Calcutta, March 5 :     The Union power ministry today scrapped the controversial two-part tariff for electricity supplied by the National Thermal Power Corporation (NTPC) to the states in the eastern region. The Central Electricity Authority (CEA) has withdrawn the final tariff notification which, if issued, would have become effective from the February power purchase bills, payable this month. A formal notice will be issued shortly informing the authorities in the eastern region that 'only a uniform availability tariff system will be applicable'. The ministry had devised the new two-part tariff structure for the interim period - a precursor to the availability tariff - to punish the eastern region for destabilising the grid by producing its own power instead of buying its allocated quota from NTPC plants. Even as power utilities in the region said the move vindicated their stand on the contentious issue, sources said the CEA was upset when NTPC refused to be part of the incentive/disincentive scheme being worked out within the two-part tariff regime. Under the scheme, the agency which drew more when the grid frequency was high would get a bonus while those drew more power during period of low frequency would have to pay a fine. Since there was no system through which the electricity boards would pay each other (incentive or disincentive), the CEA realised the tariff structure could crumble, defeating the objective of stabilising the grid. The West Bengal government heaved a sigh of relief today as the news spread. The decision taken by union power secretary V.K. Pandit on January 13 had sent a scare through the power agencies in the eastern region.