The country’s first and oldest 500MW HVDC back-to-back link, Vindhyachal, was comissioned in 1989 to interconnect the asynchronous 400kV alternating current networks of the Northern and Western regions.

Siemens will be responsible for installing latest HVDC components in order to extend the useful life of the HVDC link and ensure reliable power supply.

Siemens Gas and Power Transmission Solutions head Mirko Düsel said: “We are proud that POWERGRID trusts in Siemens engineering excellence to breathe new life in the first HVDC system in India.

“We look forward to extending the lifespan of the station and enhancing the installation’s efficiency by implementing our state-of-the-art technology.”

Siemens said that contract will be its first HVDC modernization project in India and its first refurbishment of a third-party system involving replacement of the thyristor valves.

Under the contract, Siemens will install new thyristor valves, converter cooling system, HVDC control and protection system, direct current measuring devices and surge arrestors.

The firm plans to deliver the key components for the upgrade including the thyristor valves as well as the HVDC control and protection system, from its facility in Goa, India.

The Vindhyachal HVDC system modernization work is planned to be completed in 2021.

Siemens will replace the old electrically-triggered thyristors with latest light-triggered thyristors with a higher voltage blocking capability.

The work will reduce the number of thyristors resulting in less power loss, the firm said.

The HVDC back-to-back link can be used to connect two independent neighboring transmission networks with incompatible electrical frequencies, or different operating philosophies to prevent the power increase in the short circuit levels of the network.

Additionally, the system can be used to control power transfer between two separated alternating current transmission systems.

The back-to-back HVDC station was conceived by India’s National Thermal Power Corporation (NTPC).

However, as a result of reorganization of the Indian power sector, the transmission project is now owned by the Power Grid Corporation of India.