Відео

This is on my todo list, thanks for your comment. But a quick one: You can control the reactive power by increasing or decreasing the EMF (pole wheel voltage) of the generator or add capacitors or reactors to the grid for example parallel to loads or transmission lines.

This is a good question. I may be wrong but the grid could be operated without Synchronous Generators. The behavior of Power Electronic inverters can be tuned to come close to synchronous Generators, so called grid forming devices. The requirements are a Power Supply reserve margin which emulates to some extent the rotating mass (virtual inertia), the droop and the fault ride through capabilities. Already today larger power systems operate at close to 100% renewable given optimal weather conditions. There are other important topics as well, such as the short circuit characteristics of SG which are relevant for protection relays.

The wave in a cable is much slower than in a transmission line (about 30% of the speed of a transmission line) and the surge impedance of a cable is much lower. This changes the reflection accordingly.

Good question. The resistance of the tower is included in the simulation but it is not the important. It is kind of included in the grounding resistance of the tower. If you want to see the effect, goto www.ecsp.ch and click on the image with the title power lightning protection. So you will be able to change the value of the grounding resistance by the slider appearing on it when mousover. It is free, try it...

Thanks for the question. No, the effect is not the same. Shunt reactors compensate the capacitance of a long line, i.e. reduce the overvoltage when the load is well below the line natural load. Series capacitors on the other hand compensate the inductance of the line, the line appears shorter and thus the phasor angle between the line ends will be reduced in favor of the transmission stability. There is however some interplay.

I am not sure if I understand your question right. This video is about synchronous machines only and yes, there is a voltage drop during a short circuit.

@@georgschett801 You showed that exitation current increases. So why do we need AVR??? And do we face the same problem wen we have permanent magnets?

​@@high4702 The current in the excitation coil is jumping at the instant of a short for keeping the magnetic field within the excitation coil constant as per induction law. This jump however decreases again with the transient time constant and so the excitation current returns to the level before the short. The excess current caused by the short bypasses the excitation source through a diode parallel to the excitation source as per my video. The AVR has nothing to do with the short circuit, it is regulating the steady state voltage of the Generator. In case of a hypothetical permanent magnet there would be no transient short circuit but only a subtransient, in case of the availability of a damping cage.

OK, thanks! But I am not aware of a mistake, can you please let me know?

@georgschett801 First, thank you very much for your interest. at the minute of 14:12, you said ( I open the breaker, and you can see now is how much this angle between the sending end and receiving end has been decreased) , you said before when adding the capacitor, the angle will decrease, so when we remove the capacitor, the angle is supposed to increase, or what? Or you may be mean when you open the breaker of the second line and not the breaker of the capacitor , is this right ?

@@SoherNasr-u3v I guess I see your point. When the breaker is closed, the capacitor is short circuited, i.e. not in. Only when the breaker is open, the capacitor is in. I hope this clarifies

@georgschett801 You really added valuable information to me. Thank you very much 😊

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Danke fürs Feedback!

Hello Magnus, I am not sure if I get your question right. There might be a confusion between impedance (load) angle and the angle between sending and receiving voltage source. You can use my free version of the simulator www.ecsp.,ch in order to play with the 2 sources and change the angle between two sources. So you can observe the impact of the angles and of the source voltages on the power exchange between the 2 sources. All the best, George

Thanks, I thought that the angle between Ug and Un was the load angle, is this not the case?@@georgschett801

I have assumed this: Load angle is equal to torque angle of synchronous generator pluss angle due to line impedance

No Magnus, it is the angle between the two sources. @@MagneManet

The total source angle between the 2 sources is equal to the torque angle of G1 + the angle between one side of the line and the other side of the line plus the torque angle of G2. @@MagneManet

Hello Magnus, I am not a specialist in symmetrical components for transformers but I recommend to contact P. Ramachandran who is the best transformer expert I know. His mail address is: prc3011@gmail.com. You can contact him via linkedin as well, search P Ramachandran. Best regards George.

Many thanks @@georgschett801

There is a good paper available on internet: www.nrel.gov/docs/fy11osti/51978.pdf. As far as I am aware of, the answer to your question is YES. The primary frequency reserve is very much depending on the available system inertia, which decreases with increasing variable (intermittent) generation. How much is still subject to research as well as possible remedy.

Thank you very much for you answer I will read the paper you suggested to me!

This is a classic thyristor based HVDC system based on 12 pulse rectifiers.

@@georgschett801 OK Thanks!

