Ravin Group is engaged in turnkey projects of extra high voltage cables since 2006-2007. We provide our customers with a comprehensive cable service package which encompasses system design including design and selection of cables and compatible accessories, supply of quality materials, installation, testing, commissioning and finally ensuring full safety and reliability of the installation. Our installation team consists of a highly qualified and experienced team of engineers, who work with clients and manufacturers to identify the quickest and most cost effective power solutions. Our team has been trained and experienced in various countries around the world, and they carry with them over 250 years of cumulative experience in specialty jobs. We have a cumulative experience of installation of more than 300 kms of EHV cable and 1000 joints and terminations at voltages greater than equal 220 kV.
Background
Reliance Infrastructure Limited has a consumer base of more than 27 lakhs spread across an area of 384 sq. kms, panning across suburban Mumbai from Bandra to Bhayandar and Sion to Mankhurd.
Power produced at Reliance thermal power station at Dahanu (500 MW) is transmitted at 220 kV by transmission lines terminating at three bulk supply receiving stations, viz Ghodbunder, Versova and Aarey. At these bulk supplies receiving stations power at 220 kV is stepped down to 33 kV and distributed to 63 Nos. of 33/22/11 kV receiving stations distribution area. At such 33 or 22/11 kV unmanned receiving stations power is stepped down to 11 kV as outgoing feeders in the form of open ring system. This electricity is further stepped down to 400 volts or 230 volts at 5600 DT substations to reach the door steps of consumers.
Reliance energy power system is connected to the western grid at 220 kV aarey receiving station. To augment their capacity Reliance decided to add 4 more substations out of which Ravin was involved in transmitting power at 220 kV in 3 of the substations viz. Gorai, Goregaon, Borivali and augmentation of Ghodbunder substation. Ravin’s Role in project was not just supply of cables and accessories. It encompassed making of terminations on towers at more than 45 metres height.
Highlights of the Project
1. High value EHV turnkey project.
2. Terminations to be done at 40 meters height- first of its kind in Asia- Gorai, Goregaon, Butibori
3. Tower on dumping ground at Gorai (where crane movement not possible and no digging is allowed)
Locations at Goregaon and Gorai are shown below before we commenced work
Challenges Faced
1. Transmission tower on which terminations were to be made at 40 meters on dumping ground.
2. The dumping ground was covered with an HPE sheet that could not be punctured. This obviated the need heavy machinery and lifting equipment.
3. Lifting of terminations on tower was required to be done manually as crane movement was not allowed.
4. Multitude of permission.
5. Construction of GIS Building while trenching and cable laying.
6. Criss crossing of LV, MV cables with the EHV cables.
7. Target charging date of 31st March, 2011 caused 24 hours continuous working many times.
8. Route change for contingency resulting re-excavation and re-routing of cable.
9. Substation was to be charged without GIS directly from tower (outdoor termination) to transformers
10. Lack of free space for easy movement of men machinery, drums etc.
11. MSETCL tower in a jungle area with no road access.
12. Very short time period to achieve commissioning targets.
13. Heavily congested area.
14. CRZ rules interfered in cable route.
15. Frequent interference in aggressive manner by local political parties, local goons, mohalla committees etc. is customary.
16. Weight of each cable drum is about 15 MT with apprx dimensions of 4.2m (H) X 2.5m (W).
17. Transportation of cable drum to site requires low bed trailer of 40 ft long and 10 ft wide.
18. Proper road access with sufficient width is required for transporting, handling and unloading at site in safe manner.
How Challenges were Addressed
1. Design of special lifting process and equipments for lifting terminations at a height. This design ensures there is no damage to or shifting of stress cone inside the termination.
2. Manual Lifting of terminations at Gorai- an innovative technique designed by Ravin engineering team.
3. Lifting of terminations at Goregaon with the help of crane without much aisle space for movement.
4. Meticulous project management thereby enabling simultaneous activities to achieve the target charging dates at all places.
5. Deployment of special manpower for re-routing the cable after GIS was in place.
6. Extra jointing manpower for speedy completion.
After completion of the terminations the circuits are charged and in operation for over three years.
