I m working in a CPP, which comprises of 3X5.2 MW GT & 2X6.0MW GE. Normally all m/cs run in parallel to Grid with Preselected KW mode.Pls explain Yhis mode of operation.

In the absence of Grid they run in islanding mode. Can anyone pls explain in islanding mode, all the m/cs run in which mode? If one of the m/c behave as master than what mode it should run? & what should be the mode of other m/cs which follow it.
Please explain.

Thanx in advance...

 

Hi,

Preselected mode is like you are telling to the the grid that you can generate XYZ MW & limiting it there.

In the absence of Grid, people normally sets one of their units in Island mode so that it works as master to maintain frequency. Other units can be Droop mode to share the load.

Hope this helps.

 

When a single prime mover and generator, or multiple prime movers and generators, are operated in parallel with other prime movers and generators on a "large" grid to supply a load which is much larger than any single prime mover and generator can supply, the governors of the prime movers are operated in Droop Speed Control mode. There has been a *LOT* written on control.com about Droop Speed Control. A lot. Use the search function if you want to learn more about how Droop Speed Control works and how it allows multiple prime movers driving generators to all contribute to ("share") supplying a large load (motors, lights, computers, etc.).

One of the most important aspects of operating an AC (Alternating Current) system is to maintain a stable frequency. Some parts of the world are better at this than others. But, in any case, the desired way to operate a grid is to maintain a stable frequency.

To do so, the amount of generation much exactly match the amount of the load (motors, lights, computers, etc.). If the amount of generation is greater than the total load then the frequency will be higher than desired. If the amount of generation is lower than the total load then the frequency will be lower than desired. The amount of generation on line must also be capable of being adjusted (manually or automatically) so that the amount of generation equals the total load, else the frequency will be above or below the setpoint.

For a small isolated generating station supplying a small load independent of a larger grid (sometimes referred to as operating as an "island"), it is customary to operate one prime mover's governor in Isochronous Speed Control mode, which will automatically, and very quickly, adjust the power output of the prime mover to keep the generation equal to the load to keep the frequency of the load constant. If there are other prime movers and generators being operated in parallel with the Isochronous unit, they are usually operated in Droop Speed Control mode, which allows them to contribute to supplying the load ("share" the load) with the Isochronous unit while the Isochronous unit controls the frequency.

This is a very huge question, and before continuing with the explanation I would like to know if this is the type of information you are looking for or if you have other questions.

There are lots of special cases and lots of special considerations and it's just too much to try to cover them all here. So, please let us know if this is what you're asking about, and if you require any further information, after you have used the control.com 'Search' feature to research Droop- and Isochronous Speed Control.

Last thing: The primary purpose of Droop Speed Control is to allow a prime mover and generator to share in supplying a large load while being operated in parallel with other prime movers and generators. Droop Speed Control mode presumes that there is some authority or agency or control scheme that is controlling the grid frequency. A secondary, side benefit of Droop Speed Control is that if the grid frequency is not 100% that the prime movers and generators <b>*which are not producing maximum, rated power*</b> will try to change their power output to try to help maintain the grid frequency <b>if possible</b> (if there's enough generation capacity which isn't already at maximum output).

But the primary purpose of Droop Speed Control is to allow prime movers driving generators to produce power in a stable fashion and contribute to supplying a large load when being operated in parallel with other prime movers and generators.