Thank you for supplying such a well-reasoned and detailed reply.

Specifically, ZubairKhan, let’s say a single 25MW three-phase synchronous generator driven by a combustion turbine was operating at rated frequency (rated speed) and at 11kV and supplying a load of mostly induction motors driving pumps and fans and conveyor belts, small transformers driving lights (a mix of fluorescent, incandescent and LED) and smaller motors and air conditioning units (more induction motors). There are also a few tea kettles and some computers and computer monitors. Finally the “house load” of the combustion turbine auxiliaries is also being powered by this unit. It is being operated in Isochronous Speed Control mode independent of any other synchronous generator. The total load on the machine at this instant is approximately 5.0 MW.

How would you change the load on the machine in question from 5.0MW to 19.7MW by changing the voltage and current supplied to the generator?

Further, let’s say in a more realistic setting the same machine is synchronized to a grid with tens of other machines all operating at rated frequency (rated speed) and this machine is producing 5.0 MW of a total load of 3,467 MW. It is being operated in Droop Speed Control mode. How would you increase the load of this machine from 5.0MW to 20.2MW by changing the voltage and current supplied to the machine? How much would you have to increase the voltage and current supplied to the generator, in percentage of rated voltage and current?

It would probably surprise you to learn that every minute of every day there are hundreds of ill-trained people operating synchronous generators all around the world. A lot of the reason for this is the automation (control system). A good portion of the reason is that owners don’t want to pay for proper training and governments don’t have regulations/laws mandating certification for power plant operators and so owner believe they don’t have to invest in training or pay to acquire trained, experienced employees to operate the equipment. So, your statement about proper training and experience to mitigate risk is also without much merit in many places in the world (including some very modern and industrialized nations). The only training some people receive is OJT: On the Job Training. And a lot of that is given by people who got their knowledge and experience from OJT. (Sometimes OJT is good, but most often it’s lacking, sometimes severely lacking.) And it’s the automation that prevents a lot of catastrophes and serious injuries and deaths.

But, getting back to the questions you didn’t answer and are unresolved; How does one change the load (watts; kW; MW) of a synchronous generator by changing the voltage and current supplied to the generator and how much would one have to change that voltage and current to affect a change of approximately 60% of the rated load of the machine?

Seriously, I am trying to learn something from you since you stated that was how (or at least one way) to increase the load of a synchronous generator on planet earth in our solar system driven by prime movers (turbines and reciprocating engines). I know another way, and it’s the only one I know, but if there’s another way (or maybe more?) I would like to learn.

I’m an old fart, but I am still learning new things every day. A new language (it’s a great way to keep one’s mind active and engaged), new procedures, new culture, new foods, new ways of growing foods, and new perspectives as well as different methods and materials for construction. This would be something to keep my mind engaged and active as I try to grasp the concept(s) and principles. So, help a fellow out and explain it to me, please.

Thanks!

 

nikidi.control...
First, your question reveals you lack education related to electricity! Why? Because one must know how to find the square-root of negative numbers?
Secondly, one must know how to use the REAL part a and IMAGINARY part bi or a + bi to identify the various components of the problem!!
Let me know if additional information is necessary!
Regards, Phil ([email protected])

 

Nikidi.control,

One of the most important aspects of any AC (Alternating Current) power system (generation, transmission and distribution) is maintaining a stable frequency (50 Hz or 60 Hz, usually). It's impossible to have any machine synchronized to a grid of any size that is not operating at the same frequency as all the other machines also synchronized to the same system.

Synchronized. It's a very powerful word.

Think of it like this. How can one machine be synchronized to a grid producing power at 50.17 Hz and another machine synchronized to the same grid producing power at 49.56 Hz and another machine synchronized to the same grid producing power at 50.79 Hz--and any Customer get 50.0 Hz out of the power receptacle on the wall? It's just not possible. There's no frequency smoothing or averaging mechanism one any grid anywhere in the world. There are very large mechanical forces (the result of magnetic forces at work inside the synchronous generators--ALL of them). And all the machines synchronized to the grid are effectively operating as one single machine, operating at one frequency. It has to be that way. (By the way, I'm referring to steady-state, normal operation--which is the overwhelming majority of grid operation.)

There are LOTS of analogies which have been used on Control.com over decades trying to explain AC system operation (trains; bicycles; etc.). They are all applicable and useful. Yes--when a machine is being accelerated during starting the speed increases as the fuel or energy input to the prime mover is increased. BUT, once the machine is synchronized to a grid with other generators and their prime movers increasing the fuel or energy input to the machine DOES NOT result in an appreciable increase in the machine's speed. (Nor does a decrease in fuel or energy input result in a decrease in speed when the machine is synchronized to a grid.)

Remember this about electrical power systems: Motors (which is the overwhelming majority of electricity usage (pumping water; powering air conditioners and refrigerators; driving elevators; etc.) turn amperes into torque. And, generator convert torque into amperes--torque that WOULD otherwise increase the speed of machines gets converted into amperes flowing out of the generator terminals, onto a transmission and distribution grid, and power motors and other devices which produce useful work. Electricity is just the medium for moving torque in one place (where prime movers are driving generators) to another place where motors are driving loads and producing useful work. And, on an AC power system one of the single most important aspects of grid operation is maintaining a stable frequency. That's not always easy, but it's done in MANY parts of the work every day of every week of every month of every year and every decade and for more than a century.

You as an operator or technician should understand what the control systems are doing--but it's like driving an automobile, you don't have to know how to build one and how every component works with every other component to get you from one place to another, possible while moving some "cargo" (personal things, family, pets, etc.). It helps to know as much as possible if you're troubleshooting or maintaining the equipment and answering operator's questions (and management's questions...). There are literally hundreds of YouTube videos about electricity and AC power generation. Some are MUCH BETTER than others, and some are just flat out misleading and wrong. But, they're a great place to start because many have some good visual effects which can help with establishing and understanding the basics.

You have asked a good question, and you have got some reasonably good answers. But you seem to lack some very basic fundamental understandings of AC power generation and transmission and distribution. Anyway, hope this helps even a little bit. It's not easy, but it's not difficult, either. And, it takes some thought and re-thought and study and more thought and re-thought. One of the reasons some not so good answers are given for this type of question is that there are basically two kinds of people responding. Either they are extremely knowledgeable and experienced and have forgotten what it takes to learn this stuff, or, they have just accepted the way things work and some questionable explanations and derived their own understanding and explanations. I can tell you from personal experience that some of the textbooks and reference books many people try to use to understand AC power systems and operation are written by people with ZERO actual hands-on experience and some of the stuff they write is well-meaning and even true--but they FAIL to explain the entire set of circumstances that make their explanations true. (Especially when it comes to a very important aspect of AC power generation: Droop Speed Control.) So, always read things with a questioning mind--I call it critical thinking. It's very important, and very useful in every aspect of life--not just AC power generation and transmission and distribution.