A view of the alternating current yard at the HVDC back-to-back converter station in Georgia.

Siemens to Upgrade India's Oldest HVDC Link

April 24, 2019
Project to install new thyristor valves, and HVDC control and protection system.

Siemens will upgrade India’s oldest high voltage direct current (HVDC) link, Vindhyachal, by installing its latest components. Vindhyachal was put into operation in 1989 to interconnect the asynchronous 400-kV ac networks of India's Northern and Western regions. Power Grid Corporation of India (POWERGRID), the central transmission utility of the country, chose Siemens to modernize the 500-MW HVDC back-to-back system in the central state of Madhya Pradesh. This will be the first Siemens HVDC modernization project in India and globally the company's first refurbishment of a third-party system involving replacement of the thyristor valves.

The project's scope includes the installation of new thyristor valves, converter cooling system, HVDC control and protection system, dc measuring devices and surge arrestors. The key components for the upgrade — the thyristor valves as well as the HVDC control and protection system — will be delivered from the Indian facility in Goa.

Latest light-triggered thyristors with a higher voltage blocking capability will replace the old electrically triggered thyristors. Thus, the number of thyristors will be halved, resulting in less power loss. The refurbished Vindhyachal HVDC station is expected to ensure reliable power supply. The upgrade is scheduled to be completed in 2021.

"We are proud that POWERGRID trusts in Siemens engineering excellence to breathe new life in the first HVDC system in India," said Mirko Düsel, head of Transmission Solutions at Siemens Gas and Power. "We look forward to extending the lifespan of the station and enhancing the installation's efficiency by implementing our state-of-the-art technology."

With a HVDC back-to-back link, two independent neighboring transmission networks with incompatible electrical frequencies, or different operating philosophies, are connected. Additionally, it prevents the power increase in the short circuit levels of the network. An HVDC back-to-back system can also be used for controlled power transfer between two separated ac transmission systems.

For further information on HVDC, please see www.siemens.com/hvdc.

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