On Monday, as Mumbai and its suburbs faced a major power outage, many wondered why Maximum City seldom faced power outages while the rest of the country suffered. Yet the MMR, which spreads over 4355 square kilometres including eight municipal corporations including Greater Mumbai (BMC), Thane (TMC), Kalyan-Dombivali (KDMC), Navi Mumbai (NMMC), Ulhasnagar (UMC) and other Vasai-Virar (VVMC) seldom faces power cuts.
How is it that the financial capital of the country manages this while others don’t?
For that we need to understand how power is provided.
Everywhere in the country discoms (state-run power distribution companies) and private players like Tata or Adani combine to provide power needs. Discoms total losses are massive, reportedly around Rs 49,623 crore in FY19-20.
This makes it very hard for state discoms to purchase additional power or improve its system. In most capitalistic models, the power companies cannot pass on the end-cost to the consumer.
Even an Arvind Kejriwal – an IIT graduate and former IRS officer – makes it one of his electoral planks.
As this Business Standard piece notes: “Over the years the cost of producing power has gone up. Coal prices have shot up, cheap domestic gas supply went dry and newly introduced renewable sources are costly. But your bill in the past five years would reflect that minimally. The generator included the high operation cost in the final price of power. But our power distributor, tangled in the leash of political motives can hardly pass it on to the consumer.”
However, Mumbai has a host of private power suppliers and residents who pay whatever is charged. Maharashtra’s power slab is the highest in the country. So, while Mumbaikars pay a lot for power, it also means they get uninterrupted supply.
Who provides power in Mumbai?
There are four agencies that supply power in city - Tata Power, Adani, BEST and erstwhile MSEB which is now MSEDCL.
After the trifurcation of MSEB, there are three separate state companies.
MSETCL looks after transmission (high-voltage wires), MSEDCL looks after distribution (local area network) and Mahagenco (after power generation).
What is Islanding?
The method which makes Mumbai’s system effective is called ‘Islanding’ which was first designed in 1981 by Tata Powers.
Even when there’s as system failure, the consumer remains un-affected. It involves keeping a source within an ‘island’ which can immediately keep pace with the requisite demand.
Companies like Tata and Adani have invested a great deal to ensure that power distribution remains monitored and allocated properly.
The islanding system reportedly prevented grid disturbances in Mumbai 27 out of 37 times.
An old piece on Business Standard notes: “This was designed to intentionally isolate its network during widespread external grid disturbance, enabling supply to continue for essential category consumers, avoiding a tripping of thermal generators and quick restoration of the failed system.”
Islanding works because a micro-grid disconnects a local circuit from a bigger grid and meets the power locally. In Mumbai, the islanding primary depends on Tata’s power supply which comes from a thermal plant in Trombay and hyrdo-units in Khopoli, Bhira and Bhivpuri. Adani’s supply comes from its unit Dahanu.
Kalwa is an important sub-station where the problem began.
What went wrong?
Yet, Mumbai and its surrounding areas faced a lot of issues. BEST took to Twitter to blame TATAs incoming electric supply failure. TATA Power said in a statement that MSETCL has taken an emergency shutdown for 400KV Kalwa-Padghe Line 1which was expected to be revived by 9:30 AM but couldn’t be revived.
At 9:58, the Kalwa-Padghe-2 carrying 633 MW tripped which saw the flow on Pune-Kharghar rise to 900 MW and then trip. Mumbai's islanding system was separated but it couldn't hold the 900 MW addition load.
Meanwhile, Adani Electricity said: “AEML System experienced grid disturbance due to fault outside of it. Islanding of Dahanu saved the essential supplies. Rest supplies are being restored as grid inputs get available from Maharashtra System. Please bear with us as we await Maharashtra grid restoration. Due to constraints with a few transmission lines & the Tata generation, the MH SLDC has restricted further addition of load. We're working to resolving this on priority in order to restore the power supply. Requesting customers whose supply is still affected to bear with us.”
Meanwhile, Mahatransco said that 400kV Kalwa-Talegaon PG Line was under breakdown since 1:47 PM on October 10 2020, while the 400kv Padgha-Kalwa CKT-1 was tripped over voltage at 4:33 AM. The 4001-Kalwa-Padgha-2 tripped at 10:01 AM while the 40001 Talegaon PG-Kharghar line.
Finally, the Talegaon PG-Kharghar line was hand-tripped at the Kharghar end at 10:02 AM due to heavy sparking. This led to both the 400KV bus at Kawla and Kharghar getting completely de-energised resulting in loss of Tata Unit at -5.
Hence 400kv both bus at Kalwa and Kharghar got completely De-energised (zero load) from 400kv side Resulting in loss of Tata unit-5 (500 mw).
Power cut in 2018
In June 2018, there was a widespread power outage in the city and adjoining areas due to a technical glitch and also led to sustained period of load-shedding for some consumers.
Maharashtra's Power Minister Nitin Raut said the trouble on Monday emanated from Maharashtra State Electricity Transmission Company (MSETCL) facilities during a planned maintenance work.
Tata Power, which is into both generation and distribution, attributed the outage to a simultaneous substation tripping at 1010 hrs at state-run transmission company MSETCL's two substations in the suburbs of Kalwa and Kharghar.
Power outages were reported from suburbs like Thane, Panvel, Dombivili and Kalyan as well, along with those in the island city and the suburbs.
Raut assured that power supply will resume soon, as officials were working on it on a war footing.
As the afternoon progressed, power at many pockets including the Bandra Kurla Complex business district, Lower Parel, the western suburbs and South Mumbai started resuming operations.
Diesel supply for hospital
With the number of COVID-19 infections still very high and many patients recovering in hospitals including specially-created facilities rendering services like oxygen supply, Municipal Commissioner of Mumbai I S Chahal instructed staff to bolster diesel supply to last up to eight hours and also scout for mobile diesel generator vans which are used at film shoots as a standby.
An industry source said it took longer than expected for the power supply to resume because one of the two thermal power stations in the city and its vicinity, which have to act as a ready source as part of an "islanding" system to avert such situations, took longer to start generating power.
Raut said maintenance work was on in MSETCL's 400 kv Kalwa-Padgha line when the technical fault happened in circuit number 2, which was taking the entire load at the time as circuit 1 was shut.
MSETCL is responsible for getting power till the Kalwa substation from generating stations across the state, from where distribution companies like
Tata Power and Adani Electricity take it to the consumers, the source said.
As part of islanding system, a thermal based power plant each of Adani at Dahanu and Tata Power (Trombay) are expected to supply power.
With inputs from agencies