About 100 million people in Bangladesh, out of a total of 160 million, were without electricity for about 10 hours on November 1. The rest of the population has no access to the national grid. The interruption originated at 11.30 am at a sub-station in Bheramara in Kushtia district. Soon it knocked out the 400 KV transmission line that was bringing in 445 MW of power from India.
As the national grid lost about 445 MW of power, an uncontrolled chain reaction set in. All the power plants of the country were forced to shut down. Industrial production came to a halt. Captive generators partially supplied electricity to some industries, domestic houses, hospitals, airports, commercial places and other important installations.
There were long queues for diesel oil at gas stations to feed the captive generators. The supply of CNG to automobiles was interrupted due to the outage, increasing the demand for gasoline. The traffic gradually thinned out. Even though electricity was partially restored in some areas in the afternoon, the streets became empty after sunset in the capital city as the restaurants and shopping places had closed down. By 4.30 pm, the power plants, which were brought online, tripped again, further complicating the situation. A shortage in supply of water was reported in some areas. Prices of candles and kerosene suddenly shot up. The internet and mobile phone services deteriorated. The electronic and newspaper media were also affected. By 9.00 pm, some areas got electricity back. The system was back to normal after midnight.
Even though the crisis seems to be over, questions on the blackout are still lingering in the minds of the people. How did it happen and why should it happen after so much investment in the power sector? To answer these questions, we need to understand how an electric power system operates. An electric power grid basically consists of power plants to generate electricity and transmission and distribution lines to carry the power to the consumers. There are numerous protective relays and other devices to regulate the system. The grid is controlled from a load dispatch center.
A power grid is a very delicate system in the sense that there must always be a perfect balance between the generation and the load or demand so as to maintain a constant system frequency which is 50 cycles/second in our region. Whenever there is an imbalance, the frequency will automatically change. If a generator fails, the load will instantly exceed the generation capacity, resulting in a drop in frequency. If the loss of generation is within a tolerable limit, it is possible to continue the operation of the grid by increasing the generation from the hot reserve capacity of the system which is available from the operating power plants and/or by resorting to load-shedding. On the other hand, if a significant load is lost, there will be excess generation in the system that will boost the frequency. In that case, the generation capacity must be reduced to bring down the frequency to the desired level.
A power grid collapses if the loss of generation or load is too large for the system to handle. This is exactly what happened on November 1. The tripping of the transmission line at Bheramara amounted to a loss of about 445 MW of power imported from India, as mentioned earlier. It is reported that the sub-station at Bheramara cannot handle any power beyond 400 MW. The loss of power at Bheramara reduced the frequency to 45 cycles/second and created an electric surge that finally caused the blackout throughout the country.
Can such blackouts be avoided in the future? An electric grid is a man-made system. It can never be perfect. Blackouts occur all over the world, including the most advanced countries even though the frequency of occurrences may vary from country to country.
It is obvious that a blackout can never be avoided but its frequency and severity can be reduced if modern protective and regulating devices are used and enough hot reserve margins are available in the system. In addition, modern smart grids with state-of-the-art technology are in use in many advanced countries that can detect and react to any situation in real time. Such systems can minimise the frequency of occurrences and severity of outages in addition to increasing the system efficiency.
The writer is a former chief engineer of Bangladesh Atomic Energy Commission and the author of “Rooppur and the Power Crisis.”