Power Grid Corporation of India Ltd (PGCIL) has been assigned a project to augment capacity at the Thrissur VSC HVDC station in Kerala, under the regulated tariff mechanism (RTM) route.
A proposal to this effect was recently cleared by the National Committee on Transmission (NCT). Termed as “Augmentation of 1×500 MVA, 400/220kV ICT (3rd) at Thrissur VSC HVDC Station in Kerala,” the scheme is expected cost Rs.170 crore and has a gestation period of 24 months from the date of project allocation, which is the date on which Central Transmission Utility of India (CTUIL) formally assigns the project to PGCIL.
Project rationale
The peak demand of the Kerala grid system had touched 6,000 MW on May 2, 2024. The Southern Region Load Dispatch Centre (SRLDC) had also observed high loading on the interconnecting transformers (ICT) at Kozhikode and Thrissur HVDC during the peak demand season of 2023-24.
NCT was informed that ICTs at various interstate and intrastate system substations in Kerala are heavily loaded and are not meeting “N-1” contingency criteria.
The augmentation of the Thrissur HVDC station is a step in the direction of mitigating this overloading.
Project elements
Apart from putting up a 500 MVA, 400/220kV ICT at the Thrissur HVDC station, which will be the third such at the station, two lines bays of 220kV will also be commissioned. Besides, the 220kV GIS hall associated with the HVDC station will be extended to accommodate six 220kV bays.
The Thrissur HVDC station is part of the ±320kV, 2000 MW Pugalur-Thrissur HVDC line, which in turn, is an extended component of the ±800kV, 6000 MW Raigarh – Pugalur HVDC link running from Chhattisgarh to Tamil Nadu.
De-linking of “Scheme-II” component
In a related development, NCT has also approved de-linking of a component associated with the Raigarh-Pugalur-Thrissur HVDC link.
When this massive HVDC link was awarded to PGCIL under the RTM route, in December 2014, the project had three schemes:
- Scheme-I: Raigarh–Pugalur HVDC System (±800kV, 6,000 MW)
- Scheme-II: AC system strengthening at Pugalur
- Scheme-III: Pugalur–Trichur VSC-based HVDC System (±320kV, 2000 MW)
Scheme-I and Scheme-II were commissioned and put in commercial operation in FY22. One component of Scheme-II has been pending owing to delayed commissioning of the 400/220kV Edayarpalayam substation by Tamil Nadu Transmission Corporation Ltd (TANTRANSCO). This component involved putting up four 400kV line bays at the said substation for termination of the 400kV Pugalur-Edayarpalayam and 400kV Edayarpalayam-Udumalpet lines.
As the Edayarpalayam substation is yet under construction with no concrete timeframe for its completion, the said component has been delinked from “Scheme-II” of the overall HVDC project. This component will be revived as and when clarity emerges on the commissioning schedule of the Edayarpalayam substation.
At present, the Pugalur-Edayarpalayam and Edayarpalayam-Udumalpet lines are directly connected, bypassing the Edayarpalayam substation.
For older stories on the Raigarh-Pugalur-Thrissur HVDC link, please click here.
Featured photograph (source: Hitachi Energy India) relates to an HVDC-related element in Tamil Nadu, associated with the Raigarh-Pugalur HVDC link.