The Kingsnorth high-voltage direct current transmission system in London was the only application of the technology to date for high-voltage direct current transmission for supplying inner-city substations .
It was realized in the first half of the 1970s and went into operation in 1975. It led from the Kingsnorth power station in the form of a 59 km long bipolar underground cable for a voltage of 266 kV to the converter station in Beddington . The cable ran a further 26 kilometers as a single-pole connection to the converter station in Willesden. If the Kingsnorth converter station was out of service, it was also possible to operate the system between the Beddington and Willesden stations as a single-pole HVDC transmission system. The HVDC Kingsnorth was the last HVDC to be equipped with mercury vapor rectifiers , with each converter for 266 kV consisting of two series-connected three-phase bridges for 132 kV, which were each fed via a transformer connected in star-star and one in star-delta connection. All systems built later used thyristors . The HVDC Kingsnorth was able to transmit a total output of 640 megawatts (320 megawatts per pole).
|Kingsnorth substation (out of service)|
|London Beddington Substation (out of service)|
|London-Willesden substation (out of service)|