Power grid failure: How does it happen?

Updated: Jul 31, 2012, 18:48 PM IST

Sushmita Dutta

For two consecutive days millions of people in India suffered from a crippling power crisis after power grids failed in many parts of the country.

It was one the biggest power outages in the last decade that even brought essential services like the railways and the metro trains to a grinding halt.

Why are the grids failing time and again? Here’s a look at the system and its weak points.

Electrical Grid

The power generating stations are hooked onto an interconnected network of transmission lines and substations. These generating stations supply electricity through these transmission lines. The companies responsible for distribution take the power coming through these lines and forward it to the consumers. This is how electricity reaches millions of homes.

The stability of the grids depends on a delicate equilibrium of demand-supply chain. The amount of load is directly proportional to the amount of power generated. When the equilibrium between power generated and consumed gets disturbed and the load becomes more, it leads to tripping of the line. It is duty of the power distributors to maintain the equilibrium intact so that not trigger a grid failure.

Three pillars of a power grid

A power grid consists of three sections - stations which produce electricity from fuel (fossil or non-combustible), the transmission lines which carry the power to the substations from the plants and lastly the transformers which keep a check on the voltage.

A schedule is declared by the generating plants for injection of power to the grid operators. Similarly a schedule is also drawn by the distribution stations according to which they are supposed to draw power and distribute it further.

A stable grid

The stability of a grid is determined by keeping a check on the demand and supply, as per the drawn schedule. According to the Indian Electricity Code, 49.5 Hz to 50.2 Hz is the permissible band for grid operations in India. It is supposed that a bigger grid is more stable than smaller ones.

Reasons of a grid collapse

Grids collapse due to two basic reasons. One is the failure of the equipment, like it happened a decade ago in 2002 when the northern grid collapsed, due to fog/pollution. The second trigger is power suppliers drawing excessive power from the grid. Which results in the balance of power generation and supply goes haywire with a cascading effect. This is probably the reason why the grid failed this time.

There are various reasons why an excessive withdrawal of power happens. Weather phenomenon and change in sudden climate is one reason. Most of them cannot be controlled physically but can be minimized by keeping a close check.

There is a penalty clause: ‘Unscheduled Interchange’ rate - whenever the discoms draws more than necessary power, the UI rate goes up as a penalty.

Northern states of India, like Uttar Pradesh, Punjab, Haryana and Jammu Kashmir, have been found to be habitual violators. The UI penalty has – as is evident - not been able to deter the violators. Presence of heavy industries and fast growing cities has necessitated the need for more power. But the production has not been able to cope up with the required distribution.

Power grids in India

India has five electricity grids - Northern, Eastern, North Eastern, Southern and Western. All of them are inter- connected, except the Southern grid.

The northern grid covers nine regions - Punjab, Haryana, Rajasthan, Delhi, Uttar Pradesh, Uttarakhand, Himachal Pradesh, J&K and Chandigarh.

At least six states are covered by the eastern grid. They are West Bengal, Chhattisgarh, Bihar, Jharkhand, Orissa and Sikkim.

The north eastern grid connects Arunachal Pradesh, Nagaland, Assam, Meghalaya, Manipur, Mizoram and Tripura.

Western grid covers Maharashtra, Gujarat, Madhya Pradesh and Goa.

South grid covers Tamil Nadu, Kerala, Karnataka, Andhra Pradesh and Puducherry.

All the grids are being run by the state-owned Power Grid Corporation, which operates more than 95,000 circuit km of transmission lines. One circuit km refers to one kilometer of electrical transmission line.

Grid failures apart from India

India is not the only country that suffers from grid issues. In 2003, there was a massive power failure in North America with New York plunging into darkness.

The blackout in Indonesia in 2005 had hit over 100 million people.

But India seems to have suffered arguably the worst crisis in terms of the population that got affected.