isochronous and droop

Chiranjeevi,

While you're plotting DWATT and CTIM, also plot CPD, TTXM and TTRX.

You can set the plot to record at the slowest possible rate (I forget what that is for Trend Recorder, or Trender) because you don't need high resolution (which will consume a lot of hard drive space). You can let the data gather while the unit is running (just minimize the Trend Recorder/Trender window)--it will NOT cause the unit to trip under ANY circumstances.

Please be sure to let us know what you learn!

RohitChaudhary,

22 MW + 22 MW + 35 MW = 79 MW. Where did you get 84 MW? Was that before the separation or immediatley after?

When you were separated from the grid, what was the load on the units at the time of separation?

What was the frequency at the time of separation BEFORE you switched one unit to Isochronous Speed Control?

If you have properly configured Mark VIe turbine control systems and HMIs you should have access to hourly logs of data and alarms. That information would be MOST helpful if you could retrieve it from the HMI and post it to this thread for us to review. The files will be in .dca and/or .dcaST format and should be found in folders with the same time (by hour) as the event you are trying to describe.

You appear to have been VERY lucky--to not have gone black (lost one or more units because their generator breaker(s) tripped)! So, you should consider yourselves to have avoided a bigger problem. Also the fact that you were able to re-synchronize to the grid is a very good thing!

Load shedding and frequency control schemes are so different and varied around the world it's simply mind-boggling how many differences there are. And, usually, most of them are not well tested, so it's not really known if they work or not. And, to make matters even more difficult, many times the systems change over time (grids and plant loads) and the schemes employed for load shedding and frequency control are not reviewed and modified to support the changes.

So, I'm going to say in the absence of any meaningful data (load; frequency) and because you have mentioned a load shedding scheme, that without a LOT more information it's going to be extremely difficult to try to help you understand what happened because we don't understand what happened.