Sunday morning scare: Mumbai sees 70 min power outage as state-owned power lines trip

Employees of a medical store manually browse for medicines as they were unable to access computers at Walkeshwar. Pic/Bipin Kokate

In a near repeat of the October 12, 2020 power failure in the city, electricity supply went kaput on Sunday, but only for 70 minutes. One of the state-owned power lines that bring power to the city tripped, thereby creating shortfall of 800-1,000 megawatts (MW) to the island city, some eastern and western suburbs at 9.48 am, affecting train services too.

Areas such as Carnac, Parel, Mahalaxmi, Dharavi, Backbay, Grant Road, Bandra-Kurla Complex, Wadala, Chembur, Trombay and Mankhurd were affected when the Trombay-Salsette transmission line, operated by the Maharashtra State Electricity Transmission Company (MSETCL), tripped.

Energy minister Nitin Raut

At that time, the demand in the service area of the Brihanmumbai Electric Supply and Transport Undertaking (BEST) was 414 MW and it could not supply a single unit because it buys power from others for distribution and it does not have its generation capacity. Suburban supplier Adani Electricity Mumbai Ltd shed a load of 112MW when the demand was at 877MW. Similarly, Tata Power shed a load of 383MW when its demand was 589MW. State-owned Mahavitaran's area remained unaffected.

Energy Secretary Dinesh Waghmare said alternative lines were used to shift load between after 10.08 am and all loads in Mumbai were restored in 70 minutes.

Throwback

The outage rekindled the memories of the major incident in 2020, if not in terms of the longer outage but the occurrence. In 2020, the supply in some parts of the city could be restored only after a day. However, this time, instead of 440kv, the 220kv line tripped, thus creating a relatively less impact. But, it did affect the city's embedded generation at Tata Power's Trombay plant, which also tripped as a cascading effect.

Workers carry out maintenance work on a high tension tower of Tata Power at Dharavi. File pic

After the 2020 outage, the government and Central electricity agencies had probed into it and recommended that the city's power infrastructure needed an urgent upgrade. More lines must be built to carry power from outside to cater to the growing demand, they said. The pending work of such lines was expedited by the Maharashtra Electricity Regulatory Commission (MERC) by transferring it to Adani Power, citing inordinate delay in construction by Tata Power. Early this month, the Appellate Tribunal for Electricity upheld Maharashtra regulator's decision of awarding a Rs 7,000-crore transmission project to Adani on a nomination basis, but the aggrieved petitioner Tata Power is expected to move the Supreme Court in the case.

No cyberattack: Energy minister

A possibility of cyberattacks were also probed in the 2020 outage and Maharashtra cyber department report had confirmed that a malware had hit the system and about 14 Trojan Horses and 8 GB of unaccounted data was found.

Talking about Sunday's incident, Energy Minister Nitin Raut told mid-day that it was not a cyber attack. "I have gathered all the information. There is no cyber-attack. It was purely a technical issue that our engineers and technicians resolved quickly. Our priority was to restore the supply," he said.

Nitin Raut, energy minister

The minister has ordered a top-level probe. "The responsibility will be fixed and action taken against the guilty," he said.

Blame game

While some industry experts allege that Tata Power's Trombay plant failed once again and that there was a delay in ramping up of alternative power sources to mitigate the deficit, the company claimed that its Trombay plant was intact and it did not delay to bring in power from Bhira hydro Plant. "Electricity was restored by Tata Power in around an hour," a statement said.

"At 9.50 am, in south Mumbai, Chembur, Bandra and Santacruz suburbs, along with Central and part Western Railway, power supply got affected due to tripping of MSETCL line at MSETCL Trombay receiving station that connects to Tata Power transmission system. This resulted in the tripping of Trombay generation and cascade tripping of some internal lines affecting 850 MW load of all companies in Mumbai," said Tata Power spokesperson.

Adani Electricity Mumbai Ltd spokesperson said, "Today's power outage was caused due to tripping of 220 kV transmission line and subsequent outage of Tata's Trombay power plant. Adani Electricity consumers were largely unaffected by today's power outage as we were able to ramp up our generation at Dahanu in a very short time. This helped early restoration of consumers in South Mumbai."

Action needed

In October 2021, the Energy Department submitted a report to the cabinet regarding the 2020 power outage and cited several reasons that led to the blackout. It has made recommendations, some of which are being followed to avoid recurrence of the event.

The report said the inadequate islanding mechanism and insufficient electricity generation inside the city limits, lack of coordination between the companies, load despatch centre and sub-centres, non-availability of high-tech emergency handling equipment at the load despatch centre and lack of a standard operating procedure (SOP) had caused the outage.

The first and foremost recommendation was to have a revised SOP for the planned outages, maintenance and repairing activities across companies. Other recommendations were about working on the deficiencies and causes given. Emphasis will be given on increasing electricity generation within the city limits and a task force has been formed to study the effects of new trends and technology on the Mumbai network.

The expert panel that made the recommendations said a plan has been submitted to safeguard critical information infrastructure through cyber-crisis management and that the IT infrastructure has been audited and cyber-cleansing has been taken up as the suggestions.

70 minutes
Period power supply was hit

No train services for over 20 minutes

Commuters walk on tracks between Mumbai Central and Grant Road stations on Sunday

The outage also brought local trains to a standstill. Due to cancellation of services and trains being stranded on tracks, some passengers walked on railway tracks to reach their destinations. "Trains did not move for over 20 minutes from Churchgate," said Jay Dixit, a commuter. "There was no train movement between Churchgate and Andheri. As an interim measure supply was extended from Jogeshwari substation and services were restored at 10.44 am. The regular supply was restored at 10.53 am. On WR, about 50 trains were cancelled and 140 trains delayed. The Delhi Mumbai Rajdhani arrived at Mumbai Central late by 30 minutes," WR CPRO Sumit Thakur said. "Central Railway services were affected after power supply tripped on harbour and mainlines between 9.49am and 9.52 am," said Shivaji Sutar, chief PRO, CR. A Tata Power Company statement said, "This morning, the MSETCL transmission line from Kalwa to Trombay had massive voltage fluctuations causing tripping of Trombay Salsette-1 on overload. This affected the south Mumbai electricity distribution system. However, Tata Power's Hydro plants were intact, and the Bhira Hydro Plant got islanded and synchronised. The electricity has been restored by Tata Power."

- Rajendra B. Aklekar