ABC of ABT - MP Power generating company limited

hours, and the Central stations (other than liquid fired) would not have anyresidual capability available for trading. However, in case a beneficiaryrequisitions less than its full entitlement, the Central station may at its soleoption, trade the resulting residual capacity, as described in chapter - D. If it isdone on a bilateral basis (as per second alternative), it has to be included inthe final schedule for the next day, for which the RLDC has to be advised bythe Central station by 10 PM.During the day of operation, the Central generating station would be expectedto operate in a safe and efficient manner, keeping in view its dispatchschedule and grid conditions. As long as the grid frequency is below agenerating unit’s threshold frequency (described in chapter - E and illustratedin figure - 4), the unit should deliver its full continuous output capability. Whenthe grid frequency rises above the unit’s threshold frequency and is likely toremain high, the unit should be backed down in a graded manner, irrespectiveof its dispatch schedule.Please note that the “unit load” shown in figure - 4 is the load to which agenerating unit is to be brought back after primary response to frequencyfluctuation in the grid. All generating units have to be on free - governor modeof operation (FGMO), and have to participate in primary frequency control. Forexample, if frequency rises by 0.1 Hz, the unit load should automatically andimmediately come down by 4 - 5%. Over the next 4 -5 minutes, the unit loadshould gradually be brought back to the previous level by supplementarycontrol, as long as grid frequency remains below the unit’s thresholdfrequency. When grid frequency goes above the threshold frequency, the unitload should be reduced to the level as plotted in figure - 4. The desired FGMOand supplementary control are illustrated in figure - 7. The recommended rateof supplementary control is one percent per minute, e.g. 2 MW per minute fora 200 MW unit.23