Mumbai power supply to be fully restored by 3:30 pm: Here's detailed sequence of events
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Mumbai and surroundings were hit by a sudden power failure on Monday, affecting daily life. The outage was attributed to a technical failure involving multiple tripping of power transmission lines and supply transformers.

After an unprecedented power cut, Maha Transco said that power would be restored to Navi Mumbai and Thane in the next one-and-a-half hours. As of 1:30 PM, power had been restored in several areas of Mumbai city and its suburbs. The process is expected to be completed soon and is expected to take two more hours.

Electricity supply was interrupted in Mumbai due to TATA's incoming electric supply failure, causing power loss all over Mumbai and suburbs and disrupting train traffic of Central, Eastern and Western lines, according to Brihanmumbai Electric Supply and Transport (BEST) on Monday.

According to TATA Power, "At 10.10 am there were simultaneous substation tripping in MSETCL's Kalwa, Kharghar causing a huge dip in frequency in Mumbai transmission system which led to tripping of power supply. Restoration work in progress to bring a supply from the 3 Hydro units and Trombay units."

In a video statement, Maharashtra's Power Minister Nitin Raut said maintenance work was on in Maharashtra State Electricity Transmission Company's (MahaTransco) 400 kv Kalwa-Padgha centre when the technical fault happened in circuit number 2, which was taking the entire load at the time.

"Repair and maintenance work was underway at Circuit 1 of 400 KV GIS centre and the entire load was put on Circuit 2. However, sudden technical failure in circuit 2 resulted in power being affected in most of the parts of Mumbai and Thane," Raut said.

According to information shared by MSLDC, one of the circuits, 400KV Kalwa - Padgha Circuit 2 suddenly tripped at 10.01 am, further tripping 400KV Kalwa – Kharghar due to overload at 10.02 am. Meanwhile, the Padgha- Kalwa Circuit 1 was under outage and 400KV Kalwa - Talegaon was under a shutdown.

Here's detailed sequence of events about today's power breakdown:

1. 400kv Kalwa-Talegaon PG line was already under breakdown (since 13.47 hrs 10.10.2020).

2. 400kv Padgha — Kalwa ckt-1 was tripped on over voltage at 04.33 hrs today. Outage was given for Replacement of Insulator string.

3.400kv Kalwa — Padgha -2 Tripped at 10.01 hrs on Distance Protection. Conductor Snapped at loc 1007.

4.400kv Talegaon PG- Kharghar line was handtripped at Kharghar end at 10.02 hrs due to Heavy Sparking Observed.

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).

6. Also 220kv Supply line 3 from Boiser PG Tripped at 10.05 hrs.

7. Therefore Tata load of appx. 570 (MW) & BEST load of 440 (MW) Tripped.

8. AEML, area went into islanding mode with Tripping of 700(MW) load.

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