ABC of ABT - MP Power generating company limited

DEVIATIONS FROMSCHEDULECAs mentioned earlier, the energy charge, at the specified energy charge rateof a generating station, is payable for the scheduled energy quantum. Theenergy actually supplied by the generating station may differ from whatwas scheduled. If actual energy supplied were higher than scheduled, thegenerating station would be entitled to receive a payment for the excessenergy (the deviation from schedule, technically termed as UnscheduledInterchange (UI) in Availability Tariff terminology) at a rate dependent onfrequency at that time. If the energy actually supplied is less than whatis scheduled, the generating station shall have to pay back for the energyshortfall, at the same frequency - linked rate.The relationship between the above UI rate and grid frequency, for the inter-State system, is specified by CERC. The present relationship, applicable from1.10.2004, is shown in figure - 2. When the frequency is 50.5 Hz or higher,the UI rate is zero, which means that the generating station would not get anypayment for the extra energy supplied. It would burn fuel for producing thisextra energy, but would not get reimbursed for it at all. Conversely, if theactual energy supplied were less than scheduled energy, the generatingstation would still be paid for the scheduled energy (at its energy charge rate)without having to pay back anything for the energy shortfall. It would thus beable to save on fuel cost (for the energy not generated) and retain the energycharge as net saving. There is thus a strong commercial incentive to backdown generation during high frequency situations, and help in containing thefrequency rise.10