The Western Region Electricity Board (WREB), covering the states of Maharashtra, Madhya Pradesh, Gujarat, Goa and the Union Territories of Dadra and Nagar Haveli, has adopted the availability-based tariff system from October 1, a landmark development in power sector reforms.
The Nagpur-headquartered Western Region Transmission System (WRTS) of Powergrid Corporation of India has been appointed nodal agency for monitoring and implementing the transition to availability based tariff (ABT) in the WREB.
Executive director, WRTS, Powergrid, D K Nandi said the ABT system will ensure better grid discipline as also availability of quality power for consumers. "Overdrawing of power during peak hours and sudden drop in demand during off-peak hours by members of the WREB resulted in breach of grid discipline. This can have serious repercussions causing not only power outages for long durations but also damaging power equipment and sullying the image of the country," he said.
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He said there were divergent views on adopting the ABT mechanism vis a vis other modes of maintaining grid discipline, but it was one of the best ways for resolving the problem of overdrawal. "The grid frequency has to be maintained at an optimal level of 50 hz at all times," he informed. Nandi said wide fluctuations -- with the frequency changing to the extent of one hertz in five to ten minutes -- had been recorded.
"Low frequency should lead to automatic loadshedding but, though SEBs agree in principle, the actual effort is half-hearted. The new mechanism will ensure that loadshedding takes place automatically if the frequency falls below 49 hz. The critical figure is 49.8 hz-48.5 hz, if the frequency falls below this level, there should be automatic loadshedding," Nandi said.
He said the advantage of ABT, for which Powergrid was fitting special energy meters (SEMs) at power stations and load despatch centres, would be quality power for consumers. "At 50 hz, the promised supply of 230 volts will be available. Quality voltage will no longer be a luxury. There will be maximum generation during peak load hours and equal curtailment during remaining generation days," Nandi elaborated.
He said the new mechanism will ensure that there was backing down of generation to match the system load requirement and reduction in generation during off-peak hours so that the frequency was not disturbed. He said Powergrid had also told SEBs earlier to install capacitors for improving voltage. "All generation units should be put on free governor mode operation. There should also be some option for absorbing the reactive power (BAR) during off-peak hours," Nandi said.
He said it was difficult to get SEBs to incorporate automatic loadshedding and it could be done only after much persuasion. "The ABT, in reality, is a two part tariff comprising of plant availability linked capacity charge and fuel cost linked energy charge," said Nandi.
He said, such a tariff will induce maximum plant availability for meeting demand during peak load hours. Higher rates of tariff for SEBs who overdraw will discourage such a practice. Encouragement is offered to SEBs to draw power at lower rates.
The capacity charge takes care of the total fixed cost of the generating station and its components account for interest on loan, return on equity, loan re-payment, depreciation for amortization, fixed operation and maintenance cost, insurance, taxes, interest on working capital and support costs. The fuel cost and any other variable energy related operations and maintenance cost comprises the second part of the ABT.