THE FOURTH UNIT OF THE underground hydro power station on the left bank of the Srisailam reservoir has been commissioned by the chairman and managing director of India-based Andhra Pradesh Generation Corporation (APGenco), J Parathasarathy.

With the commissioning of the unit, the installed capacity of the hydro power stations of APGenco goes up to 3282MW and its total installed power capacity will increase to 6247MW, making it the third biggest public sector power generating utility in the country next to the National Thermal Power Corporation and Maharashtra State Electricity Board.

APGenco’s installed capacity today forms about 62.4% of the total capacity of 10,000MW of Andhra Pradesh Power System.

Parathasarathy said that the remaining two units of the 6 x 150MW hydro power station were scheduled to be commissioned this year. The project is located 250m below the ground level in the midst of Rajiv Tiger Reserve Forest on the left bank of river Krishna at Srisailam.

The US$542M project was being funded by the Japanese Bank for International Cooperation to the extent of US$419M and the balance amount by APGenco.

Parathasarathy said that the power station with reversible type pump turbine motor generating units would facilitate mopping up of surplus off-peak thermal power in the system to supply power during the peak hours. In addition, it would generate cheap conventional energy with monsoon surplus flows in the river. Stabilisation of the grid and improving voltage were the additional advantages.

According to Parthasarathy APGenco’s hydroelectric stations can be best utilised for the benefit of Andhra Pradesh power system once the availability based tariff (ABT) was introduced in the southern region from 1 January 2003.

ABT is having special provision for unscheduled power withdrawals from the Central sector power stations depending upon the frequency at any given time.

The system frequency will be generally low during peak load period when APGenco’s hydro stations can be utilised to draw less from central generating stations to the advantage of the Transmission Corporation of Andhra Pradesh (APTransco).

The power generation at the project, to a certain extent, is dependent on the water level in the downstream Nagarjunasagar dam. Currently, the water level at Nagarjunasagar should be at a minimum level of 164.6m in order to utilise its backwaters for generation of power through pump mode operation. This level, according to Sanyasi Raju, Officer on Special Duty at Srisailam power project, could be reduced if some of the humps in the river-bed between Srisailam and Nagarjunasagar were removed.