in new Distribution Systems, Customer is able to manage his use of main power usage by by using other resources like PV, Wind Turbines or a backup Generator. the power from these resources is stored in battery bank in DC Form and when it will be used it is applied on inverter to get ac power again to be supplied to the Home or to Main.

that all are understood very well but what I can't Understand is How will not the power from Costumer opposite the power in main line when join to it?? and How this power distributed in the main??

and i know that in the same moment customer is ready to supply the Main, main station will reduce its generated power.

 

please somebody reply to my query !!

 

>please somebody reply to my query !!

If I understand you correctly your concern is how a 1,000,000MW grid responding if you supply says a 100W solar PV to one of its distribution network? Does the grid "really" responding in the first place taking into consideration the incremental load is almost zero percent?

It is going to be relatively long explanation. Therefore I need to know if that is your main concern after all.

 

thanks for replying and yes that what I mean .

so please explain it to me

 

Let us assuming we have a 10,000MW capacity grid system supplying 9,000MW. Total demand is 8,700MW and 300MW total system losses including losses in turbine generators. The system is operating at 50Hz electrical frequency.

If we hold generation and demand constants and assuming total power loss hasn't change then the system remains at 50Hz indefinitely.

Now we connect a bulb with rated power consumption 10watts. What do you expect to happen? What you do will not make generation to increase. It shall remain at 9,000MW. The losses and total demand will not going to change either since system voltage will hardly change at all.

A moment after the bulb is on and if you are impatient you will draw a conclusion that nothing happen. But wait. Let us see what happen after 100 hours. We use conservation of energy.<pre>
Energy generated in 100Hours = 9000 X 10^(6) X 100 X 3600J
=3.24X 10^(15) Joule

Energy consumed = (8,700+300+ 2 X 10^(-6))X 100 X 3600 = 3.2400000036 X 10^(15) Joule</pre>
If you believe nothing happen the we have created 3.6 X 10^(9) Joule out of thin air. We know this is impossible. What you want to know has a lot to do what that 3.6 X 10^(9) going to do to the grid. What it does? In order to visualize significant change let us change period of observation to 100 days. Thus<pre>
Energy generated = 7.776 X 10^(16)

Energy consumed =7.77600000864 X 10^(16)

Total net energy offset = 8.64 X 10^(7)Joule.</pre>
Where does this energy come from? It comes kinetic energy of rotating masses of the grid. For the system the size of 10,000MW kinetic energy of rotating masses of the generators and prime movers can be approximated around 8.000 X 10^(10) Joule at 50Hz. Therefore, if generation is not increased then after 100 days the system kinetic energy will reduce according to the following:<pre>
=> 8.0 X10^(10)-8.64 X 10X(7)= 7.99136 X 10*(10) J

The grid frequency will be reduced to approximately 7.99136 X 50/8 = 49.946Hz. </pre>
In reality you may ever able to see this scenario except that during the major system disturbances. This is because there are three types of loading interventions that are continuously done by authorities that operate and manage the grid. The interventions are, manual raise and lower load command, primary response associated with governor speed droop and frequency control and regulation. For speed droop and frequency control interventions they are executed based on frequency deviations above or below the scheduled frequency. When the actual frequency is lower than the actual frequency, more generation is added. Otherwise generation will be lowered. In this case the generation will be added by 10MW for 10MW for 8.64seconds to replace back kinetic energy of rotating masses that has been lost. After 8.64 seconds, system kinetic energy of rotating masses shall reset back to 50Hz. The added 10MW generation will be withdraw ed back.

In reality and modern grid system, frequency deviation correction is done as rapid as between 4-11 seconds time step per control command. The final deviation that has to be corrected is the net offset between generation and demand, which will be reflected by frequency deviation. This includes the contributions from various distributed generations that are attached at the demand side.

You can work similar example rather than using 10W bulb just use a 1000W solar PV. You are going to see that the system frequency will increase rather than decrease. After sometime the generation has to be reduced to reset the frequency back to 50Hz. Therefore the solar PV will able to reduce the amount of fuel required to power the grid equivalent to the solar PV energy contribution.

Hope my explanation is helpful.