To start with, please give us a broad idea of the underground cabling project. What is the total estimated length of cables to be used? What would be the kV rating of the cables?
The UT administration has been planning the underground cabling project since Chandigarh was selected as one of the fast-track cities under the Smart City Mission of the Union Ministry of Urban Development.
Hartek Power Pvt Ltd has bagged an order from the UT Electricity Department for laying underground electricity cables and heavy-duty electricity wiring in Sectors 7, 9, 11 and 26. To be executed at a cost of Rs.8.05 crore, the project is intended to eliminate the grave hazard posed by overhead transformers and high-tension wires that hang precariously on the edges of slip roads, road beams and parking lots in the four sectors. The UT Electricity Department has singled out these sectors to begin with as the existing power infrastructure there is more than 50 years old, which leads to frequent breakdowns and disruptions in supply.
The project involves shifting and conversion of various 11kV overhead feeders adjoining the commercial belt in the four sectors into 11kV UG XLPE cable of 300 sqmm size, and it includes the augmentation of existing 200 300kVA PM TFs with 630kVA CSS to discount the probability of calamity breakdowns and strengthen the LD system. The total length of the cables to be laid is 35.5 km and the rating of the cables is 11kV.
“The order is scheduled for completion by end-February 2021.”
When does Hartek Power expect to start work on the project and what is the envisaged completion date? Is Hartek Power planning to rope in a technical partner for this project?
The work on the project is expected to start by November last week or the first week of December. It is scheduled to be completed by February 28, 2021. We have roped in Schneider Electric as our technical partner for this project.
What type of challenges are you anticipating during project execution, especially shifting of street furniture, other underground utility infrastructure, etc. during trenching?
Reducing the damage to underground utility infrastructure during shifting and excavation presents the biggest challenge. However, we can now counter this problem with the help of visualization applications on mobile devices, which make it possible to not only visualize the utility infrastructure, but also provide accurate measurement of positions and distances between objects. These applications enable integration of traditional BIM, CAD, GIS and other types of data into augmented reality visuals. Online systems for sharing information about the location of underground infrastructure are also a big help. Backed by technical advances in this field, our professional surveyors go into the minutest of details to accurately map utility network assets and minimize the damage.
Do you feel that that this order will add to the technical qualification of Hartek Power, enabling it to bid for similar projects in future?
Yes, it will definitely add to our technical portfolio and strengthen our credentials. We are eyeing similar projects not only in Chandigarh but other upcoming Smart Cities as well. Our Smart Cities division is working towards it. The experience we gain from this project will help a lot in our future Smart City projects.
“Many such projects by UT administration are expected in the time to come.”
In Chandigarh itself, do you expect more such underground cabling projects by UT Electricity Department?
This is one of the first two underground cabling projects the UT administration has rolled out, to begin with. Many such projects will be introduced to cover the entire city in a phased manner.
In general what are the advantages of underground cabling? Do you see power utilities actively keen on shifting their overhead distribution network to the underground mode?
Underground cabling offers many advantages. It is less prone to damage from fires and harsh weather conditions like storms and hurricanes. Underground cables also significantly reduce the range of electro-magnetic field (EMF) emissions into the surrounding areas. They need a narrower surrounding strip of about 1m to10m for installation, which may go up to 30m for 400kV cables. Overhead lines, on the other hand, need a surrounding strip ranging from 20m to 200m to ensure maintenance, repairs and safety. Underground cables also add to the city’s tree line and its aesthetics by allowing bigger and shadier trees on the roadside. The risk of damage due to accidents, pilferage and sabotage is also considerably less in case of underground cables.
Finding faults in underground cables can be a tricky business. How has technology in cable fault-finding evolved in recent years?
Locating underground cable faults is not as difficult as it may seem, thanks to new detection technologies which have made the task much easier and quicker. While we have time-tested basic cable fault locating methods like sectionalising and thumping, newer fault locating methods based on sophisticated technology, like Time Domain Reflectometry, are being increasingly used. High-voltage radar methods based on arc reflection, surge pulse reflection and voltage pulse reflection are also quite popular.
We learn that the overall contract also entails converting overhead transformers into underground compact substations. Please elaborate on this aspect.
It entails dismantling of 33 transformers, including three of 500KVA rating, 23 of 300KVA rating and seven of 200KVA rating. They will be replaced by 11kV outdoor package substation consisting of 11/0.433kVV 3-phase, 50Hz, Dyn 11 vector group, copper wound 630 KVA oil-type transformer, HT switchgear (11kV 630 Amps 21KA for 3 sec. SF6 insulated RMU) and low-voltage switchgear.
Besides, Hartek Power will also supply and install 18 11kV 5-Way RMU, SCADA compatible, floor mounted with internal copper bus bars, consisting of combinations, which include one 630A fixed motorized load break switch and four fixed -type 630A motorized vacuum circuit breakers.
