Blackout warning: Scanty rain, dense fog and pollution raise risk of India’s power transmission lines tripping

In fact, a perfect storm may be brewing across several parts of north and central India, where a rain-deficient winter, dense fog conditions and atmospheric pollution have raised concerns over the tripping of power transmission lines, said three people aware of the outage concerns in India’s power system.

Fog increases moisture on power transmission lines, allowing pollutants in the air to settle on their surface. Over time, dust and grime accumulate on these lines, reducing insulation strength and leading to flashovers (a high-voltage discharge where electricity "jumps" across an unintended path—usually through the air or over the surface of an insulator), short circuits and automatic tripping of transmission and distribution lines.

If left unaddressed, such conditions can escalate and potentially lead to a grid collapse. The states at risk of power outages include Punjab, Haryana, Uttar Pradesh, Rajasthan, Delhi, Madhya Pradesh and Chhattisgarh.

While rains are the natural cleanser for transmission lines and insulators, this hasn’t been the case this year. Rainfall across the country in December was about 69% deficient compared to the 10-year average, according to data from the India Meteorological Department (IMD). Also, the deficit was wider in northwest India (84.8%) and the central region (99%).

"This year, the winters have been rain-deficient, which has raised concerns. There were rains in the last winter season and it helped in terms of cleaning the insulators, thereby reducing outage concerns. While earlier helicopters were used for cleaning of the transmission lines and insulators; now it is largely done manually with the use of chemicals," said a power sector executive requesting anonymity.

Environmental issues

“The materials used for the overhead (transmission) systems do get impacted by the elements in polluted air. Because of these environmental issues, there are issues being faced and any system has to be insulated against these elements which come in their path," said Anil Razdan, former secretary of the power ministry. “We need to be cautious of the reaction or the reactivity of the environment. Sometimes insulation may also wear off due to acidic content in the environment. There has to be a constant health check and efficiency check of the systems."

"India is witnessing more frequent and intense fog episodes this winter," IMD Director General of Meteorology Mrutyunjay Mohapatra said, attributing the trend to weak wind conditions and persistent western disturbances.

In December 2025, dense-to-very-dense fog conditions persisted for about 15-26 days, mainly across the Indo-Gangetic Plains covering Punjab, Haryana and Uttar Pradesh, Assam, Odisha and parts of the western Himalayan region, including Himachal Pradesh and Uttarakhand. Madhya Pradesh and Bihar reported 10-14 days of dense-to-very-dense fog.

Fog is classified based on visibility. Dense fog occurs when visibility reduces to 50-100 metres, while very dense fog is when visibility falls below 50 metres.

There have been several incidents of fog-related tripping including on the 400 kV Bareilly-Unnao CKT-1 transmission line in Uttar Pradesh and the 400 KV Suratgarh-Bikaner CKT-1 line in Rajasthan. Following dense fog and instances of tripping on 15 and 16 December in north India, the Grid Controller of India asked all generators and transmission service providers to "maintain high alertness in view of IMD warning of dense fog and communicate any load loss/generation loss due to the same."

Despatch centres

It also requested state load despatch centres to take quick measures to restore affected transmission elements and generation. These despatch centres coordinate between power generators (state-owned and private), transmission utilities and electricity distribution companies (discoms) to ensure that supply and demand within a state remain perfectly balanced.

The latest case in point was the tripping of a transmission line on 19 December amid heavy fog last month that resulted in an outage in industrial areas in Ludhiana.

Queries mailed to the spokespersons of the power ministry, Power Grid Corp of India Ltd and the Grid Controller of India on Tuesday remained unanswered till press time.

With more renewable capacity being added, the grid is already under pressure, given the intermittency brought about by solar and wind power. India has set an ambitious plan to install a total of 500 GW of non-fossil capacity by 2030.

Data from the Grid Controller of India, which runs the power grid, showed seven instances of grid disturbances in the northern region in December, 10 in central India, seven in the western region and three in the eastern region due to reasons including dense fog conditions and atmospheric pollution.

A severe winter this year has increased electricity demand – India's peak demand reached 241 GW this season. This assumes significance given that India's 4.98 lakh circuit kilometre (ckm) power grid is one of the world’s largest integrated networks that connects the entire country at 50 Hz frequency.

A grid collapse is the worst-case scenario. On 31 July 2012, almost 620 million people across 19 states and three Union Territories went without electricity for hours when the northern grid collapsed. Also, on 1 August that year, the northern, eastern and north-eastern grids broke down in a wider blackout.

Renewable energy

Even the availability of renewable energy does not guarantee grid stability. In February last year, amid heavy cloud cover and lower generation of solar power, there were instances of grid instability, raising concerns amid stakeholders.

The national grid operator asked all electricity companies at the time to be alert and increase supply of power to preserve the grid's stability amid cloud cover.

In April last year, Spain and Portugal, which source 80% of their power from green sources, experienced nationwide blackouts due to voltage instability and cascading protection tripping.

Senior officials in Punjab and Haryana said they are monitoring the situation daily to prevent any untoward incidents. Officials of discoms of Uttar Pradesh, Rajasthan, Delhi, Madhya Pradesh and Chhattisgarh could not be reached for comment.

Dense fog conditions have also led to cancellations and delays of flights and trains this season.

"Fog incidence this year has been higher than in previous years, largely due to increased pollution levels and prevailing climatic conditions, including scanty rainfall in December. The persistence of dense fog has cascading effects on many sectors including daily life by reducing visibility, slowing road, rail and air transport, and increasing accidents and delays," said Harminder Pal Singh, chairperson, department of environment studies, Panjab University. “It also affects economic activity, causes power line tripping and outages and worsens respiratory health due to pollution."

Scanty rain

While noting that tripping and outages have reduced over the years, a former executive with the Grid Controller of India said on condition of anonymity that scanty rains this winter can be among the factors for heightened concerns.

"Tripping instances were pretty high till 2010 in northern India. However, subsequent replacement of porcelain insulators with polymer insulators has reduced the outages. This replacement is yet to complete in some stretches, where concerns persist. Polymer insulators are pretty effective even in case of high pollution levels. Pollution is a key reason for the outages," said the former executive.

To be sure, cleaning of transmission lines and insulators is carried out in October and November before the fog and smog start to set in.

"Cleaning is done after shutting down the lines at specific stretches for a few hours. That is also quite tough and risky as we need to see that the grid is not impacted given that it is an integrated power grid," said an official with Punjab State Power Corporation Ltd.

On 15 June last year, electricity withdrawn from India’s transmission network – withdrawal refers to transmission of power from a generating facility to power distribution centres – exceeded the available capacity, raising fears about the grid’s stability. The Grid Controller of India wrote to the generators and discoms in the northern region to either lower the withdrawal or ramp up generation to avoid a blackout.