Microprocessor monitoring of an HVDC thyristor converter

Abstract The development of a microprocessor-based monitoring system for HVDC thyristor converter is reported. A modern HVDC converter is an assemblage of thyristor valves. The thyristor valve consists of a fairly large number of thyristors connected in series. The practice is to incorporate redundancy by providing a few extra thyristors so as to allow the HVDC terminal to continue to operate even if some thyristors have failed. The availability of the system shows marked improvement if the condition of thyristors is monitored. The monitoring system receives digital signals giving the status of thyristors through a fibre-optics link. These signals are processed by the microprocessor and the faulty thyristors are identified. This result is printed out by a dot-matrix printer along with the time at which the failure had occurred. An internal clock keeps record of real time in terms of seconds, minutes, hours, date, month and year. The leap year correction is also taken into account.