Triggering and monitoring system for thyristor valves for HVDC applications

Thyristor valves for HVDC applications comprise of a number of thyristors in series. Each thyristor has a local electronics unit, which is optically interfaced with the triggering and monitoring systems. The triggering system has to ensure that all thyristors in a particular valve are triggered simultaneously, and that there is no spurious triggering or no failure to trigger. The monitoring system has to receive optical data from the valve, convert it into electrical signals and analyse the data and identify the nature of the fault and take suitable action i.e. annunciation or annunciation and trip. The types of failure that are identified are failure of thyristors, fibre optic cables, transmitters, receivers or the electronics unit of the thyristor. This paper describes the design and implementation of a triggering and monitoring system for thyristor valves supplied for phase-II of the Indian National HVDC experimental line project. Phase-I of this project, rated at 100 kV, 100 MW in 6-pulse bridge configuration, was commissioned in 1989. The phase-II 6-pulse converter valves rated 100 MW, 100 kV are added electrically in series with phase-I valves upgrading total scheme to 200 MW, 200 kV in 12-pulse mono-polar mode. The complete HVDC scheme has been commissioned in the year 2000