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

8 percent

Domestic load  

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.


Image Source:IE