesla: AC (Niagara Falls)

Enjoy


Jon

[TimFox]

Old arguments:

see 1890s War of the Currents:

Thomas Alva Edison: DC (Pearl St NYC first)

Nikola Tesla: AC (Niagara Falls)

Enjoy


Jon

Of course, Pearl St in NYC was close to the loads in Manhattan.
Niagara Falls had far more available power, but is farther from Manhattan.
During the political and commercial war between the two approaches, New York State installed an electric chair for execution.
Since it used AC, Edison wanted to call the method of electrocution "Westinghousing", claiming AC was more dangerous to the general public.

[Circlotron]

A properly sized polarised snubber would look after switch contact arcing and maybe fuse clearing as well.
 And add even more to the cost, of course.

[jonpaul]

Edison's first DC dist had very limited range, perhaps a few miles.

The Manhattan DC distiruibution system persisted till the 1960s.

Tesla conceived the HV AC T&D and later Charles Proteus Steinmetz at GE worked out the mathematics, and practical AC system by 1900-1920s.

Jon

[TimFox]

Edison's first DC dist had very limited range, perhaps a few miles.

The Manhattan DC distiruibution system persisted till the 1960s.

Tesla conceived the HV AC T&D and later Charles Proteus Steinmetz at GE worked out the mathematics, and practical AC system by 1900-1920s.

Jon

DC distribution in major Eastern US cities, including NYC and Boston, led to all sorts of "AC-DC" jokes, many of which are unsuitable for a technical forum. 
The "All-American Five" 5-tube AM radios could run on either (sending the AC or DC input through a tube half-wave rectifier and supplying the heaters in series from the then 110 V AC or DC), hence the term "AC-DC" for such radios.  This included the famous E H Scott SLRM marine radio, since WW II merchant marine ships often had DC power.
The commercial distribution of DC was ended after the utility companies supplied rectifiers to operators of elevators and other DC equipment.
Funny how waves of the past are advertised as waves of the future...

[Zero999]

A properly sized polarised snubber would look after switch contact arcing and maybe fuse clearing as well.
 And add even more to the cost, of course.

That will only reduce the effect of the inductance. It will not change the fact that the arc is more difficult to quench because the current doesn't periodically stop and change direction over a hundred times per second.

[jonpaul]

DC breakers use arc chutes, compressed air, baffles to extinguish the arc.

more difficult as V and I increase.

Check breaker and fuse ratings.

j

[NiHaoMike]

As a compromise, how about pulsed DC? The interruptions would help suppress arcs the way AC does, while only requiring a single solid state switch to make the pulsed DC from constant DC.

[Zero999]

As a compromise, how about pulsed DC? The interruptions would help suppress arcs the way AC does, while only requiring a single solid state switch to make the pulsed DC from constant DC.

What advantages would that have over AC?

It is AC plus a DC bias. If it's squarewave, then there are high frequency components, which depend on the rise and fall times.

I would also expect it to be not much better than DC, because the current doesn't change direction, the arc will still be harder to break, compared to DC.

[Gyro]

Agreed. It would only save 3 diodes over an AC SMPS and need the same size reservoir cap, effectively zero cost or size saving. It still wouldn't work with induction motors or transformers.

Something I don't think anyone has mentioned is switch contact material migration with DC switches. A well known problem with car ignition contact breakers of old (with Tungsten contacts no less), resulting in a pip forming on one contact and a corresponding crater on the other. With the softer Silver based contact materials used in normal domestic switches, this migration would cause slower contact break, resulting in greater arcing, resulting in more migration, resulting in...

[Marco]

DC breakers use arc chutes, compressed air, baffles to extinguish the arc.

I feel they are too much designed like AC breakers, relying on the fault current to pass a mechanical stability point will always be kinda slow. It's the current squared which drives energy more than inductance after all.

[NiHaoMike]

What advantages would that have over AC?

Only requires one solid state switch to make from a constant DC source. And that can be on the low side to also keep the drive circuit simple.

[Siwastaja]

What advantages would that have over AC?

Only requires one solid state switch to make from a constant DC source. And that can be on the low side to also keep the drive circuit simple.

Of course it makes total sense to save $2 on a trivially cheap part and have to spend $200 elsewhere 

[Zero999]

What advantages would that have over AC?

Only requires one solid state switch to make from a constant DC source. And that can be on the low side to also keep the drive circuit simple.

It will cost more than pure DC and three phase AC. All generators still need to be synchronized, as it's still AC, power can be only delivered part time and there's the additional complexity, inefficiencies of switched mode supplies. It appears as though you haven't thought it through.

[Siwastaja]

What advantages would that have over AC?

Only requires one solid state switch to make from a constant DC source. And that can be on the low side to also keep the drive circuit simple.

It will cost more than pure DC and three phase AC. All generators still need to be synchronized, as it's still AC, power can be only delivered part time and there's the additional complexity, inefficiencies of switched mode supplies. It appears as though you haven't thought it through.

To be fair, NiHaoMike said it would be a compromise. This would be a very typical textbook example of what a compromise is, in political terms.

[Marco]

Something I don't think anyone has mentioned is switch contact material migration with DC switches. A well known problem with car ignition contact breakers of old (with Tungsten contacts no less), resulting in a pip forming on one contact and a corresponding crater on the other. With the softer Silver based contact materials used in normal domestic switches, this migration would cause slower contact break, resulting in greater arcing, resulting in more migration, resulting in...

I think a two pole switch with a couple passives would be similarly robust to a one pole switch with AC. Capacitor protects one switch during turn off, then the tank oscillates to let the other turn off with AC.

[Zero999]

What advantages would that have over AC?

Only requires one solid state switch to make from a constant DC source. And that can be on the low side to also keep the drive circuit simple.

It will cost more than pure DC and three phase AC. All generators still need to be synchronized, as it's still AC, power can be only delivered part time and there's the additional complexity, inefficiencies of switched mode supplies. It appears as though you haven't thought it through.

To be fair, NiHaoMike said it would be a compromise. This would be a very typical textbook example of what a compromise is, in political terms.

Not practical or technical then, purely political.

[TimFox]

Again, the original question (perennially posed by novices) is whether to switch the mains (i.e., the power delivered to my house from the utility company) from 60 Hz AC to DC.
I see no benefit to me from that expensive change in distribution from the 3 kV to 240 VCT transformer behind my house, fed from a local substation, and the longer distance transmission of relatively low voltage DC from that substation  roughly one mile from my property.
Should I need DC distribution within my house, I could pay for a suitable solid-state regulated rectifier and expensive circuit breakers or solid-state switches, but I see no benefit to me worth changing all of my appliances.

[David Hess]

The advantage for large appliances would be not requiring the AC to DC conversion before the inverter which is driving the motor.  I doubt that makes up for all of the disadvantages, and somewhere an even larger AC to DC conversion is necessary.

Some data centers are setup this way, but they start the centralized AC to DC conversion at a much lower voltage.

At the distribution level DC to DC conversion would replace AC transformers.  Just the last stage of AC or DC to DC conversion from 2.4 to 32 kilovolts to 240 split phase, or whatever, is not easy with power electronics.  Is this suppose to be economical and reliable compared to a large passive transformer made from copper, aluminum, and steel?

A pig pole transformer might cost $10,000.  Can it be replaced with a AC or DC to DC converter for that cost?