A POPULAR online question-and-answer platform has several queries on why electricity goes off in the local trains in Mumbai every time they cross a stretch between Mahim and Kings Circle or Vile Parle railway station.

Offline, in the real world, most train commuters are used to the few seconds of blackout, most not even battling an eyelid as darkness descends. Very few, however, know the electricity goes off because on that stretch the trains enter a “neutral zone”, which has an important safety function in case there is a power outage on the suburban railway network.

Explaining the reason, a railway engineer said the trains are powered by electricity supplied from several traction sub-stations that dot the railway network. On most railway lines, a traction sub-station normally powers trains for around 60 km after which the train falls under another sub-station.

“A gap is left between two sub-stations to synchronise the electricity supply as different sub-stations are powered by different suppliers, from Tata Power to the Maharashtra State Electricity Board,” he said.

“This gap, which normally does not extend beyond 5 metres, is called the ‘neutral zone’. In this zone, when a train is crossing one sub-station to another, the electricity is switched off and it moves forward purely on its momentum. Hence, in these neutral zones, the electricity in the trains goes off for a few seconds before the next sub-station powers it again,” he explained.

According to him, neutral zones play an important role in that if there is a power outage in one sub-station, it will not trip the other sub-stations, which would continue to function normally. This way, outage at a sub-station can be contained within the distance it supplies power, sparing the entire rail network.

The official said there are sub-stations between Mahim and Kings Circle railway station, at Tilak Nagar railway station and Kanjurmarg.

Royston Noronha (32), who travels from Mahim to CST everyday for work, said, “The lights going off between Mahim and Kings Circle has become a part of my daily commute. During the day, it does not even matter as the fans merely restart. While returning home at night, when I’m reading something, there is an interruption of a few seconds. However, most of us have become used to it and almost anticipate the lights going off once the train crosses Kings Circle station.”

Noronha, like others travelling with him, does not know the reason for the power going off. “I had asked a few people and someone told me about the height of a bridge nearby being low and, hence, electricity lines not passing under them. After a point, I stopped asking as everyone has a different story.”

Have a comment or suggestion for Life On The Local? Write to mumbai.newsline@expressindia.com with subject line: Life On The Local

📣 The Indian Express is now on Telegram. Click here to join our channel (@indianexpress) and stay updated with the latest headlines

For all the latest Mumbai News, download Indian Express App.