WHICH IS GOOD FOR LONG DISTANCE POWER TRANSMISSION AC OR DC?

Did you know this??

DC is considered very good for Long distance power transmission in comparison to AC.

I know most of you will find it very difficult to digest, and most of you will even say me wrong but reality is, you might be having incomplete knowledge .

And credit for that goes to our outdated syllabus. But don’t worry, this article will clear all of your questions and confusions regarding above topic.

Let’s me explain this by answering all possible questions in your mind.

#Question 1

If DC was better for long distance power transmission, then why Edison told tesla to help him improving his DC Power transmission ?? And why Tesla invented way for modern AC transmission ?? And why AC won the race against DC power transmission??

This might be your 1st question. So, answer is ; At the time Edison was delivering power using DC, transformer was not invented. As a result, power transmission used to be at lower voltage and higher current in DC which used to make lot of power loss due to the heating effect by higher current. And also conductor diameter required was higher. So, Tesla, who used to work for Edison, suggested the use of  Transformer and AC ,which could solve the problem of power loss. By using tansformer we can send very high power upto very longer distances by reducing the current and thereby loss. And as AC is compulsory to use a transformer, AC is still used for long distance power transmission.

Note : Nicola Tesla didn’t invent Transformer and AC but instead he integrated and developed modern way for AC generation and transmission. Tesla integreted system of generators, transmission lines, lighting, AC motors, and other circuits that made AC feasible alternative to DC.

#Question 2

What is the advantage of DC over AC in longer distance transmission??

This might be the major question for you.Okay, you might have heard About the power loss in AC due to skin effect. For those who don’t know skin effect,let me make it simple. In a conductor , AC flows only through the outer layer of the conductor instead of flowing through the whole conductor. Due to this , area for for electron flow becomes comparatively less, and less area causes more resistance, more heat and thereby more power loss.This is called skin effect. And this is the reason why wires in the transmission/distribution lines are made from strands of multiple thin wires instead of single wire.

So, point is …. skin effect do not occur in DC. As a result, if we transmit power in a longer distance using High voltage DC (HVDC) , power loss is comparatively less than in AC transmission.

This is not a single reason.

There is RMS of an AC voltage which is only  71% of the peak voltage. Since, DC waveform doesn’t have this drawback, it can transmit comparatively more power than AC.

HVDC also allows power transmission between unsynchronized AC distribution systems.So, it can help increase system stability, by preventing cascading failures in power transmission grid.

#Question_3

If DC power transmission has this much advantage then why Tesla did not recommended HVDC??

I can’t think that great scientist Tesla would not have known about skin effect but the reason is, he could have used HVDC for long distance transmission but problem is , Tesla developed(improved) AC generation and transmission technology in 1880’s and at that time power electronics was far behind.

Tesla integreted system of generators, transmission lines, lighting, AC motors, and other circuits that made AC feasible alternative to DC. Before that, not even a diode(invented in 1904) was invented,

Transistor was invented only in 1947,  Thyristor, Triac, Diac,

microcontroller were far away. Why am I talking about power electronics is that, without Transistor how could he step up the DC to High Voltage DC?? We can’t do that without Transistor. We need SMPS circuit. Just think about it , you will find your answer.

#Question_4

Then why still AC is mostly used in long distance power transmission??

Then why still AC is mostly used in long distance power transmission??

Simple answer is , delayed development of power electronics. When power electronics was in the development phase especially from 1950, infrastructure for long range AC transmission were already developed.

And it followed like a tradition because power electronics capable to handle long distance power transmission was not developed before 1980’s. First long range HVDC system was developed only in 1982 in munich. But today, Power electronics has developed a lot. Another reason why it is not used yet in Nepal is, lack of sufficient skilled manpower who can handle and work in the maintenance of such system.Since, this system would be complex than AC because it requires Rectifiers, phase controllers at generating side and power inverters at substation side and lot more new electronic equipments. But , in today’s date DC is really better option for long distance power transmission in comparison to AC. Don’t know when Nepal is gonna think about it.

#Question_5

Since DC power transmission requires, Rectifiers, inverters, and lot more new electronic equipments, don’t you think it’s maintenance cost will make it more expensive than AC power transmission??

Yes there is no doubt that maintenance and initial cost for DC power transmission will be higher than for AC but it will be expensive only for power transmission to smaller distances. For longer distance power transmission , DC will be more cheaper since power loss is less here. See the graph below for more details.

List of HVDC systems in the world??

Lots of countries including India has already developed such HVDC projects and lots of such projects are under construction in the world at present date.Check out this link4 list of HVDC projects

Here is list of few of them below :

1. HVDC Gezhouba–Shanghai (china)
2. Rio Madeira HVDC system (Brazil)
3. Rihad-Delhi 1500MW (1990)

https://en.m.wikipedia.org/wiki/List_of_HVDC_projects

Comment below if you still have any queries??

AUTHOR

#iloveelectronics

VIVEK NEPAL