How does an power plants produce constant voltage of 230V for home

[SanjKrish]

Please correct if my understanding of how voltage current working is wrong..

An electricity generator which is fuelled at a constant rate provides constant voltage across its ends say 230V.. This generator rotates at say 100 rpm and can light a bulb with gud luminosity..
( This is compared to a boy pedaling a bicycle at a plane surface for his level of energy which he can pedal at 100 rpm)

When more number of such light bulbs are connected in parallel, certainly the luminosity of the light bulbs decrease cause of increased current demand which exerts an oposing force on the turbine decreasing its speed to say 50 rpm, ( Can I still say the generator generates 230V as it is fueled at a constant rate ??)
( This is compared to a boy encountering an uphill but still pedals at his same energy level(voltage level) decreasing his speed and his pedaling to 50 rpm (lower current))

Inorder to maintain the same current flow (which is done to maintain the bulbs glow at the same luminosity) the generator is fuelled at a higher rate and the generator goes back to it orginal speed of 100 rpm.. but this time as more fuel is provided does it mean tat the voltage level is increased??? inoder to provide constant current..

Now, I am not able to make my question itself.. Sorry.. Soo confused..:shock:

How does the power plants always give 230V to homes.. is it by running the turbine at constant speed??? and how is the current taken care if not by the speed of the turbine...
Please excuse me if my questing is dumb..

 

[jiripolivka]

In the power network,the AC alternators are run in synchronism to generate 230 V, 50 Hz. As the load changes, it affects the frequency- for an overload the frequency decreases to say 48 Hz, and the network manager activates more power sources to get back to 50 Hz. In the case of an under-load, the frequency exceeds 50 Hz, say 52 Hz, and the manager can disconnect unnecessary sources to get back to 50 Hz.

In the large network, the voltage at the big generators can be up to 750 kV, to be transmitted by HV lines closer to consumers. The next level can be ~30 kV for cities and districts, then 3 kV for streets and finally down to 230 V for homes.

Voltage is adjusted by taps on local transformers to stay within 5 ..10% around 230 VAC under a nominal load. YOu can see with a voltmeter that in a home, overnight the voltage can rise to 240V while at a maximum load in the evening it could drop to 210V due to many consumers loading the network.

See Wikipedia or textbooks for more details.

 

[permute]

There are two control systems at play. The first is the mechanical system that spins the generator's rotor. Practical generators are rotating electromagnets -- not rotating permanent magnets. (PMG's do exist for aux power for powering the electormagnets).

This means the frequency and voltage can be controlled by controlling the power to the driveshaft, and the amount of current applied to the electromagnet. The "excitation system" controls the electomagnet.

 

[jiripolivka]

The power network is much more complex. If you use only one alternator and one load, you can control voltage and frequency as you wrote. In the synchronous power NETWORK, things are done a bit otherwise.

 

[SanjKrish]

jiripolivka,

I am not interested in the exact details of how a power generator works but jus a rough picture of how they maintain the voltage as constant..
To be precise I am interested in knowing the characteristics of practical voltage sources...
We know Ideal voltage source should provide infinite current but a practical voltage source cannot provide infinite current. So tell me, what factor limits this current delivering capacity of a practical voltage source

This understing is crucial for me to realise many other things... Can u give me any two voltage souces delivering the same amout of voltage but one of them could provide higher current that the other..

Say my load is 1 ohm and I have a 10V battery.. Then I should get 10Amp current ideally.. but I suppose a battery cannot deliver tat much current..
But take the case of regulated power supply which I find in my college lab that could provide 10Amp but not a battery.. so which sets the limitation on the current

 

[jiripolivka]

jiripolivka,

I am not interested in the exact details of how a power generator works but jus a rough picture of how they maintain the voltage as constant..
To be precise I am interested in knowing the characteristics of practical voltage sources...
We know Ideal voltage source should provide infinite current but a practical voltage source cannot provide infinite current. So tell me, what factor limits this current delivering capacity of a practical voltage source

This understing is crucial for me to realise many other things... Can u give me any two voltage souces delivering the same amout of voltage but one of them could provide higher current that the other..

Say my load is 1 ohm and I have a 10V battery.. Then I should get 10Amp current ideally.. but I suppose a battery cannot deliver tat much current..
But take the case of regulated power supply which I find in my college lab that could provide 10Amp but not a battery.. so which sets the limitation on the current

It is time to read some basics about electrical circuits! We can talk long without you understand important things.
To your question : each "voltage" source has its internal resistance. This limits its output current.
Analyzing a circuit you must understand the full circuit called "equivalent" circuit.

 

[Ice-Tea]

A battery has an internal resistance that introduces a voltage drop that increases as the current increases. A bench power suply and most other power supplies have a correction mechanism (voltage sensing) that will offset the effects of the internal resistance more or less. However, power supplies are limited in how much power they can deliver. Some will sense too much power is delivered and shut down completely, others will limit the current and thus voltage, some will trip a fuse,... In case of the mechanical power source, more and more power will be required on the shaft untill it will eithe be unable to keep it's speed or stall altogether.

 

[SanjKrish]

Very gud explanation Ice tea ..