The SuperGrid refers the existing high voltage transmission grid in Great Britain that was constructed in the 1960s, and to various overseas parallels, including the concept, again in the British context, of increased connectivity to our neighbours. In the code that governs the British Grid, the Grid Code [1] , the Supergrid is defined as those parts of the British electricity transmission system that are connected at voltages in excess of 200 kV (200,000 volts).
The article below refers to a particular concept for a high voltage grid (or supergrid), which is novel in that it combines with the distribution of cryogenic hydrogen, to achieve superconductivity. This is not the usual use of the term "supergrid", and from this point onwards, this page may be viewed as an article about "possible future superconducting grids with hydrogen" :
A supergrid with hydrogen is an idea for combining very long distance electric power transmission with liquid hydrogen distribution. The hydrogen is both a distributed fuel and a cryogenic coolant for the power lines, rendering them superconducting. The concept's advocates describe it as being in a "visionary" stage, for which no new scientific breakthrough is required, but requires major technological innovations before it could progress to a practical system.[2] A system for the United States is projected to require "several decades" before it could be fully implemented.[3] High-voltage direct current (HVDC) lines have the capability of transmitting similar voltages, for example a 5 gigawatt HVDC system is being constructed along the southern provinces of China without the use of superconducting cables.[4]
1.5% [5]of the energy transmitted on the British AC Supergrid is lost (transformer, heating and capacitive losses), of which a little under two-thirds, or 1% on the British supergrid, represents "DC", resistive, heating type losses. With the use of superconductors, the capacitive and transformer losses, in the unlikely event the transmission lines were still overhead, AC lines, would remain the same. Overhead lines do not lend themselves at all well physically to the incorporation of cryogenic hydrogen piping, due to the likely weight of the transmission medium and the considerable brittleness of supercooled materials. It would probably be necessary for a supercooled hydrogen-carrying transmission line to be subterranean, and this in turn means that for such a cable, if it were of any distance (e.g. over 60 km), the power would have to be converted to DC and transmitted as such, since otherwise the capacitive losses would be too high. The power electronic losses in the AC/DC converter substations to convert the AC power at either end of the cryogenic cable to/from DC, if the transmission line(s) itself were DC, would also remain exactly the same as they would have been without the use of a superconducting transmission line - but the DC type resistive losses in the transmission lines would be rendered even smaller than at present. Even before comprehensive continental and (in the case of the proposed European Super_Grid) intercontinental backbones of electrical transmission may be realized, such cables could be used to efficiently interconnect regional power grids of conventional design.