Power Cuts in Tamil Nadu – Background Information
As everyone would have undoubtedly noticed, the power situation has become very critical with only 9 – 12 hours of power available per day. This is the situation all over Tamil Nadu with the exception of Chennai where power is switched off for 1 – 2 hours only.
The power situation in Tamil Nadu was already critical with a shortfall of 3,000 MW (27%) on an average and has
become still worse, mainly for the following reasons:
1. Dependence on Wind Energy – end of the wind season
The Tamil Nadu electricity grid relies heavily on wind energy due to delays in planning and implementation of other electrical generation projects. On some days the wind energy contribution to the Tamil Nadu grid was in the order of 40% of the total generation. The windy season ended mid-September and the contribution from wind energy came down to less than 5%. (Yesterday, 13-10-2012 it was only 1.46 MU (million units) out of a total of 176.90 MU). Since Tamil Nadu has no other available electricity generation sources to replace the wind energy contribution, the drop in wind energy translated into a huge shortfall in generation capacity.
2. New Unscheduled Interchange Regime
Tamil Nadu gets an allocation from the central pool of electricity generation. This pool includes stations like Neyvelli, Kalpakkam, Ramagundam. These power stations feed into the southern grid and each state gets an allocation from the pool. Allocations are scheduled for 15 minute time blocks for each day. Any power drawn in excess of (or below) the allocated quantity in each 15 minute time block is known as “Unscheduled Interchange”, or “UI”. The amount of UI charges that a beneficiary has to pay is related to the grid frequency. The standard frequency is 50Hz and a frequency below 50 Hz indicates that the grid is getting overloaded, while a frequency above 50Hz means that there is excess generation. So if TNEB overdraws while the grid frequency is 49.4 Hz it pays higher UI charges than when they overdraw when the grid frequency is 49.8 Hz.
The amount of UI charges and related frequency bands are fixed by the Central Electricity Regulatory Commission (CERC) in Delhi. In a notification in March 2012, CERC tightened the UI regime in an attempt to get better grid discipline. The frequency at which UI charges go into a higher slab was raised from 49.5 to 49.7 Hz. TNEB went to court against this order but lost the case in August 2012. As a result the tighter UI norms became applicable in Tamil Nadu from 01-09-2012. This means that the state load despatch centre in Chennai gives unscheduled load shedding instructions to TNEB substations as soon as grid frequency goes below 49.7 Hz while earlier this was done at 49.5 Hz. In addition to heavy UI charges, beneficiaries of the central pools also risk disconnection or automatic tripping of major inter-state transmission lines or a collapse of the entire southern grid if the grid frequency is too low.
3. Delays in new power projects
A number of new power projects are in the pipe line but all of them suffer from delays for various reasons. Tamil Nadu will need to add 4,000 – 5,000 MW of generation capacity to get out of the present huge shortfalls.
4. Generation Plants under repair or maintenance
As of today (14-10-2012) about 420 MW of Tamil Nadu generation capacity is under maintenance or repair (Ennore: 2 x 110 MW, Mettur: 210 MW). In Neyvelli one unit of 250 MW is under forced outage from March 2012 due to a mechanical defect.
5. Coal Linkages
Both government-owned and private sector power stations have been facing coal shortages thereby reducing plant load factors.
Purchases from the private sector
To partially overcome these huge shortages, TNEB buys every day power from private power companies through energy exchanges. The prices at which this power is available depends on demand and supply. The price for today’s (14-10-2012) evening peak (19:00h – 21:00h) for example is Rs 9.01 per kWh (against an average billing rate of Rs. 4.99 at which TNEB sells power to the consumers). Last Friday the evening peak rate was Rs. 9.51 per kWh.
The way forward
The Tamil Nadu Government and TNEB are making efforts to accelerate the completion of power projects under construction and to fast track new projects. Efforts for a higher allocation from the central sector pool are also being made.
Power Grid Corporation of India is strengthening the north-south transmission corridor so that more power can flow from the western, eastern and northern grids to the south and vice versa. This is one of the last steps in the creation of a national grid.
When the grid becomes stable and reliable, renewable energy sources including grid connected rooftop solar systems can inject energy into the grid thereby making it less dependent on fossil fuels. (For the time being renewable energy cannot displace large scale generation capacity but it can help in reducing the consumption of fossil fuels. In other words: at this stage, renewable energy cannot replace kilowatts but it can replace kilowatt-hours).
These measures will not give immediate relief though and whatever relief comes, will be in small steps. Article from the Intranet.