TNEB escapes penalty for grid overdraw

The CERC will not penalize TNEB for failure to maintain grid discipline on several occasions during March-April 2010. It was a violation of the provisions of the Indian Electricity Grid Code.

The apex regulator took this stand following Tamil Nadu Electricity Board's assurance to ensure grid security in future and the claim of having already taken a series of corrective measures to curb grid overdraw at lower frequencies.

Earlier, the  Central Electricity Regulatory Commission issued a show-cause notice for violation of grid discipline by TNEB after the Southern Region Load Dispatch Center reported that TNEB had exceeded its quota and overdrew power during the period from March 25, 2010 to April 18, 2010.

On all of the days, during the period, the utility overdrew in excess of 3 per cent of its schedule on aggregate basis when the grid frequency was at 49.5 Hz or below.8Furthermore, during 319 time-blocks, TNEB over-drew from the grid in excess of 12% of the schedule when the frequency was below 49.5 Hz. Similarly, there were 526 time-blocks during the above period when TNEB had overdrawn from the grid at a frequency below 49.2 Hz.

Sections 5.4.2(a) and 6.4.7 of the Grid Code necessitate the state government-run power utilities to restrict their net draw from the grid to their respective schedules whenever the system frequency is below 49.5 Hz.

Moreover, manual load shedding has to be carried out by these utilities to curtail any overdraw when the grid frequency falls below 49.2 Hz, as per the Grid Code.