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naveee
naveee • Oct 12, 2012

DC transmission

how we can transmit DC voltage to transmission lines...........( in case of AC we can step up the voltage usin a step up transformer).....wat is the way to step up the DC voltage ????????
Jeffrey Arulraj
Jeffrey Arulraj • Oct 12, 2012
The voltage generated is in AC form this is done the following steps
  1. Stepped up using step up transformer
  2. This is Rectified
  3. Filtered and converted into DC
  4. this can be fed to transmission lines directly
  5. on reception end it is oscillated and converted into AC
  6. Frequency is modulated
  7. then distributed after stepping down
Jeffrey Arulraj
Jeffrey Arulraj • Oct 12, 2012
https://www.google.co.in/imgres?imgu...kF4UNuRKYXnrAfC6IHAAw&ved=0CDgQ9QEwAw&dur=786

This link will help you further

do post the clarification you need
sowmiya vd
sowmiya vd • Oct 12, 2012
A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage. It is a class of switched-mode power supply (SMPS) containing at least two semiconductor switches (a diodeand a transistor) and at least one energy storage element, a capacitor, inductor, or the two in combination. Filters made of capacitors (sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple
sowmiya vd
sowmiya vd • Oct 12, 2012
boost convertor is called stepped up converter since it steps up the source voltage
Jeffrey Arulraj
Jeffrey Arulraj • Oct 12, 2012
Yeah true but a Buck converter can be used only when the op is to be greater than the ip

But since we have an AC voltage in generating stations Buck convertors are of little use here pal
sowmiya vd
sowmiya vd • Oct 12, 2012
buck converter is used when the op is to be lesser than ip so can we use boost- buck converter?
Jeffrey Arulraj
Jeffrey Arulraj • Oct 12, 2012
Sorry yer My mistake

It is boost converter but the input of a boost converter is DC and this is not generated from a power station in general and so we don't use it in practise

Some of the commonly available HVDC transmission cable omit this as high power boost converters are costlier to design and implement
vinod1993
vinod1993 • Oct 13, 2012
naveee
how we can transmit DC voltage to transmission lines...........( in case of AC we can step up the voltage usin a step up transformer).....wat is the way to step up the DC voltage ????????
Why do you want to transmit DC?(total losses are heavy, I gather) .AC transmission is economical you know.! It reminds me of the "War of currents" which was posted by bioramani sir long ago as a reply to some thread.! 😀
https://en.wikipedia.org/wiki/War_of_Currents
Jeffrey Arulraj
Jeffrey Arulraj • Oct 13, 2012
vinod1993
Why do you want to transmit DC?(total losses are heavy, I gather) .AC transmission is economical you know.! It reminds me of the "War of currents" which was posted by bioramani sir long ago as a reply to some thread.! 😀
https://en.wikipedia.org/wiki/War_of_Currents
Pal AC losses are also there but DC losses are in the tolerable region always Overall the economy is the greatest Drawback in DC transmission
naveee
naveee • Oct 13, 2012
vinod1993
Why do you want to transmit DC?(total losses are heavy, I gather) .AC transmission is economical you know.! It reminds me of the "War of currents" which was posted by bioramani sir long ago as a reply to some thread.! 😀
https://en.wikipedia.org/wiki/War_of_Currents
thats wat i asked .... jeffrey samuel ..he said..loss are low.. its more efficeint.... too .....k sir... i got it nw 😀
Jeffrey Arulraj
Jeffrey Arulraj • Oct 13, 2012
Well I still stand by my post

The effective power transmitted in cables the DC transmission has an edge

But when taking into account the other losses due to conversion of generated AC into DC in the rectifier and all the other power devices the losses mount up to a significant amount

This is also the case with AC transmission a large amount of power is lost in transmission but the stepping down the power lost is recovered and so this is more common and useful in in the AC transmission That is why we go for AC mostly for transmission
Jeffrey Arulraj
Jeffrey Arulraj • Oct 13, 2012
Hey vinod1993 I never said that I am transmitting DC current I would be a fool do it for some miles

I am planning to transmit DC voltage through cables at higher Voltages like 220kV and 330kV at such high voltage DC current through the cables are never more than 3-10 micro amperes

At this current the Irms of AC is almost equal to DC current and so the line losses are almost same in the cable

Am I clear in my point to you all
vinod1993
vinod1993 • Oct 14, 2012
My knowledge spectrum is very confined. But my question is how do you say that the current will be very small when the voltage is very high. Current and voltage exhibits some kind of proportionality eventhough they don't obey ohm's law.!
Jeffrey Arulraj
Jeffrey Arulraj • Oct 14, 2012
What is the prime application of step up transformer can you post the role of the transformers

Then to remove all your confusion pal vinod1993 meet me in person tomorrow

Then for technical aspect of telling you Heard of "Law of conservation of power" if the voltage is increased current has to decreased to maintain constant power
grsalvi
grsalvi • Oct 14, 2012
The concept of DC transmission is called HVDC(High voltage DC) transmission.
Its a broad subject which is combination of Power electronics and Power system.
It was the topic of my first paper presentation in engineering career.😀
Few features in short :

1] The AC generated power is converted ,filtered ,stepped up and transmitted through HVDC station (also called DC link between power plant and load end).

2] Compared to AC substation ,HVDC has high capital cost but running cost is economic.

3] Most important and unique feature : reduced losses. Why ?
Many reasons : reduced span of towers,conductor size reduced ,less leakages,etc

And as mentioned above you ,the Thyristor valves (which replaced costly mercury valves ) are used for Stepping up purpose.

The incoming of advanced power electronics technology has changed the situation of war between " AC and DC" ,as now DC has equally become feasible for transmission.
Jeffrey Arulraj
Jeffrey Arulraj • Oct 14, 2012
Exactly true the Losses in HVDC transmission become lesser due to thyristor developments.

the cost will soon come down as more and more thyristor models are being designed to increase the efficiency of the DC transmission specially

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