Tamil Nadu’s electricity utility, Tangedco, wants to convert low tension (LT) lines in its transmission system to high tension (HT), to bring down transmission losses. 

Usually, HT is used for long distance transmission and is of high voltage (11kV and above), whereas LT (220V) is for shorter distances, such as delivering power to households. 

Sources in the know have told businessline that over time, Tamil Nadu has ended up building a lot of needless LT lines, because LT is cheaper than HT. But transmission losses are lower in HT, because the higher the voltage the lower the transmission losses. 

The Aggregate Technical and Commercial (AT&C) losses in Tamil Nadu’s grid is about 11.6 per cent, which is among the lowest in the country. Yet, the State wants to bring down the losses to under 10 per cent. Every percentage point reduction in AT&C losses corresponds to a gain of ₹800 crore. 

Tangedco believes that converting LT lines into HT, wherever possible, is one good way of reducing AT&C losses. It began doing so a few months ago, and has so far converted 500 km of LT into HT. But that isn’t the least comparable with the potential for conversion. Tangedco reckons that it could do about 3,000-4000 km every year for the next ten years. This would cost about ₹10,000 crore.

Sreekumar Nhalur, Member, Prayas Energy Group, a power sector think-tank, believes that there is a case for converting part of Low Voltage Distribution System to High Voltage Distribution System, with less of 415/240 V lines and more distribution transformers.

“HVDS improves tail end voltage, reduces technical losses and can reduce electricity theft. Many States have been taking up this conversion, especially to supply power to agriculture pumpsets and in urban areas with high density of consumers. HVDS requires higher onetime investment (compared to LVDS) and higher maintenance burden due to higher number of Distribution Transformers,” Nhalur told businessline.

He believes that HVDS deployment can be justified in areas where this higher investment provides good financial returns to the distribution company and better supply quality to consumers. “This is typically true for rural areas with high density of agriculture pumpsets and urban areas with high consumer density or high AT&C losses. TANGEDCO could record current circle-wise levels of AT&C losses, Distribution Transformer failures and instances of low voltage. These should be compared to expected levels after HVDS deployment, to check if the investment would provide expected benefits,” he said.

Questions over pumped storage  

Meanwhile, the Chairman and Managing Director of Tangedco, Rajesh Lakhoni, has expressed his concerns over pumped storage plants (PSP).  

In a conversation with Kapil Bansal, Partner, EY, at an Energy Transition Summit & Exposition, organised here by the Confederation of Indian Industry (CII) on Tuesday, Lakhoni expressed fears that the PSP plants might turn out to be “white elephants”. 

This, he said, is because the PSP plants, which are expensive to build, have a fixed tariff for providing energy storage services over the entire life of the plant, which could extend up to even 40 years. In contrast, batteries last about 7 years. 

At a time when battery costs are coming down fast, should one get locked for long term into PSP? If the cost of storing power in a PSP plant is about ₹4 but battery prices fall to such levels as to make battery storage cost only about, say, ₹2, then PSPs become a lost economic opportunity. 

However, Lakhoni, stressed that he was only expressing a thought; Tangedco would not stop PSP projects. 

The state government has previously said that it intends to develop PSPs. In his budget speech of February 19, 2024, Thangam Thenarasu, Minister for Finance and Human Resources Management, Government of Tamil Nadu, said that the state had identified 12 locations for setting up PSPs worth 11,500 MW, on public-private partnership mode, with a total investment of ₹60,000 crore. 

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