Sept 12 power outage: Millions in Chennai were plunged into darkness because officials awaited ‘approval’ from top
The Executive Director noted that the TNSLDC does not have an SOP in place, nor is it empowered to shed load in an emergency
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CHENNAI: The massive outage that hit most parts of Chennai, especially north Chennai, that lasted for several hours on September 12 could have been avoided if the officials concerned had implemented a load shedding of 300 MW without waiting for ‘management approval’.
This was admitted by Tamil Nadu State Load Despatch Centre (TNSLDC) officials during the last meeting of the Southern Regional Power Committee (SRPC), an admission that prompted the committee to pull up the centre for not having a standard operating procedure in place to act in the event of a major grid disturbance emergency and avoid power outage.
Also Read: Midnight outage hits TN power demand by 1,300-1,400 MW
What is worse, the TNSLDC failed to learn a lesson even after that incident, which inconvenienced millions of people, the regional panel noted, citing several such incidents in the few days before the meeting.
The outage on September 12 night happened when the transmission lines tripped. The major grid disturbance began with a 400 kV NCTPS-Manali line R-B fault at 8.11 pm. This caused an increase in power flow on the 400 kV Alamathy-Manali line, which tripped at 9.54 pm due to a B-phase line isolator fire at Alamathy.
Also Read: Chennai: Power supply back after major outage; tripping caused by fire at Alamathi substation
This had a cascading effect, leading to tripping of multiple transmission lines resulting in a load loss of 1,300 MW. As a result of this, most parts of the city were engulfed in darkness.
At the 219th meeting of the operation coordination sub-committee (OCC) of the SRPC held last month, TNSLDC said the failure of one feeder led to the tripping of the other as well because there are only two source feeders to Manali.
But the Executive Director, SRLDC, Grid-India, Bengaluru, pointed to the time gap of over an hour between transmission line tripping. The officials from the State said they could not take immediate action for want of approval. They had planned to shed some 230 kV load at Sembatty area but had approval constraint, the official noted.
The Executive Director noted that the TNSLDC does not have an SOP in place, nor is it empowered to shed load in an emergency. “For the want of a few MW load shedding, the system lost 1,300 megawatts of power,” the official said as per the meeting minutes.
Growing wiser after the incident, the TNSLDC submitted a note to the management recommending blanket approvals for taking necessary actions in case of contingencies.
The SRPC member-secretary reiterated that SLDC cannot depend on management approval. “In real-time grid operations, decisions must be made by the SLDC itself…Once TNSLDC is in real-time operations, the SLDC holds the authority. During each incident, obtaining approval is not advisable. Approvals are required for planned activities, not for real-time contingencies,” the official said.
The regional committee even noted that there have been many incidents over the 20 days prior to the meeting, and criticised that it appeared that TNSLDC was not learning from them.
The Executive Director stressed the serious concern over the failure to implement a 300 MW load shedding, which could have prevented the load loss of 1,300 MW for an extended period.
After deliberation, the OCC recommended that Tamil Nadu Transmission Corporation should investigate the recent incidents and present findings at the next meeting, focusing on identifying urgent actions, both short-term and long-term, to avoid them in future.
“Develop and implement SOPs for SLDC to empower them to act decisively during emergencies without needing approvals,” it said, adding that the corporation should ensure that the SLDC has the authority to make real-time decisions, particularly regarding load shedding during contingencies, without waiting for management approvals.
SEPT 12 NIGHT CHAOS:
~ A 400 kV NCTPS-Manali R-B fault at 8.11 pm causes a rise in power flow on the 400 kV Alamathy-Manali line
~ Leads to further tripping of 400 kV Alamathy-Manali line at 9.54 pm due to a B-phase line isolator fire at Alamathy
~ Multiple trippings also observed in 230 kV system due to overloading, affecting around 30 transmission elements at 400 kV and 230 kV levels
