No final decision has yet emerged on the proposal of enhancing the reverse flow capacity of the 800kV 6,000-MW Raigarh-Pugalur HVDC link.
In its latest meeting, the National Committee on Transmission (NCT) has proposed that a new committee would be formed that would look into the project technicalities and the underlying costs before preparing a comprehensive plan. This plan would be evaluated first by the Southern Region Power Committee (SRPC) before it is placed before NCT.
The main project technicalities would revolve around AC system strengthening of the southern and western region grids, with to view to fully exploiting the reverse capacity potential.
As reported by T&D India on October 23, 2024, the plan involves enhancing the reverse flow capacity of the HVDC link, which is from Pugalur (Tamil Nadu, Southern Region) to Raigarh (Chhattisgarh, Western Region), from the current 3,000 MW to 6,000 MW. The HVDC link currently has full capacity of 6,000 MW in the onward direction, which is from Raigarh to Pugalur.
The need to enhance the reverse capacity was felt to inject growing RE generation in the southern region into the national grid.
The new committee proposed by NCT would have representations from Central Electricity Authority (CEA), Central Transmission Utility of India Ltd (CTUIL), Power Grid Corporation of India Ltd (PGCIL, the owner of the HVDC link), Southern Region Power Committee (SRPC) and Western Region Power Committee (WRPC).
Technicalities
The most important issue in this reverse capacity augmentation is the inadequacy of existing AC systems in SR and WR. Unless these systems are upgraded, the enhanced reverse flow transfer capacity (from 3,000 MW to 6,000 MW) cannot be used.
Speaking of strengthening the AC systems in WR, one would need to augment capacities at two existing substations in Chhattisgarh – Raigarh (Kotra) and Dharamjaygarh — for which no space is available. If a new substation were to be built in place of Raigarh substation, it would mean shifting existing thermal power generation to the new installation. This, in turn, would be time-consuming as it would involve securing consent from thermal generation units connected to the Raigarh substation.
It has also been informed that even if the reverse flow capacity is enhanced to 6,000 MW, very little enhancement is expected in the TTC (total transfer capability)/ATC (available transfer capability) between SR Grid and the NEW Grid (the combined northern, eastern and western grids).
Cost estimates
The current cost estimate of upgrading the reverse capacity of the HVDC link, by itself, is Rs.1,000 crore that includes the cost of system studies. AC system upgrade at the Pugalur end in SR is expected to cost Rs.400 crore while that at the Raigarh end in WR would cost Rs1,800 crore.
Reverse flow capacity of HVDC lines
Speaking only of the three existing ±800kV HVDC lines in India, each with a transfer capacity of 6,000 MW, there is no reverse flow capacity in the case of the Champa-Kurukshetra link. In the case of Biswanath-Chariyali-Alipurduar to Agra, the reverse flow capacity is 25 per cent and the same for the Raigarh-Pugalur link is 50 per cent.
It is learnt that the upcoming ±800kV,6000 MW HVDC line between Khavda (Gujarat) and Nagpur (Maharashtra), as part of the TBCB project “Khavda V-A Power Transmission Ltd” recently won by PGCIL, will have full reverse capacity.
Featured photograph (source: GE Vernova) is for representation only