I admit that the AC introduction is oversimplified and much too negative, today I would certainly choose another approach to make the case. However the transmission losses above 1000 km are significant. The main issue however as you know is stability, which can be overcome but at increasing costs per line length. Maybe I will rework the video.

@@georgschett801 No, you didn't oversimplify. Transmission lines are simply not lowpass filters. They have no inherent bandwidth limit. If they did my work with coax cables at 60GHz would never have been possible. Your error is a common one however and stems from imagining them to be comprised of lumped elements. This analysis can be made to work, but only by allowing the number of elements to tend to infinity. So please, don't use this analogy - better to say nothing than feed erroneous ideas into the minds of those that may one day need the correct models.

Everything you say is correct. You are obviously a HF expert! Pardon me however if I still use the simplification. In power system analysis we often use a simple lumped LCR models for power flow analysis. The lumped models give quite good results for shorter transmission lines. If however we need models for longer lines, higher frequencies (switching impulse, lightning), Ferranti effects or compensation of reactive power more accurate models are used. I myself use a type of Bergeron distributed model which is common in programs such as EMTP or ATP. I guess you use similar models based on surge impedance characteristics. So again, I exaggerated the losses with my introduction and there I fully agree with you.

Good point. No the simulation does not take care of the energy lost through the walls and therefore it stays constant.

I mean, the simulation file, because when I tried to make it there were components that weren't there and it didn't match what you made, sir.

and I'm just learning, in the video it's too fast to take the components, the wave results I make are not like the ones you make in the simulation

and I'm not fluent in English, I just use translation to understand it, because of that sometimes I still don't understand what you mean, sir.

The transmission line models are available in the pro-version of the software. The free version does not support these models.@@rasras6002

www.ecsp.ch

No, I think you got it right and this is the convention I use as well. The power of a source delivering power to the system is negative where as the power consumed is positive. I share your views for the reactive power as well, so where is the misunderstanding, did I make a mistake somewhere?

Ok, from the video at 44:22, when the iteration stops. the load busses (nr 3 and 4) has negative active power and nr 4 which also is capacitive has positive reactive power i.e -1.62e+8 + j1.00e+8. The Generator busses has positive active power, slack bus also has negative reactive power even though the system is capacitive meaning generator should be underexcited and then according to passive sign convention should consume reactive power +Q. @@georgschett801

You are right (well done, you are the first one seeing this!). I was not consistent and switched between the consumer arrow system (which I normally use as you do) to the producer arrow system (unintentionally). In the producer arrow system positive is active power generation, negative is active power consumption. But the principle regarding the Gauss-Seidel iteration is the same. Thanks for your note!

Aha, then I follow, anyways, thanks for making these great videos, they are really helpful :) , @@georgschett801

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It should be so: When the battery is charging, the power is flowing from the grid to the battery, thus the phase angle at the converter should be lagging behind the grid voltage as it is shown in the simulation.

www.ecsp.ch as per link in the comment line of the UA-cam videos.

www.ecsp.ch, it is browser based no download needed.

Der is no specific module for Kwh (energy) injection but you can vary the power (phase angle or torque) of one or many sources in a network arrangement and check the corresponding impact on the power flow (voltages, currents) and so on. In the free version you can check how it works. In the pay version you have line models and 3-phase model, plus you can see the phasor analysis.

Thanks for your kind feedback. I do this with power point visual basic or for even more complex graphics I use javascript.

@@georgschett801 Really good. thank you. Do you have presentation showing 2 generators or more working in parallels visualizing the way their angle interact to changes in the system? for example if system load is increased / decreased, etc.

@@trinottuk Maybe this one is what you are looking for: ua-cam.com/video/RxzMHQ4o1jI/v-deo.html and by the way, this is exactly what you can do with the proposed simulator on www.ecsp.ch

@@georgschett801 Thank you very much. Are these presentations available for registered members?

@@trinottuk No, it is for everybody. It's all on my channel: ua-cam.com/channels/ZEYX01Nvi3qHsby1Cnls1g.html The pro-version of the simulation tool is for registered members only: www.ecsp.ch

I am not sure if this changes much because lightning can strike a tower but between towers as well. And the shielding wire must be grounded at the pols and thus even wooden poles would be conducting.

@@georgschett801 The shielding wire is not installed on 20 kV power lines. In my country there are still some 10 kV and 20 kV power lines with wood poles

www.linkedin.com/in/georg-schett-online-circuit-simulator/