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The thyristor valve was first used in HVDC systems in 1972 on the Eel River Converter Station in Canada. [23] The thyristor is a solid-state semiconductor device similar to the diode, but with an extra control terminal that is used to switch the device on at a
The last HVDC system to use mercury arc valves was the Inter-Island HVDC link between the North and South Islands of New Zealand, which used them on one of its two poles. The mercury arc valves were decommissioned on 1 August 2012, ahead of the commissioning of replacement thyristor converters.
A thyristor (/ θ aɪ ˈ r ɪ s t ər /, from a combination of Greek language θύρα, meaning "door" or "valve", and transistor [1]) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage of current in one direction but not the other, often under control of a gate electrode, that is used in high power applications ...
The converter is usually installed in a building called the valve hall. Early HVDC systems used mercury-arc valves, but since the mid-1970s, solid state devices such as thyristors have been used. Converters using thyristors or mercury-arc valves are known as line commutated converters. In thyristor-based converters, many thyristors are ...
Haywards Pole 2 thyristor valve, during maintenance shutdown In 1987, the Electricity Corporation of New Zealand began investigations to find the best means of upgrading the inter-island link. A hybrid upgrade was chosen over total replacement, for economic reasons.
A valve hall is a building which contains the valves of the static inverters of a high-voltage direct current plant. The valves consist of thyristors, or at older plants, mercury arc rectifiers. Mercury arc rectifiers are usually supported by insulators mounted on the floor, while thyristor valves may be either supported by insulators or hung ...
The thyristors, supplied by the German HVDC consortium (Siemens, AEG and Brown Boveri) used water cooling [10] for the first time in an HVDC project. Until that time, the relatively few HVDC schemes using thyristors had used either air cooling or, as on the Cahora Bassa project supplied by the same consortium, oil-cooling.
Initially these were air-cooled and used analogue control systems, and in 2011 and 2012 respectively, the thyristor valves of Bipole 1 and Bipole 2 were replaced by modern water-cooled thyristor valves and digital control systems supplied by Alstom. [9] This system remains the world's largest-capacity submarine cable HVDC system. [10]