Grid inertia likely in Tamil Nadu, thanks to aged thermal plants

At present, the installed capacity of renewable energy stands at 35 per cent in the Southern region with old thermal power plants being decommissioned. According to the Flue-gas desulfurization (FGD) phasing plan, eight units with a combined capacity of 720 MW of Kothagudem thermal power station in Telangana and 600 MW Neyveli Thermal Power Station I in Tamil Nadu were decommissioned.

“With solar and wind dominating the grid, the aged thermal power plants are being decommissioned after being deemed uneconomical. Though harnessing renewable energy is good, a rush to retire such units may impair the ability of the grid to accept more solar and wind resources in the future. It is all about a factor known as grid inertia,” said a senior Tangedco official. He warned that a power network without inertia is unstable one, suffers from issues of power quality and is susceptible to blackouts.

“The primary mechanism for providing inertia is via the presence of heavy rotating equipment such as steam turbines and gas turbines driving generators and rotating generators. In an electric system, the energy contained in generators and motors at power stations and industrial facilities provides inertia as they rotate in the same frequency as the electricity grid. This effectively acts as a buffer against rapid change. If demand for power spikes, the frequency of the grid tends to decrease. Having a lot of rotating mass on the grid acts like a shock absorber and slows the rate of change,” the official said.

To study the impact of grid inertia, the Southern Regional Power Committee could conduct a study on utilising the decommissioned generating units as synchronous condensers for providing the grid inertia, the official said.