New Delhi: The services on all the six lines of the Delhi Metro resumed by 8.45 am after two hours of disruption due to tripping of power supply, an official said here Monday.

"The services in all the six lines became normal by 8.45 am. We are receiving hydel power from Bhutan on priority basis," a Delhi Metro official said.

"We have not been able to operate all the lines for an hour from 6 a.m. to 7a.m. due to tripping of power supply. At 7 am we restored 25 percent of the trains on all the lines, and now all the trains are plying as usual," the official added.

Train services on the 190-km Metro network connecting length and breath of the national capital were affected due to power failure in the Northern Grid, the main power source for Delhi, Uttar Pradesh, Punjab, Haryana, Rajasthan, Himachal Pradesh and Jammu and Kashmir.

The Northern Grid failure also caused power cuts in large parts of Delhi.

The Delhi Metro normally operates over 2,700 trips a day, covering about 70,000 km and carrying around 1.8 million passengers on week days.

Meanwhile, operations at the Delhi airport largely remained unaffected.

"As soon as there was a disruption in power supply, all our essential services like flight arrival and departure, check-in, baggage handling, aerobridge services were shifted to our back-up system. So all these operations remained normal", an airport spokesperson said.

"We have one of the best DG (Diesel Generating) back-up system of the world. However, there might be some disruption in our non-essential services", he added.

There were reports of air conditioning not functioning in Terminal 1D and some portions of Terminal 3. Also, there was no power in some retail outlets at the airport.

"Overall ninety-five percent of our services remained unaffected", a spokesperson said.