THYRISTOR VALVE
General :A thyristor valve is made up of a number of devices connected in series to provide the required voltage rating and also of devices connected in parallel to provide the required current rating. With modern devices of high current ratings, the need for parallel connection does not arise. The number of series connected thyristor is determined by device ratings, transient overvoltages and protection philosophy.
The valves are usually placed indoor in a valve hall which is protected against contamination and dust. Valves are generally base mounted in a single, double or quadrivalve configuration. The latter results in a compact valve hall.
The valves are usually air insulated and cooled using air, water ,oil or freon. The water cooling is normally used in modern converter stations are the power losses are reduced. In a valve, the heat sinks and damping resistors are cooled by the water flowing in ducts. The main objective of the cooling system is to reduce the total thermal resistance for the heat sink.
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