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While existing transmission lines are not able to feed Mumbai’s power demands, Tata Power’s new, 3M-made aluminium lines are three times as effective. But, can the rest of India afford them?

K.R. Balasubramanyam | Print Edition: December 13, 2009

You may think that Mumbai’s famous power outages—sometimes up to 10 hours a day in suburbs such as Thane—occur because of chronic inefficiencies in generation, widespread theft of power or stratospheric growth of the city which consumes as much as 57 million units (MUs) of electricity a day, sending peak loads to levels as steep as 2,900 mega watts (MW). Yet, the surprising truth is that the problem isn’t always with a shortfall in generation. Thanks to new projects going on stream, fresh capacity of 7,530 MWwas added to the national grid, technically a part of that can be accessed by the Mumbai distributor, in 2008-09 alone. The real culprit often is something else entirely — specifically, under-equipped transmission lines that are simply unable to cope with the sheer volume of electricity that needs to be pumped to the city’s burgeoning population.

This is where Tata Power—the country’s largest private sector power generating utility with an installed capacity of 2,971 MW, of which 1,750 MW goes to Mumbai—has, in one fell swoop, transformed the problem of power in the city thanks to the equivalent of a ‘super’ cable. The company has introduced into its transmission network a new conductor called ACCR (aluminium conductor composite reinforced), made and developed by US firm 3M, that is capable of carrying two to three times the amount of power that a conventional ACSR (aluminium conductor steel reinforced) cable can. This has caused a sea change in the quality of power transmission. “This switch to 3M ACCR has given us the solution to increase the power flow reliably in Mumbai in a short time,” says Prasad Menon, Managing Director of Tata Power, which is also a distribution licensee for Mumbai City. “The enhanced line capacities have relieved the need for load shedding in case of tripping of one line during full load periods,’’ he adds.

As a first step, Tata Power has upgraded its eight kilometre-long 110 kV Borivali-Malad line — currently carrying around 900 to 950 amp but designed to carry up to 2,000 amps of current. The company had only two years ago upgraded the line with a Wolf twin ACSR conductor, but it soon turned out to be inadequate after the demand for power rose sharply. This posed a dilemma for Tata Power. After all, creating new transmission infrastructure is not that easy in Mumbai, considering that the population density is 27,000 people per sq. km as against 10,500 in New York City. Laying a second line over a column of new transmission towers would be impossible to do—the area being thickly-populated and with large number of hutments along the way. It simply had to figure out a way of ramping up capacity without tampering with the existing infrastructure. Replacing the existing lines with 3M’s ACCR was an easy solution. The company is similarly also upgrading the eight-kilometrelong Salsette-Saki link, which will be up and running by March 2010. “Tata Power is the first Indian company to install 200 km of 3M ACCR conductor,” says Kishore Rao, Managing Director, 3M Electro & Communication India. The two lines, together with 200 kilometres of conductor, are the single largest application of 3M ACCR globally.

3M ’s ACCR lines have some inherent advantages. First, they can be laid over the existing transmission towers by just replacing the conductors in use. This obviates the need for acquiring additional land and building towers, to do which costs money and time. “The same right of way (ROW) and towers of existing lines have been used, thus eliminating the need of acquiring new ROW, which is a very difficult task in congested areas of Borivali and Malad,” says Menon. According to Rao, the ACCR conductor is lighter than ACSR and doubles the capacity to carry more current (ampacity). “In the case of ACCR, the reconductoring is faster than building a new line, and the excess power can be sold quicker,” he says.

These ACCRs, you may think, will bring a stampede of companies eager to ramp up their transmission capabilities. Reality is that no other company in India other than Tata Power has decided to adopt 3M’s new souped up lines. Why? Industry experts say the ACCR conductors are six to eight times more expensive than conventional conductors (ACSR cables sell between Rs 200 and Rs 750 per metre, depending on the thickness ). The conductor, developed with the support of the US Department of Energy, is made of aluminiumoxide (alumina) fibers embedded in high-purity aluminium. The process of making it, 3M says, is difficult and time consuming. Moreover, ACCR is patented and manufactured by a single entity, namely 3M. The head of a government utility told BT that they usually purchase products through a process of tendering. Which means a good number of companies should already be making that product for competitive prices to emerge. The ACCR gets knocked out at this stage itself because 3M is its sole maker, boasting 18 patents for this technology. The result is that these enormously superior wires have had no takers, other than Tata Power, in India so far.

That could be a big mistake if you consider that a utility using this technology can recover its investment in two to three years, says Mohan Nair, General Manager for Electrical Markets Division, 3M. Plus, there are other benefits from adopting the ACCRs. First, a company will save on money spent on land acquisition and erection of new towers. Second, the cable will increase the utility’s revenues as it will be able to sell more power. It is also robust: The toughest project that 3M handled by far was laying of ACCR conductors for a 230 kV line in Vancouver Island without putting towers in water or erecting new ones. The company extensively used helicopters to execute the project last year. "The technology is ideal for establishing transmission infrastructure over mountains and rivers," says Nair.

Now if they could only do something about the rest of Mumbai’s infrastructure.

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