The power failure took place around 5 pm on the Central Secretariat-Kashmere Gate stretch of the busy line, they said.
Following the power snag, services were affected immediately between Udyog Bhawan and Model Town stations.
Due to the power failure, trains halted and passengers were left stranded at many stations, and the Delhi Metro Rail Corporation ran trains in two separate loops as services between Central Secretariat and Kashmere Gate stations were temporarily suspended initially.
The trains were later operated on a single line temporarily on the affected section till the full rectification was done, the officials said.
Yellow Line connects Samaypur Badli and HUDA City Centrein Gurgaon.
"Due to some leakage from a water pipeline inside the tunnel between New Delhi and Chawri Bazar metro stations, the power supply tripped on the Central Secretariat-Kashmere Gate section of Line-2 (Samaypur Badli- Huda City Centre) at 4.58 pm," a senior DMRC official said.
Till the rectification which took place around 6:30 pm trains were operated in two loops.
The first loop was between Central Secretariat and HUDA City Centre stations. The second one was between Kashmere Gate and Samaypur Badli stations.
Yellow Line has three main interchange facilities -- Central Secretariat station (with Violet Line), Rajiv Chowk station (Blue Line) and Kashmere Gate station (with Red Line).
Anish Kumar, who was one of the many passengers stranded at Rajiv Chowk metro station, said, the trains were halting for unusually longer time at stations.
"I took a train this evening from Botanical Garden station in Noida. Once t reached Yamuna Bank, the delay started and trains were stopping for longer duration at stations until I reached Rajiv Chowk," he said.
At Rajiv Chowk station, Kumar said he saw a train parked by the platform with its gates open, but no power supply inside the carriages.
"I waited for 10 minutes but there were no services. So I left the station and walked to my office near Patel Chowk," he said.
Soumyajeet, another passenger, said, he was on the Yellow Line and trains were stopping for longer duration at stations.
"Announcement was being made about the technical snag, but we faced lot of inconvenience," he said.