Wind power evacuation problems in Tamil Nadu –How to handle it?


India has about 17 GW wind power installed capacity and as the coal and gas resources are depleting, reliance on renewable power generation especially wind power has become significant. Due to geographical nature of the country most of the southern states are having good wind potential. The states such as Tamil Nadu has about 7 GW wind power installed capacity, which contribute about 40% of total electricity capacity of the state. The nature of wind power is that it is seasonal and about 80% of generation takes place during the monsoon months (April- July). Apart from seasonal variability wind power generation is highly variable on daily basis and looking at the Tamil Nadu wind power generation data it can be seen on a typical day the wind power variation ranges between 50 MW to 3000 MW.

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Variability in wind power generation poses greater challenge to the grid stability. Due to seasonal generation from wind power the state is not able to utilize its transmission infrastructure effectively and during high wind season the transmission line are congested and subsequently there are problems of voltage stability and power quality. For Example most of the generation from wind farms in Tamil Nadu takes place in tirunaveli and mokundal region and power is evacuated to nearby 230 KV or 400 KV substations. During monsoon season most of the hydro plants also run at full capacity and the demand of electricity to the agriculture consumers become insignificant, this becomes challenge to the system operators to evacuate power from the substations of this grid as the existing transmission lines become overloaded and southern grid is not synchronized with northern grid, which leads to backing down of wind power plants in this region, Even though there is electricity demand in other regions of the country. The states suffers already from power shortages of about 1700-3700 MW. There is also load shedding to the HT consumers of the order of 40% on base demand which effects the productivity of consumers. In order to handle power crisis in the state, government has introduced one day power holiday to all HT and LT consumers and also peak power restriction measures.

On supply side government has planned various thermal projects in joint ventures with private developers and it is expected that about 1000 MW will be available soon through koodankulam Nuclear power plant. Due to non-availability of coal the state cannot plan aggressively its conventional power on imported coal hence Tamil Nadu has an aggressive plan to add about 5000 MW of wind and about 3000 MW of solar capacity in next five years.

While state is finding difficult to handle existing wind power capacity which is about 40% of total installed capacity, it is important to address the technology and policy measures in order to deploy large amount renewables capacity in the state. This requires strengthening of the existing transmission network as well as a dedicated power evacuation facility which can evacuate power across regional boundaries by raising the existing transmission voltages from 400 KV and, if required to further enhance it at 765 KV level. Apart from this there is a need to do investment in installing the balancing generation (Gas based power generation, pumped hydro etc..) so that variability of wind generation can be absorbed through this sources. This requires significant investment and TNEB has already asked for a central assistance of 17570 million to its transmission infrastructure to absorb large amount of wind power.

This is not a new issue that suddenly popped up, however grid integration has been very well handled in countries such as Germany, Denmark and Spain and the wind penetration in this countries is over 50% of their installed capacity. There is no single solution to address the grid integration issues, however the overall system should have balancing power capacities, short term forecasting and scheduling, demand response, pumped hydro and interconnection with other regions at a high voltage levels so that, regional exchanges of power can take place the electricity to longer distances.

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