Context:In response to PM address related to turning off the lights for 9 minutes,grid managers across states have flagged the risks and are preparing for the worst case scenario as a contingency measure.
Concerns due to turning off the lights for 9 minutes
- Drastic load reduction followed by drastic load increment:
- Just before 9 pm there may be unprecedented load reduction, followed by a sudden increase in load post 9.09 pm.
- During this 9-minute lights out exercise, up to 10,000-15,000 MW of power demand could drop suddenly and then come on stream a few minutes later.
- The concern is that grid frequency should not swing beyond permissible limits, and that all generators across the country must give frequency response as per the Grid Code.
- While the possibility of the grid tripping on account of this is highly unlikely, operators expect a “jerk”.
- Current grid load is primarily on account of domestic load:
- Considering the lockdown in India;hotels and factories, malls, railway stations, airports are closed.Hence domestic load is the predominant load.
- So the lighting load as a percentage of total load is much higher now and the impact of a sudden drop in lighting load could be more accentuated than during regular times.
Strategy of Power System Operation Corporation Limited (POSOCO)
- It has prepared a separate plan for each type of power plant considering the need of the situation.
- Measures to control voltage will also be taken.
- Contingency plans include black start,starting power plants during a black-out.
Understanding the working of the grid system
- Maintaining frequency within a permissible band :
- Frequency reflects the load generation balance in the grid at a particular instant and is one of the most important parameters for assessment of the security of the country’s power system.
- The basic motive of the grid managers is to maintain frequency (demand-supply balance) round the clock to prevent the grid from tripping.
- Need of Permissible frequency range in a grid:
- Optimum permissible band in frequency needs to be maintained as all the electrical equipment and appliances at our homes are designed to perform safely and efficiently in a certain power supply band.
- An increase in frequency results in an increase in the voltage and a decrease in frequency results in decrease in voltage.
- Handling sudden increase or decrease in load:Different types of power plants have different abilities to handle sudden increase or decrease in load.
- Hydro plants:The control we have on these plants varies. In hydro plants, the water can be stored in dams to the brim and then let down.
- Coal-fired plants:It would be harder to suddenly reduce or increase their power generation. They take a while.
- Gas-fired plants:Here load changes can be much quicker.
- Nuclear plants:Here this ability is quite limited. It would be difficult to switch off or load these plants suddenly or quickly.
- Solar and wind plants:Here there is little or no control.
- During the exigency:
- The grid operator needs to ensure that there is automatic corrective response, failing which it needs to manually intervene to avert a crisis by curtailing demand or ramping generation from another source within a really short period of time.
- Handling imbalances is the most crucial function of the grid operator.
About the grid system in India
- India is one of the largest synchronous interconnected grids in the world, with an installed capacity of about 370 gigawatts and normal baseload power demand of roughly 150 gigawatts.
- Considering the nominal frequency is 50 hertz.POSOCO in India endeavours to maintain frequency within a permissible band (49.9- 50.5 hertz), primarily by balancing the demand-supply equation.
- Demand load pattern in India:
- Of India’s total electricity demand load pattern during normal times
Electricity demand load
Industrial and agricultural consumption
40 per cent
Commercial electricity consumption
30-32 per cent
About Power System Operation Corporation Ltd (POSOCO)
- It is the national electricity grid operator.
- It is a wholly owned Government of India enterprise under the Ministry of Power.
- It projects daily demand of power and regulates supply from power generators based on projections to maintain frequency (demand-supply balance) round the clock to prevent the grid from tripping.