The Delhi Metro engineers constructing the Central Secretariat-Badarpur corridor have built the highest high-tension transmission towers carrying 220 kV power lines overhead to facilitate passage of a launching girder near the Sarita Vihar flyover.
According to Delhi Metro Rail Corporation officials, this is for the first time that such type of work has been done in Delhi by raising the height of the towers from 29.5 m to a record height of 58 m without disturbing regular power supply to the local residents of Sarita Vihar. “Four towers each 58-metre-high have been built near the flyover to facilitate crossing of the launching girder on the elevated section of this under construction metro corridor. The height of the lowest conductor has been raised to 34 m from 8 m earlier to make way for the passage of the launching girder that is crossing the viaduct at a height of 27 m (the top level height of the launcher) above the existing road at the location. It was also ensured that a mandatory minimum 6 m distance was maintained between the top height of the launcher and the lowest conductor of the tower,” said a DMRC spokesperson.
The work had to be carried out in the limited space available at the location, so DMRC had to carry out a survey in different parts of the country for a way out.
The officials finally zeroed on the design used in Mumbai where a similar type arrangement and the structural drawings were arranged in consultation with the designing body.
The towers were built using a very narrow base design (7x7 sq metres) instead of using the broad base design that is very common in electricity tower construction across India.
“The 220 kV Delhi Transco transmission lines originating from the Badarpur thermal power station and feeding their 220 kV Okhla sub-station was infringing the Central Secretariat-Badarpur corridor near Sarita Vihar flyover and the Sarita Vihar metro depot area. The matter was referred to DTL for raising the height of the line. DTL informed that they did not have tower design available with them for facilitating the launching girder to cross the overhead line,” the spokesperson said.
However, the DTL suggested that the line should be taken underground from Badarpur thermal power station to Okhla.
“The approximate cost for the underground work could have gone to the tune of Rs.95 crore. Moreover, the execution time required for such work would also have delayed the metro construction by 18 to 24 months. The solution was not feasible under the circumstances,” the spokesperson said.
“The DMRC had earlier executed the work for raising the height of 220 kV power lines near Laxmi Nagar on Vikas Marg and near the Indraprastha metro station. The heights of the steel towers at Laxmi Nagar were raised to 53.5 m (two towers) and 44.5 m (one tower). The towers used in this section were of broad base design that required 20x20 metres of space for their erection. This much space was not available for Delhi Metro near the Sarita Vihar flyover area.”
The complete work was executed at a cost of Rs.2.7 crore in about 45 days with 30 people working under all safety precautions. At present, the launching of viaduct is in operation.
This challenging work was done by DMRC without disturbing the power supply to the local residents of the area and maintaining all electrical clearances as per rules.
“The DMRC has shifted nearly 50 transmission lines of varying voltage capacity till date and is in the process of shifting few more high voltage electricity lines at Badarpur and other locations on its under-construction corridors,” the spokesperson said.