Interstate system scheme planned for hydropower evacuation from Arunachal Pradesh
- September 5, 2025
A new interstate transmission system (ISTS) scheme to facilitate hydropower evacuation from upcoming projects in Arunachal Pradesh has been proposed for development under the tariff-based competitive bidding (TBCB) route.
The scheme, termed as “NERGS-III Siang Basin,” is expected to commission by end-February 2029 and has an estimated project cost of Rs.1,804 crore.
PFC Consulting Ltd (PFCCL) has been nominated as the bid process coordinator (BPC) for this interstate scheme that was cleared by the National Committee on Transmission (NCT) during its most recent meeting last month. The scheme will need final clearance from the Union power ministry before the bidder selection process could be initiated. Incidentally, PFCCL has already begun the process of selecting the technical consultant for this project.
NERGS-III Siang Basin is part of an overarching project North Eastern Region Generation Scheme (NERGS) of which one part — “NERGS-I” — is already under development, in the TBCB mode. This project housed under “NERGS-I Power Transmission Ltd” is being developed by Techno Electric & Engineering Company Ltd.
Objective
“NERGS-III Siang Basin” seeks to develop evacuation infrastructure for two upcoming hydropower projects in the Shi-Yomi district of Arunachal Pradesh – Heo (3×80 MW) and Tato-I (3×62 MW). The scheme will also support future projects in the Siang sub-basin (of the Brahmaputra basin) where hydropower potential of around 5,600 MW is expected to be harnessed by 2035.
Both Heo and Tato-I are being developed by North Eastern Electric Power Corporation Ltd (NEEPCO), a subsidiary of Central PSU NTPC Ltd, and are currently under physical construction.
Components
The main elements under “NERGS-III Siang Basin” would be a new 400/220kV GIS substation at Kaying in Arunachal Pradesh. Besides, a new 400kV GIS switching station will also be put up at Niglok in the same northeastern state. Kaying and Niglok will be connected via a 400kV double-circuit (quad) line, running around 100 km.
Niglok will also be connected to the upcoming 400/220/132kV Gogamukh substation that is coming up through an independent ISTS-TBCB scheme “NERES XVI Power Transmission Ltd” being developed by Techno Electric & Engineering Company Ltd. This connection will be achieved through a 400kV double-circuit (quad) line with running length of 125 km.
Under NERGS-III Siang Basin, the upcoming Gogamukh substation will also see the addition of two 400kV line bays in order to accommodate the Niglok-Gogamukh line discussed above.
Provision for HVDC infrastructure
The upcoming 400kV GIS Niglok switching station, which is coming up under “NERGS-III Siang Basin,” will provide space for future expansion. This expansion mainly includes the ±800kV, 6000 MW Niglok (HVDC) [LCC] terminal station. According to industry sources, this HVDC terminal station will be a reliable HVDC link to integrate the northeastern region into the National Grid. It is further learnt, though without official confirmation, that the Niglok HVDC terminal will ultimately be part of the ±800kV Raigarh-Pugalur HVDC link, through extended components. This link will supplement the role of the existing ±800kV, 6,000 MW Biswanath-Chariyali to Agra HVDC link, running from Assam to Uttar Pradesh. In operation since 2017, this is India’s first HVDC link at 800kV voltage level.
Featured photograph (source: NEEPCO) showing the switchyard and power house of NEEPCO’s Pare hydropower project in Arunachal Pradesh is for representation only.