Park Street lies under a blanket of darkness on Sunday evening, except for a few islands of illumination powered by generators and moving vehicles. Power came back to the area around 10.30pm. Picture by Sanat Kumar Sinha

Calcutta, April 19: Nearly the whole of Calcutta blacked out on its hottest April evening in years, thanks to a massive power failure reminiscent of the dark days of the ’80s in the run-up to elections.

Around 80-85 per cent of the city went without power for at least three to four hours — including the Metro, Kalighat temple and the airport for a while — before CESC briefly restored supply only to see it snapped again in some areas.

People blocked roads in several areas such as north Calcutta’s Manicktala as power failed to return even at 10.30pm, nearly six hours after all four CESC power-generating stations had collapsed at 4.45. Stocks at the Central Blood Bank in Manicktala were feared to have got infected because of the long power cut.

Patients’ families and local people smashed glass doors and damaged equipment at the Institute of Child Health, Park Circus, around 9.30pm as the sick children continued to suffer.

Power department sources said the “partial grid failure” was a throwback to the late ’80s and early ’90s — a period of overall stagnation that the Left Front wouldn’t be too keen to remind voters of as it heads into a crucial election.

Officials said the four stations had collapsed after a blast in a Liluah “current transformer” caused wild fluctuations in flow, and the isolation devices meant to protect the power stations failed to work (see chart).

Private utility CESC’s engineers revived the Titagarh and New Cossipore stations but they tripped again soon after.

Power secretary Sunil Mitra said: “After the transformer exploded, there was a surge of electricity that led to the tripping of all (CESC) units. It seems their isolation devices did not work. They will submit a report to me.”

“It’s a fact we could not isolate our system in time,” said Dilip Sen, CESC executive director, who has ordered an investigation. “There have been explosions of current transformers before but we never faced this kind of problem.”

The power cut came as the Kolkata Knight Riders started their campaign in South Africa, but the city didn’t miss much. Bad weather truncated the first game to almost a farce as Delhi Daredevils trounced Kings XI Punjab, and then the Knights got off to a terrible start against the Deccan Chargers to eventually lose by eight wickets.

Parts of south Calcutta that escaped the power failure had erupted in firework as Brendon McCullum — “usurper” of Sourav Ganguly’s captaincy crown — fell for one. But soon Sourav too was back — for one off 12 balls.

It could have been worse, though — a repeat of last year’s Eden Gardens fiasco in a pitch-dark Calcutta — had the IPL not been shifted abroad. In a coincidence, the match at Cape Town was delayed by a problem with the lights.

The torture in Calcutta came on a day the mercury had risen to 41.2 degrees Celsius, breaking a 14-year-old mark for highest April temperatures. The city had witnessed 41.1 degrees on April 30, 1995, but its all-time record for hottest April day — 43.3 degrees on April 25, 1954 — stayed unbeaten.

Several south Calcutta areas were without electricity for three to four hours. Power had not returned to many north Calcutta localities even at midnight, although CESC was able to revive all units by then.

A power department official drew a parallel with the situation two decades ago, but added that isolation devices had not been installed at all power stations those days.

“Bihar overdrew power on two occasions leading to such wild fluctuations that all the power plants in the state collapsed,” he said.