What causes power grid failure?

Recently, East, North and North-East regions of India went through a severe blackout for several hours after the sudden collapse of the northern grid.

This article endeavors to answer some general questions pertaining to Power grid.

What constitutes a Power grid?

An electricity or power grid is a network of power lines that withdraws electricity from a generating station. It has 3 main constituents:

• Generating stations– The electric power generated is enhanced to a higher voltage-at which it connects to the transmission network.
• Transmission lines – The transmission network will carry the power long distances–often across state lines, and sometimes across international boundaries, until it reaches its wholesale customer (usually the company that owns the local distribution network).
• Substations – Here, the power is reduced to a lower voltage—from a transmission level voltage to a distribution level voltage. As it leaves the substation, it enters the distribution wiring. Finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage(s).

How does it function?

• The grid functions in a narrow frequency band of 49.5Hz to 50.2Hz.
• The frequency and voltage of the grid is monitored by the load dispatch center on the basis of the drawl schedule of the respective states of every region.
• When there is excess drawl or less generation of power the grid frequency falls and it increases when there is excess supply or the less drawl.

What is the reason behind grid collapse?

• A grid fails when the frequency plunges below the lower limit of the (49.5-50.2Hz) band or shoots up beyond the upper limit.
• As a result, transmission lines stop accepting power supply and other grid constituents, including the generating stations go out of order.

How is it restored?

• Power restoration is a complicated process which involves all the grid constituents.
• The grid management authorities start restoring the transmission lines and at the same time make alternative arrangements for electricity supply.
• Generating stations are restarted.
• Among all power projects, coal-based plants take the longest to resume operations.

How is the fault detected?

• The task is difficult as the authorities have to analyze the details of per-second consumption and supply by each constituent of the grid at the time of the failure.
• As a regular exercise, the regional load dispatch center authorities keep warning states and regulatory authorities at regular intervals about possible collapse due to over drawl or less drawl of electricity.