Thomas Edison vs Tesla

Edison and westinghouse pitched the ideas for a Generator, tesla high voltage ac, edison low voltage dc.

Great shows were put on, electrocution from both power sources, DC was supposed to hurt but not kill you... well I've been zapped a couple of times at 240ac but I've felt my muscles contract from the sparks from battery terminal clips when high current flows...

So it begs the question a high powered dc low voltage placed near your heart, this should be able to kill?

I can't comment on the safety aspect, but just imagine the size of the conductors in the distribution grid if we'd have gone the DC route. There wouldn't have been enough copper in the world.

Absolutely, electrocution is indeed possible with DC (it causes more muscle contraction than AC), both AC and DC kill.

BTW DC power transmission is employed, the problem is the large cost of 100kV inverters to convert back to AC A common use is to bridge between countries that use different line frequencies or to decouple segments of a power network so they don't have to be phase-locked.

High voltage high current DC can stop your heart. Think of TV tube caps. But while pondering the question, a bit of comic relief- Edison Vs Tesla

decouple segments of a power network so they don't have to be phase-locked.

Is that how they connect all those wind turbines?


Rob

Obligatory link to The Oatmeal:

http://theoatmeal.com/comics/tesla

I don't know if it's all true but it makes me mad every time I read that.


Rob

So it begs the question a high powered dc low voltage placed near your heart, this should be able to kill?

Fibrillation can start from as low as 150uA applied at the heart.

Graynomad:

decouple segments of a power network so they don't have to be phase-locked.

Is that how they connect all those wind turbines?


Rob

Actually any and all types of power generator plants that are to supply power to a common 'grid' must be phased-locked with the grid.

retrolefty:

Graynomad:

decouple segments of a power network so they don't have to be phase-locked.

Is that how they connect all those wind turbines?


Rob

I think it varies.

Actually any and all types of power generator plants that are to supply power to a common 'grid' must be phased-locked with the grid.

They will be phase locked whether they like it or not - failure to do so blows the fuses since an efficient generator set can carry vastly higher than normal currents if mis-phased. A series of generator sets on the grid has been likened to a row of heavy pendulums connected by cotton thread - if they are not in synchrony something breaks.

MarkT:

retrolefty:

Graynomad:

decouple segments of a power network so they don’t have to be phase-locked.

Is that how they connect all those wind turbines?


Rob

I think it varies.

Actually any and all types of power generator plants that are to supply power to a common ‘grid’ must be phased-locked with the grid.

They will be phase locked whether they like it or not - failure to do so blows
the fuses since an efficient generator set can carry vastly higher than normal
currents if mis-phased. A series of generator sets on the grid has been likened
to a row of heavy pendulums connected by cotton thread - if they are not in
synchrony something breaks.

Correct. Starting up or shutting off a plants grid connected generator is a very structured process often done in coordination with grid operators to slowly ramp up and down power as such generators cannot do 0-100% and 100%-0 instantaneously. First step is to syn up with the grid and then manipulate the generator’s phase control to force a specific amount of current onto the grid.

I can’t comment on the safety aspect, but just imagine the size of the conductors in the distribution grid if we’d have gone the DC route. There wouldn’t have been enough copper in the world.

Some of the super high voltage transmission lines are DC now. To bring DC to the home requires highly efficient DC-DC converters, however. In the beginning, transformers were a very nice way to transform voltages up and down. To do this with DC requires high voltage semidonductors.

Ther used to be a dc link between england and france to make best use of nuclear plants i think.

Hi, there is a HV DC link between Tasmania and Victoria. In the cases I have seen, Wind Turbines in a wind farm supply a common HV DC bus then it is cycloinverted into the national grid.

Tom...... :)

TomGeorge: Hi, there is a HV DC link between Tasmania and Victoria. In the cases I have seen, Wind Turbines in a wind farm supply a common HV DC bus then it is cycloinverted into the national grid.

Tom...... :)

Never heard of a cycloinvertor. Wikipedia says that cyclonconverter is used to convert AC to AC not DC to AC?

http://en.wikipedia.org/wiki/Cycloconverter

cycloinvertor cyclonconverter

Depends what university you went to and what text book (remember them) was your reference.

Tom… :slight_smile:
(PS, Here we will be relying on that Vic/Tas link today, because we have a significant loss in power production at the moment due to a power station failure, and it is going to be 40DegC plus.)

TomGeorge:
cycloinvertor cyclonconverter

Depends what university you went to and what text book (remember them) was your reference.

Tom… :slight_smile:

Got it, but what about the AC to AC Vc DC to AC as applicable to wind generators?

From what I understand, and will clarify when one of their techs comes by. Each turbine outputs AC, then rectified to DC, all the turbines in the farm supply the DC bus, so no frequency sync needed. At the terminal station of the farm the converters/inverters convert the DC bus to AC supply, depending on what transmission lines they are connected to.

Tom... 8)

TomGeorge: From what I understand, and will clarify when one of their techs comes by. Each turbine outputs AC, then rectified to DC, all the turbines in the farm supply the DC bus, so no frequency sync needed. At the terminal station of the farm the converters/inverters convert the DC bus to AC supply, depending on what transmission lines they are connected to.

Tom... 8)

Ok, but that sounds like standard invertors to convert the DC bus to the AC grid, not cycloinvertor or cyclonconverter?

Some of the super high voltage transmission lines are DC now. To bring DC to the home requires highly efficient DC-DC converters, however. In the beginning, transformers were a very nice way to transform voltages up and down. To do this with DC requires high voltage semidonductors.

Ther used to be a dc link between england and france to make best use of nuclear plants i think.

In some cases it is difficult to ensure the synchronization frequency and phase in networks. It is easier to rectify the AC voltage, transport it as DC and and recreate AC after transport.

In all continental Europe the electrical network is fully synchronized but apparently it is more difficult with some islands even if the frequency is the same. :grin: