The blackout that engulfed a fourth of the capital Dhaka on Sunday night was the upshot of the city鈥檚 largest power sub-station going dead from a rare physical fault, said Power Grid Bangladesh officials on Monday.聽聽
The cause of the physical fault, which was so rare that PGB officials hotly debated whether anything like it had ever occurred in the past, may be a range of possibilities from environmental to electrical stresses.
A probe body has been given seven days by the PGB to find out what really happened on the night that caused as many as 13 porcelain insulators to crack, all at the same time, at the most critical part of the sub-station, plunging about a聽 million people into darkness for three hours or more.
鈥楬uman interference surely did not trigger it, neither was there any thunderstorm when the insulators broke,鈥� said Syed Abadullah Haider Ali, a chief engineer at the PGB, also the head of the probe body.
鈥楾he blackout was undoubtedly unprecedented,鈥� he said.
Around 9:45pm, the insulators in the 132KV line broke down, causing upper and lower wires in the electrical bus system to be entangled, triggering the grid failure all of a sudden, PGB officials said recalling the incident.
Electrical engineers were initially clueless about what was happening and then started reviving the three transformers at the sub-station in Rampura delivering power to a fourth of Dhaka through Dhaka Electricity Company Limited and Dhaka Power Distribution Company Limited.
One of the transformers could not be repaired until 11:39am on Monday.聽聽
An electrical bus system refers to a common connection point where power generators, feeders, and transmission lines are linked, ensuring a safe and smooth flow of electricity, electrical engineers explained.
鈥楢 series of insulators breaking down altogether perhaps never happened in the country,鈥� said Md Abdul Monayem Chowdhury, executive director, operation and maintenance, PGB.
High-voltage insulators can crack during production and installation due to manufacturing defects. This possibility does not apply here because the sub-station was installed more than two decades ago in 2001.
Temperature fluctuations, wind, and pollution are parts of environmental stress that can lead to cracks in high-voltage insulators over time, especially in the absence of proper monitoring and maintenance, electrical engineers said.
The lifetime of high-voltage insulators ranges from 25 to 30 years, which could be shortened depending on poor maintenance, they said.
Temperature fluctuations for quite a while became kind normal because of the impacts of climate change causing steep temperature drop such as 9C or more on many days in a year, particularly following heavy rain spells during summer or heavy fogs occurring in winter.
Dhaka also has one of the world鈥檚 worst air pollution.聽聽
The other reason, electrical engineers said, leading to cracks in the insulators could be surges in electricity supply, which could occur from power plants suddenly supplying high-voltage electricity.
鈥榃e are looking into all possibilities to prevent any such problem from recurring in future,鈥� said Monayem.
The latest malfunctioning of the national grid at one of its most important power sub-stations signifies the sorry state of the power transmission network.
This is the third time since March that the national grid failure triggered blackouts affecting hundreds of thousands of people, making the grid failure an almost a frequent matter.
The situation, however, was expected to be different for the 1,200MW first unit of the Rooppur nuclear power plant is all set to come online soon.
Over the past few months, the PGB has been trying to get power plants operate on the FGMO or free governor mode of operation in which power generators respond independently to frequency deviation in the grid.
Frequency fluctuations could be highly frequent in the national grid for power generators in operation in Bangladesh have a notorious track record of being imported without following the standard.
鈥榃e keep the system under strict monitoring always,鈥� said BM Mizanul Hassan, a chief engineer, PGB.
On April 26, 21 districts in southern, southwestern and central Bangladesh suffered blackout which the PGB later said was triggered by a loose kite string. The blackout affected millions during a heatwave.
Described as a transient fault, a short circuit, 65km off the critical Aminbazar power sub-station, triggered the March blackout, affecting thousands of Dhaka residents.
The incident caused a fire in the Aminbazar sub-station that kept burning a transformer for 12 hours on March 11.
The Aminbazar sub-station is the final entry point of about 1,000 MW of power to Dhaka. The malfunctioning of the sub-station caused a shortage of 2,277 MW of electricity.
The surprising aspect of the Aminbazar fire was that it occurred amidst grid collapsing. Grid collapse is a spontaneous response, in-built in the transmission system to prevent fire or any damage in electrical equipment.聽
The unreliable national grid has led to the building of an additional captive power generation capacity of 2,800MW operated by industries to meet own demand.
Earlier in October 2023, the Aminbazar sub-station saw one of its transformers explode, leading to outage in Dhaka due to the grid collapse.
Exactly a year ago in 2022, the national power grid collapsed, causing outages in four divisions for up to 10 hours.
There were two other occasions of grid collapse after 2014, the causes of which were never known beyond doubt.
